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Preprints
https://doi.org/10.5194/egusphere-2024-710
https://doi.org/10.5194/egusphere-2024-710
21 Mar 2024
 | 21 Mar 2024

Global and Regional Hydrological Impacts of Global Forest Expansion

James A. King, James Weber, Peter Lawrence, Stephanie Roe, Abigail L. S. Swann, and Maria Val Martin

Abstract. Large-scale reforestation, afforestation, and forest restoration schemes have gained global support as climate change mitigation strategies due to their significant carbon dioxide removal (CDR) potential. However, there has been limited research into the unintended consequences of forestation from a biophysical perspective. In the Community Earth System Model version 2 (CESM2), we apply a global forestation scenario, within a Paris Agreement-compatible warming scenario to investigate the land surface and hydroclimate response. Compared to a control scenario where land use is fixed to present-day levels, the forestation scenario is up to 2 °C cooler at low latitudes by 2100, driven by a 10 % increase in evaporative cooling in forested areas. However, afforested areas where grassland or shrubland are replaced lead to a doubling of plant water demand in some tropical regions, causing significant decreases in soil moisture (~5 % globally, 5–10 % regionally) and water availability (~10 % globally, 10–15 % regionally) in regions with increased forest cover. While there are some increases in low cloud and seasonal precipitation over the expanded tropical forests, with enhanced negative cloud radiative forcing, the impacts on large-scale precipitation and atmospheric circulation are limited. This contrasts with the precipitation response to simulated large-scale deforestation found in previous studies. The forestation scenario demonstrates local cooling benefits without major disruption to global hydrodynamics beyond those already projected to result from climate change, in addition to the cooling associated with CDR. However, the water demands of extensive forestation, especially afforestation, have implications for its viability given uncertainty in future precipitation changes.

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Journal article(s) based on this preprint

03 Sep 2024
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Global and regional hydrological impacts of global forest expansion
James A. King, James Weber, Peter Lawrence, Stephanie Roe, Abigail L. S. Swann, and Maria Val Martin
Biogeosciences, 21, 3883–3902, https://doi.org/10.5194/bg-21-3883-2024,https://doi.org/10.5194/bg-21-3883-2024, 2024
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Large-scale afforestation and reforestation are today seen as an important global climate...
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Tackling climate change by adding, restoring, or enhancing forests is gaining global support....
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