Welcome to the Evidence on Demand series of Topic Guides. The guides are being produced for Climate, Environment, Infrastructure and Livelihoods Advisers in the UK Department for International Development (DFID). There will be up to 30 Topic Guides produced 2013-2014.The purpose of the Topic Guides is to provide resources to support professional development. Each Topic Guide is written by an expert in the field. Topic Guides: Provide an overview of a topic, Present the issues and arguments relating to a topic are illustrated with examples and case studies: Stimulate thinking and questioning, Provide links to current best ‘reads’ in an annotated reading list, Provide signposts to detailed evidence and further information, Provide a glossary of terms for a topic.