Climate and humans set the place and time of Proboscidean extinction in late Quaternary of South America

Abstract

The late Quaternary extinctions have been widely debated for a long time, but the varying magnitude of human vs. climate change impacts across time and space is still an unresolved question. Here we assess the geographic range shifts in response to climate change based on Ecological Niche Models (ENMs) and modeled the timing for extinction under human hunting scenario, and both variables were used to explain the extinction dynamics of Proboscideans during a full interglacial/glacial cycle (from 126 ka to 6 ka) in South America. We found a large contraction in the geographic range size of two Proboscidean species studied (Cuvieronius hyodon and Notiomastodon platensis) across time. The largest contractions of their geographical ranges occurred in the northern part of South America, where we previously reported no evidence of coexistence among earliest humans and non-sloth megafauna, including Proboscideans. Our results herein support a strong effect of climatic changes on geographical range dynamics of Proboscideans throughout late Quaternary, although this does not fully support climate change as the single cause of their extinctions. We show that both Proboscideans were narrowly distributed on scattered patches of suitable habitats (i.e., refugia) around 11 ka, period in which the earliest humans potentially arrived in South America, increasing the population density thereafter. Under this overall unsuitable climatic condition at 11 ka, both Proboscideans would be extinct after around 550 years of human hunting, but if climatic conditions were suitable like in Last Glacial Maximum (LGM), the time-for-extinction would be at least 3 times longer under the same human hunting pressures. Thus, our findings support the "Broken Zig-Zag" model and show that South American Proboscideans might have been completely extinct due to human impacts during periods of climate crisis. We conclude, in agreement with an increasing body of evidence in the recent literature, that the late Quaternary megafaunal extinction event was the result of additive effects from different stressors, and that the relative magnitude of these impacts vary across space and time. Indeed, climate changes set the place where the Proboscideans were extinct in South America, whereas the humans set the time of these extinctions.

Differential effects of temperature change and human impact on European Late Quaternary mammalian extinctions

“…However, in spite of their predicted expansion, those species disappeared from Europe. Thus, our results indicate that not all the mammal extinctions in Europe can be directly linked to past global climatic changes (Varela et al ., ; Lima‐Ribeiro et al ., ).…”

“…These studies suggest that both global climate change and human impact played key roles in observed species extinctions. Climate warming could have led to the shrinkage of species' geographic ranges, and humans may have impacted the remaining, reduced populations (Nogues‐Bravo et al ., ; Lima‐Ribeiro et al ., ).…”

EcoClimate: a database of climate data from multiple models for past, present, and future for macroecologists and biogeographers

“…This suite of methods and ideas has been applied to diverse research purposes: guiding discovery of populations of known (Bourg et al, 2005;Guisan et al, 2006) and unknown (Raxworthy et al, 2003) species; understanding distributional dynamics under past (Banks et al, 2008a;2008b) and future (Dormann, 2007;Anderson, 2013) climates; anticipating climate change impacts on agricultural (Fraga et al, 2013) and natural (Nabout et al, 2011) extraction; mapping invasion risk (Peterson, 2003;Jiménez-Valverde et al, 2011), pest distributions (Venette et al, 2010;Estay et al, 2014), and disease trasmission (Peterson, 2014); estimating population parameters (Tôrres et al, 2012;Lima-Ribeiro and DinizFilho, 2013;Thuiller et al, 2014), species richness (Wisz and Rahbeck, 2007;LimaRibeiro et al, 2013b), and community composition (Pellissier et al, 2012); analyzing biotic interactions (Anderson et al, 2002;Wheeler et al, 2015); illuminating patterns and processes of diversification and speciation (Silva et al, 2014); characterizing dispersal (Génard and Lescourret, 2013;Saltré et al, 2015); highlighting extinction (Nogués-Bravo et al, 2008;Lima-Ribeiro et al, 2013a); testing niche conservatism (Martínez-Meyer et al, 2004;Peterson and Nyári, 2007;Jakob et al, 2010) and phylogeographic hypotheses (Collevatti et al, 2013b;Alvarado-Serrano and Knowles, 2014); establishing historical refugia (Waltari et al, 2007;…”

Agricultural intensification during the Late Holocene rather than climatic aridification drives the population dynamics and the current conservation status ofMicrotus cabrerae, an endangered Mediterranean rodent

“…Climate and anthropogenic pressures are important drivers that shape biodiversity patterns and species distributions (Lorenzen et al., ) and so are potential threat factors (Lima‐Ribeiro, Nogués‐Bravo, Terribile, Batra, & Diniz‐Filho, ), contributing to the current conservation status of threatened species. However, their implications for conservation are quite different: although anthropogenic threats can be counterbalanced by laws or conservation measures, mitigation of climatic threats is a far more complex process, limited to intensive and economically expensive actions with unpredictable outcomes (e.g.…”

“…ex situ conservation, risky translocations to theoretically suitable future areas; Cunningham, ; Dawson, Jackson, House, Prentice, & Mace, ; Weeks et al., ). Furthermore, the effects of anthropogenic and climatic drivers can be easily confounded, thereby hindering the assessment of their relative roles in taxon current conservation status, especially when analysing only current data that implies, at best, 50–60 years of continued surveillance of species occurrences (Bradshaw & Lindbladh, ; Li et al., ; Lima‐Ribeiro et al., ). Hence, it is crucial that the potential and current conservation status of threatened species are correctly assessed to facilitate the design and implementation of effective conservation and management plans, and to focus efforts on the most serious threat factors (Bolten et al., ).…”