Dealing with global climate change - Ecological Applications: Toward a Sustainable World - page 324

Predicting the ecological effects of global climate change
Evidence continues to accumulate of increases in greenhouse gases, changes to
climate and biological consequences. Climate scientists have developed models that
predict the magnitudes of future change in temperature and precipitation. The
concentration of CO 2 is expected to rise from 368 ppm to between 540 and 970 ppm
by 2100, with a concomitant rise in average global surface temperature of between
1.8 and 4.0˚C, but with considerable variation in temperature and precipitation
from place to place. Climate models are used by hydrologists to forecast patterns of
fl ooding and runoff from land, and by ocean scientists to forecast changes in sea
level and ocean currents. The models of the physical scientists are, of course, sim-
plifi cations and it is important to consider a variety of models to provide a range of
change that encompasses the most probable outcome. The role of ecologists is to
take the physical predictions and envision the consequences for species and
ecosystems.

Summary

Climate change predictions based on the ecology of individual organisms
Future species' distributions can be expected to be determined in line with their
niche requirements, life-history features and, in particular, their ability to move
from where they are now to where their optimal niche conditions will be in future.
Bioclimatic modeling of current distributions can be used to produce climate enve-
lopes for individual species. These can be superimposed onto regional templates of
predicted climate to indicate where species may occur in future.
Different threatened species might be expected to make gains or losses in habit-
able area and, in theory, the effect of climate change might be neutral. However, the
expected shifts in range towards the poles and higher in elevation will often involve
contractions in species ranges and greater risks of extinction. We might expect
global climate change to see r -species do relatively better than K -species. It seems
likely, too, that habitat generalists will be less vulnerable than habitat specialists in
a changing climate scenario. The potential ranges of invasive species can also be
expected to shift; managers can benefi t from predictions about where these might
pose problems in future.
The powers of movement of species are critically important to future distribu-
tions. Not only can we expect a general loss of biodiversity because of reductions
in habitable area. Recognizing that many species will not be able to get to newly
habitable areas, the risk to biodiversity is even greater.

Climate change predictions based on the ecology of populations
Knowledge of population dynamics, and the way birth and death rates will be modi-
fi ed as a result of climate change, can be incorporated in future management plans.
This is true for species deserving of conservation effort as well as pests (and their
natural enemies) and potential invaders that pose a biosecurity risk. Equally impor-
tant is a thorough understanding of the population consequences of climate change
for the sustainability of fi sh harvests and forestry practices.

Climate change predictions based on the ecology of communities and ecosystems
Community composition is affected by disturbances that set in train community
successions with characteristic trajectories and end points. Climate change may
change disturbance frequency (by altering storm and fi re patterns and fi res). It may