Directional changes in ecological communities and social-ecological systems: a framework for prediction based on Alaskan examples.

In this article we extend the theory of community prediction by presenting seven hypotheses for predicting community structure in a directionally changing world. The first three address well-studied community responses to environmental and ecological change: ecological communities are most likely to exhibit threshold changes in structure when perturbations cause large changes in limiting soil or sediment resources, dominant or keystone species, or attributes of disturbance regime that influence community recruitment. Four additional hypotheses address social-ecological interactions and apply to both ecological communities and social-ecological systems. Human responsiveness to short-term and local costs and benefits often leads to human actions with unintended long-term impacts, particularly those that are far from the site of decision making or are geographically dispersed. Policies are usually based on past conditions of ecosystem services rather than expected future trends. Finally, institutions that strengthen negative feedbacks between human actions and social-ecological consequences can reduce human impacts through more responsive (and thus more effective) management of public ecosystem services. Because of the large role that humans play in modifying ecosystems and ecosystem services, it is particularly important to test and improve social-ecological hypotheses as a basis for shaping appropriate policies for long-term ecosystem resilience.