Intentional and unintentional changes to avian and mammalian diversities in the U.K.

Rewilding is emerging as a promising restoration strategy to tackle challenges of global change and maintain the persistence of natural ecosystems and their biodiversity. However, it has also been criticised for lacking a consistent definition and insufficient knowledge about its possible outcomes. Here, we explored the effects of rewilding on filling functional gaps created by native species extirpation. We contrasted rewilding with three other mechanisms for change in community composition – species introduction, unassisted colonisation, and extirpation – with regard to their impacts on avian and mammalian diversity changes in the UK. We show that: (i) while rewilding increases functional diversity most on average, introduced/naturalised birds contribute more functional uniqueness to native functional space than other groups of birds; and (ii) functional diversity change caused by ‘rewilded’ species was species-dependent and idiosyncratic. Our results suggest that although rewilding can expand or infill native functional trait space to some extent, such effects of specific programmes may need careful assessment.

再野化（Rewilding）正逐渐成为应对全球变化挑战、维持自然生态系统及其生物多样性存续的极具前景的修复策略。然而，该策略也因缺乏统一界定，且对其潜在后果的认知不足而饱受诟病。本研究探究了再野化对填补本土物种局部灭绝所造成的功能空缺的效应。我们针对英国鸟类与哺乳动物多样性变化的影响，将再野化与群落组成变化的另外三种机制——物种引入、无辅助定植、局部灭绝——进行了对比分析。研究结果显示：其一，尽管再野化在整体上平均提升功能多样性的效果最为显著，但与其他鸟类类群相比，引入/归化鸟类可为本土功能空间贡献更多的功能独特性；其二，由“再野化物种”所引发的功能多样性变化具有物种依赖性与个体特异性。本研究结果表明，尽管再野化可在一定程度上拓展或填补本土功能性状空间，但特定再野化项目的此类效应仍需开展审慎评估。