An inside account of the meteoric rise and disillusioning fall of ecosystem services-an idea once heralded as the way forward for conservation. Biologists Unite explores political realignments in global biodiversity conservation through the story of ecosystem services- an emergent field of science dedicated to analyzing, and where possible measuring, the many valuable "services" nature provides to humanity. What is at stake in ongoing attempts to recast nature as "natural capital"? Why did this way of thinking gain such widespread currency among conservationists? And what can the contemporary embrace of nature-based solutions like ecosystem services tell us about the changing politics of environmentalism more broadly? Daniel Chiu Suarez offers an intimate, inside perspective on these hotly debated questions- an ethnographic portrait of ecosystem services shown through the predicaments of its core champions - chief among them, life scientists, endeavoring to "mainstream" the idea across a range of governance contexts - as they were forced to learn on the job (and very much the hard way) how to reckon with the political character and radical implications of our dire planetary conjuncture. Drawing on years of participant observation conducted around two influential initiatives - the Natural Capital Project and the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) - the book narrates the meteoric rise of ecosystem services, but also how fragile this strategy turned out to be when put to the test.