I housands of scientists predict
                                              that the earth's climate will
                                              change because human activities
                                              are altering the chemical composi-
                                              tion of the atmosphere through
                                              the buildup of greenhouse gases.
                                              The heat-trapping property of such
                                              gases as carbon dioxide, methane,
                                              nitrous oxide, and chloroflurocar-
                                              bons is undisputed. Greenhouse
                                              gases are released into the atmos-
                                              phere in large quantities by
                                              motorized vehicles,  utilities, facto-
                                              ries, appliances, and landfills.

                                              Although there is uncertainty
                                              about exactly how  and when the
                                              earth's climate will respond to
                                              higher concentrations of green-
                                              house gases, observations indi-
                                              cate that detectable  changes are
                                              underway. Temperatures will
                                              most likely rise by an average of
                                              2 to 6°F over the next century,
                                              along with measurable changes
                                              in precipitation, soil moisture,
                                              and sea level. All of these
                                              changes could  have adverse
                                              effects on many ecological sys-
                                              tems, as  well as on human
                                              health and the economy.

   Inform yourself and other. To keep
   up with the Latest scientific
   developments, check out EPA's
   climate change website at Or
   call EPA's National Service Center for
   Environmental Publications (NSCEP)
   at 1-800-490-9198 and ask for
   information on climate change.
   Encourage more research. If you work for
   an organization that carries out related
   scientific studies, suggest including a
   dimate change component to the research.
   Reduce greenhouse gases. Use a more
   fuel-efficient (or non-motorized) mode
   of transportation. CarpooL Purchase
   electronic devices and appliances with the
   ENERGY STAR* label Plant trees.
   Office of Policy (2171)
   401 M Street, SW
   Washington, DC  20460

  & $ Printed on Recycled Paper
                                                            United States
                                                            Environmental Protection
                                                                                                                                                                                                Office of Policy (2171)
                           May 1999

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M        —

              Cl IMAT  [  CHANGE
                                                            Global warming could affect the
                                                            abundance and distribution of birds
                                                            in the United States. Changes in cli-
                                                            mate may change nesting and feeding
                                                            habitats, migratory stopover areas,
                                                            and the availability of key food
                                                            sources. Some impacts may be posi-
                                                            tive, making conditions more favor-
                                                            able for certain kinds of birds. But
                                                            climate change also  could lead to
                                                            reduced breeding success in some
                                                            species and some localities, raising
                                                            the possibility of regional population
                                                            declines and extinctions.

                                                            Birds require specific environmental
                                                            conditions to survive and  raise their
                                                            young. Nesting, for example, is timed
                                                            to coincide with favorable weather
                                                            and food availability. If a trend
                                                            toward warmer spring weather leads
                                                            birds to nest earlier, their breeding
                                                            success may suffer if primary food
                                                            sources are not yet available when
                                                            nestlings hatch.

                                                            Birds are more mobile than most
                                                            other animals, and they simply can
                                                            fly to a new location if a former  site
                                                            is no longer suitable. But global
                                                            warming  may make it difficult for
                                                            some species to find new  habitats.
                                                            Plant and animal communities that
                                                            provide optimal habitat today may be
                                                            fundamentally altered in the future as
                                                            the climate changes. A recent study
                                                            suggests that ecological communities
                                                            may not simply shift their range
                                                            northward in  response to warming,
                                                            but instead may undergo complex
                                                            changes as interacting species are
                                                            affected in different ways by the
                                                            changing climate.
                                              Changes in temperature and precipi-
                                              tation predicted under global warm-
                                              ing could  affect the nesting habitats
                                              of ducks and other waterfowl. Accord-
                                              ing to one study, global warming could
                                              cause breeding populations of ducks in
                                              the north-central United States to
                                              decline by more than half—from 5 mil-
                                              lion birds today to between 2.1 and
                                              2.7 million by the year 2060.

                                              Why? Warmer temperatures and more
                                              frequent droughts could cause hun-
                                              dreds of thousands of ponds in the
                                              prairie pothole  region of the north-
                                              central U.S.  to  dry  up. The potholes
                                              account for  only 10 percent of North
                                              America's  waterfowl breeding habitat,
                                              but they produce 50 to 80 percent of
                                              the continent's ducks. The pothole
                                              region also serves as an important
                                              stopover point for migrating water-
                                              fowl.  Although  many of the affected
                                              ducks may move north into Canada,
                                              studies suggest that climate change
                                              may affect breeding habitats in
                                              Canadian prairies and forests as well.
                                              Populations of sooty shearwaters off
                                              the coast of California and Washington
                                              declined by 90 percent between 1987
                                              and 1994, a period when sea surface
                                              temperatures increased. The decline
                                              represents a potential loss of more
                                              than 4 million  birds. The warmer water
                                              triggers a reduction in upwelling, a
                                              circulatory process that brings nutri-
                                              ent-rich water to the ocean's surface.
                                              Over the past two decades, reduced
                                              upwelling apparently has caused a 70
                                              percent decrease in zooplankton, a key
                                              food source for shearwaters and the
                                              small fish that the shearwaters eat.