“狮子、老虎和熊。噢，我的天!”是经典电影《绿野仙踪》中由Dorothy及她的惊恐的同伴所唱的副歌。事实上，多个世纪以来食肉动物一直在人(和牲畜)中引发着深度的恐惧。但是，在一篇回顾性论文中，William Ripple及其同事凸显了这些捕食者——像先前提到过的狮子、老虎和熊等——对全球生态系统具有稳定作用，而且他们说，现在正是保护这些食肉物种的时候。Ripple及其他作者分析了最近的研究，旨在回顾世界上31个最大的哺乳类食肉动物的状态、所受威胁及生态重要性。从各个方面看，他们发现了顶端食肉动物——狮子、豹子、狼、美洲狮、澳洲野狗及其他食肉动物——在保持生态系统平衡方面的例子。据文章的作者披露，通过一系列直接与间接的影响，大型食肉动物帮助增进了生物多样性、缓冲了气候变化并管控了疾病。例如灰狼——它们目前是美国落基山脉及大湖地区大规模猎杀活动的焦点——会发挥若干有益的、级联效应;例如控制食草性猎物的种群数量，其结果是使木本植物繁茂生长并存储更多的碳。文章的作者还发现了由大型食肉动物种群的改变所引起的作物受损、河流结构改变以及在鸟类、哺乳类、两栖类、爬行类及无脊椎动物种群中的各种变化。他们对最近的数据所作的审查显示，食肉动物的作用比研究人员过去所意识到的要复杂得多，而自然资源保护者需要发现能够促使人类与食肉动物和平共处的策略——这是一项有史以来就很难完成的工作。据文章的作者披露，到目前为止，猎人们一直无法取代或复制这些顶级捕食动物在野外的级联、稳定效应，而对食肉动物、被捕食动物及植物相互作用的研究是必要的。由Richard Roberts撰写的相关文章提出，驱使袋獾与塔斯马尼亚虎灭绝的并非澳洲野狗，而是人类及气候的改变。
Large carnivores face serious threats and are experiencing massive declines in their populations and geographic ranges around the world. We highlight how these threats have affected the conservation status and ecological functioning of the 31 largest mammalian carnivores on Earth. Consistent with theory, empirical studies increasingly show that large carnivores have substantial effects on the structure and function of diverse ecosystems. Significant cascading trophic interactions, mediated by their prey or sympatric mesopredators, arise when some of these carnivores are extirpated from or repatriated to ecosystems. Unexpected effects of trophic cascades on various taxa and processes include changes to bird, mammal, invertebrate, and herpetofauna abundance or richness; subsidies to scavengers; altered disease dynamics; carbon sequestration; modified stream morphology; and crop damage. Promoting tolerance and coexistence with large carnivores is a crucial societal challenge that will ultimately determine the fate of Earth’s largest carnivores and all that depends upon them, including humans.
The largest terrestrial species in the order Carnivora are wide-ranging and rare because of their positions at the top of food webs. They are some of the world’s most admired mammals and, ironically, some of the most imperiled. Most have experienced substantial population declines and range contractions throughout the world during the past two centuries. Because of the high metabolic demands that come with endothermy and large body size, these carnivores often require large prey and expansive habitats. These food requirements and wide-ranging behavior often bring them into conflict with humans and livestock. This, in addition to human intolerance, renders them vulnerable to extinction. Large carnivores face enormous threats that have caused massive declines in their populations and geographic ranges, including habitat loss and degradation,persecution, utilization, and depletion of prey. We highlight how these threats can affect theconservation status and ecological roles of this planet’s 31 largest carnivores.
Large-bodied animals play essential roles in ecosystem structuring and stability through both indirect and direct trophic effects. In recent times, humans have disrupted this trophic structure through both habitat destruction and active extirpation of large predators, resulting in large declines in numbers and vast contractions in their geographic ranges. Ripple et al. (10.1126/science.1241484; see the Perspective by Roberts) review the status, threats, and ecological importance of the 31 largest mammalian carnivores globally. These species are responsible for a suite of direct and indirect stabilizing effects in ecosystems. Current levels of decline are likely to result in ecologically ineffective population densities and can lead to ecosystem instability. The preservation of large carnivores can be challenging because of their need for large ranges and their potential for human conflict. However, the authors demonstrate that the preservation of large carnivores is ecologically important and that the need for conservation action is immediate, given the severity of the threats they face.