Cropland expansion outweighs the monetary effect of declining natural vegetation on ecosystem services in sub-Saharan Africa

Changes in land cover and land degradation alter natural ecosystems, thereby affecting the services these ecosystems provide. However, there have been few attempts to estimate the effects of land cover change and land degradation on ecosystem services at large spatial scales and under the strong influence of human activities. Here, we used the European Space Agency Climate Change Initiative land cover maps (1992-2015) and the value transfer valuation method to estimate the changes in ecosystem services value (ESV) in response to land cover change in sub-Saharan Africa (SSA). Moreover, we estimated the loss of ESV due to land degradation by using the long-term (1992-2015) trend in the annual normalized difference vegetation index as a proxy for longterm biomass productivity decline. Our results revealed that, between 1992 and 2015, cropland increased by about 20 million ha, largely at the expense of forest and shrubland. The total estimated ESV of SSA was about US $9 trillion year(-1), of which 55% was derived from cropland and deciduous forest, with comparable contributions. Land cover change resulted in a net increase in the total ESV by US$125 billion year(-1) (1992-2015), albeit with an ESV loss of US$60 billion year -1 from the conversion of evergreen forest and shrubland. Overall, cropland expansion accounted for about 60% of the increase in the total ESV (US$125 billion year(-1)), thereby outweighing the decrease in ESV due to the decline in natural vegetation. Land degradation hotspots covered about 5% of SSA, resulting in a total ESV loss of about US$56 billion year(-1), of which nearly 65% was due to the degradation of forests and croplands. Changes in ESV varied across sub-regions, climate zones, and countries, depending on the dominant land cover change and the extent of land degradation. Our results provide useful insights for making informed decisions towards sustainable use and management of ecosystems.