Spatial assessment of the impact of land use and land cover change on supply of ecosystem services in Phewa watershed, Nepal

Community-managed forested landscapes are complex social-ecological systems that supply a variety of ecosystem services (ES) to society. The flow of these services depends on land use and land cover (LULC) changes, ecological factors such as types, pattern and composition of vegetation, as well as anthropogenic factors. ES assessment helps to deal with the complexity of the interrelationships among LULC, ES supply and societal benefits. Using the case of the Phewa watershed, Nepal, this paper presents a quantitative and qualitative assessment of priority ES to understand how the supply of ES and their societal benefits have changed over the past 40 years. LULC changes were analysed using satellite images, ecosystem services were assessed using biophysical data and expressed spatially using ArcGIS. Results reveal a substantial reversal of land degradation and indicate forest recovery over the last 40 years. Dense forests increased by 1471 ha (88%) while sparse forests, grasslands and agricultural lands declined by 26%, 77% and 15%, respectively. These significant changes in LULC had a positive impact on ES due to the conversion of agricultural/grasslands and degraded forests to dense forests. ES varied significantly across the watershed. Dense forests provided relatively higher sediment retention (soil erosion rate decreased from > 30 ton ha(1) yr(1) to < 15 ton ha(-1) yr(-1)), carbon stocks (from < 50 m(3) ha(-1) to > 100 m(3) ha(-1)), habitat provision, and raw materials than other types of land cover, but reduced the water discharge. Increased aesthetic value from the restored landscape provides higher opportunities for recreation and ecotourism. Analysis of benefit-relevant indicators revealed that the perceived societal benefits from most of the ES were significantly lower than the potential supply of ES in the watershed.