Deforestation Drives Desiccation in Global Monsoon Region

Global monsoon system is a major component of the Earth's climate system and carries about two-thirds of the world's population. How large-scale deforestation induced changes in water cycle and energy balance may modify global monsoon system and its underlying mechanisms are not well understood. Here, we use simulations of 11 models participating in the Land Use Model Intercomparison Project in the framework of the Coupled Model Intercomparison Project, phase 6 to study the response of global monsoon precipitation and atmospheric circulation to large-scale deforestation. Global deforestation of about 38% induces annual precipitation reduction of about -15.01 mm yr(-1) (Multi-Model Ensemble) in global monsoon regions and -26.15 mm yr(-1) in land monsoon regions. The precipitation reduction is particularly pronounced in the Northern Hemisphere Summer Monsoon (NHSM) regions with decreased precipitation by 16.83 mm in the summer monsoon season from May to September along with weakened circulation intensity. Deforestation causes asymmetrical temperature response in the northern high latitudes and Southern Hemisphere Tropics, leading to decreased hemispheric thermal contrast, which reduces the meridional pressure gradient and weakens the convergence of cross-equatorial flows into the NHSM trough regions, thereby decreasing the NHSM circulation and precipitation intensity. The deforestation-induced hemispheric temperature asymmetry also increases the northward cross-equatorial atmosphere heat transport (c-eq AHT) that drives southward shift of Intertropical Convergence Zone, which suppresses the NHSM precipitation. Our results show that the drying monsoon region in response to deforestation is fairly consistent among the models implying the adverse effects of large-scale deforestation beyond the region of land use change.

Automated summary

The study reveals that large-scale deforestation has significant impacts on the global monsoon system, leading to reduced precipitation in both the global monsoon regions and the land monsoon regions. The precipitation reduction is particularly pronounced in the Northern Hemisphere Summer Monsoon regions. Deforestation also causes asymmetrical temperature response, weakening the circulation intensity and leading to decreased monsoon circulation and precipitation intensity.