Ecologists have developed a number of concepts and parameters, some of which have
been adopted by those seeking to manage the environment. The most widely used are
maximum sustainable yield and carrying capacity (Box 3.1). These should be treated
with caution. Maximum sustainable yield may be correctly calculated, but if the environment
changes a reasonable resource exploitation strategy could lead to over-exploitation.
Maximum sustainable yield calculations can thus give a false sense of security. A given
ecosystem may have more than one carrying capacity, depending on factors such as the
intensity of use and the technology available. Some organisms, including humans, adjust
to their environment through boom and bust, feeding and multiplying during good times,
and in bad suffering population decline, migrating or hibernating; calculating carrying capacities for such situations can be difficult. Biogeophysical carrying capacity may
differ from the behavioural carrying capacity, such that a population could be fed and
otherwise sustained but feel crowded and stressed to a degree that limits their survival.