Ecosystem services in changing social-ecological systems

• Ecosystems in the Omo-Turkana Basin (OTB) provide a host of provisioning, regulating, supporting and cultural services to people. They enable the rearing of 20% of the Ethiopian cattle population, 5% of the Kenyan fish production, and support drinking water, sediment retention and soil fertility for millions of people dependent on subsistence agriculture and pastoralism. Most importantly, ecosystems provide a home and identity to the diverse people who live in the dynamic and at-times challenging conditions of this area. • The basin’s social-ecological system is constantly changing due to regional demand for water, energy and food. The demand for hydropower and irrigated agriculture, in particular, drives many of the large-scale development interventions in both the Ethiopian and the Kenyan portion of the basin, which in turn impact rural livelihoods especially for indigenous peoples in the Lower Omo Valley. • In recent decades, two main trends have occurred in ecosystem services across the basin: first, since the 1980s, 5.5% of the highlands experienced a net loss of closed-canopy forests and all the services they provide, probably due to agricultural expansion. At the same time, 12% of the lower-lying areas experienced an increase in open woodlands due to changing climate. When coupled with an overall reduction in desert areas, this may lead to potentially positive outcomes for carbon sequestration. Second, since construction of the Gibe III dam, typical seasonal hydrological oscillations – e.g., water-level patterns in the Omo River and Lake Turkana – have been reduced, which has resulted in a reduction in temporarily flooded areas normally used for recession agriculture, grazing and potentially fish stocks in Lake Turkana. • The continuous changes in the basin require adaptation measures that are as diverse as the basin’s ecosystems and the people who depend on them. Ecosystems, livelihoods and well-being in the OTB are intertwined with river flow dynamics. Environmental flow releases from dams may be able to partially restore ecosystem services, but their planning needs to take into account the strong trade-offs between flood risks and benefits