STATE OF THE GREAT LAKES 2005
WHAT ARE THE MAJOR STRESSORS IMPACTING LAKE SUPERIOR?
Chemical contamination, shoreline development, non-native invasive species, habitat loss, wetland loss and
degradation, and forest fragmentation are among the major stressors impacting Lake Superior.
Pressures
Chemical contamination
Over the last 30 years, concentrations of nearly all
measured contaminants in fish and the water column
have declined in Lake Superior, with the exception of
toxaphene. Between 1986 and 1997, concentrations of
toxic organic contaminants in the water column
declined more than 50 percent. However,
concentrations of dieldrin, mercury, PCBs, and
toxaphene in Lake Superior continue to exceed the
most stringent water quality standards. Because of
its remote location, limited industrial activity, and
large surface area to watershed ratio, Lake Superior
receives the majority of its contaminant loadings via
atmospheric deposition, especially with regard to
PCBs, mercury and toxaphene. Canada's prairie
provinces and the southern United States appear to
be sources of lindane to Lake Superior.
Shoreline development
Development of the shoreline, including
construction of recreational homes, is one of the
most pressing issues facing Lake Superior. For
example, the Keweenaw Peninsula has seen
unprecedented growth in the past 20 years with 50
percent of the homes now classified as recreational
or second homes.
Non-native invasive species
Lake Superior has the highest ratio of non-native
invasive species to native species of all the Great
Lakes. Sea lampreys kill thousands of lake trout each
year. Invasive round goby and ruffe fishes have
colonized some nearshore habitats and could
negatively impact the nearshore cool-water fish
community. Other invasive species predicted to have
significant impacts on the native community include
the gypsy moth, emerald ash borer, Asian
longhorned beetle, rusty crayfish, and exotic
buckthorns.
Lake Superior
Lake Michigan
Lake Huron
Lake Ontario
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Lake Erie
Habitat loss
Although nearshore and open water habitats of Lake
Superior are of high quality and promote an
abundance of trout, whitefish and herring, habitat
loss in tributaries and embayments is a concern. Most
of the habitat loss in Lake Superior has occurred in
these areas, including the eight Areas of Concern.
These tributaries are significantly degraded by
stressors such as agriculture, mining, hydroelectric
dams, industrial effluents and waste, wetland
dredging and filling, non-point source pollution,
shoreline development, and land use practices that
increase surface runoff and erosion.
Habitat loss and harvest and management of select
species have caused dramatic changes to wildlife
communities over the past 150 years. Eighteen animal
species in the Lake Superior watershed, including
mammals, birds, insects, reptiles, and amphibians,
are listed as endangered by the federal governments.
In addition, 400 species (300 of which are plants) are
listed by provincial or state jurisdictions as
endangered, threatened, or of special concern.
A Lake Superior cobble beach. Photo: U.S. EPA Great Lakes
National Program Office.
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LAKE SUPERIOR STRESSORS
Wetland loss and degradation
Wetlands account for 15 percent of the Lake Superior
basin in the United States and up to 25 percent in
Canada. The greatest threats to Lake Superior's
remaining wetlands are wetland draining and filling,
toxic contamination, water level regulation and site-
specific stresses such as shoreline development.
Other threats include invasive species and
diminished water quality.
Forest fragmentation
Forest fragmentation and changes in forest
composition are two of the seminal changes to the
Lake Superior region since settlement times.
Beginning in the 1880s, Lake Superior forests in the
United States were almost entirely clear-cut. Aspen,
birch, fir and poplar have increased since this time
while spruce and pines have been severely reduced.
Forest cover is anticipated to remain the same or to
slightly increase in future years. Forest fragmentation
of hardwoods will continue to increase due to
development and road construction.
Current Actions
Canada and the United States are continuing their
commitment to protect, restore, and maintain Lake
Superior through activities outlined in the Lakewide
Management Plan (LaMP) and implemented through
the Binational Program to Restore and Protect the
Lake Superior Basin. The LaMP addresses both a
Zero Discharge Demonstration Program (ZDDP) for
critical pollutants and a broader ecosystem program.
The ZDDP targets nine critical pollutants for zero
emissions and zero discharge to the Lake Superior
basin. The eight designated Areas of Concern are
addressed through the development of Remedial
Action Plans.
Monitoring in Lake Superior in 2005 - 2006
emphasizes critical pollutants and the lower food
web. Rehabilitation of critical aquatic habitats is
underway and several wildlife and fish species have
been restored.
Actions Needed
Critical actions needed to preserve, protect and
maintain the Lake Superior ecosystem include better
land use change modelling and monitoring;
continued restoration and preservation efforts on
degraded tributary and embayment aquatic habitat;
protection of shoreline and other habitats from
development; prevention of the introduction of non-
native species; and continued monitoring of and
reduction efforts for critical pollutants.
Global warming, climate change, increasing water
temperature, large-scale water export, emerging
chemicals (such as pharmaceuticals and personal
health care products), and proposed new or
expanded industrial facilities are critical issues for
Lake Superior that need to be monitored.
For More Information
For further information related to the state of Lake
Superior, refer to the State of the Great Lakes 2005
report, which, along with other Great Lakes
references, can be accessed at
www.epa.gov/glnpo/solec. The Lake Superior
Lakewide Management Plan 2004 can be accessed at
www.epa.gov/glnpo/lakesuperior/index.html
Lake Superior's north shore. Photo: U.S. EPA Great Lakes
National Program Office.
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