Environmental Engineering Reference
In-Depth Information
years—a change that required thousands of years in the geological past. One
might argue that this, nevertheless, is a minor change. But remember, this
is 3 to 5 degrees above a 15 degree Celsius global mean temperature—or a
12 to 30 percent change.
The key issue in conducting assessments of climate change on species is
that it cannot be done using the long-standing, time-tested tradition of con-
ducting hypothetico-deductive research in which one carries out detailed
experiments to test hypotheses that lead to cause-effect insights.This natu-
rally creates a dilemma for environmental policy because one cannot obtain
the kind of strong empirical evidence normally needed to effect policy
change. One way to circumvent this limitation is to develop forecasting tools
(models) that build upon the physiological models that have been calibrated
empirically via small scale, replicated experiments and link them with large-
scale output from climate models.This approach links the ecology of or-
ganisms at smaller scales with climate change data that are relevant at much
larger scales (Pacala and Hurtt 1993).We can then examine, through com-
puter simulations, the climate sensitivity of a species (i.e., how much a
species' geographic range distribution changes with a change in climate).
Forecasting Effects on Wildlife Species
Such an exercise was undertaken to evaluate the sensitivity to climate
warming on several mammal species (elk, white-tailed deer, Columbian
ground squirrel [
Spermophilus columbianus
], and eastern chipmunk [
Tamias
striatus
) within the continental United States (Johnston and Schmitz 1997).
These species were chosen for several reasons. First, they represent the kind
of species that immediately come to mind when society thinks about bio-
diversity. Second, the ability to cope with heat stress varies with body size,
and the species chosen are near the endpoints of the spectrum of body sizes
of North American mammals. Finally, climate change effects will differ be-
tween the western and eastern United States. The first two species have
largely eastern distributions, and the latter two have western distributions.
Climate change is expected to affect wildlife species in two ways. First,
it could
directly
affect an animal species by compromising its ability to cope
with anticipated levels of heat.This arises because excessive heat can have in-
jurious effects on biochemical and physiological processes especially in lo-
cations where species already are living close to lethal temperature limits.
Second, climate change is likely to impact wildlife species
indirectly
by caus-
ing sweeping changes in continental scale distributions of their habitat.
