Journal of Applied Ecology 45(1), 181-192, 2007.
Abstract.
1. Effective decision-making in environmental management requires
the consideration of multiple objectives that may conflict. Common optimization
methods use weights on the multiple objectives to aggregate them into a single
value, neglecting valuable insight into the relationships among the objectives
in the management problem.
2.We present a multi-objective optimization procedure that approximates the
non-dominated Pareto frontier without the use of weightings, allowing for visualization
of the trade-offs among objectives. The non-dominated Pareto frontier is approximated
by the simultaneous optimization of a vector objective function; two vector
objective functions are defined as non-dominated if improvement with respect
to one objective is at the detriment of another objective.
3.We demonstrate the method with a case study for the optimum distribution of
forest fuels treatments that reduce the impact of fire on a forest. The multiple
objectives are to protect habitat of an endangered species, protect late successional
forest reserves and minimize the total area treated. In the comparison of three
optimization searches, the number of non-dominated solutions increases with
the dimensions of the objective space, but with only two objectives the search
is ineffective in minimizing fire impact in the different landscape types. Key
challenges include the extensive computation time required to approximate the
non-dominated set, and reducing the number of solutions that are analysed in
detail.
4.Synthesis and applications. The multi-objective optimization program presented
can be adapted to other environmental management problems, and easily incorporates
a wide range of quantifiable objectives. This tool provides decision-makers
with a set of alternatives that estimates the full range of trade-offs among
multiple objectives and provides a common ground from which dialogue can come
to an informed compromise and decision in environmental management problems.