Trans-Himalayan irrigation oases in transition: climate change and socio-economic transformation threatening traditional land use systems in the Mustang District, Nepal

The livelihoods of more than one billion of the world's population in the highlands and associated lowlands depend on ecosystem services provided by mountain landscapes. The array of benefits allocated to mountain socio-ecosystems include e.g. biodiversity, freshwater-related services such as storage, purification, and pervasive supply, and cultural services like ethnic and cultural diversity. The Nepalese Mustang District incorporates these ecosystem services in a unique ensemble. Few regions in the world comparably combine a cultural heritage that has evolved and adapted to the harsh climate over millennia, recent rapid socioeconomic transformations and environmental changes. Rising temperatures, decreasing snow cover accompanied by an increase in precipitation variability threaten the livelihoods of the rural population in the Mustang district that depends largely on irrigation-based agriculture. Therefore, local water availability, access to water resources, and sustainable management are essential to secure local livelihoods. In the early 1990s, various settlements within the Mustang District were investigated in detail, including functional mapping of buildings and land-use plots. In 2018, roughly 30 years later, a thorough re-mapping clearly illustrates massive changes in ecosystem and socio-economy. The recent finalization of a continuous road within the former periphery of the Annapurna Conservation Area enables a pronounced market orientation including cash crops. A significant change in crop rotations combined with a massive increase in fruit tree cultivation is evident within the past 30 years. Moreover, the analyses of optical satellite imagery (Landsat MSS/TM/ETM+/OLI and Sentinel-2A MSI) reveal multi-temporal changes of the cryosphere within the catchments indicating an overall drastic loss of 40% of glacierized area compared to the former Little Ice Age glacial extent. The observed changes in the cryosphere constraint the water availability securing the local livelihoods, while at the same time, the water demand is increasing. Combined analyses demonstrate that the transformations observed are indicative and applicable to the whole region.