Ecological Condition

Air, water, land—these are elements of “the environment” that the Environmental Protection Agency (EPA) seeks to protect. But assessing the state of the environment requires looking at a bigger picture. Air, water, and land are connected by natural cycles. For example, nitrogen-laden topsoil eroded from the Midwest may travel down the Mississippi River and pollute the Gulf of Mexico, or chemicals released to the air in the Great Lakes region may find their way into the waters in the Northeast. Living things inhabit virtually all of the nation’s air, water, and land and are affected by innumerable natural and human events.

How can researchers, managers, policymakers, and the public track this big picture? One forward-looking way is to link the state of the nation’s air, water, land, and living organisms into a broad framework termed “ecological condition”—the sum total of the physical, chemical, and biological components of ecosystems and how they interact. Ecological condition is ever changing, multifaceted, and specific to place and ecosystem. Understanding ecological condition is crucial because humans depend on, and are responsible for, the nation’s ecosystems—forests, grasslands, shrublands, farmlands, urban and suburban environments, fresh waters, and coasts and oceans. These systems provide food, fiber, and shelter, as well as “housekeeping” functions ranging from water filtration and crop pollination to waste decomposition and recycling.

Trends in ecological condition, like disease trends described in Chapter 4 – Human Health, reflect the outcome of many different events and activities, both natural and human induced. Ecosystem condition is the result of natural resource management at national and state levels, local zoning and land use decisions, pollution and pollution prevention activities, natural disturbances, and many other factors. EPA is one of many federal, state, tribal, and local government and private partners working to understand ecological condition and to protect the nation’s ecosystems. Most EPA programs focus on managing environmental stressors, such as minimizing chemicals in air and water or reducing toxic substances and hazardous waste. Measuring ecological condition will help EPA systematically assess how its management of stressors affects overall ecosystem health.

This chapter is organized around the framework of six essential ecological attributes developed by EPA’s Science Advisory Board (SAB) (Exhibit 5-1): landscape condition, biotic condition, chemical and physical characteristics, ecological processes, hydrology and geomorphology, and natural disturbance regimes. Within each of these areas, indicators have been defined for each of the six ecosystem or land cover types identified by the H. John Heinz Center for Science Economics, and the Environment (Exhibit 5-2). The Technical Document for this EPA report describes each of these indicators, including the available data, data limitations, and data sources.¹

This chapter describes some of these indicators, including indicators for which national data are available and others for which national data are limited. In addition, the chapter illustrates some examples of promising approaches for using ecological condition to evaluate environmental protection efforts. The chapter closes by summarizing both the state of data for assessing ecological condition and key challenges.

Exhibit 5-1: EPA Science Advisory Board essential ecological attributes

	Description	Example Indicators
Landscape Condition	The extent, composition, and pattern of habitats in a landscape.	- Status and change in extent of ecosystems
Biotic Condition	The condition or viability of communities, populations, and individual biota.	- Imperiled species in the U.S. - At-risk native species - Trends in invasive and non-invasive birds in grasslands and shrublands
Ecological Processes	Metabolic function of ecosystems - energy flow, element cycling, and the production, consumption, and decomposition of organic matter.	- Primary productivity - Movement of nitrogen
Chemical and Physical Characteristics	Physical parameters (e.g., temperature) and concentrations of chemical substances (e.g., nitrogen) present in the environment.	- Nitrate, phosphate, and other chemical levels in streams
Hydrology and Geomorphology	The interplay of water flow and land forms.	- Soil erosion - Change in stream flow rates
Natural Disturbance Regimes	The historical function of discrete and recurrent disturbances that shape ecosystems.	- Forest disturbances: fire, insects, and disease

Source: EPA, Science Advisory Board. Framework for Assessing and Reporting on Ecological Condition, June 2002.

Exhibit 5-2: Ecosystem types as described by The Heinz Center

Ecosystem Type	Description
Forest Lands	Lands at least 10 percent covered by trees of any size, at least 1 acre in extent.
Grasslands and Shrublands	Lands in which the dominant vegetation is grasses and other non-woody vegetation or where shrubs (with or without scattered trees) are the norm. This ecosystem type includes bare rock deserts, alpine meadows, and arctic tundra.
Farmlands	Lands used for production of annual and perennial crops and livestock and areas on the larger farm landscape (e.g., field borders and windbreaks, small woodlots, grasslands and shrubland areas, wetlands, farmsteads, small villages and other built-up areas) within or adjacent to croplands.
Urban and Suburban	Places where the land is primarily devoted to buildings, houses, roads, concrete, grassy lawns, and other elements of human use and construction.
Fresh Waters	Rivers and streams, including those that flow part of the year; lakes, ponds, and reservoirs; ground water; fresh water wetlands, vegetated margins of streams and rivers (riparian areas).
Coasts and Oceans	Estuaries and ocean waters under U.S. jurisdiction Estuaries are partially enclosed bodies of water (including bays, sounds, lagoons, and fjords) considered to begin at the upper end of tidal or saltwater influence and end where they meet the ocean.

Source: The Heinz Center. The State of the Nation's Ecosystems. 2002.

What is the ecological condition of the United States?

Basic questions about the health of the nation’s ecosystems and the overall ecological condition of the U.S. have proven difficult to answer in a few summary statements. Ecosystems are dynamic assemblages of organisms that change and adapt continuously to a variety of natural disturbances and stressors, such as fires and floods, as well as to pollutants and land use changes. A variety of ecosystem management practices are used to support human survival and economic growth.

Because of these complexities, measuring ecological condition goes beyond monitoring air or water to determine whether pollutant concentrations or temperatures exceed a legal standard. Trying to characterize overall condition by looking at only one factor, such as stressors, is like the blindfolded men trying to describe an elephant after touching only one part of the animal. In the same way, we cannot determine the overall condition of an ecosystem by looking at isolated environmental measures, such as insect outbreaks in a forest, chemical concentrations in water, or declines in the number of certain species. Assessments of ecological condition must incorporate measures of different characteristics, potentially at different times and different places within a system. The importance of multidimensional measurements to understand multidimensional systems is described in more detail in “Ecological Condition as an Environmental Result” later in this chapter. This section illustrates indicators that provide insights into the six attributes identified by the Science Advisory Board.

Recent Ecological Condition Research Efforts

The chapter presents initial work toward identifying indicators to help answer the question, “What is the ecological condition of the United States?” This work draws primarily on two previous research efforts:

Framework for Assessing and Reporting on Ecological Condition² developed by EPA’s Science Advisory Board (SAB). The SAB Framework designates “essential ecological attributes” (Exhibit 5-1) that provide a means to examine ecological condition as well as to consider the effects of stressors on condition.
The State of the Nation’s Ecosystems: Measuring the Lands, Waters, and Living Resources of the United States,³ a nationwide effort of government and the private sector led by The H. John Heinz III Center for Science, Economics and the Environment (The Heinz Center). Many of the indicators in this chapter and in the Technical Document accompanying this report are derived from the Heinz report.

Chapter 5: Ecological Condition

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