Restoration ecology, resilience, and the axes of change.
The Earth system is undergoing rapid, profound anthropogenic change. The primary axes of change include not only the climate system, but also the spread of invasive species, altered biogeochemical and hydrological cycles, modified disturbance regimes, and land degradation and conversion. These factors are influencing the distribution of species and the structure and function of ecosystems worldwide, interacting with climatic stressors that may preclude the persistence of many current species distributions and communities. Ecological disturbances such as wildfires and insect outbreaks can interact with climate variability to precipitate abrupt change on landscape scales. Such changes may limit the feasibility of historically based ecological restoration in many (although by no means all) instances. An alternative emerging approach is based on reinforcing the ecological processes that comprise resilience: resistance, recovery, and reorganization. While resistance and recovery processes fall within a conventional restoration framework, managing populations and ecosystems for reorganization represents a departure from a reference-based restoration approach. When applied to ecosystem management, resilience-based management supplements traditional ecological restoration where stressors of change make the reestablishment of historical communities difficult or maladaptive. We illustrate these ideas with examples drawn primarily from the interior of western North America.