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Conservation of Biological Diversity in the Great Lakes Basin Ecosystem:  Issues and Opportunities

Introduction  back to top

North America is home to one of the world's most remarkable ecosystems. Carved out by glaciers during the last ice age, the Great Lakes contain nearly 20% of the earth's fresh water. Only the polar ice caps contain more. This wealth of water and the glacially-sculpted landscape of the basin support a tremendous abundance and diversity of life.

As the last glaciers began retreating some 14,000 years ago, they left an ecological frontier rich in new habitats that were rapidly exploited by species immigrating from the east, south and west. These biological pioneers formed new communities that could thrive in the specialized environments created by the glaciers and sustained by the Great Lakes. As populations adapted to the special conditions in the basin, new forms of life began to evolve, further enriching the biological diversity of this unique area.

Geologically, the Great Lakes ecosystem is very young and can be thought of as an evolutionary laboratory. Species that have evolved here have done so in a remarkably short period of time, and the processes that support their continuing adaptation in this dynamic environment need to be safeguarded. Species and community types at the margins of their ranges, or with their last occurrences here, are also an important part of this evolutionary laboratory. These features are most likely to respond to environmental pressures and evolve into new forms of life that are best suited to survive in the Great Lakes ecosystem.

The lakes, and the basin that they drain, have played a major role in the history and development of the United States and Canada. The basin supports more than one- tenth of the U.S. population and more than one- fourth of the population of Canada. Nearly 25% of the total Canadian agricultural production and 7% of the U.S. agricultural production occur in the basin. Some of the world's largest concentrations of industrial capacity are located around the Great Lakes.

Human use has adversely impacted the basin ecosystem. In the last 20 years, much has been done to stem the input of nutrients and toxic chemicals into the basin, initiating a rebound in the health of the ecosystem. Although some lake communities have undergone major changes, and some species have been lost, the ecosystem as a whole still supports special biological resources. However, certain human activities continue to pose threats to the maintenance of biological diversity in the Great Lakes basin.

Purpose of This Document
This paper serves to begin a dialogue on how these special biodiversity resources should be identified and protected in the Great Lakes basin. In this paper, significant biodiversity elements of the basin are identified. Threats to those resources are described and, in general terms, evaluated. Based on this information, recommendations are provided for the protection of biological diversity in the Great Lakes ecosystem. These are strategic in nature, designed to suggest broad direction, stimulate discussion and solicit advice for the protection of biological diversity in the basin. Finally, a range of tools available for biodiversity protection is outlined.

General Methodology
In this document, the principles of Natural Heritage programs, built in partnership between The Nature Conservancy and state governments, are used to identify the key biodiversity resources of the Great Lakes ecosystem. These biodiversity resources are the natural communities and species that are important to the preservation of the range of life that occurs in the basin. The Heritage methodology provides a means of focusing action on those elements most critical to the maintenance of biological diversity.

The threats to these key biodiversity resources are analyzed by assessing the key ecological systems that sustain the resources and by describing the principal stresses to those systems. These stresses are then attributed to human activities that are the source of the predominant stresses. In this fashion, a set of biological diversity protection priorities is developed.

Throughout the preparation of this document, advice on the key resources, principal threats and potential protection strategies has been sought from agencies, organizations and individuals active in the protection and restoration of the Great Lakes ecosystem. This advice has been solicited in the form of discussions, structured interviews and review of draft portions of this analysis.

Biological Diversity back to top

What is Biological Diversity and Why Should it be Conserved?
Biological diversity, or biodiversity, is the range of life on our planet. A more thorough definition is presented by botanist Peter H. Raven: "At the simplest level, biodiversity is the sum total of all the plants, animals, fungi and microorganisms in the world, or in a particular area; all of their individual variation; and all of the interactions between them. It is the set of living organisms that make up the fabric of the planet Earth and allow it to function as it does, by capturing energy from the sun and using it to drive all of life's processes; by forming communities of organisms that have, through the several billion years of life's history on Earth, altered the nature of the atmosphere, the soil and the water of our planet; and by making possible the sustainability of our planet through their life activities now." (Raven 1994)

It is not known how many species occur on our planet. Presently, about 1.4 million species have been named. It has been estimated that there are perhaps 9 million more that have not been identified. What is known is that they are vanishing at an unprecedented rate. Reliable estimates show extinctions occurring at a rate several orders of magnitude above "background" in some ecological systems. (Wilson 1992, Hoose 1981)

The reasons for protecting biological diversity are complex, but they fall into four major categories.

First, loss of diversity generally weakens entire natural systems. Healthy ecosystems tend to have many natural checks and balances. Every species plays a role in maintaining this system. When simplified by the loss of diversity, the system becomes more susceptible to natural and artificial perturbations. The chances of a system- wide collapse increase. In parts of the midwestern United States, for example, it was only the remnant areas of natural prairies that kept soil intact during the dust bowl years of the 1930s. (Roush 1982)

Simplified ecosystems are almost always expensive to maintain. For example, when synthetic chemicals are relied upon to control pests, the target species are not the only ones affected. Their natural predators are almost always killed or driven away, exacerbating the pest problem. In the meantime, people are unintentionally breeding pesticide- resistant pests. A process has begun where people become perpetual guardians of the affected area, which requires the expenditure of financial resources and human ingenuity to keep the system going.

A second reason for protecting biological diversity is that it represents one of our greatest untapped resources. Great benefits can be reaped from a single species. About 20 species provide 90% of the world's food. Of these 20, just three-- wheat, maize and rice--supply over one half of that food. American wheat farmers need new varieties every five to 15 years to compete with pests and diseases. Wild strains of wheat are critical genetic reservoirs for these new varieties. In 1970, for example, the U.S. corn crop was threatened by a new race of corn leaf blight that had reduced corn yields by 50% in many states. The gene that creates resistance to the blight was discovered in a wild strain of corn found only in Mexico.

Further, every species is a potential source of human medicine. In 1980, a published report identified the market value of prescription drugs from higher plants at over $3 billion. Organic alkaloids, a class of chemical compounds used in medicines, are found in an estimated 20% of plant species. Yet only 2% of plant species have been screened for these compounds. (Hoose 1981)

The third reason for protecting diversity is that humans benefit from natural areas and depend on healthy ecosystems. The natural world supplies our air, our water, our food and supports human economic activity . Further, humans are creatures that evolved in a diverse natural environment between forest and grasslands. People need to be reassured that such places remain. When people speak of "going to the country," they generally mean more than getting out of town. For reasons of their own sanity and well being, they need a holistic, organic experience. Prolonged exposure to urban monotony produces neuroses, for which cultural and natural diversity are a cure.

Historically, the lack of attention to biological diversity, and the ecological processes it supports, has resulted in economic hardships for segments of the basin's human population. The first Europeans that settled in the basin came in pursuit of fur-bearing animals, exhausted the populations and were forced to move on to areas more rich in pelts. In the early 1800s, the virgin forests of the basin appeared to be without limit. They were harvested to support the building boom in the basin, often with a view to farming the cleared land. Frequently, poorer soils could not support agriculture after the forests were cleared, the farms failed, and the forests have yet to be fully regenerated. The Great Lakes commercial fishery reached its peak in the late 1800s. An entire industry, and the families it supported, suffered because of the introduction of exotic species, the overharvest of the lakes and pollution. Today, only pockets remain of the once large commercial fishery. (Botts and Krushelnicki, 1987)

The final reason for protecting biological diversity is that species and natural systems are intrinsically valuable. The above reasons have focused on the benefits of the natural world to humans. All things possess intrinsic value simply because they exist.

Using Natural Heritage Programs to Inventory Biological Diversity
In order to protect the biological diversity of a system the size of the Great Lakes basin, a sound targeting scheme must be developed. Since diversity includes all living organisms in the basin, and protection resources are finite, decisions must be made about how to most wisely invest those limited resources. In other words, it is important to know where to act first.

As a starting point, the diversity of life must be inventoried. It must be determined what species, communities and natural systems exist. Through a comprehensive inventory, those components needing protection can be identified, their requirements for survival better understood and the best and most defensible examples can be located. Second, the inventory needs to be analyzed to select those examples that require the most immediate attention and have the best chance for survival.

Fortunately, much of this work has been done in the Great Lakes basin. Naturalists began inventory work soon after European settlers came to the area. A body of literature was compiled on the natural features of the basin. Government agencies, academic institutions and others have maintained herbaria, natural history museums and the like. Knowledge of the biological resources of the Great Lakes, however, remains imperfect. The open waters and lake bottoms, for example, have proven somewhat difficult to systematically inventory, as have the more remote terrestrial portions of the basin. These data gaps have influenced the conclusions of this analysis and highlight the need for a more complete biological inventory of the Great Lakes ecosystem.

State and provincial governments, in partnership with The Nature Conservancy, have established Natural Heritage programs that have assembled previous inventory work and. supplementing it with additional surveys, analyze the data to identify biodiversity resources that require protection. Heritage Programs refer to these resources as the "elements" of biological diversity. An element can be either a natural ecological community or an individual species.

Natural Heritage programs use a two-tiered inventory and targeting scheme. First, all natural communities that occur within a given state (or province) are targeted as biodiversity elements. The rationale is that by protecting high-quality examples of natural communities, a sizable portion of the natural diversity within a given political jurisdiction can be protected. Natural communities form a "coarse filter," accounting for most, but not all, animal and plant diversity.

The second tier of inventory and targeting focuses on species that are too rare to be protected simply by preserving representative examples of natural communities. An inventory of such species forms a "fine filter," capturing the remaining elements of diversity. A plant or animal species becomes an "element" meriting protection after committees of scientists review the species list for a given area and decide which are declining, rare or endangered.

Each community and rare species element is evaluated by scientists and given a rank that reflects its conservation status. The status of elements is ranked at both the global and state or provincial level. It is unlikely that a common species will become a priority element. For example, although the blue jay is a bird species and part of the diversity of life, it is relatively secure throughout its range and is probably not the most important species to protect today. The piping plover, on the other hand, has been declining in its range and is a higher priority because it requires immediate attention to ensure its survival.

Five types of global ranks are assigned. An element is critically imperiled if it is extremely rare, such as occurring in five places or less, or is highly vulnerable to extinction. Elements that occur in six to 20 places or are vulnerable to extinction are considered imperiled. Rare elements may be locally abundant, but occur in only 21 to 100 locations or may be vulnerable to range-wide extinction. When an element appears to not be at risk, it is ranked as apparently secure, or demonstrably secure.

When an element is found to occur at a specific site, it is assigned an occurrence rank that reflects its quality, condition, viability and defensibility at that site. An element receives a separate occurrence rank for each site where it is found. Each occurrence is evaluated and rated by scientists using a uniform analysis process. The four ranks used include excellent, good, marginal and poor. These ratings allow protection activity to be directed at those places where priority elements have the best chance of surviving. (See Appendix 2 for a complete description of the Heritage Ranking system.)

The first Natural Heritage program within the Great Lakes basin was begun in the state of Ohio in the mid-1970s. The most recent program in the U.S. portion of the basin was established in the state of Illinois in 1986.

Recognizing the utility of the Natural Heritage methodology to target the protection of biological diversity, the International Joint Commission's Science Advisory Board issued a challenge in 1987 to The Nature Conservancy and the Nature Conservancy of Canada to assemble heritage data for the basin. (IJC 1988) Work began that year to build a Conservation Data Center in the province of Ontario.

Because the programs in the U.S. portion of the basin were begun at different times, and targeted different elements, work also began on a framework to unify the variety of elements, particularly community types, across the basin. A preliminary classification of regional community types was developed, and is now undergoing review and revision. Within the last year, a functional basin-wide heritage data system has been established for the Great Lakes. (Crispin 1994) The data presented in this overview are drawn from that system.

The Great Lakes Ecosystem back to top

What is the Great Lakes Ecosystem?
When one looks at a map of the Great Lakes basin, or any lake basin for that matter, eyes are drawn to the fields of blue color that represent the open water. In reality, lake ecosystems are composites of the open water system, shoreline systems and systems that occur in the upper watershed. These systems are interrelated and interdependent. Figure 1 is a schematic representation of the major features in the Great Lakes ecosystem.

A graphic showing of the Great Lakes Ecosystem Schematic
Figure 1.  (To see a larger view, click on the graphic)

The open lakes are connected to the more inland portions of the watershed by the movement of surface water, groundwater and living organisms. Rivers and streams supply lakes with water and nutrients, and provide spawning and nursery areas for anadromous fish. The tributaries, in turn, depend on upland vegetation to regulate the nutrients and solids entering the waterways, and for input of energy and material such as the autumn leaf fall.

The interconnectedness of the various systems that comprise the Great Lakes ecosystem can be illustrated by certain wildlife species. For example, the hooded merganser that is hatched in a tree cavity will be raised in sheltered shallows, only to take to the open water when it is old enough to begin feeding on fish and other open water organisms. (Caduto 1990)

The health of the lakes and their biological diversity is directly related to the health of each component of the ecosystem. Similarly, the lakes are adversely affected when disturbances occur in one of the systems. For example, alterations in the upper watershed can impact the entire lake ecosystem. When a forest is cleared, not only is the physical structure of the terrestrial ecosystem altered, the tributary streams, coastal areas and the open lake can also be affected. When vegetation is removed near a tributary, precipitation is allowed to run off directly into the river or stream, causing flows in these streams to increase much more quickly (following rainfall). This run-off also picks up more soil than it otherwise would, and the load of sediment in the tributary will be increased. The increased sediments can destroy the habitat required by fish and insect species and can prevent the spawning of anadromous fishes which spend most of their lives in the open lake. These sediments can also accelerate the formation of sand bars and blockages at rivermouths, altering nearby coasts.

The Great Lakes Today
The size of the Great Lakes ecosystem is difficult to comprehend, even for those who live and work in the basin. The lakes themselves contain over 5,500 cubic miles of water. They cover a surface area of about 94,000 square miles. The watershed that drains into these lakes is just over 201,000 square miles. The system extends from roughly 41 to 51 degrees north latitude and 75 to 93 degrees west longitude. (Botts and Krushelnicki 1987)

Because of the large size and unique position of the watershed, climate, soils and topography vary across the basin. In the north, the climate is cold, and the relatively thin, acidic soils are underlain by granite bedrock. Prior to European settlement, these lands were covered with conifer forests.

Great Lakes Ecosystem Schematic (see Figure 1)
In the southern portion of the basin, the climate is warmer, and the deeper soils are composed of glacial drift including sands, silts, clays, gravel and boulders. These southern soils are typically fertile and amenable to agriculture. The original deciduous forests, prairies and swamps have given way to extensive agricultural and urban development.

The lakes themselves exert a profound effect on the climate of the system. Acting as a giant heat sink, the over 5,000 cubic miles of water moderate the temperatures of the surrounding land, cooling the summers and warming the winters. This results in a milder climate in portions of the basin compared to other locations of similar latitude. The lakes also act as a giant humidifier, increasing the moisture content of the air throughout the year. This increased humidity also causes increased precipitation in some areas of the basin. The winter winds generally blow from northwest to southeast across the basin. As the winds blow across the warmer water, they pick up moisture. This results in "snow belts" on the south and east shores of the lakes. These areas typically receive between 60 and 135 inches of snow each winter.

During the summer season, the northern part of the basin generally continues to receive cool, dry air masses from the northwest. In the southern part of the basin, humid, tropical air originating in the Gulf of Mexico competes with these cooler Canadian weather systems. The precipitation produced by these weather systems that is not evaporated or transpired is stored as groundwater or transported to tributaries as run-off, and is ultimately deposited in the lakes.

Although part of a single system, each lake basin possesses unique features. Lake Superior is the largest of the Great Lakes. Its volume of 2,900 cubic miles could easily hold all of the other Great Lakes combined. Water that enters the lake stays in the basin for an average of 191 years. The drainage basin of 49,300 square miles contains parts of three U.S. states--Minnesota, Wisconsin and Michigan and part of the province of Ontario. Approximately 90% of the basin is forested because the soils are ill-suited to agriculture and the climate is cool.

The second largest lake, Lake Michigan is entirely within the United States and drains parts of four states--Wisconsin, Illinois, Indiana and Michigan. Its volume (1,180 cubic miles) is less than one half of Lake Superior's. Water that enters the lake has an average residence time of 99 years. The lake receives water and nutrients from a 45,600-square-mile watershed. The northern and northwestern shores of the lake are bordered by Silurian dolomite of the Niagara escarpment. The southern and eastern shores contain extensive dune systems. The lake interacts extensively with estuarine, marsh and interdunal wetland systems in these areas.

Lake Huron drains the largest watershed in the basin--51,700 square miles. It has a volume of 850 cubic miles. The lake is bisected by the Niagara Escarpment, which runs east from Michigan's upper peninsula, forming Drummond and Manitoulin Islands and the Bruce Peninsula that separates the main body of the lake from Georgian Bay. The upper portion of the watershed is generally forested and the southern portion is agricultural and urban. Sections of Michigan and Ontario are contained in the watershed.

Lake Erie is the smallest of the Great Lakes (116 cubic miles) and has the shortest retention time, about 2.6 years. It drains a watershed of 30,140 square miles that is almost completely urban or agricultural. Because Lake Erie is relatively shallow and is exposed to prevailing winds, it is especially susceptible to intense wave action and wind-generated changes in lake level. These changes, know as "seiches," alternately flood and drain the coastal wetland systems of southeastern Michigan, northwest Ohio and southern Ontario. The basin also contains portions of northeast Indiana, western New York and Pennsylvania.

Lake Ontario receives the outflow from all of the other Great Lakes. It has a volume of 393 cubic miles and an average retention time of six years. Its watershed includes portions of Ontario and New York, and covers 24,720 square miles. The western part of the Canadian portion of the basin is highly urbanized, and the remainder is largely in agriculture. In New York, specialty agriculture, dairy farming and general farming are the primary land uses within the watershed.

An Abbreviated Natural History of the Great Lakes
The Great Lakes are the only glacial feature that is visible from the moon. They were formed over several glacial episodes beginning 500,000 years ago and ending with the retreat of the Wisconsinan glaciers. The final substage of the Wisconsinan glaciers began retreating some 14,000 years ago and left the basin about 9,500 years ago. The Great Lakes basin they created is a showcase of glacial geomorphology and a rich repository of biological diversity. (Dorr and Eschmann 1971, Daniel and Sullivan 1981)

Glacial Mechanics. The Great Lakes began as lowlands, probably river valleys associated with an ancestor of the St. Lawrence River. The glacial ice advanced into these valleys in great lobes, as much as two miles thick. Contrary to what might be imagined, glaciers are not frozen to their beds. Rather, the ice in contact with the ground melts, enters cracks and periodically freezes and then thaws. Material of all sizes, from boulders to powdery glacial "flour," becomes incorporated into the ice.

The preglacial bed of the Great Lakes was composed of relatively soft sedimentary rock such as sandstones and shales. (Dorr and Eschmann 1971) The glaciers were able to scour out the shape of the basins seen today. Where they encountered more resistant bedrock, such as the Silurian dolomite of the Niagara Escarpment, only the overlying layers were removed. Today, this escarpment forms the Door Peninsula, the northern edge of Lake Michigan and the Straits of Mackinac, Manitoulin Island, the Bruce Peninsula, underlies Niagara Falls and continues south of the New York shore of Lake Ontario. (Chapman and Putnam 1984, Botts and Krushelnicki 1987)

When a glacial advance is "halted," the leading edge of the ice is stationary. This does not mean, however, that the glacier is not moving. In fact, when a glacier is stationary, the leading edge is simply melting away at the same rate as the ice is advancing. The material entrained in the ice, known as glacial drift, is deposited in terminal moraines. These moraines appear as ridges on the post-glacial landscape and take the shape of the ice front that deposited them. Moraines can be found throughout the Great Lakes basin. Perhaps the most famous is the Kettle Moraine in southeast Wisconsin, that begins near the Illinois border and runs northeast almost to Green Bay.

Glacial drift is deposited in two ways. Glacial till is material that is deposited directly from the melting ice. It is a jumble of particles of all sizes, including large boulders, smaller rocks and various sized pieces of ice. Moraines are formed of till. Glacial outwash, alternatively, is material that is carried from the glacier by meltwater. Because large, heavy objects such as boulders are difficult for streams to carry, they fall out first closer to the ice front. Smaller items such as sand, smaller rocks and gravel are carried further away. Areas having substantial amounts of well-sorted sands and gravel are usually significant groundwater storage and transmission areas known as aquifers. (Daniel and Sullivan 1981)

The Early Great Lakes. As the glaciers retreated, a series of proglacial lakes began to form between terminal moraines and the receding ice fronts in the southern part of the basin. These impoundments were the first Great Lakes. These lakes continually changed over time, following the glacial front northward. Outwash fans and alluvial plains formed where ancient glacial rivers drained into the proglacial lakes. The sandy pine plains of north-central lower Michigan is a good example of outwash. (Dorr and Eschmann 1971)

Photo: Map showing Lakeplains of the Great Lakes Basin
Figure 2.  Lakeplains of the Great Lakes Basin

As the proglacial lakes moved northward, they receded from the southern portion of their basins. Where these lakes had receded, the relatively flat, former lake bottoms were covered with alternating layers of relatively fine grained, lacustrine sediments and coarser, more clastic sediments. These areas are known as lakeplains. Because of the nature of deposits, and their proximity to the modern lakes, the water table is often high in these areas. Both the Chicago area and the Great Black Swamp in northwest Ohio, for example, were formally covered by proglacial lakes. (Lafferty 1979) Figure 2 shows the lakeplains and tributaries found in the basin.

It is common to find ancient beach ridges deposited on lakeplains. These were left behind as proglacial lakes receded to their present positions. The Ridges Sanctuary in Door County, Wisconsin, contains 16 parallel former beach ridges of the predecessors to modern Lake Michigan. (Mahan 1993) Another ancient beach ridges runs from the present day Maumee River, past the western boundary of Toledo and into southern Michigan.

When the glaciers retreated from the basin, a new outlet channel was uncovered which increased the outflow from the system and lowered lake levels. This caused the rivers flowing into the lakes to cut deeper and wider in order to reach the lower lakes. The Carp River Gorge, just west of St. Ignace, Michigan, illustrates this downcutting.
As the glaciers receded, boreal conifer forests, composed mainly of spruce and fir, dominated the basin. Areas with thin soils supported arctic communities, remnants of which can still be seen along the rocky shores of Lake Superior.

Birth of the Modern Ecosystem. As the last ice left the basin, the earth's crust, which had been compressed by the miles of glacier riding on top of it, began to rise. This process is known as crustal rebound. As the crust first rose, so did the level of the outlets from the ancestral Great Lakes. As the outlets rose, the lakes began to refill, and their levels also rose. Crustal rebound still accounts for the approximate .5-inches-per-year rise in the elevation of the town of Superior, Wisconsin--a rate greater than the rise in any active North American mountain system. (Daniel and Sullivan 1981)

River mouths that were formed to reach the previously lower lakes were drowned by the higher waters. Many eventually became rivermouth estuaries, such as at the Mink River in Wisconsin and the Severn River in southern Ontario. Baymouth bars and spits were often formed by the (Lakeplains Map see Figure 2) deposition of sediments around these rivers. Examples include Chequamegon Point and the sand spits at the St. Louis River on Lake Superior, some of the largest examples in the world of this geologic phenomenon. Sometimes river mouths were transformed into embayment lakes such as Crystal Lake and Glen Lake in Michigan. (Mahan 1993, Dorr and Eschmann 1971)

During the period of high water levels, wave action and lake currents deposited sediments that shaped shoreline features still present today. It was during this time that sand dune systems developed on what is now Lakes Michigan's eastern shore. Warren Dunes, Sleeping Bear Dunes National Lakeshore and the dunes at Ludington State Park are some examples.

Following the glacial retreat, the climate of the Great Lakes basin gradually became warmer and dryer. Oak and pine forests replaced spruce and fir in the north, while oak savannas and prairies covered large areas throughout the southern basin. This period peaked about 7000 years ago. Then, as the climate again cooled and precipitation increased, oak forests retreated to the southern basin. Prairie and savanna contracted in extent, and became largely restricted to the "prairie peninsula" that extends from the Chicago area northeastward into Michigan and Ontario. (Barnes and Wagner 1981)
About 2500 years ago, changes in various outlets caused lake levels to fall to approximately their present levels.

Special Biodiversity Features of the back to top
Great Lakes  Ecosystem

The glacial history of the Great Lakes basin and the tremendous influence of the lakes themselves create unique conditions that support a wealth of biological diversity, including many species and communities of global significance. The basin's sand dunes, coastal marshes, rocky shorelines, lakeplain prairies, savannas, forests, fens and other landscapes contain features that are either unique to or are best represented within the Great Lakes basin. The remarkable biodiversity of the Great Lakes basin is illustrated by the Indiana Dunes National Lakeshore. This park ranks third of all U.S. National Parks in plant diversity, even though its acreage totals less than 3% than either of the top two (Great Smoky Mountains and Grand Canyon). (National Park Service, 1987)

The network of state and provincial Natural Heritage programs, which identify and track the status of key biodiversity features, has identified 131 elements within the Great Lakes basin that are critically imperiled, imperiled or rare on a global scale. These include animal and plant species as well as natural community types. Table 1 lists these elements with ranks indicating their global imperilment, as determined by the Natural Heritage programs.

Table 1 also includes a rating for each element that indicates the "global context" of its occurrence with the Great Lakes basin i.e. the proportion of its global range that lies with the basin. A rating of 1 is given to elements that occur only within the basin (endemics); a rating of 2 indicates that over half an element's range and/or many of its best occurrences lie within the basin; a rating of 3 is given to those with less than half their range in the basin; and a rating of 4 is assigned to those that occur in the basin only at the margin of a much larger range. 

Thirty-one of the globally significant elements identified in Table 1 are natural community types. Natural Heritage programs identify and rank all community types within the region and inventory high-quality examples of each type as a basis for conserving thousands of common species that contribute to ecosystem health. Because ecological communities embody most of the species diversity in the basin, Table 1 includes 13 additional community types that, while not globally rare, are prominent components of the basin's landscape.

Chart showing: Globally Significant Biodiversity Features of the Great Lakes
Figure 3.  Globally Significant Biodiversity Features of the Great Lakes

Of the 131 globally significant elements, 22 have been ranked as critically imperiled, 30 as imperiled and 79 as rare (Figure 3). For the purposes of this analysis, elements with intermediate ranks were attributed to the higher (more imperiled) rank. Ranks are assigned by consultation among Heritage scientists and other experts. They evaluate the size of an element's range, known or estimated numbers, extent and health of occurrences, degree and nature of threats, and any special factors that contribute to its vulnerability. (See Appendix 2 for a full explanation of element ranks.) Element ranking provides a means of targeting protection resources toward those biological resources at the greatest risk of being lost.

Globally Significant Biodiversity Features of the Great Lakes (see Figure 3)

Map showing areas supporting significant biodiversity
Figure 4.  (To view a larger image, click on map above)

Natural Heritage programs have documented the occurrence of these elements at over 2800 locations throughout the Great Lakes drainage (Figure 4). While this represents a wealth of information for conservation planning, it is important to note that much is still not known about the biological diversity of the basin. Certain geographic areas, especially in the northern portions of the basin, have not yet been properly inventoried. In addition, inventories are seriously incomplete for certain element groups, including aquatic elements, invertebrates and non-vascular plants such as mosses and lichens. Inventories of aquatic biological diversity have focused largely on mollusks, fish and vascular plants. The presence in the basin of several globally imperiled elements in these groups suggests that there is aquatic biodiversity of global importance, especially at the community level, that has not yet been documented. Much more will need to be learned about the aquatic communities of the basin--their diversity and composition, distribution, condition and conservation needs--to target protection activities most effectively. The following analysis is the first time that the biodiversity of an ecosystem of this scale has been described in detail using Natural Heritage data.

Critically Imperiled Elements
Twenty-two species and communities have been identified as critically imperiled on a global scale. They include three community types, three species of freshwater mollusks, one snail, two fish, one bird, one turtle, seven insects and four plants. Seventeen (77%) of these elements occur entirely or predominantly within the basin or have their best examples here. The global existence of these elements depends upon their survival in the Great Lakes basin.

Critically imperiled species that are endemic (entirely restricted) to the Great Lakes drainage include the Michigan monkey-flower (Mimulus glabratus var. michiganensis) which grows in cold seeps and streams, usually at the base of bluffs along ancient glacial shorelines. Its worldwide distribution consists of small colonies at only about 12 locations in northern Michigan. The well-known Kirtland's warbler (Dendroica kirtlandii) breeds only in the jack pine barrens of Figure 4 EO Map northern lower Michigan. A plant species new to science, a moonwort (Botrychium acuminatum), was recently discovered on the Grand Sable Dunes of Lake Superior. The world's last known population of the white catspaw pearly mussel (Epioblasma obliquata perobliqua) is found in Fish Creek, a small tributary of the Maumee River in Indiana and Ohio. The copper redhorse (Moxostoma hubbsii) is a fish whose world distribution is limited to the lower Richelieu River (which drains Lake Champlain) and the adjacent St. Lawrence River.

Some of the last, best examples of the continent's most imperiled savanna communities lie along the lakeplains of the southern Great Lakes. The St. Clair River Delta, the Windsor area, the southern shores of Lake Michigan and the Chiwaukee/Illinois Dunes area harbor especially large, rich examples of this system, which has been decimated throughout most of its range.

Globally Imperiled Elements
Thirty species and communities of the basin have been identified as imperiled on a global scale. They include eight communities, five insects, nine plants, two snakes, one bat, four mollusks and one bird. Of these, 13 (43%) occur exclusively or predominantly within the Great Lakes basin, or have many of their best examples within the basin.

Among the imperiled elements that depend heavily upon the Great Lakes ecosystem is a unique community of arctic and prairie species that persists from the colder, then dryer climatic periods following glaciation. Often called by the Scandinavian name "alvar," (alkaline scrub/grassland in Table 1) these communities are scattered in an arc that follows the Niagaran Escarpment from upper Michigan through southern Ontario and to northwestern New York. Never widespread, this remarkable open bedrock landscape remains intact in only a handful of places. Among the important species it supports is the endemic lakeside daisy (Hymenoxis acaulis var. glabra), which is almost entirely restricted to Manitoulin Island and the Bruce Peninsula of Ontario.

Among the other imperiled communities unique to the Great Lakes ecosystem are the interdunal wetland (alkaline shoredunes pond-marsh in Table 1) and alkaline rockshore communities. These systems are created and maintained by the effects of wind, waves, temperature and water levels along the Great Lake coasts. In portions of the southern lakeplain, scattered shallow, sandy depressions support distinctive pond communities (infertile pond-marsh in Table 1) analogous to those of the Atlantic coastal plain.

The southern lakeplain also harbors examples of two globally imperiled prairie types--tallgrass prairie and wet prairie--that are outstanding in size and quality. The prairies of the lakeplain are considered by many to be distinctive in ecological character, enhancing their significance. In addition, these prairies support many of the best remaining populations of the globally imperiled prairie white-fringed orchid (Platanthera leucophaea).

The Great Lakes basin is critical to the survival of two globally imperiled butterflies. The Karner blue (Lycaeides melissa samuelis) depends upon the barrens communities of the sandy lakeplains and glacial outwash areas of the basin. In contrast, Mitchell's satyr (Neonympha mitchellii) frequents the southern basin's wealth of high-quality fens. Other globally significant invertebrate species undoubtedly exist within the basin, but except for butterflies and mollusks, few groups have been well inventoried.

Globally Rare Elements
Seventy-nine species and communities are ranked as globally rare. These include 20 natural community types, 36 plant species, seven fish, three birds, nine insects and four mollusks. Of those, 33 (42%) exist exclusively or are best represented within the Great Lakes basin. This category includes many shoreline features characteristic of the Great Lakes coasts, which occur rather extensively within a limited zone. These communities and species are integral to the ecological function and the special natural character of the Great Lakes coasts.

The extensive freshwater marshes of the Great Lakes coasts are unique in ecological character, size and variety. They occupy a remarkable diversity of settings, each resulting in different ecological dynamics and species composition. They range from small wetlands nestled in scattered bays to extensive shoreline wetlands such as those of southwestern Lake Erie, freshwater estuaries such as the Kakagon Sloughs of northern Wisconsin and the enormous freshwater delta marshes of the St. Clair River.

Perhaps more than any other system, the Great Lakes sand dunes characterize the uniqueness and remarkable beauty of these coasts. One of the largest systems of freshwater sand dunes in the world, they range from high, forested dunes and linear dune ridges commonly backing sand beaches, to active dune fields covering thousands of acres, such as those near Ludington, Michigan. As plants and animals adapted to the unique dune environment, several evolved into new species and varieties. The dune thistle (Cirsium pitcheri), Houghton's goldenrod (Solidago houghtonii) and the Lake Huron locust (Trimerotropis huroniana) are examples of recently evolved species endemic to the Great Lakes dunes.

Several types of fens are among the globally rare communities that are especially well-developed and have many of their best occurrences in the basin. Fens develop where mineral soils are saturated with nutrient-rich groundwater. Large areas of highly calcareous glacial deposits create ideal conditions for the formation of fens in extensive areas of the basin. Southern fens, such as those along the Pigeon River in northwest Indiana and Liberty Fen near Jackson, Michigan, contain many prairie species. Fens in the northern portions of the basin occur principally on lakeplains. They vary from forested to shrub-dominated to open. Several, such as the Shingleton and Summerby fens of Michigan's upper peninsula, support species typically found only in northern arctic regions.

The Great Lakes themselves support several fish of global significance. Among the basin's globally rare fish is a recently-evolved complex of deepwater fish known as ciscoes. These fish played dominant ecological and economic roles in the fisheries of the Great Lakes. Overharvest, however, drove several into extinction (longjaw cisco Coregonus alpenae, deepwater cisco Coregonus johannae, and blackfin cisco Coregonus nigripinnus). Most of those still surviving are considered imperiled (shortnose cisco Coreogonus reighardii) or rare (kiyi Coreogonus kiyi; shortjaw cisco Coreogonus zenithicus).

Another globally rare fish of the Great Lakes is the lake sturgeon (Acipenser fulvescens). Once abundant in the lakes, it was especially vulnerable to rapid changes in the Great Lakes ecosystem because of its slow maturation rate. This fish often requires 25 years to reach reproductive age. The sturgeon is now extremely restricted in the basin, and reproduction is thought to be poor or nonexistent in many areas. Two globally rare fish of stream habitats, the pugnose shiner (Notropus anogenus) and the greater redhorse (Moxostoma valenciennesi), also have large portions of their world ranges within the basin.

Overall, 62 (nearly 50%) of the basin's globally significant biodiversity elements are found nowhere else in the world, occur predominantly in the basin or have many of their best examples here. Figure 5 illustrates the proportion of rare, imperiled and critically imperiled elements that are endemic to or strongly associated with the Great Lakes basin.

Characteristics of Great Lakes Biodiversity Features (see Figure 5)

Figure 5: Characteristics of Great Lakes Biodiversity Features

The global existence of these elements depends upon their survival within the Great Lakes ecosystem. The integrity of the ecosystem, in turn, is intricately interwoven with the health of many of these communities and species. They define the unique biological character of this ecosystem and underscore the importance of preserving its biological diversity. (See Table 1)

Human Activities in the Watershed back to top

Human activities, both historic and current, have altered and will continue to impact the Great Lakes ecosystem and the biological diversity it sustains.

When European explorers "discovered" the basin in the 16th century, there were an estimated 60,000 to 117,000 Native Americans residing around the lakes. (Botts and Krushelnicki 1987) They lived throughout the basin, hunting, fishing and raising crops such as corn, squash, beans and tobacco. The Native American's life-style was compatible with the natural systems of the basin. They lived together in small bands, and simply moved on when the resources became stressed. (Mahan 1993)

Although the first white explorers were drawn to the basin in search of a water passage to Asia, the first more-or-less permanent settlers were attracted by the abundance of fur-bearing animals. To protect the fur trade, a series of forts and settlements sprung up on the channels that connect the lakes to one another. The traffic in furs decreased in the basin as the stocks were depleted and more productive areas were discovered further west. Settlement of the region continued, however.

Converting the Landscape
To support the growing cities, a timber industry was born. By the 1830s, commercial logging had begun in Canada. Within a few years, it had spread to Michigan, Minnesota and Wisconsin. The early loggers initially harvested the virgin white pines of the basin. These trees could reach 200 feet in height and each produce 6000 board-feet of lumber each. After exhausting the pines, they turned their attention to other species, such as the maples, oaks and walnuts. Also by the mid-1800s, all of the land available for agriculture in the basin had been settled.

The clearing of the Great Lakes watershed during settlement was the initial, massive human stress on the ecosystem. Where timber was harvested, not only were the forest systems eliminated, but the trees were floated down the closest streams that could get them to a lake. The riparian vegetation was removed, the stream banks were trampled and the stream bottoms disrupted. Any rain that fell drained over the ground surface as sheet run-off, and the fish-spawning habitats that were not destroyed by the transport of logs were covered in sediment. Where the natural landscape was converted to agriculture, wetlands were lost, forests were burned and prairies plowed under.

Connecting the Waterways
As cities began to spring up at the mouths of rivers, canals were cut to provide cheap transportation. By 1825, the Erie Canal had linked the Hudson River and Lake Erie, and the Lachine Canal allowed the worst rapids on the St. Lawrence River to be by-passed. Other canals, such as the Miami and Erie Canal, had linked the Ohio River to Lake Erie. In 1829, the Welland Canal had bypassed Niagara Falls, joining Lake Ontario to the rest of the lakes.

By connecting formerly separated water bodies, these canals allowed the growth of a Great Lakes shipping industry, but they also ushered in the invasion of non-native species. The canals themselves, and the ship traffic they carried, allowed species such as the alewife (Alosa psuedoharengus), the sea lamprey (Petromyzon marinus), the Eurasian river ruffe (Gymnocephalus cernuus), and other exotic aquatic species to enter the system and compete with native species.

Overharvesting the Lakes
The fish of the Great Lakes were an important resource to the Native Americans who first inhabited the basin, and were highly valued by the Europeans that followed. Commercial fishing began on the lakes in about 1820 and increased until the peak years of the late 1800s. Records show that approximately 147 million pounds of fish were commercially harvested in 1889 and 1899. The commercial fishery began to decline during the 1950s in response to human-induced pressures such as introductions of exotic species, overfishing, the loss of habitat and pollution.

Industrial and Human Expansion
The wastes generated by the growth of the human population and the resulting economic activities created the second major system-wide stress placed on the Great Lakes basin.

As the cities grew, manufacturing became an increasingly important economic force in the basin. Iron and steel manufacturing made efficient use of iron ore from Minnesota, limestone from quarries throughout the basin, and coal from the nearby Appalachian plateau, all facilitated by the cheap transportation of large quantities of material by water. Major concentrations of this industry exist in the basin today, along the south shore of Lake Michigan, at Detroit, the south shore of Lake Erie and in Canada at Sault Ste. Marie, Hamilton and Nanticoke. The pulp and paper industry makes use of the abundant timber and water resources of the basin, and is concentrated around the Lake Superior shore, the Fox River in Wisconsin and along the Welland Canal in Ontario where the sulphite paper-making process was invented. (Botts and Krushelnicki 1987) Major concentrations of chemical manufacturing grew up along the Niagara River, the St. Clair River and near Saginaw Bay.

The human population of the basin continued to prosper and grow. Today the basin supports a population of slightly over almost 38 million. It remains the center of the U.S. and Canadian paper, steel and automobile industries.

As the health of the Great Lakes fishery declined in the 1950s and the chemical water quality of the basin reached its worst levels in the late 1960s and early 1970s, it became once again apparent that the resources of the basin were not limitless. The Great Lake Fisheries Commission was formed to seek a bi-national solution to the fisheries problem, and has been successful in controlling the impact of the sea lamprey. Strong pollution control programs have been developed in the United States. Both the United States and Canada are working to meet the Great Lakes Water Quality Agreement monitored by the International Joint Commission. Actions by citizens, industries, governments and private organizations have slowed the assault on the Great Lakes ecosystem, allowing it to begin cleaning itself, and setting the stage for recovery.

While much has been accomplished, human activities continue to pose threats to the Great Lakes ecosystem and its biological diversity. These activities must be identified, their threats evaluated and then methods developed to help reduce or eliminate the impacts.

Identifying and Evaluating Threats to the Biological  back to top Diversity Of the Great Lakes Ecosystem

To protect the special communities and species of the Great Lakes basin, the ecological processes that support them need to be safeguarded. To accomplish this, stresses that threaten those processes need to be identified, evaluated and then addressed to minimize or eliminate their negative impacts.

This analysis was conducted by a team of scientists from the Natural Heritage programs and Conservancy offices and Conservancy protection specialists. The team reviewed Heritage information compiled from specific occurrences of the special elements. This information included the global ranks for each element and the element occurrence ranks for each location where the element occurs in the basin. (See Appendix 2 for a description of these ranks.) The data also included the global context index which describes whether an element is unique to the basin, best represented within the basin, has a range that overlaps with the basin, or is incidental to the basin. In addition, the team utilized the Heritage programs data on threats to individual elements and their occurrences, as well as the management needs and protection urgency for certain areas.

Using this information and professional experience, the team conducted an analysis of the threats to Great Lakes biological diversity. This process was similar in many ways to that used by the U.S. Environmental Protection Agency to conduct "relative risk evaluations." A series of specific questions were asked, and the team formed by consensus each qualitative response, usually a choice between a "high," "medium" or "low" ranking. As with other relative risk evaluations, this process was iterative; this particular analysis was repeated four times. The results, while not identical, varied just slightly between each iteration. The iterative nature of the process did enhance the quality of this product. The results of this analysis should not be viewed as the last word on threats to the biological diversity of the basin ecosystem, but as a first look that is probably very close to the mark.

Since it would be impractical, even counterproductive in some cases, to analyze and react to the stresses for each element, it is useful to group elements by common conservation needs. To accomplish this, elements with similar ecological requirements were identified and grouped by the ecological systems that they share in common (i.e. coastal shore system, inland-terrestrial system). For purposes of this analysis, elements occurring in more than one system were attributed to the system with which they are most frequently associated. Then the key ecological processes that sustain each of the seven systems were identified and described. The team, in turn, evaluated the relative significance of each system's contribution to supporting biological diversity in the basin using a number of factors detailed below.

Next the team identified 16 stresses that directly threaten these ecological systems and the biodiversity elements they contain. They then evaluated those stresses on the basis of the severity and scope of impact on each group of elements. Finally, the team linked the stresses with 11 types of human activities that cause them. Because human activities often are associated with multiple stresses on natural systems, these sources were evaluated for their contribution to each major type of stress.

Based on this information, protection measures can be strategically targeted at sources of ecological stress that cause the greatest damage or threat to the basin's outstanding biodiversity elements.

An Overview of Systems that Sustain Biological Diversity back to top

By identifying biodiversity elements with similar ecological and conservation requirements, the team grouped the elements by the ecological systems they share in common. These seven systems are: the open lake, coastal shore, coastal marsh, lakeplain, tributary and connecting channel, inland terrestrial upland, and inland wetland. The inland systems are found in the upper portions of the watershed.

Four of the seven--the lakes, coastal marsh, coastal shore and lakeplain--are unique to the Great Lakes basin, and the latter two support a disproportionate amount of the basin's special biological diversity. Figure 6 shows the relative proportions of the 61 Great Lakes-dependant (global context index of 1 or 2), globally significant elements associated with each of these major systems.

Figure 6.  Globally Significant Biodiversity Features Strongly 
Associated with Great Lakes Systems

Globally Significant Biodiversity Features Strongly Associated with Great Lakes Systems (see Figure 6)

Figure 7

Figure 7 is a simplified schematic showing the relationship of these systems. The biological diversity and ecological processes associated with each is discussed below.

Open Lake System (Great Lakes)
Globally Significant Biological Diversity. The Great Lakes are unique in the world. They are among the world's largest freshwater bodies and the only ones of such scale located in a temperate climate. This creates an ecologically unique setting for adaptation and evolution of immigrant biota. Although they are still in their geologic infancy, the lakes already supported several endemic fish at the time of European colonization. The blue pike (Stizostedion vitreum glaucum) and several evolving species of ciscoes (Coregonus spp.) had already differentiated. (Bailey & Smith 1981)
Although portions of the lakes appear to support high-quality benthic communities, overall documentation of the character and quality of invertebrate biota is still scanty. The lakes' biotic communities also have not been systematically described or ranked from a biodiversity standpoint. However, they would presumably rank as globally rare to imperiled, due to restricted distribution, high level of threat, ecological fragility and widespread damage.

Key Ecological Processes. The Great Lakes are at the heart of the basin ecosystem and exert a far-reaching climatic influence over the entire region. (Albert et. al. 1986) Water levels, surface and groundwater interactions, wind, waves and longshore sediment transport are the dominant forces shaping some 11,000 lineal miles of coastal ecosystems. Although the Great Lakes cover 1/3 of the basin's area and dominate it geographically and ecologically, their open waters are not expected to be particularly biologically diverse and productive compared to the near shore areas. The most abundant life forms in the open waters of lakes are phytoplankton or algae, which convert the energy of sunlight and chemical nutrients found in the surrounding waters to biomass via photosynthesis. Because light is only able to penetrate a limited distance into the water column, phytoplankton are restricted to the upper layers of the Great Lakes.

Phytoplankton are the primary food for zooplankton, the most common animals in open lake environments. Zooplankton form the second link in the food chain of the open waters. These minute animals swim and drift in the open water. They eat by straining fine food particles from the water, and tend to feed where phytoplankton are most abundant. Planktivorous fish form the third link in the open water food chain. They include smelts, herring, shad, lake whitefish, sunfish and numerous species of minnows. These fish, in turn, fall prey to the larger piscivorous fishes. Examples of these "fish-eating" fishes include lake trout, lake sturgeon, northern pike and muskellunge. Most fish spend critical portions of their life cycle in the near shore environments, or even in tributary streams. Lake trout, for example, spawn on relatively shallow rocky ledges. Other fish, such as the lake sturgeon, begin their lives and reproduce on gravel beds in tributaries. Still others require the shelter and structure of coastal marshes.

The top predators in the open lake waters consist of raptors such as the osprey (Pandion haliaetus) and bald eagle (Haliaeetus leucocephalus), water birds such as terns and cormorants, and humans. (Colburn et. al. 1990) Most of the basin's colonial nesting bird populations depend upon the lakes for their food source, and large numbers of migrating waterfowl rely on them for feeding and staging areas. The lakes provide the bulk of the basin's human population with drinking water, commerce and recreation.

Coastal Shore System
Globally Significant Biological Diversity. The coastal zone is dominated by the effects of the Great Lakes, including wind, wave action, hydrology, temperature and humidity. The species and communities of the coast are adapted to these dynamic processes. Of the globally significant biodiversity elements (species and communities) that occur entirely or largely within the Great Lakes basin, nearly 30% are associated with coastal shore systems.

The Great Lakes contain some of the most extensive freshwater sand dunes on earth. These dunes support more endemic species than any other part of the Great Lakes basin. Immigrant species, coming from the Atlantic coast and the prairies, colonized the dunes after they formed during periods of high lake levels. Because of the singular and dynamic nature of this environment, new species, such as the dune thistle (Cirsium pitcheri), Houghton's goldenrod (Solidago houghtonii) and the Lake Huron locust (Trimerotropis huroniana), evolved. Unique natural communities of Great Lakes dunes include open dunes, interdunal wetlands, jack pine barrens and sand beaches.
Since large dune areas are scattered throughout the Great Lakes, there are many large, high-quality examples of most globally significant dune elements. This presents an opportunity to design large-scale conservation strategies that protect these elements while they are still in relatively good condition.

Other shoreline communities distinctive to the Great Lakes include bedrock shores, cobble/gravel shores and sand beaches. Associated species of global significance include the endemic dwarf lake iris (Iris lacustris) and ram's head lady's slipper (Cypripedium arietinum).

Key Ecological Processes. Dunes and sand beaches are both critical to and dependent on the transport of sediments along the Great Lakes shores. Sandy sediments from eroding banks and tributary mouths are carried by longshore currents and accrete to form dunes, as well as bars and spits that shelter of many highly productive marshes. Lake level fluctuations are also important in this cycle of erosion, sediment transport and dune maintenance. Shoreline systems absorb the brunt of wind and wave energy from the lakes, buffering the inland systems from those disruptive forces.

Coastal Marsh System
Globally Significant Biological Diversity. Great Lakes coastal marshes represent another system distinct to the Great Lakes. Although they support relatively few species that are globally rare, these marshes sustain a tremendous number and diversity of resident and migratory species. Their ecological uniqueness comes from the fact that they are dominated by large lake processes, including major water level fluctuations, severe wave action and wind tides or "seiches." (Herdendorf 1992) They span a diversity of types, including extensive freshwater estuaries, lagoons and one of the world's largest freshwater deltas at the mouth of the St. Clair River.

Coastal marshes exist throughout the Great Lakes drainage system, from the St. Louis River estuary at the western end of Lake Superior to the coastal lagoon complex at the eastern end of Lake Ontario and the extensive wetlands of the Berthier-Sorel Archipelago in Lac St-Pierre in the freshwater portion of the St. Lawrence River. Although many have been impaired or partially destroyed, a large number of extensive, high-quality marshes still exist.

Data are still being collected and analyzed to clarify the types of marshes around the Great Lakes and to assess their imperilment. Most types appear likely to emerge as globally rare, due to their limited numbers and distribution, high level of threat and vulnerability to disruption.

Key Ecological Processes. Much of the biological productivity and diversity in the Great Lakes aquatic ecosystem is concentrated in the coastal zone, especially the coastal wetlands. Freshwater marshes play a pivotal role in the aquatic ecosystem of the Great Lakes, storing and cycling nutrients and organic material from the land into the aquatic food web. They sustain large numbers of common or regionally rare bird, mammal, herptile and invertebrate species, including many land-based species that feed from the highly productive marshes. Most of the lakes' fish species depend upon them for some portion of their life cycles (Whillans 1990), and large populations of migratory birds rely on them for staging and feeding areas.

Short-and long-term fluctuations in lake levels play a critical role in maintaining both marsh and shoreline systems. In the marshes, periodic inundation re-sets succession and maintains the highly productive herb-dominated system. (Keddy 1990) The processes of sediment inputs and longshore transport are important in maintaining bars and spits that shelter waters of many highly productive marshes, such as those at Long Point, Ontario, or the Kakagon Sloughs in northern Wisconsin.

Lakeplain System
Globally Significant Biological Diversity.
Lakeplains occur where the ancestral Great Lakes occupied different basins than those present today. These former lakebeds are characterized by low topography with sandy, silty or clay soils and a high water table. The major topographic features are linear sandy beach ridges that were formed as the lakes receded in incremental stages. Around the southern lakes, these areas supported extensive prairies and savannas, swamps and wet meadows, sand barrens and coastal plain ponds.

The glacial lakeplain systems of the Great Lakes support the highest number of globally significant biodiversity elements in the basin. Of those that are restricted to or have their best examples within the basin, about 22% occur in lakeplain systems. Among them are the lakeplain prairies and savannas, which represent outstanding examples of two of North America's most imperiled communities. In addition, the prairies and savannas that occur on the lakeplain have species compositions that are particularly rich and unique to the lakeplains. Communities found in the lakeplain system include wet sand prairies, wet silt/loam prairies, flatwoods (wet forests), rich woodland/savanna and sand barrens. Globally imperiled species that occur in these communities include the prairie white-fringed orchid (Plantanthera leucophaea) and the Karner blue butterfly (Lycaeides samuelis). Lakeplain prairies, barrens and savannas are concentrated around Saginaw Bay, the St. Clair River Delta, southern lakes Michigan and Huron and western Lake Erie. While much of the southern lakeplain was drained for agriculture or urban growth, a number of sizable areas remain largely intact, especially nearest the lakes and/or on particularly sandy soils.

Another biologically important element of the lakeplain is the coastal plain pond community. Like the sandy ponds of the Atlantic coastal plain, these are shallow depressions in the sandy lakeplain that intersect the water table, and are characterized by fluctuating water levels. Although these communities are often small by nature, many high-quality examples remain, especially around southeastern Lake Michigan. Several form large complexes, interspersed with sand barrens.

In the northern lakeplains, fens and wet swales occupy the low areas between old beach ridges. Globally significant elements of the northern lakeplains include the endemic Michigan monkey-flower (Mimulus glabratus var. michiganensis) and the rich fen communities, both of which are fed by mineral-rich groundwater flowing from the base of ancient shoreline escarpments. The basin's alkaline/shrub grassland communities (alvars), occur primarily on the lakeplain. Unlike the southern lakeplain, which has been heavily impacted by agriculture and urbanization, large areas of northern lakeplain communities remain relatively intact.

Key Ecological Processes. Groundwater movement is a dominant process in maintaining most lakeplain systems, and natural hydrologic regimes are crucial to the survival of key communities and species. For prairies and savannas, especially those nearest the lakes, fluctuations in lake levels probably help limit woody succession and maintain the open prairie/savanna conditions. Fire probably also played an important role in maintaining these communities. Groundwater discharge is the dominant process supporting the fens of the northern lakeplain. In alvar communities, complex surface and groundwater drainage patterns appear important.

Hydrologic fluctuations are essential to coastal plain ponds communities. Many characteristic and rare species of these communities are tiny annual plants that can remain in the seed bank from year to year until favorable moisture conditions stimulate germination. When this happens, they quickly reach maturity and set seed before drought or inundation ensues. Manipulation of groundwater regimes can disrupt this delicate cycle and alter the dynamic conditions upon which this community depends.

The lakeplains probably played an important historical role in floodwater retention both during periods of high rainfall and subsequent cycles of high lake levels. With development and drainage of much of the lakeplain, that capacity is reduced, and flooding exacerbated. Because the lakeplains are contiguous with the coastal systems, they also function as an ecological backstop during high lake levels, when species and communities from the coastal wetlands may migrate inland to survive flooding.

Tributary and Connecting Channel System
Globally Significant Biological Diversity.
Great Lakes tributaries support about 15% of those globally significant biodiversity elements that occur predominantly or exclusively within the basin. Most are mussels that occur in certain drainages of lakes St. Clair and Erie. These occurrences represent outliers of the world's richest freshwater mussel fauna, which entered the basin when the ancient Great Lakes drained southwest to the Mississippi. Because many of those species are now imperiled throughout their entire ranges, the relict populations of the Great Lakes drainages have become important to their global survival. For instance, the last known population of the white catspaw pearly mussel (Epioblasma obliquata perobliqua) is in Fish Creek, an upper tributary of the Maumee.

Other tributary elements of global significance include two endemic species: the copper redhorse (Moxostoma hubbsii), a fish restricted to the lower Richilieu River and adjacent St. Lawrence River in Quebec, and the Hungerford's crawling water beetle (Brychius hungerfordi), which is known only from the Maple River of northwest lower Michigan. Two globally significant dragonfly species have also been identified in several Wisconsin streams. Three globally rare fish species inhabit Great Lakes tributaries, one of which, the pugnose shiner (Notropis anogenus), has most of its range within the basin.

Aside from several individual species, the biota of the basin's tributaries has not been well documented and evaluated from the standpoint of biological diversity. It is likely that additional elements of global significance have probably escaped notice, judging from the fact that globally significant elements have been identified among virtually all groups inventoried to any extent. In addition, aquatic communities have largely not been included in the Heritage programs' biodiversity inventories, so there is no shared process to evaluate the rarity and significance of community elements in tributaries.

Key Ecological Processes. Tributaries are the primary conduit for drainage of waters from the basin's landscape to the Great Lakes. Tributaries also transport sediments, nutrients and organic material throughout the watershed. Biodiversity elements of tributaries depend upon the oxygenation of water and the balance of nutrients and organic materials to maintain favorable habitat conditions. Although delivery of sediments to nourish longshore processes is an important function of tributaries, excessive loading can be damaging to stream biota, especially bottom-dwelling invertebrates. Excessive sediments can also damage estuarine marshes. Tributaries provide important spawning habitat for several Great Lakes fish, as well as migration corridors for other biota.

Inland Terrestrial System
Globally Significant Biological Diversity.
The inland terrestrial (upland) portion of the Great Lakes watershed supports a diverse biota, including numerous forest types, as well as barrens, prairies, and bedrock communities. Of globally significant elements that are exclusively or largely restricted to the Great Lakes basin, around 8% are associated with the inland terrestrial system.

Most inland terrestrial communities have distributions that extend beyond the Great Lakes basin and are not globally rare or imperiled, although they have been extensively altered since European settlement. Several of these communities form major components of the landscape and have some of their best examples within the basin. They include dry southern forest, dry-mesic southern forest, dry-mesic northern forest, mesic northern forest, and mesic southern forest. Each is represented by large, excellent-quality occurrences in the basin. Examples include the northern hardwood forests of Michigan's Porcupine Mountains, Huron Mountains and Sylvania Recreation Area.

Forest communities typically contain only a few rare species. Among them are three globally significant species of moonwort, a small fern, that are found primarily in northern Great Lakes forests. Neotropical migratory birds are one of the principle faunal groups dependent upon forest systems. These birds spend their summers in the Great Lakes basin, but migrate south during the winters.

One inland terrestrial community type of global significance is barrens. Although many barrens in the basin are associated with the lakeplain, often along the edges where tributaries deposited outwash fans, northern Wisconsin and Michigan support extensive areas of oak and pine barrens on well-drained sandy outwash. In Michigan, this community supports the endemic Kirtland's warbler (Dendroica kirtlandii).
Upland prairie remnants are scattered in the southwest portion of the basin, but outside of the lakeplains, do not generally represent the preponderance or best examples of these types.

Key Processes and Ecological Linkages. The strongest unifying factors among the inland terrestrial biota are the distinctive glaciated landscape of the Great Lakes basin, and the major climatic effects of the Great Lakes themselves (moderation of temperature and increased humidity and precipitation). The biota of this system, in turn, influence major processes of the Great Lakes ecosystem. The inland terrestrial system covers a large percentage of the basin and forms the principle collector for precipitation inputs to the rest of the system. Through their character and health, inland terrestrial communities influence the rate, periodicity and quality of incoming precipitation, and direct its flow to surface drainage and groundwater recharge. The ecological integrity of this system is also important in controlling erosion, which is a major factor in the ecological health of tributaries and coastal areas. The inland terrestrial system provides migration corridors and habitat for portions of the life cycles of species principally associated with other systems as well.

Barrens communities and species depend upon regular fires to recycle nutrients into the relatively sterile soils and to maintain the successional conditions to which many barrens species are adapted.

Inland Wetland System
Globally Significant Biological Diversity.
Because of its exemplary and youthful glacial topography, the Great Lakes basin supports a great variety of wetland communities, several of which have the heart of their ranges and many of their finest occurrences in the basin. Principle among these is a variety of fen communities: nutrient poor, nutrient rich, alkaline, shrub-and herb-dominated, and forest-dominated. Many are extensive in size and of high quality. Several globally significant species are associated with these communities, such as the Mitchell's satyr (Neonympha mitchellii). In all, the inland wetland system supports 18% of the globally significant biodiversity elements that are restricted to or have their best examples within the Gerat Lakes basin.

Many extensive, excellent-quality occurrences of other major wetland communities exist within the basin. These include forested bog (upper midwest), permanent marsh, wet meadow, shrub-herb bog, and wet forest (upper midwest). Several other wet forested and unforested community types of global significance may have their best examples within the basin, however inventory data on many of these communities, especially northern types, is far from complete.

This category might also include inland lakes of the basin, however there is currently no basin-wide classification and inventory of lake communities on which to base a biodiversity assessment.

Key Ecological Processes. Key wetland communities and species in the inland watershed depend primarily upon supply and quality of water. Those in isolated basins depend primarily upon groundwater, while those along lakes and streams depend on both incoming surface and groundwaters.

Wetlands act as important reservoirs for water within the basin's drainage system, regulating volumes, periodicity, sediment content and chemical/temperature characteristics. They also serve as centers of nutrient retention, storage and exchange. (Wetzel 1992) Wetlands are often highly productive from a biological standpoint and are important to the life cycles of many species, including many upland species which breed or feed in wetlands.

Identifying Systems Which Best Support Biological Diversity
Having identified and described the seven ecological systems that support biological diversity in the basin, the team then determined which systems are the most important to biodiversity protection. Coastal marshes, coastal shores and lakeplains were found to sustain the greatest number of communities and species important to biodiversity protection in the basin.

Four factors were used to evaluate each system: (1) the relative number of globally significant elements, (2) the number of elements unique to the Great Lakes ecosystem, (3) the quality and viability of the system components and (4) the relative amount of ecological support provided to other systems in the ecosystem. The first two factors have already been discussed in some detail. The latter factors bear a bit more elaboration.

To estimate the quality and viability of each system, the team looked at the frequency, acreage and quality of community elements, such as wet prairie, beach/shoredunes and rich woodland/savanna. Heritage program occurrence ranks were used to evaluate the quality of community elements. A very high quality and viability score was assigned when there was a high frequency of large-sized community element occurrences of excellent quality. (For a definition of element occurrence ranks, see Appendix 2.) A high score was assigned when there was a high frequency of large-sized occurrences of good-quality communities, or a moderate frequency of large, high-quality communities. A moderate score indicates that only moderately-sized community elements occur, with few or none of excellent quality. A low score would indicate the absence of viable communities.

Where the data were not satisfactory to support a decision or rating, a conservative estimate was used. This occurred with open lakes, and tributaries and connecting channels. The data reflects that the information is not known and that a score of moderate was used to complete the analysis.

Systems were evaluated not only for their own biodiversity values, but for the direct and indirect support they provide to the biological diversity of other systems in the basin. To score the relative amount of ecosystem services supplied by each system to the others, the material and energy flows from a given system to each of the others, as well as the direct support by that given system to biological elements of each the other systems, were evaluated. Examples of material flows include movement of surface and groundwaters, climatic effects and soil and sediment movement. Energy flows include, for example, the movement of chemical nutrients. Biological support includes such aspects as the support provided by tributary systems for anadromous fishes, which mature in the open waters but spawn in streams. This information is summarized in the Key Ecological Processes discussions above. Where a system supplies or regulates a predominant amount of the material, energy and biological cycles upon which a large number of other systems depend, it scores higher than systems that are more isolated.

Table 2 summarizes the above discussion, and shows the relative significance of each system's contribution to supporting overall biological diversity in the Great Lakes basin. The results are an arithmetic average of the scores assigned by the team. As shown on the table, the scores double for each increase in significance for each factor evaluated. The ranking of systems summarized in Table 2 is the first step in identifying priority threats to the biodiversity resources of the basin.

Stresses Impairing Systems that Support Biological back to top Diversity

As a second step in evaluating the priority threats to biological diversity in the Great Lakes ecosystem, the stresses that can potentially impair that diversity need to be understood. Then the human activities that create those stresses need to be identified.
Sixteen stresses in the Great Lakes basin have been identified and grouped into five major categories: alteration of chemical regime, alteration of hydrology, alteration of physical processes, direct alteration of habitat and alteration of biological structure. These categories are discussed below.

Each of the individual stresses was evaluated using ratings generated by the following two questions:

How severe is the effect of the current levels of stress likely to be on the biodiversity features of each individual system?

  • High-the stress is likely to cause the elimination of the system
  • Medium-the stress is likely to eliminate the most sensitive elements of the system
  • Low-the stress is likely to somewhat impair the system

How widespread will this effect be in biological and geographic terms?

  • High-system wide
  • Medium-affects a moderate number of biodiversity elements and/or occurs through a moderate range
  • Low-highly localized

To calculate a composite rating for each stress, a numeric score was assigned to each answer. The scores were a geometric series, doubling for each incremental increase of severity or scope. Severity and scope scores for each individual system were averaged and then multiplied by the relative significance score calculated in the previous section. (A system that was highly significant was considered to be twice as important as a system that was moderately important.) These weighted averages were then totaled for each individual stress. A summary of the findings is presented in Table 3.

A weighted average was used for the purposes of this evaluation because a stress is more significant when it impacts a system that: is composed of elements that are more globally imperiled; contains elements that are unique or endemic to the basin; or contains healthy, large-scale element occurrences and contributes a higher amount of ecological "goods and services" to other systems that sustain biological diversity resources.

From this analysis, a set of priority stresses was identified. The most important category of stresses are alterations of the physical processes that operate in the basin. Especially significant are the alteration of lake levels, the alteration of stream flows and the destruction of habitat. These stresses affect a variety of systems, and tend to be less reversible than stresses in other categories. Another important stress to Great Lakes biodiversity resources is increased biological competition. Again this stress affects a range of systems and is difficult to reverse once it occurs.

Alteration of Chemical Regime
This category includes several individual stresses. The addition of toxic compounds to an aquatic system such as a stream or the open waters of the lakes, and to coastal marshes can cause outright death or chronic impairments such as diminished reproductive success or inhibition of growth. These toxic inputs include discrete, identifiable discharges from industries and municipalities, runoff of pesticides and herbicides from agricultural, silvicultural, commercial and residential activities, and releases from contaminated sediments.

Toxic chemicals have created problems in the Great Lakes, but the installation of controls and increased care in chemical use have greatly reduced the input of these pollutants. The elements of globally important aquatic diversity tend to exist where these threats, while important, are not relatively severe. Top predators in the aquatic system, however, remain threatened by bioaccumulative substances previously released into the environment that damage reproductive functions. Elements in other systems of the basin are typically not at significant risk from toxic chemicals.

Aquatic systems, coastal marshes and inland wetlands are threatened by increased introduction of nutrients. Increases in the level of phosphates and certain nitrogen compounds cause explosions of microorganisms that deplete oxygen supplies required by aquatic fauna, affecting the entire stream or lake system. At present, nutrient enrichment is a moderate threat to aquatic systems, but this may increase in the future as phosphorous compounds may be added to treat drinking water supplies. Nutrients are not a major threat to other systems.

Changes in the acid-base balance of natural systems is a concern to all systems in the basin. The atmospheric deposition of acids can cause damage to plants, and to those creatures that depend on surface waters. This stress is not causing major damage to the biodiversity elements of the basin, but may do so in the future.

Salinity changes, brought on by road salting, can threaten elements in tributaries and those associated with upland wetlands.

Alteration of Hydrology
This category includes several individual stresses. The alteration of lakes levels and natural fluctuations threatens the biodiversity elements of coastal marshes and dune systems. Interruption of these dynamic features reduces the flushing of nutrients and organic matter and decreases primary productivity. (Weller 1987) These alterations can also eliminate important marsh species that require low water levels for regeneration or to reduce competition from woody plants. Marshes could become reduced to narrow bands between open water and swamps. (Keddy and Reznicek 1986) These stresses are severe and occur throughout the coastal marshes and dune systems.

When the amount and event frequency of stream flows are altered, the biodiversity elements in those streams can become stressed. At low flows, there may not be sufficient water in spawning habitat. The lake sturgeon (Acipenser fulvescens), for example, is suffering from this stress. At high flows, particularly when they occur quickly, habitat for fish and benthic organisms can be lost to scouring. This presents a serious stress on tributary and lake elements that depend on streams for spawning.

Alteration of the water table from irrigation, mining excavations, land drainage and the like presents the most widespread stress in this category, in terms of the number of systems and elements affected. For example, lakeplain prairies, wetland communities--particularly in the upper watershed--and the species that depend on them, are adversely affected when the water table is lowered. Soil moisture can be greatly reduced, causing drought conditions. Wetlands may shrink in size or dry out completely, potentially killing species not adapted to drought. This stress is important and moderately widespread across the elements in the basin.

Alteration of Physical Processes
Stresses included in this category include the alteration of temperature, altered longshore transport processes, and increased sedimentation and siltation.

Temperature increases that threaten biodiversity resources are highly localized, and primarily limited to aquatic systems. Where watersheds have riparian vegetation removed, flows reduced, and/or wetlands destroyed, the water temperature rises. This is a stress, for example, to the spawning grounds of the lake sturgeon (Acipenser fulvescens).

Where the transport of sediments by longshore currents are interrupted by shoreline armor, jetties and other structures, dune communities, beach communities, coastal marsh communities and the species that they support suffer from sand starvation. This stress is probably more important to the sheltered coastal marshes and sand beaches than it is to dune communities and unsheltered coastal marshes. The stress is somewhat common to both systems.

Sedimentation blankets streams, rivermouths, coastal marshes and the nearshore areas of the lakes with a layer of soil. Suspended sediment blocks light penetration, can reduce primary productivity of phytoplankton and can reduce submergent aquatic vegetation, especially in coastal marshes. This stress eliminates spawning habitat for certain fish and habitat for organisms such as freshwater mussels which require a coarse substrate to secure themselves for filter feeding. This stress is very important in agricultural portions of the basin, which are often chemically clean enough to allow globally rare species to exist, but are threatened by soil eroding from the land at a rate above that which naturally occurs. Sedimentation is also significant in areas where logging or development associated with construction is undertaken.

Another important stress is the interruption of natural disturbance regimes. For the elements in the Great Lakes basin, the most important example of this stress is the removal of fire. The suppression of fire is a moderate stress to the prairies and savannas of lakeplain systems that are not sufficiently wet to allow the water table to prevent the succession of woody plants. The importance of periodic fires to inland systems is not well understood, but may prove to be significant as well.

Direct Alteration of Habitat
This category includes individual stresses such as the filling or draining of wetlands, conversion to another land use and clear-cutting of timber stands. All of these stresses operate in one or more of several ways: directly eliminating species and communities, fragmenting the support system, increasing "edge" effects, eliminating connectivity and compressing natural areas to the point where populations become too small to remain viable.

Coastal and inland wetlands are threatened by draining activities and the associated alteration of hydrology, and by the filling of wetlands during the construction of new homes, shopping centers, and industrial and recreational facilities. Species and communities are lost when they are covered with fill material. Other disruptions include hydrologic alterations through diking and flow barriers such as roads. These problems are often greatest in estuarine marshes where cities utilize river mouths as transportation corridors and for disposal of wastes.

Lakeplain communities and the species they sustain are threatened by drainage often associated with the conversion to agricultural and residential uses. This often proceeds in a checkerboard fashion, first compressing and fragmenting these natural systems. Plant and animal populations become isolated and decline because their movement, dispersal, gene flow and access to resources are restricted. This sets the stage for local extinctions, particularly of highly niche-specific species like the Karner blue butterfly (Lycaeides samuelis) or the prairie white-fringed orchid (Platanthera leucophaea). Compression of the lakeplain system to a narrow band representing the wettest segment nearest the lake may also have severe implications for prairie/savanna elements by preventing landward migration to higher refugia during periods of elevated lake levels. This is a serious threat especially in the southern portion of the basin.

One of the greatest threats to dunes and other upland coastal elements is recreational and residential development. This destroys and fragments communities and populations, impairs system functions such as sand transport and impoverishes natural diversity. Dunes are also prone to accelerated erosion. For example, large, relatively unvegetated blowouts develop in parabolic dunes when pedestrian or vehicular traffic, or removal of overstory vegetation, destabilizes sand and exposes it to wind erosion.

The channelization of streams and rivers, and the draining or paving of floodplains alter flow regimes that support conditions to which aquatic biota are adapted and create excessive bank erosion.

Timber harvest and conversion to agriculture or other uses have been the major historical disruptions to the forest systems of the basin. They are moderate threats. Probably the principle ongoing stress, primarily in the northern part of the basin, involves overharvest or improper forest harvest techniques. In the southern portions of the basin, fragmentation and conversion to urban and residential uses probably remains the principle threat.

Alteration of Biological Structure
This category includes alteration of forage base, increased competition and increased predation/grazing.

The accidental and intentional introduction of exotics into aquatic systems (lamprey, alewives, pacific salmonids and newer invaders such as the zebra mussel) have dramatically altered the community structure of the lakes. These species often alter the forage base in aquatic systems. The zebra mussel, for example, is causing some shifts in phytoplankton composition, which in conjunction with increased grazing and predation from introduced zooplankton and higher fishes, is causing shifts in the entire lake food web.

Increased competition is a concern in all systems. Non-native species can "crowd out" species that are important components of natural communities. Purple loosestrife (Lythrum salicaria) for example, is a serious threat to coastal marshes and wetlands, as are exotic fish species such as the brown carp (Carpiodes cyprinus) and the river ruffe (Gymnocephalus cernuus). A number of exotic invaders disrupt the structure of forest communities, principally in the herbaceous and shrub layers.

Disease has significantly altered some of the basin's forest communities and continues as a serious threat. Disease is also a threat to forested wetland communities, affecting dominant species such as American elm (Ulmus americana) and black spruce (Picea mariana).

The historic overharvest of fisheries resources has had a serious impact on biological diversity. Several of the endemic fishes--formerly dominant species--have been eliminated, and others, such as the shortnose cisco (Coregonus reighardi) and the globally rare lake sturgeon (Acipenser fulvescens) now have severely restricted distributions.

The macrofauna of some streams has been directly manipulated by fisheries management. This may range from introduction of desired game species, to direct elimination of a broad range of species that may compete with those desired. This is generally done to restore or enhance a fisheries resource. However, this alters the diversity and structure of the fish community and can have devastating direct and indirect effects on invertebrate communities as well, such as the rotenone poisoning of mussels when streams are cleared of "rough" species. 

Human Sources of Stress back to top

For each of the above stresses, there is at least one, and usually several, ultimate cause(s) of the stress. The causes may be natural or human-induced. This analysis focuses on the human-induced causes of stress. These human sources result from various misuses of land, water and/or other natural resources, and from other activities that are not compatible with a healthy ecosystem. It is not the intent of this analysis to lay blame on those involved in the activities that might adversely impact on the ecosystem. Rather, this analysis provides a way of identifying those source of stress that are of strategic importance to the protection of Great Lakes biological diversity, allows for the development of conservation strategies that are relevant to the entire system, and helps to identify which partnerships are most important to develop.

To identify the sources of stress to the biodiversity resources of the Great Lakes basin, element information from the Heritage programs was evaluated, and cross checked with literature and individuals knowledgeable about the occurrences of important elements in the basin. This long list of potential sources of stress was then distilled into 11 categories based on which sources can be addressed by similar conservation strategies. Discussed below, these categories are: agriculture, air emissions, development, exotic species, in-place pollutants, mining, solid waste disposal, recreation, resource management, water discharges and water level management.

The team determined that the sources representing the highest priority threats to biological diversity in the Great Lakes system are development, water level management and agriculture. Other high-priority sources include recreation, mining, exotic species and the management of renewable resources. Focusing on these activities will be the most effective way to protect the biological diversity of the basin, and will guide the formation of meaningful conservation partnerships.

To evaluate the relative contributions of these sources to the stresses threatening the biological diversity of the basin, the team rated each source based on the following two questions:

What is the relative contribution of this source to each stress at present?

If no new action is taken, what will the relative contribution of this source be to each stress in 10 years?

  • High-the most important single source, or one of several large sources of stress
  • Medium-one of many sources
  • Low-contributes a small percentage of the stress

The same weighted average approach discussed in the section above was followed to calculate source scores. Each of the above was assigned a numeric score. The scores were selected from a geometric series, doubling for each increment of increasing contribution. The current and future scores for each stress were averaged and multiplied by the result of the stress evaluation discussed above. (A high-scoring stress was twice as important as a moderate stress, which was, in turn, twice as important as a low-scoring stress). Again, this weighted average approach was used because the source of a more severe stress was considered to be more important than a source causing a less severe stress. Table 4 summarizes the findings of this section.

Agriculture includes agriculture-related groundwater contamination, livestock grazing, watering and handling, conversion of natural communities to cultivation, compression of natural systems due to agricultural activities and run-off from row cropping and related activities. Agriculture is most intense in the southern and eastern portions of the basin. Lakeplain systems are especially threatened by agriculture.

Air Emissions includes fixed sources such as incinerators, boilers, industrial operations and fireplaces, mobile source emissions, and volatilization from landfills, sewage treatment plants and lake surfaces. This source is of particular concern because, although emissions are concentrated near urban and industrial centers, the effects can be widespread. The most important emissions are of toxic material and precursors to acid deposition. The team found information on the source to be poorly developed. It is likely that new scientific information would cause this source to be identified as more important.

Development includes vacation home and resort development, urban growth, urban run-off, marina development, road building and maintenance, bridge construction and airport construction. Development affects a wide range of systems. It causes the addition of chemicals to natural systems, the physical modification, destruction and fragmentation of habitat and changes of stream characteristics.

Exotic Species includes releases from the shipping industry, angler/aquarist releases, invasion of plant species from all sources and stocking of non-native fish or game species.

In-place Pollutants are pollutants which have previously been released and are now cycling through the system. They are found in the water column, the air, soils and sediments. Of primary concern are the persistent toxic substances placed into the ecosystem years ago. Also of some importance are nutrients that have found their way into "sinks" in the system.

Mining includes the extraction of minerals, sands and gravel. The extraction of minerals such as copper is concentrated in the northern part of the basin. Sand and gravel operations, however, are found throughout the basin. These latter operations extract glacial till and can cause disruptions in the groundwater and surface water regimes and destroy habitat.

Solid Waste Disposal includes the location, construction and operation of landfills.

Recreation includes increased visitation to relatively undisturbed areas, hunting and fishing, recreational boat traffic and the use of off-road vehicles.

Resource Management is the operation of forest land for timber production, the management of game species and the management of fisheries resources. All of these generally involve managing for particular species of economic value, sometimes to the detriment of other resources. Forests are often managed for fiber production, converting a natural system into a monoculture. When forests are harvested, valuable habitat can be lost. Increased competition between species, loss of forage base, increased predation and other alterations of natural biological interactions can occur.

Water Discharges include the effluents from sewage treatment, industrial operations and septic systems. Of primary concern is the discharge of toxic materials and chemical nutrients. Although controlled at present, the level of nutrients in discharges from sewage treatment facilities may increase in response to drinking water treatments.

Water Level Management includes the construction of dikes and dams, lock and reservoir operations and the dredging and disposal of spoils.

This evaluation identifies agricultural practices, the management of water levels and development as the primary sources of stress to the biological diversity of the Great Lakes ecosystem. This does not imply that the other sources of stress are unimportant, or do not require continued attention. Indeed, in any smaller scale, such as an individual watershed, while it is likely that the strategic sources of stress identified above are likely to be present, the primary sources of stress may be different. This strategic analysis is not intended to replace a thorough analysis of the threats to biological diversity for any single location in the basin.

The results of this preliminary evaluation of the risks to the biological diversity of the Great Lakes ecosystem is consistent with other evaluations of global biodiversity. In a 1987 report to the U.S. Congress, the Office of Technology Assessment concluded that the primary threat to biological diversity was the "unsustainable development" of natural areas. This included "changed hydrology" and the "modernization of farming systems" characterized by the use of capital inputs such as manufactured fertilizer. (OTA 1987) Similarly, in a 1990 study of the world's biological diversity, the World Bank, the World Resources Institute, the International Union for the Conservation of Nature and Natural Resources and Conservation International/World Wildlife Fund listed "habitat alteration, especially conversion to agriculture," as a primary threat to biodiversity. (McNelly et. al. 1990)

This analysis is somewhat different than these broader studies because of its focus on a particular ecosystem, the Great Lakes. It also differs because it is based on the specific biological features of this system. This analysis goes beyond the scope of the World Bank study in that it takes what that study characterizes as "primarily a list of symptoms," such as habitat destruction and evaluates the activities that cause those symptoms. By identifying the sources of stress to the biological diversity of the Great Lakes ecosystem, the stage is set for identifying the economic and social causes of the stresses. Only by identifying and meeting the human needs of the ecosystem can its biological diversity be protected over the long term.

Recommendations and Strategic Opportunities for the back to top Conservation of Biological Diversity in the Great Lakes Ecosystem

Protecting the biological diversity of the Great Lakes ecosystem requires that major threats to its key components be effectively addressed. This is a difficult proposition in any setting; however in the Great Lakes, several factors complicate the challenge. First is the sheer size of the Great Lakes ecosystem and the number and diversity of important biological components that occur within it. Second is the complexity and variety of ecological processes and systems that support those biological components. Third is the multiplicity of stresses, many of which are long standing, widespread and deeply embedded in the ecology and economy of the basin.

To protect the system's biological diversity in the face of these challenges, conservation actions must be undertaken in a strategic way. Efforts need to focus first on those systems that are most important to the basin's biological diversity and are the most threatened. They also need to concentrate on those stresses that negatively impact the most biological diversity and take place in socioeconomic and political settings that represent the diversity of challenges that occur in the basin. Integral to all of this is an ever- growing understanding of what these species and communities need to survive. Focusing on these issues, a toolbox of conservation techniques and strategies can be developed that is tailored to the conservation needs and challenges in the basin (see Appendix 3).

Four major recommendations are offered here to advance the protection of biological diversity in the basin:

  1. Develop strategically coordinated, locally-based projects that collectively address the most significant systems and stresses;
  2. Improve the basic and applied science necessary for biodiversity conservation;
  3. Increase awareness of the basin's biological diversity and of methods to conserve that diversity;
  4. Increase the support of regional institutions, both governmental and private, for the protection of biological diversity.

These recommendations are discussed in further detail below.

1. Develop Strategically Coordinated, Locally-based Projects That Collectively Address the Most Significant Systems and Stresses
Biodiversity protection activities need to be focused where they will do the most good for the biological character of the basin. Because of the sheer size of the basin, and the limited availability of protection resources, it is impossible to act everywhere at once. Coordinated biodiversity protection initiatives should be undertaken. Through such a coordinated system of projects, not only would diversity be protected by local efforts, but the capacity of the Great Lakes community to carry out biodiversity protection would be increased as people build reservoirs of tools and experience. To ensure maximum benefit to the basin ecosystem, several basic factors should be weighed in undertaking these biodiversity conservation initiatives. These factors are: the protection of key ecological processes in key systems, the formulation of creative and widely applicable approaches to important threats, and the selection of project settings relevant to the basin. (Appendix 4 illustrates how these factors might be applied to areas that support significant biodiversity in the basin).

Local projects should be concentrated on those ecological systems that are especially important to the basin's biological diversity. This analysis identified three such ecological systems: coastal marshes, coastal shores and lakeplains. These systems contain a disproportionate amount of the basin's unique, globally significant biodiversity elements and have large, high- quality examples of these elements. Work which is targeted to protect these systems will be of the greatest strategic value to the larger ecosystem. This does not mean that conservation activities should not occur in other systems. On the contrary, this analysis identifies the high degree of functional importance of inland systems such as upland forests and wetlands. Often, it will be necessary to undertake management activities in those areas to protect biodiversity elements that occur in the strategically more significant systems.

Local projects collectively should address a diversity of important threats. Priority attention should be given to projects that design agricultural practices that are compatible with key biodiversity elements, that remedy potentially adverse impacts from the management of water levels and that allow the human goals of residential or commercial development to be met without injuring biota dependent upon the Great Lakes ecosystem for their survival. By addressing these threats first, the basin community can counter those stresses with the most severe impacts to biological diversity. This approach will also build expertise in understanding the nature of the threats in a local setting, and design innovative solutions that will have basin- wide relevance.

It is important to understand that these strategically important stresses are the inadvertent byproducts of people trying to survive in the basin. Rather than condemning those involved in these activities, it is more productive to engage them in constructive partnerships that will protect biological diversity. The economic, social and political roots of these activities must be understood and ways found to satisfy the human needs that underlie them in the process of protecting the biological character of the basin. Key biological elements can best be conserved by identifying and supporting activities that are ecologically and economically sustainable.

A system of conservation tools that address the needs and desires of individuals, groups, corporations and government organizations needs to be developed. These tools will need to vary in terms of their strength, the duration of protection provided, the speed with which they can be used and their cost. They must lend themselves to being used independently, in sequence or in combination. Six types of conservation tools are reviewed in Appendix 3: education, registry, management agreements, acquisition, designation of public lands and regulation. These tools can encourage the protection of biological diversity by providing information, recognition, stewardship assistance, cash, tax relief and legal prohibitions. All of these techniques have been used successfully in the Great Lakes basin. Local projects need to test and improve the above tools in order to enhance the collective ability of those in the basin to protect biological diversity.

Projects must be guided by the collective expertise and interests of the diverse human cultures present in the basin. A variety of socio- economic conditions and cultures exist in the Great Lakes basin, and the protection of biological diversity can be advanced by tapping the skills and abilities of these diverse groups.

Developing Successful Local Projects. At the project level, success hinges on several key factors. The first is a clear biological goal; successful projects are designed to protect specific elements that have documented biodiversity value in the Great Lakes and global contexts. Data from the Natural Heritage programs is of great value in identifying areas that contain high quality resources of global significance. These elements are identifiable, and the identification is shared within the scientific community. The survival of these species and communities is the reason for the project's existence, and the ultimate indicator of its success. These elements are not merely "indicators" of success for a set of actions, but the reason for which those actions are occurring.

The second key ingredient of successful projects is a sound, ecologically-based design. This design must be based on the needs of key communities and species, as determined by scientists who are familiar with the ecological requirements of those elements and principle threats to their survival. The scale of these projects will most likely be that of an entire landscape or watershed. To protect a coastal marsh system, for example, it may be necessary to carry out conservation activities in the forested uplands. The ecological design should focus on the protection of key ecological processes, and should be appropriate to the scale of those processes. It is essential that this sound scientific design be developed before considering financial, political and legal parameters.

Third, the protection plan needs to be overlaid with legal, financial, political and other factors that might be relevant to the project. Before any protection activity starts, it is essential that the project be given careful thought and survives a "triage" test. This test is a measure of the likelihood of success of a given project. Every project has obstacles, and the size of those obstacles seems to vary directly with the biological importance and degree of threat. There needs to be a objective look at the wisdom of investing scarce resources in projects that do not stand a good chance of success.

Fourth, the correct partners must be engaged. In general, biodiversity conservation projects require an array of experience, resources and actors. Landowners, funders, scientists, attorneys and laborers are usually involved. In large-scale projects, no one organization can get the job done alone. Each project is unique and will require its own set of partners. The composition of this group should be driven by the needs of the project and not out of a desire to build partnerships for their own sake. Every partner should make a tangible contribution to the conservation of the resource being conserved. Likewise, everyone having a tangible contribution to make should be a partner.

Such partnerships must be sustainable over the long term. The essential ingredient to a sustainable solution is "ownership" of the solution by those individuals that it most affects. To ensure that such ownership is cultivated, projects must be truly local in nature, done by the residents of the project area, not to the residents of the project area.

Fifth, there must be continuing re-alignment between the project needs, the protection tools and available resources. It is generally not possible to completely anticipate all issues before beginning conservation work. As projects move along, new needs will be identified. These needs must be satisfied by drawing on expanded financial resources, and/or by designing new conservation tools.

Last, successful projects should continually improve knowledge about the biological values that are being protected. The nature of the scientific process assures that, while knowledge is ever increasing, there will never be complete knowledge on any topic. Projects, therefore, should not be held up because all information is not available; instead the project should incorporate relevant applied sciences (e.g. monitoring, evaluation, etc.) so that conservation actions can be adjusted when necessary.

2. Improve the Basic and Applied Science Necessary for Biodiversity Conservation
This paper's stress analysis was affected by incomplete knowledge of the biodiversity of aquatic systems, an imperfect understanding of the ecological processes at work in the basin and incomplete inventories in potentially important areas of the basin. In its most recent evaluation of ongoing scientific investigations, the Council of Great Lakes Research Managers reported that research into the nature of the physical environment, organisms, habitat, ecosystem dynamics and ecological indicators comprised only about 20% of the active projects that were relevant to the basin, and received only about 14% of the funds spent in research. (IJC 1992)

The biodiversity elements of aquatic systems are not entirely understood. The Natural Heritage programs do not routinely identify and evaluate natural communities present in river, stream and lake environments, and a basin-wide scheme for doing so is not in place. Species data is difficult to collect because aquatic organisms are submerged, sometimes distant from shore and, in general, not easily accessible. There is an opportunity and a need to develop and apply an aquatic community classification system and to work with non-traditional conservation partners to collect information to identify key biological resources.

The best available sources of scientific information on the protection of biological diversity are the Natural Heritage programs operated by state and provincial governments in the basin. These programs must continue to be supported and in some instances expanded. For example, neither the Lake Superior basin nor the southern portions of the Lake Ontario basin have been thoroughly inventoried . The collection and analysis of element occurrence data here should be increased.
The ecological processes that operate in the basin need to be better understood at the basin scale and at more local scales. The use of remote sensing equipment and the operation of targeted research activities can help increase the understand of how the Great Lakes ecosystem works.

In addition to better understanding the biological elements of the basin and the ecological processes that sustain them, the economic and social roots of the human threats to those elements need to be better understood and articulated. An increased awareness of why such stresses occur is an essential component of building a economy that is more compatible with a healthy Great Lakes ecosystem.

3. Increase Awareness of the Biological Diversity in the Basin and of Methods to Conserve That Diversity
It is commonly accepted that the biological elements that occur in tropical rain forests are important, highly threatened and need to be conserved. Unfortunately, the same understanding does not exist for the important and threatened biological elements of the Great Lakes ecosystem. Information and outreach activities need to be expanded at several levels.

First, there is a need to increase the awareness of, and appreciation for, the unique biological character of the basin and the role that the component communities and species play in sustaining a healthy ecosystem. This should not only take the form of information aimed at a general audience, but also locally targeted information, particularly in areas supporting important biological resources. Such information could include printed material, film and/or video products, interpretive programs and increased attention to the biological values of the Great Lakes ecosystem by print and electronic media.

Second, there can be improved environmental education in schools and communities throughout the basin. There has been good success in developing and expanding environmental education programs throughout the Great Lakes. These emerging programs need to be used to better inform the better inform the basin's youth about their biological heritage. These efforts are likely to be most effective when they explain the specific biological resources and ecological processes of a local area to residents of that area.

Third, the existing landowner contact programs in the basin provide targeted educational activities often resulting in direct protection of special elements. These programs require ongoing support and can be expanded to highlight elements of basin-wide significance.

Fourth, a network of conservation partners needs to be nurtured and sustained. As the conservation challenges in the basin are met, new tools will be designed to overcome those obstacles. It is imperative that individuals and organizations undertaking on-the-ground conservation work have the ability to share lessons learned and mistakes made. Because elements of global significance and the important threats to those resources are found throughout the basin, a basin-wide network that facilitates this teaching and learning is critical. Particularly important are the lessons learned in designing new protection techniques and those that involve the ongoing management of biological elements. This information can be of direct value to protection projects throughout the basin.

4. Increasing the Support of Regional Institutions, Both Governmental and Private, for the Protection of Biological Diversity
The diversity of life in the basin underpins its ecological function. Biological diversity is also a measurable and sensitive barometer of the ecosystem's health, or its "biological integrity". A focus on biological diversity gives tangible meaning to the already stated U.S. and Canadian governments' goal of restoring and maintaining the biological integrity of the ecosystem as stated in the Great Lakes Water Quality Agreement.

As discharges become cleaner and contaminants are removed or rendered inert by ecological processes, the prevention of future problems will become the dominant theme in the environmental management of the Great Lakes. The programs that have been successfully targeted at remediating the environmental problems in the basin were driven by strong statutory mandates, bolstered by regulations and often only successful after lengthy and expensive litigation.

Governments now have the opportunity to learn how to be driven by the mission of protecting and preserving the integrity of the ecosystem, rather than by the rules and regulations that were used to restore it. A large number of government programs could be used to support the conservation of biological diversity. These range from the planning programs where governments decide how to manage their lands to direct assistance programs that encourage conservation practices on farmland. Rather than develop new, elaborate schemes to manage the conservation of diversity in a top-down fashion, governments can support on-the-ground conservation activities through their existing efforts. Such support could include the provision of advice and technical support, financial assistance and the transfer of lessons learned.

Several specific opportunities exist for governments in the basin. For example, both Canada and the United States are signatories to the Convention on Biological Diversity developed at the 1992 United Nations Conference on Environment and Development. The two nations have agreed to conserve biological diversity, sustainably use its components and fairly share the benefits which accrue. The Great Lakes ecosystem could be used as a laboratory for binational cooperation for inventory, conservation and sustainability. The developing National Biological Survey in the United States and the Canadian Biodiversity Conservation Plan (under development) could make tangible contributions.

Local watershed councils, conservation authorities, conservation districts and pollution control agencies may wish to integrate the conservation of Great Lakes biodiversity into their routine activities. By managing on a watershed basis and by balancing remedial programs with an increased emphasis on preventing environmental damage, these organizations can positively contribute to the protection of the key biological components of the Great Lakes ecosystem.

In the United States, the 15 agencies that drafted the joint federal and state five-year strategy for the Great Lakes, "Protecting the Great Lakes-- Our Environmental Goals and How We Plan to Achieve Them," have the opportunity to specifically consider the protection of biological diversity as the plan is re-evaluated. In Canada, Ontario's emerging Natural Heritage Areas Strategy and the Great Lakes Wetlands Conservation Action Plan provide opportunities north of the border.

Other actors will become increasingly involved in biodiversity conservation. The state of Michigan has recently adopted a biodiversity conservation act which directs that state activities be coordinated to protect biological diversity. Several nongovernmental organizations active in the basin, including the Sierra Club, the National Wildlife Federation and the National Audubon Society, have begun work on biodiversity conservation initiatives.

Where regional institutions, such as corporations and philanthropic organizations, operate in the private sector, they can support the work of local organizations by enhancing the ability of these groups to access financial resources and share information. Private corporations can also manage their own lands for conservation purposes when possible.

Although significant challenges remain, the governments, industries and people of the basin have shared important victories in restoring the environmental quality of this ecosystem. The Great Lakes can continue to be a place where innovative environmental management approaches are created, tested and institutionalized. The conservation of biological diversity is an important and logical next step. 


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