Box 3.1
Ecological concepts and parameters which are useful for
environmental management
● Maximum sustainable yield
The fraction of primary production (as organic matter) in excess of what is used
for metabolism (net primary production) that it is feasible to remove on an ongoing
basis without destroying the primary productivity (i.e. ‘safe harvest’). Under US law,
maximum sustainable yield would be defined as: maintenance in perpetuity of a high
level of annual or regular periodic output of renewable resources.
● Carrying capacity
Definitions vary and can be imprecise. Examples include: the maximum number of
individuals that can be supported in a given environment (often expressed in kg live
weight per km2); the amount of biological matter a system can yield, for consumption
by organisms, over a given period of time without impairing its ability to continue
producing; the maximum population of a given species that can be supported indefinitely
in a particular region by a system, allowing for seasonal and random changes,
without any degradation of the natural resource base.
● Assimilative capacity
The limiting resource may not be an input such as food or water, it may be inability
to deal with outputs (waste products). A given environment has some capacity to
purify pollutants up to a point where the pollutant(s) hinder or wholly destroy that
capacity – this is termed the assimilative capacity.