Megafauna diversity and functional declines in Europe from the Last Interglacial to the present

<b>Aim:</b> Reconstructing megafauna diversity in a past before anthropogenic impacts is crucial for developing targeted restoration strategies. We estimated the diversity and functional decline of European megafauna in the present compared to the nearest in time climate period analogue to the present but prior to the worldwide diffusion of Homo sapiens.<b>Location: </b>Europe.<b>Time period: </b>Last Interglacial (LIG; ca. 127,000 years ago) to present.<b>Major taxa studied: </b>Wild, large (≥10 kg) terrestrial mammals.<b>Methods: </b>We assessed the distribution of 48 European megafauna species during the LIG using hindcasting modelling and fossil records. Then, we estimated the decline in megafauna community diversity and potential trait-based functional effects from the LIG to the present, accounting for climate differences between the two periods.<b>Results: </b>Species richness and community biomass dropped by 70.8% (± 11.7%) and by 94.5% (± 9.9%). Functional diversity dropped by 80.3% (± 15.3%) for herbivores and by 64.9% (± 29.1%) for carnivores, while trait-informed potential vegetation and meat consumptions dropped by 82.3% (± 13.4%) and 60.5% (± 26.0%). The loss in megafauna diversity and associated ecological processes were high everywhere, but particularly in western Europe for carnivores and in the East European Plain for herbivores. Potential megafauna richness in the two periods were similar if only climate-driven differences were considered.<b>Main conclusions: </b>Severe, size-biased defaunation has degraded megafauna assemblages and megafauna-mediated ecological processes across Europe from the LIG to the present. These patterns cannot be explained by climate differences between the two periods, thus were likely driven by prehistoric Homo sapiens. The results suggest that the structure of wild ecosystems of the present strongly deviates from the evolutionary norm, with decreased functional heterogeneity and decreased fluxes of biogeochemical compounds across the trophic networks, highlighting the importance of ambitious policies of megafauna community restoration to support ecosystems functioning.

**研究目的：** 重建未受人类活动影响之前的史前巨型动物群（megafauna）多样性，对于制定针对性的生态修复策略至关重要。本研究以当前气候时段为参照，对比了与当前气候最接近的末次间冰期（Last Interglacial, LIG；约12.7万年前）——即智人（Homo sapiens）在全球扩散之前的时段——的欧洲巨型动物群多样性与功能衰退情况。
**研究区域：** 欧洲。
**研究时段：** 末次间冰期（约12.7万年前）至今。
**研究类群：** 体重≥10千克的野生陆生哺乳动物。
**研究方法：** 我们通过回溯模拟建模与化石记录，重建了末次间冰期欧洲48种巨型动物群的分布范围；随后估算了从末次间冰期至今的巨型动物群群落多样性下降幅度，以及基于功能性状的潜在生态功能影响，并考量了两个时段间的气候差异。
**研究结果：** 物种丰富度与群落生物量分别下降了70.8%（±11.7%）与94.5%（±9.9%）。植食性动物的功能多样性下降了80.3%（±15.3%），肉食性动物则下降了64.9%（±29.1%）；而以功能性状为基础的潜在植被调控效应与肉食资源供给能力分别下降了82.3%（±13.4%）与60.5%（±26.0%）。巨型动物群多样性及相关生态过程的丧失在全域均较为显著，其中肉食性动物的丧失尤以西欧为重，植食性动物则以东欧平原最为突出。若仅考虑气候驱动的差异，两个时段的潜在巨型动物群丰富度并无显著差异。
**主要结论：** 从末次间冰期至今，欧洲全域的巨型动物群群落及其介导的生态过程均因严重的、体型选择性的动物区系耗竭而发生退化。上述格局无法通过两个时段的气候差异加以解释，因此其驱动因素应为史前智人。本研究结果表明，当前野生生态系统的结构已严重偏离演化基准，表现为功能异质性下降以及营养网络内生物地球化学物质通量降低，这凸显了推行高标准的巨型动物群群落修复政策以支撑生态系统功能运转的重要性。