Hydrologic Cycle Impacts of Large-Scale Reforestation at Global and Regional Scales

Reforestation is a key nature-based solution for mitigating climate change. However, changes in land cover through reforestation can significantly influence the climate and hydrological cycle, affecting water availability and other critical components of the Earth system. Understanding these impacts is essential for developing effective climate adaptation strategies and ensuring sustainable land management in the coming decades.This study leverages simulations with the Canadian Earth System Model (CanESM5.1), a state-of-the-art Earth system model, to quantify hydrological responses to two large-scale reforestation scenarios. The first scenario reverses historical deforestation, restoring tree cover to pre-industrial levels by the year 2070, while the second implements a sustainable reforestation strategy by the same year. To isolate the effects of reforestation, a reference simulation with land-cover fixed at the year 2015 configuration is also conducted. The study employs a two-stage simulation framework—historical (1850–2015) and future (2015–2200)—with multiple ensemble members, using SSP1-2.6 forcing to align with the Paris Agreement’s climate goals.Preliminary results reveal that large-scale reforestation induces statistically significant climate and hydrological responses at both regional and global scales. These findings highlight the potential for unintended consequences of land-based climate mitigation strategies, emphasizing the need for holistic assessments to guide future land management and policy decisions.