Geoscience Reference
In-Depth Information
bears have a problem because of habitat
destruction. Another response of gigantic
proportions is the saga of the spruce bark
beetle (
Dendroctonus rufipennis),
), which has
killed spruce trees in a three-million-acre
zone of south central Alaska. The problem
is warmer winters, which have not allowed
the normal winter die-off of beetles, and
warmer summers, which have promoted
faster reproduction of the beetles.
trees have tended to stay put so far, but
short-lived plants such as herbs and vari-
ous annuals have moved both north (in the
Northern Hemisphere) and to higher eleva-
tions. Since all plants don't respond to cli-
mate change in the same way and at the
same rate, the ecosystem must change, af-
fecting all living organisms in the system.
birds
plants
Birds have faced a lot of hazards during the
last century, including loss of habitat, hunt-
ing, the use of ddt, and the introduction
of competing invasive species. Now global
change must be added to the list of perils
facing the world's birds. The
2010 State of
the Birds Report
, the U.S. Fish and Wildlife
Service, and several environmental groups
have summarized the risks that global
change will create for birds. The sixty-seven
species of oceanic birds (albatrosses, petrels)
are at greatest global risk, because they re-
produce slowly and face problems from a ris-
ing, warming ocean. Birds in coastal regions
(salt marsh sparrows, plovers), arctic and
alpine regions (White Tailed Ptarmigan,
Black Turnstone), and grasslands (grouse),
as well as land birds from islands (Puerto
Rican Parrot), face an intermediate level of
risk. Birds from arid lands (Gilded Flicker,
Costas Hummingbird), wetlands (various
waterfowl), and forests (warblers, flycatch-
ers) are least vulnerable to climate change.
The problems for migratory birds (swifts,
nightjars) include the timing of food ap-
One big problem is how to separate the ef-
fects of the many hazards facing plants,
such as invasive plants and herbicides,
from the impacts of global change. None of
these natural and human impacts occurs
in complete independence from the others.
The ramifications of the aforementioned
massive spruce kill-off in Alaska provide
an example of the complexity of ecosys-
tem changes related to global change. Or-
ganisms that depend on spruce forests
as a habitat are of course affected. Some
grazing wildlife may benefit because of the
formation of patches of grass as the forest
becomes more open. The potential for for-
est fires is greatly increased by the wood
debris on the forest floor, and local lakes
and streams have larger volumes of water
because the dead trees are no longer losing
water to the atmosphere by transpiration.
Some plant species have been expanding
their range in response to global warming.
In a very general way, long-lived bushes and
