Although climate change often is thought of as a gradual, quasi-continuous process, ecosystems can change both dramatically and rapidly if they are pushed past critical ecosystem ‘thresholds,’ sometimes changing to a fundamentally different state. Understanding the potential for such threshold dynamics, as well as their ecological and economic implications, is of keen interest to policy makers as they work to 1) identify the potential costs and benefits of different climate change mitigation policies and 2) develop climate adaptation strategies. The objectives of the symposium are to 1) describe specific ecosystem threshold dynamics that are relatively well understood and 2) discuss how decision makers, including natural resource managers, might cope with threshold dynamics when developing climate change policy or adaptation strategies. The symposium will begin with a brief overview of the session, which will be followed by an introductory talk that discusses the concept of ecosystem thresholds. Next, three case studies will be examined in detail: 1) the loss of whitebark pine in the Greater Yellowstone Ecosystem from mountain pine beetle outbreaks and increasing temperatures; 2) the loss of snowpack in the Rockies and implications for fire frequency and intensity; and 3) the loss of coral reef cover from warming and acidification. The case studies will be followed by a discussion of methods that can be used to convey scientific uncertainty regarding thresholds and their potential impacts to policy makers. The next talk will focus on how natural resource managers can integrate information about thresholds into their adaptation planning. We will conclude with a presentation regarding whether and how thresholds can and have informed high level policy making in the U.S. government. Finally, a panel discussion will provide an opportunity for audience feedback and interaction among panel members.