Climate change is a critical issue for our time. Ecosystems are changing in response to climate: fire seasons are longer and forest fires are larger and more frequent; snowmelt in the western US occurs earlier; agricultural production is approaching critical thresholds in some areas; critical habitat is lost or threatened. Recent synthesis and assessments by the US Climate Change Science Program show that the scope and magnitude of climate change impacts often exceed expectations for both the extent and rate of change. As a result, natural resource managers are adapting to climate change either intentionally or unintentionally, often without any larger framework or understanding for those actions. Management designed to adapt to climate change is rarely evaluated, and effects and adaptation are often separated when they should be linked. Maintaining ecosystem function is critical to sustainability, and will rely heavily on understanding the effects of climate change on natural resources and the potential for adaptation to those changes.