What's so special about alternative stable states?

Background/Question/Methods

The presence of alternative stable states in some ecological systems has generated much interest and concern by introducing the possibility that small external perturbations can cause large and long-lasting changes to the community.  While alternative stable states only appear under certain circumstances, virtually all ecological communities are characterized by alternative states in general (i.e. a mix of stable and unstable states).  If unstable states are associated with long transient dynamics, then these systems might behave quite similarly to those with alternative stable states in the presence of stochasticity.  Here, I compare two stochastic models for insect outbreaks - one with multiple stable states and one with a single stable dynamical state coexisting with unstable states - to explore their similarities and differences and determine if and when it is significant that a system has multiple states that are stable.

Results/Conclusions

The dynamics described by the two models are extremely similar, and both display certain quantitative properties usually associated with alternative stable states.  These results reveal that in a stochastic setting, some communities with a single stable state warrant much the same special interest and concern that we normally direct toward communities with alternative stable states.