Department of Ecology & Evolutionary Biology, Princeton University, Princeton, New Jersey 08544, USA.
Nature. 2018 Jan 18;553(7688):328-332. doi: 10.1038/nature25194. Epub 2018 Jan 10.
Large-mammal populations are ecological linchpins, and their worldwide decline and extinction disrupts many ecosystem functions and services. Reversal of this trend will require an understanding of the determinants of population decline, to enable more accurate predictions of when and where collapses will occur and to guide the development of effective conservation and restoration policies. Many correlates of large-mammal declines are known, including low reproductive rates, overhunting, and habitat destruction. However, persistent uncertainty about the effects of one widespread factor-armed conflict-complicates conservation-planning and priority-setting efforts. Case studies have revealed that conflict can have either positive or negative local impacts on wildlife, but the direction and magnitude of its net effect over large spatiotemporal scales have not previously been quantified. Here we show that conflict frequency predicts the occurrence and severity of population declines among wild large herbivores in African protected areas from 1946 to 2010. Conflict was extensive during this period, occurring in 71% of protected areas, and conflict frequency was the single most important predictor of wildlife population trends among the variables that we analysed. Population trajectories were stable in peacetime, fell significantly below replacement with only slight increases in conflict frequency (one conflict-year per two-to-five decades), and were almost invariably negative in high-conflict sites, both in the full 65-year dataset and in an analysis restricted to recent decades (1989-2010). Yet total population collapse was infrequent, indicating that war-torn faunas can often recover. Human population density was also correlated (positively) with wildlife population trajectories in recent years; however, we found no significant effect, in either timespan, of species body mass, protected-area size, conflict intensity (human fatalities), drought frequency, presence of extractable mineral resources, or various metrics of development and governance. Our results suggest that sustained conservation activity in conflict zones-and rapid interventions following ceasefires-may help to save many at-risk populations and species.
大型哺乳动物是生态系统的关键物种，其数量在全球范围内的减少和灭绝会破坏许多生态系统功能和服务。扭转这一趋势需要了解种群减少的决定因素，以便更准确地预测何时何地会发生崩溃，并指导制定有效的保护和恢复政策。许多大型哺乳动物减少的相关因素是已知的，包括低繁殖率、过度捕猎和栖息地破坏。然而，人们对一个普遍因素——武装冲突——的影响仍存在持续的不确定性，这使得保护规划和优先事项的确定变得复杂。案例研究表明，冲突对野生动物可能产生积极或消极的局部影响，但在大时空尺度上其净效应的方向和程度以前尚未量化。在这里，我们表明，冲突频率可以预测非洲保护区内野生大型食草动物在 1946 年至 2010 年期间的种群减少的发生和严重程度。在这段时间里，冲突非常广泛，发生在 71%的保护区内，在我们分析的变量中，冲突频率是野生动物种群趋势的唯一最重要的预测因子。在和平时期，种群轨迹是稳定的，仅在冲突频率略有增加的情况下（每两个到五个十年发生一次冲突年），就会明显低于替代水平，而在高冲突地区，无论是在完整的 65 年数据集还是在仅分析最近几十年（1989-2010 年）的分析中，种群轨迹几乎总是负面的。然而，总种群崩溃并不常见，这表明饱受战争蹂躏的动物群通常可以恢复。人类人口密度也与近年来野生动物种群轨迹呈正相关；然而，我们发现，在两个时间段内，物种体重、保护区面积、冲突强度（人类死亡）、干旱频率、可提取矿产资源的存在以及发展和治理的各种指标都没有对野生动物种群产生显著影响。我们的研究结果表明，在冲突地区持续开展保护活动，并在停火后迅速干预，可能有助于拯救许多处于危险中的种群和物种。
