Grassi Giacomo, Pilli Roberto, House Jo, Federici Sandro, Kurz Werner A
Giacomo Grassi, European Commission, Joint Research Centre, 21027, Ispra, VA, Italy.
Roberto Pilli, European Commission, Joint Research Centre, 21027, Ispra, VA, Italy.
Carbon Balance Manag. 2018 May 17;13(1):8. doi: 10.1186/s13021-018-0096-2.
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 CO/year (capped at 70-80 Mt CO/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.
《巴黎协定》下各国气候目标的可信度和有效性要求，在所有温室气体（GHG）部门，核算的减排成果应反映出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。这对林业部门来说具有挑战性，因为由于过去的管理和自然干扰导致的与年龄相关的林分动态变化，未来的净排放量可能会发生变化，而与实际管理活动无关。《京都议定书》（2013 - 2020年）实施的解决方案是将减排核算为与预测的（前瞻性的）“森林参考水平”的偏差，该参考水平考虑了与年龄相关的动态变化，但也允许纳入已批准政策的假定未来实施情况。这引发了争议，因为具有夸大未来采伐量的不可核实的反事实情景可能导致在实际管理没有变化的情况下产生减排量，或者相反，在核算中未能反映政策驱动的净排放量增加。相反，在这里我们描述了一种基于记录的历史森林管理实践的预测延续来设定参考水平的方法，即反映与年龄相关的动态变化，但不考虑政策的未来影响。我们使用碳预算模型说明了在欧盟层面实施这种方法的一种可能方式。
利用欧盟国家数据，我们表明2013年至2016年期间的森林碳汇大于《京都议定书》下2013 - 2020年欧盟参考水平中假定的碳汇，这将导致每年110 - 120百万吨二氧化碳的减排量（上限为每年70 - 80百万吨二氧化碳，相当于1990年欧盟总排放量的1.3%）。通过对历史记录的管理实践（2000 - 2009年）的延续进行建模，我们表明这些减排量主要是由于参考水平中纳入了从未实现的政策假定的采伐量增加。采用我们提出的方法，预计采伐量将会增加（在欧盟层面，相对于2000 - 2009年，2030年增加12%），但增长速度比当前森林参考水平慢，且仅是由于与年龄相关的动态变化所致，即成熟森林中生长量的增加。
我们基于科学的方法与欧盟2020年后气候立法兼容，有助于确保只有与历史记录的森林管理实践延续的真实偏差才被计入气候目标，从而提高了温室气体各部门之间的一致性和可比性。当因与年龄相关的动态变化而合理时，它为各国在未来参考水平中增加采伐量提供了灵活性。它为关于森林核算（特别是生物能源方面）的两极分化辩论提供了一个政策中立的解决方案，并支持了《巴黎协定》下林业部门减排的可信度。
