When is active restoration cost effective?

Background/Question/Methods

Invasive species are one of the most pressing environmental problems so controlling the spread of an invasive species is a particularly important problem in bioeconomics. The approach is to choose a strategy that minimizes the overall cost, taking into account the cost of damages and the cost of controls in an appropriate fashion. However, this is only part of the full environmental problem, since after removal of an invasive species, habitat must be restored to return to a state that provides appropriate ecosystem services such as controlling storm surges or providing habitat. Thus, choosing how and when to restore in an optimal fashion is important and has not been well studied. The problem is to determine when and how to spend resources on restoration, both after removal of an invasive species or, in other circumstances, with compromised ecological systems.

Results/Conclusions

Here we show that there is a simple rule that can be used to determine when to spend resources on restoration, namely restoration should take place until a certain ``restoration capacity'', and, possibly, again at the last stage of the recovery process. Restoration capacity is approximately where the potential benefit from yet damaged regions equals to the natural recovery-rate times the cost of slow active restoration. The rule is surprisingly simple and can provide a useful rule of thumb when managing a real system. This result also can be applied to other cases of damaged ecosystems and helps provide approaches for rebuilding ecosystems in general, such as those that have been damaged by overfishing or underwent desertification. We show how the results can be applied to the problems of recovery of endangered species and of translocation for dealing with mitigating the effects of global change.