Despite unprecedented worldwide biodiversity loss, conservation is not at the forefront of national or international development programs. The concept of ecosystem services was intended to help conservationists demonstrate the benefits of biodiversity for human well-being, but services are not yet seen to truly address human need with current approaches focusing mostly on financial gain from service provision. To promote development strategies that integrate conservation and service protection, we develop the first prioritization scheme for protecting ecosystem services in the world's watersheds and compare our results with global conservation schemes. We ask the following two principal questions: 1. Which watersheds are high priorities for biodiversity conservation (according to several prioritization schemes), water provision, flood mitigation, and carbon storage? 2. What are the relationships between watershed rankings by these various indices of biodiversity conservation and ecosystem services?

Results/Conclusions

We show that, by explicitly incorporating human need into prioritization strategies, service-protection priorities are squarely focussed on the world's poorest, most densely populated regions. We identify watersheds in Southeast Asia and East Africa as the most crucial priorities for service protection and biodiversity conservation, including Irrawaddy - recently devastated by cyclone Nargis. Emphasising human need is a substantial improvement over dollar-based, ecosystem-service valuations that undervalue the requirements of the world's poor, and our approach offers great hope for reconciling conservation and human development goals.