The Role of Afforestation in Modulating Arid Climate

Afforestation and greening initiatives are increasingly considered viable strategies for mitigating climate change, particularly in arid regions. In this study, we assess the climate impacts of large-scale afforestation in the Arabian Peninsula (AP). The afforestation is represented by replacing sandy bare soil with woody savanna vegetation, assumed to be naturally sustained by rainfall, in the absence of overgrazing. Using a 30-year regional climate model simulation, we prescribe afforestation within a circular area of 4.5° radius (approximately 71.9 million hectares) centered at 24.2°N, 44.3°E. The afforestation modifies surface characteristics, including darker albedo (0.25 vs. 0.38 for bare soil), a green fraction of 0.3, and a leaf area index (LAI) of 0.1.

Our results show that the afforestation slows down near-surface winds and due to darker surface, increases sensible heat flux, leading to enhanced warming of the atmosphere over vegetated areas. Despite these warming effects, the additional vegetation promotes higher rainfall due to increased moisture availability and reduction of subsidence. This study underscores the dual role of afforestation in modulating regional climate, serving as both a climate mitigation measure and a potential warming source, depending on regional conditions. These findings highlight the importance of considering water availability and local climate factors when designing greening policies for arid regions.