Through the Endangered Species Act’s Habitat Conservation Plan (HCP) program and California’s Natural Community Conservation Planning program, endangered species conservation in the United States has evolved considerably. In particular, areawide, multiagency HCPs, many of which developed in California, introduced the possibility of a more comprehensive, adaptive, and collaborative approach to conservation. Synthesizing research, interviews, and dialogue sessions, this Article aims to instruct future areawide, multiagency HCP efforts about the potential trade offs of particular design alternatives, particularly in light of emerging challenges such as climate change. It concludes that regulators and applicants must clearly engage stakeholders about the underlying trade offs among plan scale, depth, duration, cost, certainty, and efficacy to better promote effective, multijurisdictional, large-scale, and adaptive conservation planning.