Environmental Engineering Reference
In-Depth Information
Figure 4.4.
Decision curve representing different possible solutions to a management
trade-off between maximizing forest abundance (and attendant ecosystem services),
depicted by solid circle, and maximizing deer herd size (i.e., deer at carrying capacity K)
at the expense of forest cover, depicted by the solid square. Intermediate solutions could
range from modest deer population size with plenty of forest cover (SB) to modest for-
est cover and maximum offspring production rate (MP) of the deer herd.The figure also
illustrates that predators do not determine carrying capacity of the deer: they limit deer
population sizes below their carrying capacity. The degree of predator limitation (PL)
depends upon whether predators are inefficient (PL
1
) or highly efficient (PL
2
) at captur-
ing and subduing the deer. (After Sinclair 1997.)
sustain, that is there are sufficient resources in the forest such that deer births
are balanced by deer deaths.This is the
biological
carrying capacity for the
deer herd in the preserve.This, however, comes at the expense of a vast for-
est. Between these endpoints are many different combinations of deer and
forests that are possible to achieve through management.
This line of reasoning now focuses the deer management issue on the
appropriate explicit question: How many deer are we willing to allow in
the preserve? Thus depicting the problem in terms of an explicit trade-off
is a useful management concept because it now allows us to make our val-
ues explicit (Sinclair 1997). For example, suppose that society wants a high
percentage of the preserve covered by forest so that it is able to view plenty
of songbirds and such wildlife. This value might be achieved when deer
population size is at or near a level depicted by the open square labeled “SB.”
