Millions of men, women and children around the world move in anticipation or as a response to environmental stress every year. Disruptions such as cyclones, floods and wildfires destroy homes and assets, and contribute to the displacement of people. Slow-onset processes – such as sea-level rise changes in rainfall patterns and droughts – contribute to pressures on livelihoods, and access to food and water, that can contribute to decisions to move away in search of more tenable living conditions. Advances in meteorological and other sciences which inform about the dynamics and pace of climate change indicate that disruptions ranging from extreme weather events to large scale changes in ecosystems are occurring at a pace and intensity unlike any other known period of time on Earth. Anthropogenic climate change is expected to increasingly affect migration and other forms of people moving to manage these changing risks.

This chapter provides an up-to-date overview of environmental change and the spectrum of human mobility. It first explores different perspectives on environmental change and migration, ranging from the view that human mobility including migration is a security issue, that it is an issue of protection, and that it is a matter of adaptation and managing risks associated with environmental change. The chapter then provides examples of environmental migration from empirical research around the world. It then summarizes recent developments in the international policy sphere on the topic. The conclusion draws out the implications for research, policy and practice.