Ecosystem adaptation: Do ecosystems maximise resilience?

The response of an ecological system to perturbation can be described in terms of its resilience, essentially a measure of the time the system takes to return to its prior state. The resilience of an ecosystem is the result of interactions of the biota and their environment and will therefore change as the biota evolve and environmental conditions change. Ecological systems exist within the constraints of thermodynamic laws that prescribe the transfer of energy. Ecologically defined ‘‘thermodynamic imperatives,’’ such as entropy, exergy, and ascendency, provide whole-ecosystem selection pressures that constrain the evolution of individuals within an ecosystem in addition to the selection pressures of individual evolution. The essence of these whole-ecosystem selection pressures may be captured by metrics. We have used a ‘‘genetic algorithm’’ to optimize these metrics, simulating the adaptation of a model ecosystem biota. Our simulations suggest the hypothesis that, within the constraints of the external environment and the genetic potential of their constituent biota, ecosystems will evolve to the state most resilient to perturbation.