Environmental Engineering Reference
In-Depth Information
community may grow or a new employment opportunity arise, the price for the
harvested species may change, global climate change may erode the ecological
value of the site, alien species may invade, etc.
If management is to be able to respond effectively to these inevitable dynamic
processes, it has to be adaptive. That is, there needs to be
feedback
between
monitoring and management action, so that as information about the system is
collected it is used to improve management. This should be done at two scales.
First, year on year, new data will be collected which can improve our understand-
ing of the system and reduce uncertainty about how it works. This should be auto-
matically included in the decision-making process for the next year, when quotas
are set or licences granted (Box 7.8). Second, periodically there needs to be a full
appraisal of the system, following the steps outlined in Section 7.5.2, so that
the managers can re-evaluate their understanding of the system as a whole and
possibly revamp the management plan.
Active adaptive management is much more radical. The idea is that managers
should actively set out to
learn
about the system, rather than reviewing and revis-
ing based on what they observe. Learning about the system may involve having
different harvest levels in different parts of the area, which might give information
about the functional form of density dependence and about the linearity of catch
Box 7.8
Adaptive Harvesting Management for ducks in the United States.
Since 1995, the USFWS have been using adaptive management in their setting of
harvest quotas for duck-hunting. They have a set of possible regulatory tools,
such as changes in season length and numbers that can be shot on a particular
occasion. They also have a set of models which describe duck population dyna-
mics. Because they are not certain about key features of duck ecology, there are
several alternative models, which are weighted according to the level of support
that data from previous years give them. Each year, new data become available on
duck population sizes and on environmental conditions from population moni-
toring and hunter surveys. These data are entered into the models, and a range of
regulatory options for that year is evaluated. The best option is chosen based on
their management objective (to maximise the duck harvest in the long term).
Then monitoring of the harvest is carried out, these data are entered into the
population models, and the cycle begins again.
This is adaptive management because the models are learning from year to year
based on the new data that become available. But it is passive adaptive manage-
ment, because there is no active attempt to experiment in order to learn more
about the system.
Source
: U.S. Fish and Wildlife Service,
http://www.fws.gov/migratorybirds/
