Unexpectedly large impact of forest management and grazing on global vegetation biomass

Carbon stocks (碳储量) in vegetation (植物) have a key role in the climate system (气候系统). However, the magnitude (量级), patterns and uncertainties (不确定) of carbon stocks and the effect of land use (土地利用) on the stocks remain poorly quantified. Here we show, using state-of-the-art (使用最先进技术的) datasets, that vegetation currently stores around 450 petagrams (十亿吨) of carbon. In the hypothetical (假设的) absence of land use, potential vegetation would store around 916 petagrams of carbon, under current climate conditions. This difference highlights the massive (大量的) effect of land use on biomass stocks. Deforestation (森林砍伐) and other land-cover changes (土地覆盖变化) are responsible for 53–58% of the difference between current and potential biomass stocks. Land management (土地管理) effects (the biomass stock changes induced by land use within the same land cover) contribute 42–47%, but have been underestimated (低估) in the literature (文献). Therefore, avoiding deforestation is necessary but not sufficient for mitigation (缓解) of climate change. Our results imply that trade-offs (权衡) exist between conserving carbon stocks on managed land and raising (增加的) the contribution of biomass to raw material and energy supply for the mitigation of climate change. Efforts to raise biomass stocks are currently verifiable only in temperate forests (温带森林), where their potential is limited. By contrast, large uncertainties hinder (阻碍) verification in the tropical forest (热带森林), where the largest potential is located, pointing to challenges for the upcoming (即将出现的) stocktaking exercises under the Paris agreement (巴黎协议).

植被的碳储量对于气候系统具有非常重要的作用。然而，碳储量的量级、模式和不确定以及土地利用对于碳储量的影响仍然缺乏量化。本文利用目前最新的数据显示目前的植被碳储量约为4500亿吨。在不考虑土地利用的前提下，现今的气候条件能够潜在固碳的量大约在9160亿吨左右。这两者之间的差异说明了土地利用对于生物量存储的影响。森林砍伐和一些其它的土地覆盖变化对于实际和潜在的生物量存储间差异贡献约53–58%。土地管理的影响大约贡献42–47%，而这部分往往在文献中是被低估的。因此，避免森林砍伐对于气候变化的缓解是必要的，但并不是充分的。本文的结果显示管理土地上的碳储量保存与缓解气候变化所增加的原材料和能源供应之间的权衡。生物量存储增加目前仅在温带森林中可核实，但其潜力受限。相反，大的不确定性阻碍了热带森林中生物量存储的核实，最大部分的潜力指向了巴黎协议下即将到来的估量挑战。

通讯：Karl-Heinz Erb (https://www.aau.at/en/social-ecology/team/erb-karlheinz/)

个人简介：1999年，维也纳大学，生态学学士；2003年，维也纳大学，生态学博士；2008年，克拉根福大学，社会生态学授课。

doi: 10.1038/nature25138