Animal migrations are spectacular phenomena that have fascinated humanity for millennia. They also play vital roles in ecosystem processes, transferring nutrients, carbon, energy and genes, and supporting cultural resources and traditions. However, migratory populations are in an alarming decline due to the manifold threats they face in our rapidly changing world. This issue of environmental SCIENTIST explores the complexities of animal migration and the actions needed to reverse declines in the numbers of terrestrial, marine and avian travellers making these impressive journeys. Read about the system considerations of migration, the importance of international cooperation for saiga antelope conservation, the fascinating multigenerational monarch butterfly migration, and initiatives to improve the future of the European eel.