Why is it happening?
There are three major factors that influence species decline:
- Habitat loss, degradation and fragmentation
- Over-harvesting
- Pollution and chemical contaminants
Habitat Loss
Nothing more profoundly affects the ability of species to live
than habitat loss. Imagine three-quarters of your home being swept
away by a bulldozer with only one remaining wall to provide privacy
for you and your partner, and the most direct and safe route to
the food market blocked. This is the scenario that our wildlife
faces when wetlands, forestlands, prairies and beach areas are
paved over, our shorelines bulkheaded, intertidal areas dredged,
large overwater structures are placed on pilings, and pipes and
cables are laid on the ocean floor.
Habitat loss occurs due to:
- Conversion to other uses such as agriculture, development
or bare land
- Fragmentation
- Degradation
Once native habitat is converted to other uses, the remaining
habitat often becomes isolated in a fragmented (cut up) landscape
of multiple land uses. Wildlife populations associated with these
fragmented habitats are often subjected to isolation from other
breeding populations, competition and predation from other species
and increased conflicts with other land uses.13
For example, the Sockeye Salmon in Sakinaw Lake in BC illustrates
how even partial modification in habitat can have a dramatic effect.
The number of adults returning to Sakinaw Lake to spawn has dropped
from an average of 1,000 adults annually in 1987 to less than
80 in 2002. The lake was dammed at the outlet to transport logs
to the ocean and log storage near the outlet blocked migration.
Residential development and recreational boating degraded spawning
beaches because stream flows were diverted to prevent flooding
and a boat ramp was constructed through the middle of one of the
major spawning beaches.14
Habitat Loss and Degradation
Marine species occupy different habitats as they migrate, including
the Sockeye's northern Pacific migration near Alaska and many
bird species that utilize wetlands located near the shore or even
old growth forests. A significant percentage of the Puget Sound
Georgia Basin shoreline has been manipulated in some way from
its natural, dynamic state. The area where the land meets the
sea – or the nearshore – is one of the most productive
ecosystem types known in addition to wetlands.
These land-meet-the-sea habitats provide nurseries (similar to
the ones you have for your babies) for developing aquatic creatures,
shelter for hiding from predators or heat, and places to spawn.
In addition, the nearshore habitat protects the shoreline from
erosion, filters pollutants from the water and in the case of
salt marshes, reduces flooding by retaining stormwater during
high-flow periods.15
Nearshore activities that cause habitat degradation include:
- Bulkheads/armoring
- Docks and piers
- Dredging
- Log rafting
- Mooring buoys
- Stairways
- Lawns
Beach and nearshore environments are dynamic, which means they
constantly shift and change, creating and maintaining a diverse
array of habitats and food sources. When humans "tidy up"
and alter these environments, we dramatically change the course
of energy, water, sediments and wind patterns (See the Urbanization
and Forest Change Indicator for tips on shoreline ownership
and soft armoring techniques).
Chemical Contamination
The Puget Sound Georgia Basin has a long legacy of intensive
industrial activities including industrial wastewater discharges,
mining, pulp and paper mills, oil refineries, and smelting. In
addition, contamination from these sources are excerbated by overall
polluted surface runoff, groundwater contamination, and atmospheric
deposition of contaminants (pollutants carried by wind or vaporized
by incineration and physical degradation of products).16
These chemicals fall into two broad categories:
- Metals and metal compounds such as arsenic, cadmium,
copper, lead, mercury and tributyltin. In the marine environment,
metals can act in various ways. Some attach to particles in
the water column while others partition directly into bottom
sediments. Their effect on resources varies widely with the
metal and chemical compound involved. Mercury is of particular
interest since it accumulates in long-lived fish and has profound
human health effects. TBT has profound effects on oysters.17
Metals are associated primarily with manufacturing, and can
enter the environment through fossil fuel combustion (cars,
boats, railroads, farm equipment), use of anti-fouling paints
for vessels, disposal of fluorescent lamps and solid waste
disposal/sewage sludge application.18
- Organic Compounds such as polychlorinated biphenyls
(PCBs); polycyclic aromatic hydrocarbons (PAHs), pesticides,
dioxins and furans (from chlorine bleaching of pulp); phthalate
esters (used in cosmetics and plastics) and polybrominated diphenyl
ethers (PBDEs; used as flame retardants on computers, furniture,
clothing, carpets). These synthetic substances are persistent
which means they do not readily degrade, and some bioconcentrate,
increasing each successive feeder in the marine food web, including
birds. In some cases, they degrade to more toxic compounds.
Marine species that tend to feed off the ocean bottom, such as
English sole, are affected by PAHs and fish living in or migrating
through industrial bays accumulate heavy metals and other contaminants
to a greater degree. Exposure can cause:
- Immune suppression
- Endocrine disruption
- Thinning eggshells
- Lesions and tumors
- Reproductive failure
- Genetic damage19
Resident Northern and Southern Orca Killer Whales are some of
the most contaminated marine mammals in the world because they
have bioaccumulated these chemical contaminants through the entire
food web.43
Over-Harvesting
In the early twentieth century, over harvesting of wildlife (both
plants and animals) for food or pelts was the most important threat
to wildlife. It was a factor in driving species like the passenger
pigeon and the great auk to extinction, and it reduced the numbers
of eskimo curlews to such low numbers that they were never able
to recover. Today, species such as the right whale, sea otter,
aurora trout and american ginseng are either over harvested or
are still suffering the after effects of previous over harvesting.
Several species are also threatened by excessive trade. These
species are harvested as a food resource and for their pelts.
They are also taken from the wild and traded for their medicinal
properties, as hunting trophies, as ornamental plants or as pets.
Some of the coveted Canadian species are the peregrine falcon,
the goldenseal, orchids, sturgeons and bears. This trade is controlled
by the Convention on International Trade in Endangered Species
of Wild Fauna and Flora (CITES) in Canada and worldwide.20
2002-2004 Updates: Basis for Listing or Designation
- Cultus Lake Sockeye Salmon (BC): These biologically
distinct salmon have been subject to over-fishing from 1952-1997
in which the fishery annually killed an average of 67 percent
of the adults before they spawned in the lake (vs. a sustainable
level of 56 percent). Since 1995, there has been very high pre-spawn
mortality associated with an unusually early migration into
freshwater (two months earlier). In addition, because the fish
are spending more time in freshwater environments due to earlier
migration to Cultus Lake, the parasite parvicapsula,
normally present in these waters, is having a disproportionate
impact on mortality.21
- Sakinaw Lake Sockeye Salmon (BC): Between 1991 and
2002 there was an 87 percent reduction in returning salmon to
Sakinaw Lake, with a 99 percent reduction over three generations
(12 years). This decline is associated with overfishing that
continued despite observed declines since 1987, spawning beaches
degraded by historic logging, milling and booming, damming of
the outlet and boat ramp construction through the middle of
a major spawning beach.22
- Northern and Southern Resident Killer Whales: Seasonally,
both resident pods are exposed to high levels of chemical contaminants
through their food web. Loss of stream and lake habitat for
salmon, the primary food source for resident Killer Whales,
has been rapidly declining with development and polluted runoff.
Food web contamination appears to be worse in Puget Sound than
the Georgia Basin. Resident Puget Sound Chinook salmon have
40 nanograms/gram of PCBs in their fat as opposed to 5 ng/g
in Coastal BC, or three times higher than BC. Toxic chemical
concentrations in Killer Whales and contamination of food sources
have been compounded by excessive boat traffic and other acoustical
interruptions from military testing.23
- Bocaccio: Bocaccio are being caught accidentally by
commercial trawlers fishing for other species. A bocaccio's
swim bladder cannot accommodate the rapid change in pressure
as it is brought to the surface, and most die. Other reasons
for population decline come from natural predators such as harbour
seals and northern elephant seals. Young bocaccio are prey for
seabirds.24
- Steller Sea Lion: There are only three breeding locations
in British Columbia. Although the population is increasing,
they are sensitive to human disturbance while on land. They
are listed because of the continuing threats including the possibility
of acute oil spills. There are unexplained declines in other
populations to the north and west of British Columbia. Steller
sea lions have in the past been shot. Other causes of decline
include incidental take in fishing gear, entanglement in debris,
catastrophic accidents, environmental contaminants, and displacement
or degradation of their habitat. They are also susceptible to
fluctuating prey populations, predation by killer whales, and
disease.25
- Grey Whale – Northeast Pacific population: The
principle threat to the eastern North Pacific population of
grey whales probably lies in increased human activity in the
breeding lagoons. Certain lagoons or parts of lagoons have already
become unsuitable because of boat traffic and salt extraction,
and any continuation of this trend could eventually put the
entire population at risk. Other causes of population decline
are increased noise that interferes with migration, increased
boat traffic in feeding areas and migration paths causing increased
boat strikes, entanglement in fishing gear and toxics in the
sediments of feeding areas.26
- Harbour Porpoise – Pacific Ocean population: Incidental
mortality in a number of fisheries in British Columbia has been
documented, particularly in gillnet fisheries. The estimated
number killed in salmon gillnets in southern British Columbia
was <100 individuals in 2001. Harbour porpoises are known
to be susceptible to disturbance by vessel traffic and loud
underwater sound sources, such as acoustic harassment devices
associated with aquaculture operations. Natural sources of mortality
in the province include predation by sharks or killer whales.27
Marine Species at Risk