Vegetation-driven evapotranspiration enhancements modulate the climate in the Nile River basin

Nile River basin (NRB), Northeastern Africa. Despite substantial recent vegetation changes in the NRB, their influence on local temperature and precipitation remains uncertain, limiting effective climate adaptation, land management, and water-resource planning in this region. This study examines how vegetation dynamics affect regional climate and the biogeophysical mechanisms driving vegetation–climate feedbacks from 1982 to 2020 using the Community Earth System Model version 2 (CESM2), combined with long-term remote sensing data and a regression model capturing bidirectional interactions between leaf area index (LAI) and climate variables. About 54 % of the basin’s vegetated areas show significant increases in LAI. In most regions, enhanced vegetation density exerts a cooling effect through increased evapotranspiration, reducing temperature across 43 % of vegetated land, particularly in forest- and shrub-dominated areas. However, in high-elevation regions of Ethiopia, Kenya, and Uganda, vegetation induced surface warming effect by reducing albedo and enhancing solar energy absorption. Overall, vegetation change contributes to a net basin cooling of 0.02 ± 0.006 °C per decade, offsetting 9.5 ± 2.9 % of NRB warming over 39 years. Impacts on precipitation are weak and spatially inconsistent, with only semi-arid regions showing slight positive feedback. Seasonal variability is strong, evapotranspiration-driven cooling and positive precipitation responses dominate June–September and October–January, whereas radiative warming and negative precipitation responses prevail from February–May. Non-radiative processes are the primary drivers of climate responses to vegetation change. These findings highlight the importance of incorporating vegetation dynamics into climate mitigation, adaptation strategies, and model refinement. • Vegetation increased in 54 % of the Nile Basin, cooling 43 % via evapotranspiration. • Highland vegetation changes caused local warming due to reduced surface albedo. • Overall, enhanced vegetation led to a net cooling of 0.02°C per decade in the basin. • Vegetation impacts on precipitation were weak, seasonal, and spatially inconsistent. • Vegetation-climate feedbacks were driven mainly by non-radiative processes.