The purpose of these Key Sheets is to provide DFID Natural Resource Advisers with an easy and up-to-date point of reference on issues relating to development in the natural environment. The sheets are designed for those who are managing change and who are concerned to make well-informed implementation decisions. They aim to distil theoretical debate and field experience so that it becomes easily accessible and useful across a range of situations. Their purpose is to assist in the process of decisionmaking rather than to provide definitive answers.