Variable drivers trigger future change in water yield capacity of terrestrial ecosystems in Africa: An intensification of reduction and unevenness

Predicting the water-related services of terrestrial ecosystems in a changing climate is of great significance for managing rich ecosystems in water-scarce areas. Water yield capacity (WYC), which characterizes water resource availability, was thrown into sharp focus of this study. The spatiotemporal trends of WYC and their dynamics by potential climate shifts were evaluated based on calculative WYC and climate zones for historical period (2001–2018) and future scenarios (both 2050 and 2100 under SSP1-2.6 or SSP5-8.5 scenarios). The multiple factors affecting WYC in the recent past were identified as the basis for explaining the future tendency in WYC. All analyses were conducted from the perspective of holistic continental scale and specific basin scale so as to explore the contrast between various scales. The results showed that the total WYC both in whole Africa and the four major basins (the Congo, the Nile, the Niger and the Zambezi) are projected to decrease in 2050 and 2100 compared with that in 2018, under both SSP1-2.6 or SSP5-8.5 scenarios describing future pathways with low or high greenhouse gas emissions, respectively. The areas producing WYC will be more concentrated, suggesting that the proportion of areas contributing to the top 50% of this function across Africa will drop from current 10.5% to 4.94% in 2100 under SSP5-8.5 scenario. As climate zones are likely to shift in the future, the WYC will reduce most in the areas experiencing the conversion between tropical monsoon and tropical rainforest climates. In addition, WYC was driven by precipitation, temperature, net primary productivity (NPP) and landscape pattern (connectivity and diversity), which had spatial scale effect. The results add evidence for unstable availability of water resources provided by terrestrial ecosystems in a multi-scale manner.