Strategies for 21st-century environmental management and conservation under global change require a strong understanding of the biological mechanisms that mediate responses to climate- and ...human-driven change to successfully mitigate range contractions, extinctions, and the degradation of ecosystem services. Biodiversity responses to past rapid warming events can be followed in situ and over extended periods, using cross-disciplinary approaches that provide cost-effective and scalable information for species' conservation and the maintenance of resilient ecosystems in many bioregions. Beyond the intrinsic knowledge gain such integrative research will increasingly provide the context, tools, and relevant case studies to assist in mitigating climate-driven biodiversity losses in the 21st century and beyond.
Large-bodied mammals are a rich and diversified faunal group in tropical rainforests. However, knowledge on community size and composition, and on species’ distribution and ecology remains often ...scant and inadequate against their chronic status of threats. We used camera trapping to detect mammals in the forests of the Eastern Arc Mountains (EAM) of Tanzania, a world renowned region for biodiversity comprised by a series of distinct and ancient mountain ranges partially covered in moist montane forest. We conducted surveys from 2003 to 2011 in eight of the 12 mountain blocks in Tanzania, and, through an overall sampling effort of 11,500 camera days, we detected 43 species. We normalized species richness and species’ detection events by effort, and used these metrics to assess the effect of habitat and human disturbance variables. We found that rarefied richness is positively affected by forest area at the block level, and that richness at forest patch level is also affected by forest area as well as surrounding human density (negative effect). For a subset of 17 species, we found consistent patterns of avoidance or tolerance of human disturbance and forest edges, and increased occurrence in areas at higher elevation, matching the historical forest loss that in most mountains occurred at lower elevation. Our study provides ecological insights that are novel for most species and sites, and reveals a general trend of negative impact of human disturbance on both community size and species’ relative abundance. Increased protection of the EAM forests in Tanzania is of urgent importance for the persistence of diversified mammal communities.
Processes leading to range contractions and population declines of Arctic megafauna during the late Pleistocene and early Holocene are uncertain, with intense debate on the roles of human hunting, ...climatic change, and their synergy. Obstacles to a resolution have included an overreliance on correlative rather than process‐explicit approaches for inferring drivers of distributional and demographic change. Here, we disentangle the ecological mechanisms and threats that were integral in the decline and extinction of the muskox (Ovibos moschatus) in Eurasia and in its expansion in North America using process‐explicit macroecological models. The approach integrates modern and fossil occurrence records, ancient DNA, spatiotemporal reconstructions of past climatic change, species‐specific population ecology, and the growth and spread of anatomically modern humans. We show that accurately reconstructing inferences of past demographic changes for muskox over the last 21,000 years require high dispersal abilities, large maximum densities, and a small Allee effect. Analyses of validated process‐explicit projections indicate that climatic change was the primary driver of muskox distribution shifts and demographic changes across its previously extensive (circumpolar) range, with populations responding negatively to rapid warming events. Regional analyses show that the range collapse and extinction of the muskox in Europe (~13,000 years ago) was likely caused by humans operating in synergy with climatic warming. In Canada and Greenland, climatic change and human activities probably combined to drive recent population sizes. The impact of past climatic change on the range and extinction dynamics of muskox during the Pleistocene–Holocene transition signals a vulnerability of this species to future increased warming. By better establishing the ecological processes that shaped the distribution of the muskox through space and time, we show that process‐explicit macroecological models have important applications for the future conservation and management of this iconic species in a warming Arctic.
We reconstructed 21,000 years of climate‐ and human‐driven range dynamics of muskox by integrating modern occurrence records, fossil records, paleoclimate reconstructions, ancient DNA sequences, human expansion models and spatially explicit process‐explicit macroecological models. Models that could reconcile inferences of demographic change from fossils were used to determine the likely chains of causality responsible for the contemporary distribution of muskox. We show that climatic change was a primary driver of the structure and dynamics of the distribution of muskox, with human activities, and their interactions with climatic changes, being important in some regions.
The extinction of the woolly rhinoceros ( Coelodonta antiquitatis ) at the onset of the Holocene remains an enigma, with conflicting evidence regarding its cause and spatiotemporal dynamics. This ...partly reflects challenges in determining demographic responses of late Quaternary megafauna to climatic and anthropogenic causal drivers with available genetic and paleontological techniques. Here, we show that elucidating mechanisms of ancient extinctions can benefit from a detailed understanding of fine-scale metapopulation dynamics, operating over many millennia. Using an abundant fossil record, ancient DNA, and high-resolution simulation models, we untangle the ecological mechanisms and causal drivers that are likely to have been integral in the decline and later extinction of the woolly rhinoceros. Our 52,000-y reconstruction of distribution-wide metapopulation dynamics supports a pathway to extinction that began long before the Holocene, when the combination of cooling temperatures and low but sustained hunting by humans trapped woolly rhinoceroses in suboptimal habitats along the southern edge of their range. Modeling indicates that this ecological trap intensified after the end of the last ice age, preventing colonization of newly formed suitable habitats, weakening stabilizing metapopulation processes, triggering the extinction of the woolly rhinoceros in the early Holocene. Our findings suggest that fragmentation and resultant metapopulation dynamics should be explicitly considered in explanations of late Quaternary megafauna extinctions, sending a clarion call to the fragility of the remaining large-bodied grazers restricted to disjunct fragments of poor-quality habitat due to anthropogenic environmental change.
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