Risks to mitigation potential of forests Much recent attention has focused on the potential of trees and forests to mitigate ongoing climate change by acting as sinks for carbon. Anderegg et al. review the growing evidence that forests' climate mitigation potential is increasingly at risk from a range of adversities that limit forest growth and health. These include physical factors such as drought and fire and biotic factors, including the depredations of insect herbivores and fungal pathogens. Full assessment and quantification of these risks, which themselves are influenced by climate, is key to achieving science-based policy outcomes for effective land and forest management. Science, this issue p. eaaz7005 BACKGROUND Forests have considerable potential to help mitigate human-caused climate change and provide society with a broad range of cobenefits. Local, national, and international efforts have developed policies and economic incentives to protect and enhance forest carbon sinks—ranging from the Bonn Challenge to restore deforested areas to the development of forest carbon offset projects around the world. However, these policies do not always account for important ecological and climate-related risks and limits to forest stability (i.e., permanence). Widespread climate-induced forest die-off has been observed in forests globally and creates a dangerous carbon cycle feedback, both by releasing large amounts of carbon stored in forest ecosystems to the atmosphere and by reducing the size of the future forest carbon sink. Climate-driven risks may fundamentally compromise forest carbon stocks and sinks in the 21st century. Understanding and quantifying climate-driven risks to forest stability are crucial components needed to forecast the integrity of forest carbon sinks and the extent to which they can contribute toward the Paris Agreement goal to limit warming well below 2°C. Thus, rigorous scientific assessment of the risks and limitations to widespread deployment of forests as natural climate solutions is urgently needed. ADVANCES Many forest-based natural climate solutions do not yet rely on the best available scientific information and ecological tools to assess the risks to forest stability from climate-driven forest dieback caused by fire, drought, biotic agents, and other disturbances. Crucially, many of these permanence risks are projected to increase in the 21st century because of climate change, and thus estimates based on historical data will underestimate the true risks that forests face. Forest climate policy needs to fully account for the permanence risks because they could fundamentally undermine the effectiveness of forest-based climate solutions. Here, we synthesize current scientific understanding of the climate-driven risks to forests and highlight key issues for maximizing the effectiveness of forests as natural climate solutions. We lay out a roadmap for quantifying current and forecasting future risks to forest stability using recent advances in vegetation physiology, disturbance ecology, mechanistic vegetation modeling, large-scale ecological observation networks, and remote sensing. Finally, we review current efforts to use forests as natural climate solutions and discuss how these programs and policies presently consider and could more fully embrace physiological, climatic, and permanence uncertainty about the future of forest carbon stores and the terrestrial carbon sink. OUTLOOK The scientific community agrees that forests can contribute to global efforts to mitigate human-caused climate change. The community also recognizes that using forests as natural climate solutions must not distract from rapid reductions in emissions from fossil fuel combustion. Furthermore, responsibly using forests as natural climate solutions requires rigorous quantification of risks to forest stability, forests’ carbon storage potential, cobenefits for species conservation and ecosystem services, and full climate feedbacks from albedo and other effects. Combining long-term satellite records with forest plot data can provide rigorous, spatially explicit estimates of climate change–driven stresses and disturbances that decrease productivity and increase mortality. Current vegetation models also hold substantial promise to quantify forest risks and inform forest management and policies, which currently rely predominantly on historical data. A more-holistic understanding and quantification of risks to forest stability will help policy-makers effectively use forests as natural climate solutions. Scientific advances have increased our ability to characterize risks associated with a number of biotic and abiotic factors, including risks associated with fire, drought, and biotic agent outbreaks. While the models that are used to predict disturbance risks of these types represent the cutting edge in ecology and Earth system science to date, relatively little infrastructure and few tools have been developed to interface between scientists and foresters, land managers, and policy-makers to ensure that science-based risks and opportunities are fully accounted for in policy and management contexts. To enable effective policy and management decisions, these tools must be openly accessible, transparent, modular, applicable across scales, and usable by a wide range of stakeholders. Strengthening this science-policy link is a critical next step in moving forward with leveraging forests in climate change mitigation efforts. Effective use of forests as natural climate solutions depends on accounting for climate-driven risks, such as fire and drought. Leveraging cutting-edge scientific tools holds great promise for improving and guiding the use of forests as natural climate solutions, both in estimating the potential of carbon storage and in estimating the risks to forest carbon storage. ILLUSTRATION: DAVID MEIKLE Forests have considerable potential to help mitigate human-caused climate change and provide society with many cobenefits. However, climate-driven risks may fundamentally compromise forest carbon sinks in the 21st century. Here, we synthesize the current understanding of climate-driven risks to forest stability from fire, drought, biotic agents, and other disturbances. We review how efforts to use forests as natural climate solutions presently consider and could more fully embrace current scientific knowledge to account for these climate-driven risks. Recent advances in vegetation physiology, disturbance ecology, mechanistic vegetation modeling, large-scale ecological observation networks, and remote sensing are improving current estimates and forecasts of the risks to forest stability. A more holistic understanding and quantification of such risks will help policy-makers and other stakeholders effectively use forests as natural climate solutions.

中文翻译：

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气候驱动的森林气候减缓潜力的风险

森林减缓潜力的风险 最近的很多注意力都集中在树木和森林作为碳汇减缓气候变化的潜力上。安德雷格等人。审查越来越多的证据表明，森林减缓气候变化的潜力越来越受到一系列限制森林生长和健康的逆境的威胁。其中包括干旱和火灾等物理因素和生物因素，包括昆虫食草动物和真菌病原体的掠夺。对这些本身受气候影响的风险进行全面评估和量化，是实现有效土地和森林管理的基于科学的政策成果的关键。科学，这个问题 p。eaaz7005 背景 森林在帮助缓解人为气候变化和为社会提供广泛的协同效益方面具有相当大的潜力。地方、国家和国际努力制定了政策和经济激励措施来保护和增强森林碳汇——从波恩挑战恢复森林砍伐地区到在世界各地发展森林碳抵消项目。然而，这些政策并不总是考虑到重要的生态和气候相关风险以及森林稳定性（即永久性）的限制。在全球森林中已经观察到广泛的气候引起的森林死亡，并通过将森林生态系统中储存的大量碳释放到大气中以及减少未来森林碳汇的规模，造成了危险的碳循环反馈。气候驱动的风险可能会从根本上损害 21 世纪的森林碳储量和汇。了解和量化气候驱动的森林稳定性风险是预测森林碳汇完整性以及它们可以在多大程度上促进巴黎协定将变暖控制在远低于 2°C 的目标所需的关键组成部分。因此，迫切需要对广泛部署森林作为自然气候解决方案的风险和限制进行严格的科学评估。进展 许多以森林为基础的自然气候解决方案尚未依靠现有的最佳科学信息和生态工具来评估由火灾、干旱、生物因子和其他干扰引起的气候驱动的森林枯死对森林稳定性的风险。至关重要的是，由于气候变化，许多这些永久性风险预计将在 21 世纪增加，因此基于历史数据的估计将低估森林面临的真正风险。森林气候政策需要充分考虑永久性风险，因为它们可能从根本上破坏以森林为基础的气候解决方案的有效性。在这里，我们综合了当前对气候驱动的森林风险的科学理解，并强调了最大限度地提高森林作为自然气候解决方案的有效性的关键问题。我们利用植被生理学、干扰生态学、机械植被建模、大规模生态观测网络和遥感方面的最新进展，制定了量化当前和预测未来森林稳定性风险的路线图。最后，我们回顾了当前使用森林作为自然气候解决方案的努力，并讨论了这些计划和政策目前如何考虑并能够更充分地接受关于森林碳储存和陆地碳汇未来的生理、气候和永久性不确定性。展望 科学界一致认为，森林可以为减缓人为气候变化的全球努力做出贡献。社区还认识到，使用森林作为自然气候解决方案绝不能分散对化石燃料燃烧排放的快速减少的注意力。此外，负责任地利用森林作为自然气候解决方案需要严格量化森林稳定性风险、森林碳储存潜力、物种保护和生态系统服务的协同效益，以及来自反照率和其他影响的完整气候反馈。将长期卫星记录与森林地块数据相结合，可以提供对气候变化驱动的压力和干扰的严格、空间明确的估计，这些压力和干扰会降低生产力并增加死亡率。当前的植被模型在量化森林风险和为森林管理和政策提供信息方面也有很大的希望，目前这些模型主要依赖于历史数据。对森林稳定性风险的更全面理解和量化将有助于决策者有效地利用森林作为自然气候解决方案。科学进步提高了我们表征与许多生物和非生物因素相关的风险的能力，包括与火灾、干旱和生物病原体爆发相关的风险。虽然用于预测这些类型的干扰风险的模型代表了迄今为止生态学和地球系统科学的前沿，但相对较少的基础设施和工具已经开发出来，科学家和林务人员、土地管理者和政策制定者之间的接口确保在政策和管理背景下充分考虑基于科学的风险和机遇。为了实现有效的政策和管理决策，这些工具必须是可公开访问的、透明的、模块化的、适用于各种规模的，并且可供广泛的利益相关者使用。加强这种科学与政策的联系是在气候变化减缓工作中利用森林推进的关键下一步。有效利用森林作为自然气候解决方案取决于考虑气候驱动的风险，比如火灾和干旱。利用尖端科学工具在改善和指导森林作为自然气候解决方案的使用方面具有广阔的前景，无论是在估计碳储存的潜力还是在估计森林碳储存的风险方面。插图：DAVID MEIKLE 森林在帮助缓解人为引起的气候变化和为社会提供许多协同效益方面具有相当大的潜力。然而，气候驱动的风险可能会从根本上损害 21 世纪的森林碳汇。在这里，我们综合了当前对气候驱动的火灾、干旱、生物因子和其他干扰对森林稳定性的风险的理解。我们回顾了目前使用森林作为自然气候解决方案的努力如何考虑并可以更充分地采用当前的科学知识来解释这些气候驱动的风险。植被生理学、干扰生态学、机械植被建模、大规模生态观测网络和遥感方面的最新进展正在改进当前对森林稳定性风险的估计和预测。更全面地了解和量化此类风险将有助于政策制定者和其他利益相关者有效地利用森林作为自然气候解决方案。