The Rio+20 Earth Summit in late June will focus on sustainable development. In this episode of Nature's Voice we look at the RSPB's work in the Gola Rainforest of Sierra Leone which employs local people to conserve the forest while improving their lives. It's an illustration of sustainable development at work and we investigate a project in the forest to electronically tag one of the elusive and endangered pygmy hippos who live there. The task is to gather vital information to help them survive....but first they have to catch one.