Loss Of Megafauna Research Articles

After the mammoths: The ecological legacy of late Pleistocene megafauna extinctions

Abstract The significant extinctions in Earth history have largely been unpredictable in terms of what species perish and what traits make species susceptible. The extinctions occurring during the late Pleistocene are unusual in this regard, because they were strongly size-selective and targeted exclusively large-bodied animals (i.e., megafauna, >1 ton) and disproportionately, large-bodied herbivores. Because these animals are also at particular risk today, the aftermath of the late Pleistocene extinctions can provide insights into how the loss or decline of contemporary large-bodied animals may influence ecosystems. Here, we review the ecological consequences of the late Pleistocene extinctions on major aspects of the environment, on communities and ecosystems, as well as on the diet, distribution and behavior of surviving mammals. We find the consequences of the loss of megafauna were pervasive and left legacies detectable in all parts of the Earth system. Furthermore, we find that the ecological roles that extinct and modern megafauna play in the Earth system are not replicated by smaller-bodied animals. Our review highlights the important perspectives that paleoecology can provide for modern conservation efforts.

Paleobiology of a large mammal community from the late Pleistocene of Sonora, Mexico

AbstractA paleontological deposit near San Clemente de Térapa represents one of the very few Rancholabrean North American Land Mammal Age sites within Sonora, Mexico. During that time, grasslands were common, and the climate included cooler and drier summers and wetter winters than currently experienced in northern Mexico. Here, we demonstrate restructuring in the mammalian community associated with environmental change over the past 40,000 years at Térapa. The fossil community has a similar number of carnivores and herbivores whereas the modern community consists mostly of carnivores. There was also a 97% decrease in mean body size (from 289 kg to 9 kg) because of the loss of megafauna. We further provide an updated review of ungulates and carnivores, recognizing two distinct morphotypes ofEquus, includingE.scottiand a slighter species; as well asPlatygonus compressus;Camelops hesternus;Canis dirus; andLynx rufus;and the first regional records ofPalaeolama mirifica,Procyon lotor, andSmilodoncf.S.fatalis. The Térapa mammals presented here provide a more comprehensive understanding of the faunal community restructuring that occurred in northern Mexico from the late Pleistocene to present day, indicating further potential biodiversity loss with continued warming and drying of the region.

Past and future potential range changes in one of the last large vertebrates of the Australian continent, the emu Dromaius novaehollandiae

In Australia, significant shifts in species distribution have occurred with the loss of megafauna, changes in indigenous Australian fire regime and land-use changes with European settlement. The emu, one of the last megafaunal species in Australia, has likely undergone substantial distribution changes, particularly near the east coast of Australia where urbanisation is extensive and some populations have declined. We modelled emu distribution across the continental mainland and across the Great Dividing Range region (GDR) of eastern Australia, under historical, present and future climates. We predicted shifts in emu distribution using ensemble modelling, hindcasting and forecasting distribution from current emu occurrence data. Emus have expanded their range northward into central Australia over the 6000 years modelled here. Areas west of the GDR have become more suitable since the mid-Holocene, which was unsuitable then due to high precipitation seasonality. However, the east coast of Australia has become climatically sub-optimal and will remain so for at least 50 years. The north east of NSW encompasses the range of the only listed endangered population, which now occurs at the margins of optimal climatic conditions for emus. Being at the fringe of suitable climatic conditions may put this population at higher risk of further decline from non-climatic anthropogenic disturbances e.g. depredation by introduced foxes and pigs. The limited scientific knowledge about wild emu ecology and biology currently available limits our ability to quantify these risks.

Demographic History and Genomic Response to Environmental Changes in a Rapid Radiation of Wild Rats.

For organisms to survive and prosper in a harsh environment, particularly under rapid climate change, poses tremendous challenges. Recent studies have highlighted the continued loss of megafauna in terrestrial ecosystems and the subsequent surge of small mammals, such as rodents, bats, lagomorphs, and insectivores. However, the ecological partitioning of these animals will likely lead to large variation in their responses to environmental change. In the present study, we investigated the evolutionary history and genetic adaptations of white-bellied rats (Niviventer Marshall, 1976), which are widespread in the natural terrestrial ecosystems in Asia but also known as important zoonotic pathogen vectors and transmitters. The southeastern Qinghai-Tibet Plateau was inferred as the origin center of this genus, with parallel diversification in temperate and tropical niches. Demographic history analyses from mitochondrial and nuclear sequences of Niviventer demonstrated population size increases and range expansion for species in Southeast Asia, and habitat generalists elsewhere. Unexpectedly, population increases were seen in N. eha, which inhabits the highest elevation among Niviventer species. Genome scans of nuclear exons revealed that among the congeneric species, N. eha has the largest number of positively selected genes. Protein functions of these genes are mainly related to olfaction, taste, and tumor suppression. Extensive genetic modification presents a major strategy in response to global changes in these alpine species.

Wildlife differentially affect tree and liana regeneration in a tropical forest: An 18‐year study of experimental terrestrial defaunation versus artificially abundant herbivores

Abstract Hunting and land use change modify native herbivore abundances and cause cascading effects in natural ecosystems. The outcomes for vegetation depend on changes to specific plant–animal interactions, such as seed dispersal or predation, or physical disturbances. We experimentally manipulated terrestrial wildlife populations in a primary lowland forest in Malaysia over an 18‐year period (1996–2014) to understand how artificially high or low animal densities affect tree and liana regeneration. Our study site retains a diverse wildlife community and artificially high densities of native wild pigs (Sus scrofa) that are sustained by crop raiding in distant oil palm plantations. We used fencing that excluded terrestrial animals >1 kg to experimentally simulate conditions similar to those in defaunated forests. These two treatments – abnormally high pig abundances and megafauna loss from hunting – represent common outcomes in disturbed Southeast Asian forests and are characteristic of many forests globally. We focused on trees and lianas because they are the two dominant woody life‐forms in tropical forests and crucial determinants of forest structure and function. We found that liana sapling abundances (30–100 cm height) increased by 86% in unfenced control plots with wildlife but were stable in exclosures. In contrast, tree abundances did not change in unfenced control plots but increased by 83% in exclosures without wildlife. Evidence of scaring on surviving stems suggested that these inverted outcomes were driven by selective use of tree saplings for wild pig nests. Lianas may also have greater tolerance to wildlife disturbances like nest building. By the end of the study, lianas comprised 38% of all saplings in unfenced controls but just 14% in exclosures. Synthesis and applications. We conclude that artificially abundant wildlife, such as crop‐raiding wild pigs, may shift tropical forest understories towards lianas while defaunation may shift it towards trees. These results highlight that ecological cascades from hunting or land use change can alter plant functional types and reshape to long‐term patterns of forest succession and change. Managing unnatural wild boar populations may be required to conserve native plant communities in both their native and exotic ranges.

Trophic rewilding as a climate change mitigation strategy?

The loss of megafauna at the terminal Pleistocene has been linked to a wide range of Earth-system-level changes, such as altered greenhouse gas budgets, fire regimes and biome-level vegetation changes. Given these influences and feedbacks, might part of the solution for mitigating anthropogenic climate change lie in the restoration of extant megafauna to ecosystems? Here, we explore the potential role of trophic rewilding on Earth's climate system. We first provide a novel synthesis of the various ways that megafauna interact with the major drivers of anthropogenic climate change, including greenhouse gas storage and emission, aerosols and albedo. We then explore the role of rewilding as a mitigation tool at two scales: (i) current and near-future opportunities for national or regional climate change mitigation portfolios, and (ii) more radical opportunities at the global scale. Finally, we identify major knowledge gaps that complicate the complete characterization of rewilding as a climate change mitigation strategy. Our perspective is urgent since we are losing the Earth's last remaining megafauna, and with it a potential option to address climate change.This article is part of the theme issue 'Trophic rewilding: consequences for ecosystems under global change'.

The importance of ecological memory for trophic rewilding as an ecosystem restoration approach.

Increasing human pressure on strongly defaunated ecosystems is characteristic of the Anthropocene and calls for proactive restoration approaches that promote self-sustaining, functioning ecosystems. However, the suitability of novel restoration concepts such as trophic rewilding is still under discussion given fragmentary empirical data and limited theory development. Here, we develop a theoretical framework that integrates the concept of 'ecological memory' into trophic rewilding. The ecological memory of an ecosystem is defined as an ecosystem's accumulated abiotic and biotic material and information legacies from past dynamics. By summarising existing knowledge about the ecological effects of megafauna extinction and rewilding across a large range of spatial and temporal scales, we identify two key drivers of ecosystem responses to trophic rewilding: (i) impact potential of (re)introduced megafauna, and (ii) ecological memory characterising the focal ecosystem. The impact potential of (re)introduced megafauna species can be estimated from species properties such as lifetime per capita engineering capacity, population density, home range size and niche overlap with resident species. The importance of ecological memory characterising the focal ecosystem depends on (i) the absolute time since megafauna loss, (ii) the speed of abiotic and biotic turnover, (iii) the strength of species interactions characterising the focal ecosystem, and (iv) the compensatory capacity of surrounding source ecosystems. These properties related to the focal and surrounding ecosystems mediate material and information legacies (its ecological memory) and modulate the net ecosystem impact of (re)introduced megafauna species. We provide practical advice about how to quantify all these properties while highlighting the strong link between ecological memory and historically contingent ecosystem trajectories. With this newly established ecological memory-rewilding framework, we hope to guide future empirical studies that investigate the ecological effects of trophic rewilding and other ecosystem-restoration approaches. The proposed integrated conceptual framework should also assist managers and decision makers to anticipate the possible trajectories of ecosystem dynamics after restoration actions and to weigh plausible alternatives. This will help practitioners to develop adaptive management strategies for trophic rewilding that could facilitate sustainable management of functioning ecosystems in an increasingly human-dominated world.

Assessing the role of megafauna in tropical forest ecosystems and biogeochemical cycles – the potential of vegetation models

Megafauna (terrestrial vertebrate herbivores > 5 kg) can have disproportionate direct and indirect effects on forest structure, function, and biogeochemical cycles. We reviewed the literature investigating these effects on tropical forest dynamics and biogeochemical cycles in relation to ecology, paleoecology, and vegetation modelling. We highlight the limitations of field‐based studies in evaluating the long‐term consequences of loss of megafauna. These limitations are due to inherent space‐time restrictions of field‐studies and a research focus on seed dispersal services provided by large animals. We further present evidence of a research gap concerning the role of megafauna in carbon cycling in tropical ecosystems. Specifically, changes in aboveground biomass might not be noticeable in short‐term studies because of slow vegetation dynamics requiring decades to respond to disturbance (i.e. defaunation). Nutrient cycling has received even less attention in relation to the role of megafauna in tropical forests. We present an approach to investigate the effects of megafauna from new perspectives and with various tools (notably, vegetation models), which can simulate long‐term dynamics in different environmental and megafauna density scenarios. Vegetation models could facilitate interaction between plant–animal ecology and biogeochemistry research. We present practical examples on how to integrate plant–animal interactions in vegetation models to further our understanding of the role of large herbivores in tropical forests.

Coalescence Models Reveal the Rise of the White-Bellied Rat (Niviventer confucianus) Following the Loss of Asian Megafauna

Rodents are the major remaining mammals in many terrestrial ecosystems after the historical loss of megafauna and large-bodied taxa. Niviventer confucianus is a dominant habitat generalist in natural forests in most of China. It is also recorded as an important vector of diverse zoonotic diseases. Here, three mitochondrial and one nuclear DNA fragments were sequenced from samples covering most of the species range to study intraspecific genetic diversification and demographic history. Molecular voucher specimens of N. confucianus revealed that its assumed distribution range has been overestimated because of the hitherto unrecognized separation from parapatric species. Phylogenetic inferences recognized three geographically delimited intraspecific lineages that diverged at approximately 1.28 and 0.68 Mya. Hengduan Mountains, the east margin of Qinghai Tibetan Plateau, and the mountains surrounding Sichuan Basin were recognized as the major geographical barriers. Demographic analysis revealed dramatic population growth in southwest, central, and northern China in the late Pleistocene, but only slight growth in Yunnan/Tibet. The population boom apparently coincided with the reduction of predation and competition from the loss of megafauna in the late Pleistocene. Distributional ranges were inferred to be fairly stable through the late Quaternary glacial-interglacial climatic oscillations, possibly enabled by the species’ seed hoarding behavior and wide climatic tolerance. The demographic history of N. confucianus suggests that these rodents directly profited from the loss of megafauna, while their most recent increases potentially led to the proliferation of zoonotic disease by this species.

African Environmental Change from the Pleistocene to the Anthropocene

This review explores what past environmental change in Africa—and African people's response to it—can teach us about how to cope with life in the Anthropocene. Organized around four drivers of change—climate; agriculture and pastoralism; megafauna; and imperialism, colonialism, and capitalism (ICC)—our review zooms in on key regions and debates, including desertification; rangeland degradation; megafauna loss; and land grabbing. Multiscale climate change is a recurring theme in the continent's history, interacting with increasingly intense human activities from several million years onward, leading to oscillating, contingent environmental changes and societally adaptive responses. With high levels of poverty, fast population growth, and potentially dramatic impacts expected from future climate change, Africa is emblematic of the kinds of social and ecological precariousness many fear will characterize the future globally. African people's innovation and adaptation to contingency may place them among the avant-garde with respect to thinking about Anthropocene conditions, strategies, and possibilities.

Ecological and evolutionary legacy of megafauna extinctions.

For hundreds of millions of years, large vertebrates (megafauna) have inhabited most of the ecosystems on our planet. During the late Quaternary, notably during the Late Pleistocene and the early Holocene, Earth experienced a rapid extinction of large, terrestrial vertebrates. While much attention has been paid to understanding the causes of this massive megafauna extinction, less attention has been given to understanding the impacts of loss of megafauna on other organisms with whom they interacted. In this review, we discuss how the loss of megafauna disrupted and reshaped ecological interactions, and explore the ecological consequences of the ongoing decline of large vertebrates. Numerous late Quaternary extinct species of predators, parasites, commensals and mutualistic partners were associated with megafauna and were probably lost due to their strict dependence upon them (co-extinctions). Moreover, many extant species have megafauna-adapted traits that provided evolutionary benefits under past megafauna-rich conditions, but are now of no or limited use (anachronisms). Morphological evolution and behavioural changes allowed some of these species partially to overcome the absence of megafauna. Although the extinction of megafauna led to a number of co-extinction events, several species that likely co-evolved with megafauna established new interactions with humans and their domestic animals. Species that were highly specialized in interactions with megafauna, such as large predators, specialized parasites, and large commensalists (e.g. scavengers, dung beetles), and could not adapt to new hosts or prey were more likely to die out. Partners that were less megafauna dependent persisted because of behavioural plasticity or by shifting their dependency to humans via domestication, facilitation or pathogen spill-over, or through interactions with domestic megafauna. We argue that the ongoing extinction of the extant megafauna in the Anthropocene will catalyse another wave of co-extinctions due to the enormous diversity of key ecological interactions and functional roles provided by the megafauna.

Correction: Corrigendum: Coherent assessments of Europe's marine fishes show regional divergence and megafauna loss

Nature Ecology & Evolution 1, 0170 (2017); published 26 May 2017; corrected 12 June 2017. In the original version of this Article, the European Commission was mistakenly included as an affiliation for Christos D. Maravelias. His contribution to this work was exclusively completed while at the Hellenic Centre for Marine Research.

Coherent assessments of Europe’s marine fishes show regional divergence and megafauna loss

Europe has a long tradition of exploiting marine fishes and is promoting marine economic activity through its Blue Growth strategy. This increase in anthropogenic pressure, along with climate change, threatens the biodiversity of fishes and food security. Here, we examine the conservation status of 1,020 species of European marine fishes and identify factors that contribute to their extinction risk. Large fish species (greater than 1.5 m total length) are most at risk; half of these are threatened with extinction, predominantly sharks, rays and sturgeons. This analysis was based on the latest International Union for Conservation of Nature (IUCN) European regional Red List of marine fishes, which was coherent with assessments of the status of fish stocks carried out independently by fisheries management agencies: no species classified by IUCN as threatened were considered sustainable by these agencies. A remarkable geographic divergence in stock status was also evident: in northern Europe, most stocks were not overfished, whereas in the Mediterranean Sea, almost all stocks were overfished. As Europe proceeds with its sustainable Blue Growth agenda, two main issues stand out as needing priority actions in relation to its marine fishes: the conservation of marine fish megafauna and the sustainability of Mediterranean fish stocks. Assessing the conservation status of 1,020 European marine fishes reveals half of large (>1.5 m) fishes are threatened with extinction and stock status diverges geographically: almost all Mediterranean stock is overfished, most northern European stock is not.

Variable impact of late-Quaternary megafaunal extinction in causing ecological state shifts in North and South America

Loss of megafauna, an aspect of defaunation, can precipitate many ecological changes over short time scales. We examine whether megafauna loss can also explain features of lasting ecological state shifts that occurred as the Pleistocene gave way to the Holocene. We compare ecological impacts of late-Quaternary megafauna extinction in five American regions: southwestern Patagonia, the Pampas, northeastern United States, northwestern United States, and Beringia. We find that major ecological state shifts were consistent with expectations of defaunation in North American sites but not in South American ones. The differential responses highlight two factors necessary for defaunation to trigger lasting ecological state shifts discernable in the fossil record: (i) lost megafauna need to have been effective ecosystem engineers, like proboscideans; and (ii) historical contingencies must have provided the ecosystem with plant species likely to respond to megafaunal loss. These findings help in identifying modern ecosystems that are most at risk for disappearing should current pressures on the ecosystems' large animals continue and highlight the critical role of both individual species ecologies and ecosystem context in predicting the lasting impacts of defaunation currently underway.

Perspective: Losing time? Incorporating a deeper temporal perspective into modern ecology

opinion and perspectives ISSN 1948-6596 perspective Losing time? Incorporating a deeper temporal perspective into modern ecology Felisa A. Smith 1 and Alison G. Boyer 2 Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA. fasmith@unm.edu; http://biology.unm.edu/fasmith/ Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37996, USA. alison.boyer@utk.edu; http://eeb.bio.utk.edu/boyer/index.html Abstract. Ecologists readily acknowledge that a temporal perspective is essential for untangling ecological complexity, yet most studies remain of relatively short duration. Despite a number of excellent essays on the topic, only recently have ecologists begun to explicitly incorporate a historical component. Here we provide several concrete examples drawn largely from our own work that clearly illustrate how the adoption of a longer temporal perspective produces results significantly at odds with those obtained when relying solely on modern data. We focus on projects in the areas of conservation, global change and macroecology because such work often relies on broad-scale or synthetic data that may be heavily influenced by historic or prehistoric anthropogenic factors. Our analysis suggests that considerable care should be taken when extrapolating from studies of extant systems. Few, if any, modern systems have been unaffected by anthropogenic influences. We encourage the further integration between paleoecologists and ecologists, who have been historically segregated into different departments, scientific societies and scientific cultures. Keywords: climate change, conservation, macroecology, paleoecology, palaeoecology, woodrat The pronghorn (Antilocapra americana) is a quintessential symbol of the Great Plains. As the fastest land mammal in the Americas, it can reach close to ~100 km/h and can sustain speeds of 45 km/h for long distances (Byers 1997). Much of its physiology, morphology and life history reflect an optimization for being swift; pronghorn have oversized hearts and lungs, a 320° field of vision, hollow hair and overlong gestation for their size (Byers 1997). Understanding the selective pressures that led to such specialized adaptations is difficult without the knowledge that the pronghorn co-evolved with a suite of now extinct predators, including the American cheetah (Micracinonyx trumani) (Byers 1997, Barlow 2001). As the only surviving member of the once speciose North American family Antilocapridae, the pronghorn no longer has effective natural predators. Consequently, many of its social, morphological and physiological traits have little apparent modern selective value (Byers 1997). Ecologists recognize the anachronistic nature of animals like the pronghorn, but more as a curiosity rather than as a concrete example of the substantial alteration of ecosystems that occurred in the late Quaternary. Although work investigating the ecology and life-history characteristics of tropical and temperate plants has proposed that numerous adaptations for dispersal or regrowth arose in response to foraging by now-extinct megafauna (Janzen and Martin 1982, Wing and Tiffney 1987, Barlow 2001), in general, the implications of the prehistoric loss of megafauna in the late Pleistocene have been overlooked. Yet, these animals undoubtedly played key roles in terms of ecosystem structure and function; their abrupt disappearance some 11,000 years ago must have profoundly influenced ecosystem dynamics (Martin 1967, Donlan et al. 2005). How many other life-history, ecological or distributional features of extant animals and plants are due in some part to now-extinct components of the ecosystem? © 2012 the authors; journal compilation © 2012 The International Biogeography Society — frontiers of biogeography 4.1, 2012

Plio-Pleistocene Climate and Faunal Change in Central Eastern Australia

Understanding the responses of Plio-Pleistocene terrestrial vertebrates to long-term trends in climate change in central eastern Australia has advanced considerably in recent years following the recovery and documentation of a series of remarkable fossil assemblages. The middle Pliocene Chinchilla Local Fauna of SE Queensland preserves a diverse suite of vertebrate taxa suggestive of a paleoenvironment consisting of wetlands, closed wet forest, open woodlands, and grasslands. Local extinctions of numerous arboreal and terrestrial woodland species suggest that significant faunal and habitat reorganization occurred between the Pliocene and Pleistocene, in part, reflecting the expansion of open woodlands and grasslands. Middle Pleistocene deposits in the Mt Etna region of central eastern Queensland contain extensive fossil assemblages of rainforest-adapted vertebrates dated >500–280 ka. Such faunal assemblages show remarkable long-term stability despite being subjected to numerous glacial-interglacial climatic shifts. However, sometime between 280–205 ka, a major faunal turnover/ extinction event occurred, where the previously dominant rainforest-adapted faunas gave way to xeric-adapted forms. Independent paleoclimatic records suggest that this shift was a result of increased climatic variability and weakened northern monsoons. Late Pleistocene deposits of the Darling Downs, SE Queensland, provide an important temporal extension to the Mt Etna region. Recent studies have demonstrated minimally, a three stage extinction of local megafauna (giant land mammals, birds and lizards). Associated radiometric and optical dating indicates that the progressive loss of megafauna from the region was initiated at least 75 kyr before the continental colonisation of humans. The progressive changes in megafaunal community dynamics were most likely driven by intense climatic changes (i.e., increased aridity) associated with the last glacial cycle. The potential role of humans in the final extinctions (posthuman colonisation) is unclear. However, if humans did

Late Pleistocene sedimentology, taphonomy and megafauna extinction on the Darling Downs, southeastern Queensland

The Kings Creek catchment, southeastern Queensland, contains a variety of Pleistocene – Holocene depositional settings. Fluvial depositional accumulation processes in the catchment reflect both high-energy channel and low-energy episodic overbank deposition. The lithofacies and depositional environments of locality QML796 were examined in detail to aid interpretation of taphonomic accumulation patterns of large and small taxa in the deposit. The basal fossiliferous unit was deposited in a meandering channel and passes upward into overbank deposits that include ephemeral interfluve channels and splays. The most striking taphonomic observations on vertebrates at the locality include: (i) low representation of post-cranial elements; (ii) high degree of bone breakage; (iii) variable abrasion with most identifiable bone elements having a low to moderate degree of abrasion; (iv) low rates of bone weathering; (v) a low degree of carnivore bone modification; and (vi) a low degree of articulated or associated specimens. Collectively, these data suggest that the material was transported into the deposit from the surrounding proximal floodplain and that the assemblages reflect substantial hydraulic sorting. However, despite that, sequential faunal horizons show a stepwise decrease in taxonomic diversity that cannot be explained by sampling or taphonomic bias. The decreasing diversity includes loss of some, but not all, megafauna and is consistent with a progressive local loss of megafauna in the catchment over an extended interval of time. Data are consistent with a climate change model for megafauna extinction but not with nearly simultaneous extinction of megafauna as required by the human-induced blitzkrieg extinction hypothesis.