The credibility and effectiveness of country climate targets under the Paris Agreement requires that, in all greenhouse gas (GHG) sectors, the accounted mitigation outcomes reflect genuine deviations from the type and magnitude of activities generating emissions in the base year or baseline. This is challenging for the forestry sector, as the future net emissions can change irrespective of actual management activities, because of age-related stand dynamics resulting from past management and natural disturbances. The solution implemented under the Kyoto Protocol (2013–2020) was accounting mitigation as deviation from a projected (forward-looking) “forest reference level”, which considered the age-related dynamics but also allowed including the assumed future implementation of approved policies. This caused controversies, as unverifiable counterfactual scenarios with inflated future harvest could lead to credits where no change in management has actually occurred, or conversely, failing to reflect in the accounts a policy-driven increase in net emissions. Instead, here we describe an approach to set reference levels based on the projected continuation of documented historical forest management practice, i.e. reflecting age-related dynamics but not the future impact of policies. We illustrate a possible method to implement this approach at the level of the European Union (EU) using the Carbon Budget Model. Using EU country data, we show that forest sinks between 2013 and 2016 were greater than that assumed in the 2013–2020 EU reference level under the Kyoto Protocol, which would lead to credits of 110–120 Mt CO2/year (capped at 70–80 Mt CO2/year, equivalent to 1.3% of 1990 EU total emissions). By modelling the continuation of management practice documented historically (2000–2009), we show that these credits are mostly due to the inclusion in the reference levels of policy-assumed harvest increases that never materialized. With our proposed approach, harvest is expected to increase (12% in 2030 at EU-level, relative to 2000–2009), but more slowly than in current forest reference levels, and only because of age-related dynamics, i.e. increased growing stocks in maturing forests. Our science-based approach, compatible with the EU post-2020 climate legislation, helps to ensure that only genuine deviations from the continuation of historically documented forest management practices are accounted toward climate targets, therefore enhancing the consistency and comparability across GHG sectors. It provides flexibility for countries to increase harvest in future reference levels when justified by age-related dynamics. It offers a policy-neutral solution to the polarized debate on forest accounting (especially on bioenergy) and supports the credibility of forest sector mitigation under the Paris Agreement.

中文翻译：

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基于科学的方法对管理森林的缓解进行可靠的核算。


《巴黎协定》规定的国家气候目标的可信度和有效性要求，在所有温室气体 (GHG) 部门中，核算的缓解成果必须反映与基准年或基线中产生排放的活动类型和规模的真实偏差。这对林业部门来说是一个挑战，因为无论实际管理活动如何，未来的净排放量都可能发生变化，因为过去的管理和自然干扰造成了与年龄相关的林分动态。根据《京都议定书》（2013-2020）实施的解决方案是将缓解措施视为与预计（前瞻性）“森林参考水平”的偏差，该水平考虑了与年龄相关的动态，但也允许包括假设的未来实施已批准政策的情况。这引起了争议，因为未来收成膨胀的无法验证的反事实情景可能会导致管理实际上没有发生变化的信贷，或者相反，无法在账户中反映政策驱动的净排放量的增加。相反，我们在这里描述了一种根据记录的历史森林管理实践的预计延续性设定参考水平的方法，即反映与年龄相关的动态，但不反映政策的未来影响。我们展示了使用碳预算模型在欧盟 (EU) 层面实施此方法的可能方法。使用欧盟国家数据，我们显示 2013 年至 2016 年期间的森林汇大于《京都议定书》下 2013 年至 2020 年欧盟参考水平的假设，这将导致每年 110-120 公吨二氧化碳的信用额度（上限为 70-每年 80 公吨二氧化碳，相当于 1990 年欧盟总排放量的 1.3%）。 通过对历史（2000-2009）记录的管理实践的延续进行建模，我们表明，这些信用主要是由于纳入了从未实现的政策假设的收成增加的参考水平。根据我们提出的方法，预计收获量将增加（2030 年欧盟水平相对于 2000-2009 年增加 12%），但速度比当前森林参考水平慢，并且只是因为年龄相关的动态，即生长蓄积增加在成熟的森林中。我们基于科学的方法与欧盟 2020 年后气候立法兼容，有助于确保只有真正偏离历史记录的森林管理实践的情况才会被纳入气候目标中，从而提高温室气体部门之间的一致性和可比性。当与年龄相关的动态证明合理时，它为各国提供了在未来参考水平上增加收成的灵活性。它为有关森林核算（特别是生物能源）的两极分化辩论提供了政策中立的解决方案，并支持《巴黎协定》下森林部门减排的可信度。