Where the world’s major biodiversity hotspots lie on the world map may be well known, but planning protected areas within these sizable patches requires working out the hotspots’ hottest parts — a controversial task. Most conservation strategies focus on saving individual species, but Claire Kremen and Alison Cameron of the University of California, Berkeley, and their colleagues have considered the Madagascan ecosystem as a complex web of co-habiting species1 (#B1) . The method, they say, could be rolled out for use anywhere around the globe.