Climate change has major implications for sustainable use and conservation of natural resources. Many natural systems are already under severe stress and may be unable to sustain historical use patterns; resource management decisions can also exacerbate or mitigate climate change by affecting the balance of greenhouse gases in the atmosphere. This Article describes the legal and scientific basis for recognizing agencies’ obligations to assess and respond to climate change, drawing insights from a survey of U.S. litigation involving forests, fisheries, rangelands, and freshwater resources. The cases suggest litigants have been somewhat successful in driving more rigorous assessments of climate change. However, agencies still frequently conclude that climate impacts are too uncertain or insignificant to warrant a response, and courts will generally defer unless the agency has overlooked or arbitrarily dismissed actionable scientific information. This underscores the importance of collaboration among resource managers, legal advocates, and scientists to develop, disseminate, and communicate scientific information that can meaningfully inform these decisions.