Global Vegetation Greening Is Exacerbating Soil Dryness

Recent decades have witnessed a concurrent increase in global vegetation greenness and soil dryness, with the latter manifested through intensified soil droughts and declining soil moisture trends. Despite previous insight into the damage of soil dryness on vegetation, whether and to what extent vegetation greening has in turn exacerbated soil dryness remains virtually unknown. This limits our ability to anticipate water resource crises and adapt to climate change. Here we evaluated the effects of vegetation greenness on soil drought (ESD) and soil moisture trend (EST) from 1982 to 2020. Results indicated that ESD and EST were negative in 71% and 59% of vegetated places, respectively, mainly manifested as exacerbated soil drought and accelerated soil drying trend induced by vegetation greening. Across the aridity gradient, both effects peaked in the semi-arid or dry sub-humid zone before diminishing toward the humid zone. And vegetation exerted stronger ESD and EST than both effects of precipitation and temperature in 19% and 44% of vegetated places, respectively. Notably, negative ESD and EST significantly intensified over time, driven primarily by increasing transpiration dominance in evapotranspiration partitioning. Yet, some Earth system models poorly simulated these effects of vegetation on soil dryness and even distorted their temporal evolution. These findings highlight the urgent need for sustainable ecological management to mitigate hydrological risk associated with global greening.