碳税政策对农业土地利用变化及其碳排放的影响

农业生态系统具有碳源和碳汇的双重特征,其在减缓气候变化中的重要性已得到国际社会的广泛认可。相较于技术手段的创新,碳税、补贴等经济手段被认为是较为简单、可行、易出台的碳排放减缓政策。采用气候变化综合评估模型-GOPer-GC模型,构建国际碳税情景,模拟分析了2008年至2050年碳税政策的实施对全球各区域农业土地覆被及土地利用变化碳排放的影响。模拟结果表明,情景2和情景3中全球农业土地利用变化累计碳排放分别达到49.6 GtC和23.1 GtC,明显低于基准情景的累计排放量51.9 GtC。这说明,实施碳税政策后,相较于将碳税收入用作一般性财政收入,将碳税收入补贴至农业部门在一定程度上减缓农业碳排放。此外,林业部门获取更多的碳税补贴时,多数区域农业土地利用变化碳排放规模大幅减少,主因是耕地变为林地、草地变为林地面积的增加。情景3中,中国的碳汇量较其他情景显著增加,主要来自耕地变为林地、草地变为林地,累计碳汇量分别达到1.7和3.7 GtC。因此,对于中国、美国、印度等大部分区域来说,碳税收入更多地补贴至林业部门有利于在整体上减缓农业碳排放,而欧盟、日本、东亚、马来西亚、印度尼西亚、俄罗斯、东欧地区,碳税收入平均补贴至种植业、畜牧业和林业反而具有相对更好的减排效果。

Effect of carbon tax policy on agricultural land use change and its carbon emission

Agricultural ecosystems can act not only as a carbon source, but also as a carbon sink. Its importance in mitigating carbon emission has been widely recognized by the international community.Compared with advanced technologies, carbon tax, subsidies, and other economic measures are considered to be relatively simple and feasible to govern climate change. Based on integrated assessment model GOPer-GC (Governance and development policy simulator on global climate model), we constructed international carbon tax scenarios and simulated their effects on agricultural land cover and its carbon emissions from 2008 to 2050. The simulation results showed that cumulative carbon emission due to global agricultural land use change in scenarios 2 and 3 was 49.6 and 23.1 GtC, respectively, which were significantly lower than that in the baseline scenario. This indicated that instead of carbon tax income as a general revenue, carbon tax income as a subsidy for the agricultural sector can reduce carbon emissions of the agricultural land use change. Additionally, the subsidy policy, considering that the forestry sector gets more carbon tax income than farming and animal husbandry sector, significantly reduces carbon emission due to land use change, mainly due to the increase in the conversion of crop land and grassland to woodland. China''s carbon sinks, contributed from the conversion of crop land and grassland to woodland, increased obviously in scenario 3. In this scenario, converting cropland and grassland to woodland in China contributed 1.7 GtC and 3.7 GtC of carbon sink respectively. Therefore, for most regions, such as China, the United States and India, increasing the subsidy of the forestry sector will be an effective way to mitigate agricultural carbon emission due to land use change. In the EU, Japan, East Asia, Malaysia, Indonesia, Russia, and Eastern Europe, the same subsidy in crops, livestock, and forestry resulted in a relatively obvious reduction in emission.