Compound atmospheric and soil droughts amplify the global loss of vegetation productivity

Atmospheric droughts (high vapor-pressure deficit, VPD), soil droughts (low soil moisture, SM), and their compound occurrence (compound droughts, CDs) impose varying stress on terrestrial vegetation, yet their relative global impacts on productivity remain poorly quantified. Here, we assessed losses of gross primary productivity (GPP) during growing seasons from 1982 to 2018 under high VPD alone, low SM alone, and CDs. CDs caused the greatest GPP reductions ( − 8.94 g C m⁻² per event), nearly four times the losses from high VPD ( − 2.24 g C m⁻²) or low SM ( − 2.20 g C m⁻²) events. Broadleaf forests were most affected by CDs and high VPD, while needleleaf forests were more sensitive to low SM. Meteorological factors, particularly temperature and precipitation, were key drivers of the three types of droughts contributing to GPP losses. GPP reductions from high VPD were broadly associated with temperature, while drivers under low SM varied spatially. Vegetation recovery after CDs was slower than after high VPD or low SM events in over 60% of regions, and it was more difficult to fully achieve. Our findings clarify how atmospheric and soil droughts jointly limit productivity, providing insight for improved assessments of vegetation carbon uptake under changing climate conditions.