Mapping and Assessment of Ecosystem Services Supply and Demand of the Kilombero Valley Floodplain, Tanzania

Abstract

Effective land use planning requires mapping and assessing ecosystem service supply and demand to inform policy and decision-makers about ecosystem service tradeoffs that are suited for long-term ecological management. This study examined the ecosystem services supply and demand of the Kilombero Valley Floodplain in Southeastern Tanzania. The supply-demand budget index was calculated using land use data from 1990, 2010, and 2016 and an expert-based matrix model examined the dynamic change of supply and demand for the 17 ecosystem services (7 regulating, 8 provisioning, and 2 cultural). The spatial analytic features of ArcGIS 10.2 were utilized to build ecosystem services evaluation matrices and regionally explicit supply, demand, and supply-demand budget maps. The study found that between 1990 and 2016, the supply of ecosystem services within the Kilombero Valley floodplain decreased substantially while the demand for ecosystem services increased spatially towards the core low-lying area of the valley. Furthermore, the average ecosystem service supply-demand budget index declined from 1.8 in 1990 to 1.6 in 2016, with few exceptions of food production, pollination, and freshwater supply, where ecosystem service supply exceeds demand. The decline is linked to deforestation, agricultural expansion, agropastoralists immigration, and encroachment to the wetland area. Thus, this study recommends that the government should create effective land use plans for each ward and village in the Kilombero District, establish afforestation programs, local irrigation schemes for smallholder farmers, and enforce environmental by-laws to ensure sustainable ecological management in the Kilombero Valley Floodplain and its ecosystems.