Vegetation greening exacerbates drought in the Tarim River Basin, Arid Regions of Central Asia

Here, we selected the Tarim River Basin (TRB), a typical arid region in Central Asia, and employed a dynamic counterfactual scenario framework based on trend differencing to quantify the contribution of vegetation greening to the Standardized Precipitation-Evapotranspiration Index (SPEI) and the Standardized Soil Moisture Index (SSMI) from 1990 to 2022, evaluate its net benefit on drought, and reveal the underlying mechanisms.

The results show that vegetation greening mitigates meteorological drought at a rate of 0.0004 yr-1, but exacerbates soil drought at a rate of -0.0013 yr-1, the net benefit shows an overall downward trend (-0.0009 yr-1). In 68% of the greening area, soil water consumption outweighs meteorological improvement. This is explained by water constraints in extremely arid regions: although vegetation greening enhances transpiration, increases relative humidity and precipitation, the limited soil moisture of TRB means that the same transpiration-induced water loss causes more severe soil drought than in humid regions, so negative effects far outweigh positive ones.