The Environmental Pressures module examines how the Horn’s arid and semi-arid geography is related to underdevelopment and conflict. Materials guide exploration of how cycles of drought affect the livelihoods of agricultural and pastoralist communities, compounding the problem of poverty throughout the region. A general introduction to the region’s varied ecosystems is complemented with information on patterns of land use and production, the prevalence of food insecurity, and the nature of humanitarian responses. A major lesson explores classic and contemporary issues confronting pastoralists across the region. One case study under this theme illustrates how water scarcity has affected the wellbeing of pastoralists in Djibouti and Somalia. Another case study discusses how land and water scarcity have been associated with communal conflicts in Ethiopia. A related exercise asks students to assess contrasting expert arguments on the role of environmental stress in promoting conflict across the Horn.