Migration refers to the movement of people between locations. There are multiple causes and consequences of migration. Anthropologists study migration through multi-sited research considering both macro-level global factors and micro-level local issues. Migration can be categorized based on spatial boundaries as internal, international, or transnational migration, or based on reasons for moving such as labor, being displaced, or institutional migration. Environmental issues like climate change are also a growing cause of migration as some communities are the first to suffer consequences like rising sea levels or disappearing glaciers.