Jones Jason P H, Baker Justin S, Austin Kemen, Latta Greg, Wade Christopher M, Cai Yongxia, Aramayo-Lipa Lindsay, Beach Robert, Ohrel Sara B, Ragnauth Shaun, Creason Jared, Cole Jeff
RTI International, 3040 Cornwallis Rd., Durham, NC 27709, USA.
University of Idaho, 875 Perimeter Dr. MS 1139, Moscow, ID 83844, USA.
J For Econ. 2019;34(3-4):205-231. doi: 10.1561/112.00000449.
In recent decades, the carbon sink provided by the U.S. forest sector has offset a sizable portion of domestic greenhouse gas (GHG) emissions. In the future, the magnitude of this sink has important implications not only for projected U.S. net GHG emissions under a reference case but also for the cost of achieving a given mitigation target. The larger the contribution of the forest sector towards reducing net GHG emissions, the less mitigation is needed from other sectors. Conversely, if the forest sector begins to contribute a smaller sink, or even becomes a net source, mitigation requirements from other sectors may need to become more stringent and costlier to achieve economy wide emissions targets. There is acknowledged uncertainty in estimates of the carbon sink provided by the U.S. forest sector, attributable to large ranges in the projections of, among other things, future economic conditions, population growth, policy implementation, and technological advancement. We examined these drivers in the context of an economic model of the agricultural and forestry sectors, to demonstrate the importance of cross-sector interactions on projections of emissions and carbon sequestration. Using this model, we compared detailed scenarios that differ in their assumptions of demand for agriculture and forestry products, trade, rates of (sub)urbanization, and limits on timber harvest on protected lands. We found that a scenario assuming higher demand and more trade for forest products resulted in increased forest growth and larger net GHG sequestration, while a scenario featuring higher agricultural demand, ceteris paribus led to forest land conversion and increased anthropogenic emissions. Importantly, when high demand scenarios are implemented conjunctively, agricultural sector emissions under a high income-growth world with increased livestock-product demand are fully displaced by substantial GHG sequestration from the forest sector with increased forest product demand. This finding highlights the potential limitations of single-sector modeling approaches that ignore important interaction effects between sectors.
近几十年来，美国林业部门提供的碳汇抵消了国内相当一部分温室气体排放。未来，这一碳汇的规模不仅对参考情景下美国预计的温室气体净排放量具有重要影响，而且对实现既定减排目标的成本也有重要意义。林业部门对减少温室气体净排放的贡献越大，其他部门所需的减排量就越少。相反，如果林业部门开始提供较小的碳汇，甚至成为净排放源，那么其他部门实现全经济范围排放目标的减排要求可能会变得更加严格且成本更高。美国林业部门提供的碳汇估计存在公认的不确定性，这归因于对未来经济状况、人口增长、政策实施和技术进步等方面预测的大范围波动。我们在农业和林业部门的经济模型背景下研究了这些驱动因素，以证明跨部门相互作用对排放和碳固存预测的重要性。使用该模型，我们比较了在农产品和林产品需求假设、贸易、（半）城市化率以及受保护土地木材采伐限制等方面存在差异的详细情景。我们发现，假设林产品需求更高且贸易更多的情景会导致森林生长增加和更大的温室气体净固存，而在其他条件相同的情况下，以农业需求更高为特征的情景会导致林地转变和人为排放增加。重要的是，当同时实施高需求情景时，在高收入增长且畜产品需求增加的世界中，农业部门的排放会被森林部门因林产品需求增加而大量增加的温室气体固存完全抵消。这一发现凸显了忽视部门间重要相互作用影响的单部门建模方法的潜在局限性。
