A bioenergy-focused versus a reforestation-focused mitigation pathway yields disparate carbon storage and climate responses

Yanyan Cheng; David M Lawrence; Ming Pan; Baoqing Zhang; Neal T Graham; Peter J Lawrence; Zhongfang Liu; Xiaogang He

doi:10.1073/pnas.2306775121

A bioenergy-focused versus a reforestation-focused mitigation pathway yields disparate carbon storage and climate responses

Proc Natl Acad Sci U S A. 2024 Feb 13;121(7):e2306775121. doi: 10.1073/pnas.2306775121. Epub 2024 Feb 5.

Authors

Yanyan Cheng¹, David M Lawrence², Ming Pan³, Baoqing Zhang⁴, Neal T Graham⁵, Peter J Lawrence², Zhongfang Liu⁶, Xiaogang He⁷

Affiliations

¹ Department of Industrial Systems Engineering and Management, National University of Singapore, 117576, Singapore.
² Climate and Global Dynamics Laboratory, National Science Foundation National Center for Atmospheric Research, Boulder, CO 80305.
³ Center for Western Weather and Water Extremes, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093.
⁴ Key Laboratory of Western China's Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou, Gansu 730000, China.
⁵ Joint Global Change Research Institute, Pacific Northwest National Laboratory, College Park, MD 20740.
⁶ State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China.
⁷ Department of Civil and Environmental Engineering, National University of Singapore, 117576, Singapore.

Abstract

Limiting global warming to 2 °C requires urgent action on land-based mitigation. This study evaluates the biogeochemical and biogeophysical implications of two alternative land-based mitigation scenarios that aim to achieve the same radiative forcing. One scenario is primarily driven by bioenergy expansion (SSP226Lu-BIOCROP), while the other involves re/afforestation (SSP126Lu-REFOREST). We find that overall, SSP126Lu-REFOREST is a more efficient strategy for removing CO₂ from the atmosphere by 2100, resulting in a net carbon sink of 242 ~ 483 PgC with smaller uncertainties compared to SSP226Lu-BIOCROP, which exhibits a wider range of -78 ~ 621 PgC. However, SSP126Lu-REFOREST leads to a relatively warmer planetary climate than SSP226Lu-BIOCROP, and this relative warming can be intensified in certain re/afforested regions where local climates are not favorable for tree growth. Despite the cooling effect on a global scale, SSP226Lu-BIOCROP reshuffles regional warming hotspots, amplifying summer temperatures in vulnerable tropical regions such as Central Africa and Southeast Asia. Our findings highlight the need for strategic land use planning to identify suitable regions for re/afforestation and bioenergy expansion, thereby improving the likelihood of achieving the intended climate mitigation outcomes.

Keywords: BECCS; bioenergy; carbon dioxide removal; climate mitigation; reforestation.

Abstract

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