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. This study investigates the potential impacts of afforestation on land precipitation (P), evapotranspiration (E) and water availability (P − E) at global and country scales, finding that afforestation amplifies seasonal and spatial contrasts in P − E.