Large-Scale Quantification and Correlates of Ungulate Carrion Production in the Anthropocene

Carrion production is one of the most crucial yet neglected and understudied processes in food webs and ecosystems. In this study, we performed a large-scale estimation of the maximum potential production and spatial distribution of ungulate carrion biomass from five major sources in peninsular Spain, both anthropogenic (livestock, big game hunting, roadkills) and natural (predation, natural mortality). Using standardized ungulate carrion biomass (kg/year/100km2) estimates, we evaluated the relationship between ungulate carrion production and two ecosystem-level factors: global human modification (GHM) and primary productivity (NDVI). We found that anthropogenic carrion sources supplied about 60 times more ungulate carrion biomass than natural sources (mean = 90,172 vs. 1533 kg/year/100km2, respectively). Within anthropogenic carrion sources, livestock was by far the major carrion provider (91.1% of the annual production), followed by big game hunting (7.86%) and roadkills (0.05%). Within natural carrion sources, predation of ungulates provided more carrion (0.81%) than natural mortality (0.13%). Likewise, we found that the spatial distribution of carrion differed among carrion sources, with anthropogenic carrion being more aggregated in space than natural carrion. Our models showed that GHM was positively related to carrion production from livestock and roadkills, and that wild ungulate carrion supplied by natural sources and big game hunting was more frequently generated in more productive areas (higher NDVI). These findings indicate a disconnection between the main ungulate carrion source (livestock) and primary productivity. Ongoing socio-economic changes in developed countries (for example increase of intensive livestock husbandry and rewilding processes) could lead to additional alteration of carrion production processes, with potential negative impacts at the community and ecosystem levels. Overall, we highlight that carrion biomass quantification should be considered a crucial tool in evaluating ecosystem health and delineating efficient ecosystem management guidelines in the Anthropocene. JM was supported by a Basque Government predoctoral grant (PRE_2018_2_0112), ACA by a contract Juan de la Cierva Incorporación (IJCI-2014-20744; Spanish Ministry of Economy and Competitiveness, Spain) and a Post Doc contract Programa Viçent Mut of Govern Balear (PD/039/2017, Spain), MM by a Ramón y Cajal research contract from the MINECO (RYC-2015-19231), ZMR and LNA by contracts cofounded by the Generalitat Valenciana and the European Social Fund (APOSTD/2019/016 and ACIF/2019/056, respectively), and by a Ramón y Cajal research contract from the MINECO (RYC-2019-027216-I) and by the Generalitat Valenciana (SEJI/2018/024). This study was partially funded by the Spanish Ministry of Economy, Industry and Competitiveness and EU ERDF funds through the projects RTI2018-099609-B-C21, CIAGRO-UMH, and CGL2017-89905-R.