Environmental Engineering Reference
In-Depth Information
DIRECT EFFECTS
Following the approach outlined in Box 3.1, the direct effects of climate on
wildlife species was evaluated by gathering data on solar radiation, environ-
mental temperature, physical (conduction, convection), and physiological
processes (evaporative cooling) for different locations within and outside of
each species known geographic range.These values were then compared
against the climate envelope defined for each species by a climate-space
model.An example climate-space diagram for current (1990s) temperature
and incoming solar radiation is presented for elk in figure 3.4.The data val-
ues lie in the midrange of the climate envelope, which is to be expected if
each species were living at or near its climate optimum. Figure 3.4 also pres-
ents the expected combinations of air temperatures and solar radiation ex-
changes that elk are expected to encounter under a doubling of atmospheric
CO
2
in the hottest part of the year (July climate) within their current ge-
ographic ranges.All of the data points still fall within the climate envelope,
indicating that these particular species should have the physiological capac-
ity to tolerate anticipated levels of climate warming. Note, however, that the
data cluster has moved toward the edge of the climate envelope, relative to
1990s, indicating that conditions will move away from the optimum.This im-
plies that elk may see a decline in fitness at their current locations and so may
have to migrate to new geographic locations that offer optimal conditions.
These conclusions extend also to the other three mammal species studied.
INDIRECT EFFECTS
It is likely that the impact of global warming extends far beyond the direct
effects it has on wildlife species. Indirect effects including response of
wildlife to shifting habitat are also likely to be of significant importance.
Thus, a more complex analysis is required to examine the effects of distri-
butional changes in vegetation communities that comprise habitat on the
distribution of wildlife species. Such an analysis requires obtaining fore-
casts of climate change effects on the geographic distribution of vegetation
communities and relating that to the distribution of wildlife species (e.g.,
Johnston and Schmitz 1997).
Geographically explicit information on climate change effects on plant
communities has been generated by the VEMAP project (VEMAP mem-
bers 1995).This project developed very detailed models that simulated the
physical processes determining the biotic composition of vegetation com-
munities.These models were then linked with GCM forecasts for current
