Drought Propagation as a Nonlinear Amplifier of Ecohydrological Damage

Escalating droughts are posing unprecedented challenges to environmental stability and sustainable development. In particular, meteorological drought can propagate to soil and ecological droughts, triggering cascading disruptions in ecosystem functioning. However, whether the ecohydrological damage—the sum of standardized vegetation greenness and soil moisture losses—is disproportionately amplified through drought propagation has not been systematically assessed, which severely limits our ability to anticipate catastrophic drought cascades and implement timely adaptation strategies. Using global remote sensing data, we found that ecohydrological damage reached 162% to 310% of the initial meteorological drought intensity, due to prolonged drought duration and increased peak intensity. Once meteorological drought intensity exceeded the standardized threshold of 2.18, ecohydrological damage escalated nonlinearly. Externally, soil and ecological droughts were more sensitive to meteorological droughts driven by precipitation deficits and potential evapotranspiration surpluses, respectively, but the former propagated more efficiently. Internally, vegetation–soil feedbacks promoted the propagation from soil to ecological drought, while dampened the reverse process, resulting in the greatest ecohydrological damage when meteorological drought first triggered soil drought and then ecological drought. Declining ecosystem resilience and increasing climate variability may exacerbate future drought propagation and its damage. These insights are critical for advancing early warning systems and mitigating cascading drought losses.