PNAS:巨动物群与生态系统功能

英国牛津大学环境变化研究所《巨动物群与生态系统功能：从更新世到人类世特刊》的一系列论文说，大型哺乳动物在塑造环境方面起到了一个重要作用，但是它们容易受到可能导致灭绝的环境变化和人类压力的伤害，重新引入巨动物群的举措可能受到对巨动物群和它们的环境的相互作用的理解不充分的妨碍。这些论文探索了巨动物群如何可能影响它们的环境，以及这些环境如何随着地球大型动物始于更新世末期一直持续到今天的逐渐衰退而发生变化。巨动物群可能影响了全球甲烷浓度和地表反照率，通过影响树木和草的覆盖以及火的发生率从而塑造生态系统的结构，而且在营养物质的循环与输送方面起到了一个关键作用。一项研究探索了在超过13,000年前的北美巨动物群物种衰退的开始和人类在美洲开始定居之间的联系。另一项研究提出，人类狩猎可能间接地导致了大海牛的灭绝，这是由于对海獭的过度狩猎可能改变了这种海牛的大型褐藻栖息地，剥夺了这种海牛的一个食物来源。而另一项研究发现，与过去的观念形成对比的是，巨动物群的的种群可能一直被狩猎幼年动物的捕食所限制。重新引入巨动物群从而恢复营养相互作用和生态系统服务的举措可能受到对巨动物群的有限理解的妨碍，几乎没有对重新野化举措中的这类因素进行实验研究。对过去的巨动物群的流失的环境影响的研究，诸如晚更新世灭绝期间的环境影响，可能揭示出关键物种在它们各自的生态系统中的作用，以及如果现有的巨动物群灭绝，生态系统如何可能受到影响。这些论文证明了巨动物群灭绝的某些影响如何可能持续数千年，而且可能塑造现代世界的生态和功能运作。

原文链接：

science for a wilder Anthropocene: Synthesis and future directions for trophic rewilding research

原文摘要：

Trophic rewilding is an ecological restoration strategy that uses species introductions to restore top-down trophic interactions and associated trophic cASCades to promote self-regulating biodiverse ecosystems. Given the importance of large animals in trophic cascades and their widespread losses and resulting trophic downgrading, it often focuses on restoring functional megafaunas. Trophic rewilding is increasingly being implemented for conservation, but remains controversial. Here, we provide a synthesis of its current scientific basis, highlighting trophic cascades as the key conceptual framework, discussing the main lessons learned from ongoing rewilding projects, systematically reviewing the current literature, and highlighting unintentional rewilding and spontaneous wildlife comebacks as underused sources of information. Together, these lines of evidence show that trophic cascades may be restored via species reintroductions and ecological replacements. It is clear, however, that megafauna effects may be affected by poorly understood trophic complexity effects and interactions with landscape settings, human activities, and other factors. Unfortunately, empirical research on trophic rewilding is still rare, fragmented, and geographically biased, with the literature dominated by essays and opinion pieces. We highlight the need for applied programs to include hypothesis testing and science-based monitoring, and outline priorities for future research, notably assessing the role of trophic complexity, interplay with landscape settings, land use, and climate change, as well as developing the global scope for rewilding and tools to optimize benefits and reduce human–wildlife conflicts. Finally, we recommend developing a decision framework for species selection, building on functional and phylogenetic information and with attention to the potential contribution from synthetic biology.

doi: 10.1073/PNAS.1502556112

作者：Jens-Christian Svenn