This chapter reviews a wide range of published and unpublished documents in search of evidence of environmental causes of forced migration, and of the environmental impact of refugees. Calculating the population ‘at risk’ from sea-level rise is a long way from predicting mass flight of a ‘refugee’ nature with its attendant need for international protection and assistance. In searching for evidence of the environmental impacts of refugees, it is helpful to start with the question of what is meant by environmental impacts – or indeed what are the ‘impacts’ that are most expected, or considered most relevant in refugee-affected areas. Impacts on water supply and quality may have considerable effects of relevance to the health of refugee and host populations. One beneficial impact of refugee settlement, or more specifically of refugee assistance programmes, may be the provision of much-needed boreholes which improve the quantity and quality of drinking water.