Spatiotemporal inequality in land water availability amplified by global tree restoration

Afforestation can influence evapotranspiration (E) and precipitation (P), thereby altering water availability (known as P − E) on land. However, such effects on P − E have rarely been examined in the context of seasonal and spatial variations in background P − E conditions. Here we show the impacts of global tree restoration on P − E under spatiotemporally varying P − E conditions. Afforestation amplifies seasonal contrasts in P − E, resulting in higher P − E in the high P − E season and/or lower P − E in the low P − E season, over approximately two-thirds of the land area. Afforestation also amplifies spatial contrasts in P − E, leading to higher P − E in the high P − E regions but lower P − E in the low P − E regions. This study underscores the importance of considering background P − E conditions when evaluating the hydrological effects of afforestation, with important implications for both forestry and water management.