Tanzanian toad

A stark reminder of the ever growing pressure on the environment is happening in a room in a New York zoo. One of the buildings there is likely to become the only remaining habitat of a rare toad. The Kihanse Spray Toad has existed until now only at one water fall in Africa, the Kihanse Falls. But the falls are now drying up because of a hydroelectric project. It is the cruellest clash between economic gain to a people and the environment. The BBC's Stephen Evans reports.