植树造林（造林和再造林）可通过将碳固存在生物质和土壤中来缓解气候变化。然而，由于对碳固存率（特别是在土壤中）和土地可用性的估计不一，全球造林的缓解潜力仍不确定。
研究组绘制了全球土壤碳变化图，揭示了造林带来的碳收益和损失，主要是表层土壤。限制土地可用性以避免反照率引起的意外变暖，并保护水和生物多样性（全球可用于造林的3.89亿公顷），到2050年将固存39.9拍克碳，远低于此前的估计。随着土地进一步限制在现有的政策承诺范围内（1.2亿公顷），这一估计降至12.5拍克碳。因此，实现更大程度的缓解需要扩大专门的造林面积，并加强潜力巨大但尚未开发国家的承诺。
附：英文原文
Title: Land availability and policy commitments limit global climate mitigation from forestation
Author: Yijie Wang, Yakun Zhu, Susan C. Cook-Patton, Wenjuan Sun, Wen Zhang, Philippe Ciais, Tingting Li, Pete Smith, Wenping Yuan, Xudong Zhu, Josep G. Canadell, Xiaopeng Deng, Yifan Xu, Hao Xu, Chao Yue, Zhangcai Qin
Issue&Volume: 2025-08-28
Abstract: Forestation (afforestation and reforestation) could mitigate climate change by sequestering carbon within biomass and soils. However, global mitigation from forestation remains uncertain owing to varying estimates of carbon sequestration rates (notably in soil) and land availability. In this study, we developed global maps of soil carbon change that reveal carbon gains and losses with forestation, primarily in the topsoil. Constraining land availability to avoid unintended albedo-induced warming and safeguard water and biodiversity (389 million hectares available for forestation globally) would sequester 39.9 petagrams of carbon by 2050, substantially below previous estimates. This estimate drops to 12.5 petagrams of carbon with land further limited to existing policy commitments (120 million hectares). Achieving greater mitigation requires expanding dedicated forestation areas and strengthening commitments from nations with considerable but untapped potential.
DOI: adj6841
Source: https://www.science.org/doi/10.1126/science.adj6841