Under § 7 of the federal Endangered Species Act (ESA or the Act),'federal agencies must ensure that actions they authorize, fund, or carry out are" not likely to jeopardize the continued existence of any endangered species or threatened species or result in the destruction or adverse modification of habitat of such species." 2 For species with low and declining populations, applying this standard is legally and scientifically difficult. 3 The US Fish and Wildlife Service (FWS) faced this problem in its recent biological opinion (BiOp) analyzing impacts to threatened Delta smelt from water project operations in the California Delta. FWS concluded the" species' recent abundance trends strongly suggest it is in the midst of demographic collapse," and most recent surveys to locate smelt have failed to find them.'Nevertheless, FWS approved agency actions that will likely increase extinction risk for Delta smelt.

Synthesis research in ecology and environmental science improves understanding, advances theory, identifies research priorities, and supports management strategies by linking data, ideas, and tools. Accelerating environmental challenges increases the need to focus synthesis science on the most pressing questions. To leverage input from the broader research community, we convened a virtual workshop with participants from many countries and disciplines to examine how and where synthesis can address key questions and themes in ecology and environmental science in the coming decade. Seven priority research topics emerged: (1) diversity, equity, inclusion, and justice (DEIJ), (2) human and natural systems, (3) actionable and use-inspired science, (4) scale, (5) generality, (6) complexity and resilience, and (7) predictability. Additionally, two issues regarding the general practice of synthesis emerged: the need for increased participant diversity and inclusive research practices; and increased and improved data flow, access, and skill-building. These topics and practices provide a strategic vision for future synthesis in ecology and environmental science.