U.S. Fish & Wildlife Service
Possible Impacts on Fish and Wildlife
in the United States
A Summary of the Intergovernmental
Panel on Climate Change Fourth
With the weight of scientific data pointing
to the changes in the environment due to
increasing concentrations of greenhouse
gases—called climate change—the U.S.
Fish and Wildlife Service (Service) has
begun monitoring and analyzing impacts
of climate change on fish and wildlife
and working toward solutions to help
species adapt to their changing habitats.
Representing a compilation of the work
of hundreds of the world’s top scientists,
the Intergovernmental Panel on Climate
Change (IPCC) Assessment Reports are
important to the Service’s understanding
about how it can meet this challenge.
The IPCC is a scientific organization
set up by the World Meteorological
Organization and the United Nations
Environmental Program. It assesses,
analyzes, and reports on the latest science
on climate change and its human and
environmental impacts. Hundreds of the
world’s most respected scientists have
contributed to the IPCC’s Assessment
Reports of the state of knowledge on
climate change. Many U.S. scientists
have contributed to the findings in
IPCC Assessment Reports, and these
reports are a highly credible source of
information on climate change science.
What does the IPCC say about the impact
of climate change on natural systems and
what does it mean for the future of our
fish and wildlife?
In its most recent Assessment Report*
the IPCC recounts the best and most
current evidence of the effects of
warming on natural systems on all
continents and most oceans. Of more than
29,000 observational data series around
the world, examined by the IPCC, more
than 89 percent are consistent with the
direction of change expected in response
to global warming.
n Reduced sea ice in the Arctic is
linked to reduced body condition and
reproductive success of polar bears
because they cannot remain on the
ice long enough to obtain an adequate
quantity of their favored prey – ringed
seals. Because of this threat to its
habitat, the polar bear has been listed
as threatened under the Endangered
n Reduced snowpack in the mountains,
combined with earlier seasonal melting
caused by rising temperatures, is
projected to increase winter flooding,
increase the intensity and length of
late summer droughts, and reduce the
availability of water, especially in the
western United States. Having enough
water is becoming an increasingly
difficult challenge for western fish and
n Spring is arriving earlier, and plants
and animals are being found farther
and farther north of their historic
ranges in the U.S. Wildlife biologists
are concerned that this will mean some
migratory bird species may not arrive
in their breeding habitats when — or
where — their particular food species
n Oceans, lakes and streams are
changing — warming is evident and
is linked to changes in distribution
of algae, plankton, and fish, as well
as changes in salinity, oxygen levels,
and circulation. These changes are
happening much faster than species
can adapt, and some changes will have
profound consequences for the future
of aquatic life.
n Because of changes in the contributions
of Greenland and Antarctic ice flow
and feedback mechanisms that cause
warming of the atmosphere to be
influenced by warming of the oceans,
the future rate of sea level rise remains
uncertain. But it is a real phenomenon
linked to climate change. Sea level
rise is causing increased loss of
coastal lands to erosion, washing away
wetlands and other habitat for coastal
fish and wildlife species.
n Increasing uptake of carbon from the
atmosphere by the ocean is changing
ocean chemistry, causing surface
waters to become more acidic. This
threatens sea creatures with external,
carbon-based shells, including corals
and many plankton species that
support the ocean’s entire food chain.
n Warming of waters in rivers and
streams may make these habitats
less able to support the spawning of
salmon, trout, and other anadromous
fish species that have significant
economic value to recreational and
In addition, the IPCC identifies other
ecosystems likely to be affected by
climate change, including tundra and
boreal forest and mountain regions
(because of sensitivity to warming);
Mediterranean-type ecosystems because
of reduction in rainfall; and tropical
rainforests where precipitation declines.
The IPCC concludes that warming and
sea level rise would continue for centuries
even if greenhouse gas emissions are
stabilized now, making climate change the
greatest single conservation challenge
we face in the new millennium. The U.S.
Fish and Wildlife Service is working to
anticipate and address this challenge to
fulfill its unique role in protecting fish
and wildlife habitats and maintaining
biodiversity in our world—today and into
* IPCC, 2007: Summary for
Policymakers. In: Climate Change 2007:
Impacts, Adaptation and Vulnerability.
Contribution of Working Group II to
the Fourth Assessment Report of the
Intergovernmental Panel on Climate
Change, M.L. Parry, O.F. Canziani, J.P.
Palutikof, P.J. van der Linden and C.E.
Hanson, Eds., Cambridge University
Press, Cambridge, UK, 7-22.
For more information on how the U.S.
Fish and Wildlife Service is working with
others to conserve the nature of America
in a changing climate, visit http://www.
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