Environmental Research Centre, Duke Kunshan University, Kunshan, Jiangsu, China.
Nicholas School of Environment, Duke University, Durham, NC, USA.
Glob Chang Biol. 2021 Oct;27(19):4745-4757. doi: 10.1111/gcb.15781. Epub 2021 Jul 28.
Habitat degradation and land-use change driven by the livestock sector are among the major causes of global biodiversity loss. Forests are crucial in maintaining biodiversity and mitigating climate change. Apart from continuing deforestation, forests also face increasing pressure from livestock grazing in the system, which is less understood compared to grasslands. Through a meta-analysis of 156 articles with 1936 data entries, this study assesses the effect of livestock on forest biodiversity, structure, and functions, varying with livestock types, livestock density, grazing history, and climatic factors. Our results show that livestock overall had a negative impact on the forest structure and functions, reduced species abundance but increased richness. Medium and large mammals, plant communities, and soil were more negatively affected compared to other groups such as birds and invertebrates. Livestock also influenced the role of forests in mitigating climate change. They changed forest carbon stock by reducing plant biomass; however, they did not significantly impact the soil carbon stock or soil greenhouse gas emissions. Ecosystem attributes were more affected in warmer and drier regions and by single species grazing than the mixed grazing. Past livestock grazing history moderates the impacts of livestock, with the strongest negative effect occurred with a history of 1-5 years. Nonetheless, livestock activities also had a positive impact on forest management, such as reducing forest flammability. Our results also indicate the lack of studies on how higher trophic levels respond to livestock disturbances and how grazing intensity moderates the effect, which includes grazing duration and livestock density. The complex responses of forests to livestock in different conditions call for more adaptive management depending on the conservation targets and evolution history.
畜牧业导致的生境退化和土地利用变化是全球生物多样性丧失的主要原因之一。森林对于维持生物多样性和减缓气候变化至关重要。除了持续的森林砍伐外，森林还面临着来自牲畜放牧的日益增加的压力，与草原相比，人们对牲畜放牧对森林生物多样性、结构和功能的影响了解较少。本研究通过对 156 篇文章的荟萃分析，共涉及 1936 个数据条目，评估了牲畜对森林生物多样性、结构和功能的影响，其影响随牲畜类型、牲畜密度、放牧历史和气候因素而变化。研究结果表明，牲畜总体上对森林结构和功能产生了负面影响，减少了物种丰度但增加了物种丰富度。与鸟类和无脊椎动物等其他群体相比，大中型哺乳动物、植物群落和土壤受到的影响更大。牲畜还影响了森林在减缓气候变化方面的作用。它们通过减少植物生物量来改变森林碳储量；然而，它们对土壤碳储量或土壤温室气体排放没有显著影响。在温暖和干燥的地区以及单一物种放牧比混合放牧的情况下，生态系统属性受到的影响更大。过去的牲畜放牧历史会调节牲畜的影响，历史在 1-5 年之间时，负面影响最大。尽管如此，牲畜活动也对森林管理产生了积极影响，例如降低森林可燃性。研究结果还表明，缺乏关于更高营养级如何对牲畜干扰做出反应以及放牧强度如何调节这种反应（包括放牧持续时间和牲畜密度）的研究。森林对不同条件下牲畜的复杂反应需要根据保护目标和进化历史进行更具适应性的管理。
