Anthropogenic Extinction Research Articles

Anthropogenic extinctions explain most size and trophic mismatches between large mammalian primary consumers from Amazonian and African rainforests

Anthropogenic extinctions explain most size and trophic mismatches between large mammalian primary consumers from Amazonian and African rainforests

The global loss of avian functional and phylogenetic diversity from anthropogenic extinctions.

Humans have been driving a global erosion of species richness for millennia, but the consequences of past extinctions for other dimensions of biodiversity-functional and phylogenetic diversity-are poorly understood. In this work, we show that, since the Late Pleistocene, the extinction of 610 bird species has caused a disproportionate loss of the global avian functional space along with ~3 billion years of unique evolutionary history. For island endemics, proportional losses have been even greater. Projected future extinctions of more than 1000 species over the next two centuries will incur further substantial reductions in functional and phylogenetic diversity. These results highlight the severe consequences of the ongoing biodiversity crisis and the urgent need to identify the ecological functions being lost through extinction.

Convergent evolution toward a slow pace of life predisposes insular endotherms to anthropogenic extinctions.

Island vertebrates have evolved a number of morphological, physiological, and life history characteristics that set them apart from their mainland relatives. However, to date, the evolution of metabolism and its impact on the vulnerability to extinction of insular vertebrates remains poorly understood. This study used metabolic data from 2813 species of tetrapod vertebrates, including 695 ectothermic and 2118 endothermic species, to reveal that island mammals and birds evolved convergent metabolic strategies toward a slow pace of life. Insularity was associated with shifts toward slower metabolic rates and greater generation lengths in endotherms, while insularity just drove the evolution of longer generation lengths in ectotherms. Notably, a slow pace of life has exacerbated the extinction of insular endemic species in the face of anthropogenic threats. These findings have important implications for understanding physiological adaptations associated with the island syndrome and formulating conservation strategies across taxonomic groups with different metabolic modes.

Grasping extinction: the natural history museum as haptic space in the work of Clarke, Robinson and Jamie

ABSTRACT This article examines depictions of natural history museums in a selection of poems and essays drawn from Gillian Clarke’s Zoology (2017), Jane Robinson’s Journey to the Sleeping Whale (2018) and Kathleen Jamie’s Sightlines (2012). These texts present the museum as a place in which we confront extinction through conflicting emotions: a space of care and protection, built on acts of violence. My analysis explores how physical prehension, real or imagined, contributes to mental prehension, and thus helps us to grasp the sixth mass extinction. I examine how metonymical relations connect museums to damaged environments, including zones, like the ocean, that are perceived as sacrifice zones in the making. I contrast Clarke’s sequence of poems ‘Behind Glass’, where ekphrasis connects the beauty of endangered specimens with protected landscapes, to Robinson’s ‘Memories of Flight at the Life Museum’ and Jamie’s ‘Voyager, Chief’ and ‘The Hvalsalen’, which emphasise the collection’s dependence on the depletion of lands and oceans. This leads me to outline two textual approaches to the natural history museum: the first reads the specimen as a synecdoche for endangered, yet protected environments, while the second connects the collection, metonymically and metaphorically, to anthropogenic extinction and sacrifice zones.

Biodiversity-ecosystem function relationships change in sign and magnitude across the Hill diversity spectrum.

Motivated by accelerating anthropogenic extinctions, decades of biodiversity-ecosystem function (BEF) experiments show that ecosystem function declines with species loss from local communities. Yet, at the local scale, changes in species' total and relative abundances are more common than species loss. The consensus best biodiversity measures are Hill numbers, which use a scaling parameter, ℓ, to emphasize rarer versus more common species. Shifting that emphasis captures distinct, function-relevant biodiversity gradients beyond species richness. Here, we hypothesized that Hill numbers that emphasize rare species more than richness does may distinguish large, complex and presumably higher-functioning assemblages from smaller and simpler ones. In this study, we tested which values of ℓ produce the strongest BEF relationships in community datasets of ecosystem functions provided by wild, free-living organisms. We found that ℓ values that emphasized rare species more than richness does most often correlated most strongly with ecosystem functions. As emphasis shifted to more common species, BEF correlations were often weak and/or negative. We argue that unconventional Hill diversities that shift emphasis towards rarer species may be useful for describing biodiversity change, and that employing a wide spectrum of Hill numbers can clarify mechanisms underlying BEF relationships. This article is part of the theme issue 'Detecting and attributing the causes of biodiversity change: needs, gaps and solutions'.

Resolving when (and where) the Thylacine went extinct

Like the Dodo and Passenger Pigeon before it, the predatory marsupial Thylacine (Thylacinus cynocephalus), or ‘Tasmanian tiger’, has become an iconic symbol of anthropogenic extinction. The last captive animal died in 1936, but even today reports of the Thylacine's possible ongoing survival in remote regions of Tasmania are newsworthy and capture the public's imagination. Extirpated from mainland Australia in the mid-Holocene, the island of Tasmania became the species' final stronghold. Following European settlement in the 1800s, the Thylacine was relentlessly persecuted and pushed to the margins of its range, although many sightings were reported thereafter—even well beyond the 1930s. To gain a new depth of insight into the extinction of the Thylacine, we assembled an exhaustive database of 1237 observational records from Tasmania (from 1910 onwards), quantified their uncertainty, and charted the patterns these revealed. We also developed a new method to visualize the species' 20th-century spatio-temporal dynamics, to map potential post-bounty refugia and pinpoint the most-likely location of the final persisting subpopulation. A direct reading of the high-quality records (confirmed kills and captures, in combination with sightings by past Thylacine hunters and trappers, wildlife professionals and experienced bushmen) implies a most-likely extinction date within four decades following the last capture (i.e., 1940s to 1970s). However, uncertainty modelling of the entire sighting record, where each observation is assigned a probability and the whole dataset is then subject to a sensitivity analysis, suggests that extinction might have been as recent as the late 1980s to early 2000s, with a small chance of persistence in the remote south-western wilderness areas. Beyond the intrinsically fascinating problem of reconstructing the final fate of the Thylacine, the new spatio-temporal mapping of extirpation developed herein would also be useful for conservation prioritization and search efforts for other rare taxa of uncertain status.

Novel plant–frugivore network on Mauritius is unlikely to compensate for the extinction of seed dispersers

Insular communities are particularly vulnerable to anthropogenic extinctions and introductions. Changes in composition of island frugivore communities may affect seed dispersal within the native plant community, risking ecological shifts and ultimately co-extinction cascades. Introduced species could potentially mitigate these risks by replacing ecological functions of extinct species, but conclusive evidence is lacking. Here, we investigate changes in plant–frugivore interactions involving frugivorous birds, mammals and reptiles in Mauritius, an oceanic island with an exceptionally well-specified frugivore community and well-described species introduction history. We demonstrate substantial losses of binary interaction partnerships (at the species level) resulting from native species extinctions, but also gains of equal numbers of novel interactions with introduced species, potentially supporting the idea that non-native species might compensate for lost seed dispersal. However, closer investigation of animal seed handling behaviour reveals that most interactions with seed dispersers are replaced by ecologically different interactions with seed predators. Therefore, restoration of seed dispersal functionality in this novel plant–frugivore community is unlikely.

A natural terminal Pleistocene decline of African penguin populations enhances their anthropogenic extinction risk

The African penguin Spheniscus demersus, endemic to the coast of southern Africa, has suffered anthropogenic-driven population declines since 1900 and is now listed as Endangered on the IUCN Red List. Conservation efforts currently underway are informed by the species’ adaptive response with respect to colonisation capacity and breeding success, vulnerability because of anthropogenic competition for prey species, and global climate change. Here, we show how the available nesting habitat of African penguins likely declined precipitously post the Last Glacial Maximum, driven by island inundation as sea levels rose naturally, before anthropogenic global warming. The average size and numbers of islands around the southern African coast decreased almost tenfold between ∼15 kya and the mid Holocene (∼7 kya). In addition, the geographic distribution of islands shifted predominantly away from the South African west to the south and east coasts. The natural decline of island habitat likely caused a decline in the penguin population, which is likely relevant in current assessments of the vulnerability of this species to novel anthropogenic drivers of population decline. The status of the African penguin as a post-Pleistocene refugial species has amplified its extinction risk due to anthropogenic impacts, despite natural resilience to paleoclimatic change afforded by an apparent capacity for habitat colonisation and evident persistence through late-Pleistocene bottlenecks.

The ethics of species extinctions

Abstract This review provides an overview of the ethics of extinctions with a focus on the Western analytical environmental ethics literature. It thereby gives special attention to the possible philosophical grounds for Michael Soulé’s assertion that the untimely ‘extinction of populations and species is bad’. Illustrating such debates in environmental ethics, the guiding question for this review concerns why – or when – anthropogenic extinctions are bad or wrong, which also includes the question of when that might not be the case (i.e. which extinctions are even desirable). After providing an explanation of the disciplinary perspective taken (section “Introduction”), the concept of extinction and its history within that literature are introduced (section “Understanding extinction”). Then, in section “Why (or when) might anthropogenic extinctions be morally problematic?”, different reasons for why anthropogenic extinctions might be morally problematic are presented based on the loss of species’ value, harm to nonhuman individuals, the loss of valuable biological variety and duties to future generations. This section concludes by also considering cases where anthropogenic extinctions might be justified. Section “How to respond to extinctions?” then addresses a selection of topics concerning risks and de-extinction technologies. Finally, the section on “Extinction studies” introduces other viewpoints on the ethics of extinction from the extinction studies literature, followed by the “Conclusion”.

Nuclear Weapons and Extinction As Progress

Nuclear weapons have delivered more near-extinction encounters than any other anthropogenic threat, but for the three decades after the Cold War discussion of this threat was relatively sidelined. This paper points to some of the historical connections between 'war-ending' weapons, deterrence logic and its breakdown, and the binding between the sublimation of politics into commerce and an extinction logic held within it. It firstly gestures towards roots in the ideal of market mediation as civilisation rising in the eighteenth century; secondly it looks at some writing on the conception of nuclear weapons and the surprisingly long history of awareness of anthropogenic extinction risk this brings; thirdly it suggests that a post-Cold War revival of the binding of market realism to progress that had led to the 'weapon to end war', and the condition of deterrence, helps explain the fall in discussions of nuclear extinction; and fourthly it notes that current proliferation and destabilisation question this deep and largely unspoken conventional wisdom over nuclear 'non-violence'. It points to various moments in the imagination and realisation of viable nuclear weapons and their embedding in democratic regimes in Atlantic powers in particular, and to points of serious scientific consideration of extinction during the Cold War, and suggests that the long naturalisation of nuclear weapons has taught us to 'live extinction' in a way that speaks to other anthropogenic risks. Climate and nuclear crises indeed can be read as nodes on a trajectory of extraction and exchange defining a narrow conception of progress that has extinction as its telos. Ideas of 'total' deterrence become widespread during the imperial rivalries following this extractive-productive ethics, and take nuclear form as early as the first decades of the twentieth century. After 'stable' deterrence, though, as nuclear arsenals remained to back the Anglo-American 'victory' in the Cold War, these arsenals reached the apotheosis of their long depoliticising, dehumanising mission, standing as a silent horizon absorbing conflict and helping to explain a lack of political 'newness' often felt during late neoliberalism. With the more recent complex and largely obscured re-arming, nuclear weapons are being rediscovered as both an existential threat and an imperative to rethink the scope of political action.

Measurement report: The importance of biomass burning in light extinction and direct radiative effect of urban aerosol during the COVID-19 lockdown in Xi'an, China

Abstract. Due to the complexity of emission sources, a better understanding of aerosol optical properties is required to mitigate climate change in China. Here, an intensive real-time measurement campaign was conducted in an urban area of China before and during the COVID-19 lockdown in order to explore the impacts of anthropogenic activities on aerosol light extinction and the direct radiative effect (DRE). The mean light extinction coefficient (bext) decreased from 774.7 ± 298.1 Mm−1 during the normal period to 544.3 ± 179.4 Mm−1 during the lockdown period. A generalised additive model analysis indicated that the large decline in bext (29.7 %) was due to sharp reductions in anthropogenic emissions. Chemical calculation of bext based on a ridge regression analysis showed that organic aerosol (OA) was the largest contributor to bext in both periods (45.1 %–61.4 %), and the contributions of two oxygenated OAs to bext increased by 3.0 %–14.6 % during the lockdown. A hybrid environmental receptor model combined with chemical and optical variables identified six sources of bext. It was found that bext from traffic-related emissions, coal combustion, fugitive dust, the nitrate and secondary OA (SOA) source, and the sulfate and SOA source decreased by 21.4 %–97.9 % in the lockdown, whereas bext from biomass burning increased by 27.1 %, mainly driven by the undiminished need for residential cooking and heating. An atmospheric radiative transfer model was further used to illustrate that biomass burning, rather than traffic-related emissions, became the largest positive effect (10.0 ± 10.9 W m−2) on aerosol DRE in the atmosphere during the lockdown. Our study provides insights into aerosol bext and DRE from anthropogenic sources, and the results imply the importance of controlling biomass burning for tackling climate change in China in the future.

Deterministic assembly and anthropogenic extinctions drive convergence of island bird communities

AbstractAimWhether entire communities of organisms converge towards predictable structural properties in similar environmental conditions remains controversial. We tested for community convergence in birds by comparing the structure of oceanic archipelago assemblages with their respective regional species pools.LocationEighteen major oceanic archipelagos of volcanic origin with global distribution.Major taxa studiedTerrestrial birds.MethodsWe compiled a comprehensive database of morphological trait and phylogenetic data for 6,579 bird species, including species known to have become extinct owing to human activities. We quantified morphological and phylogenetic dissimilarity among species between pairs of archipelagos, using a modified version of the mean nearest taxon distance. We tested for convergence by estimating whether overall mean turnover among archipelagos and pairwise turnover between archipelagos were lower than expected by chance.ResultsFor all land birds, we found that turnover in body plan, body mass and phylogeny among archipelagos was significantly lower than expected. Seventeen (of 18) archipelagos showed significant body plan and phylogenetic similarity with at least one other archipelago. Similar convergent patterns of community assembly were detected in different subsamples of the data (extant species, endemics, native non‐endemics, and Passeriformes only). Convergence was more pronounced for extant species than for extant and extinct species combined.Main conclusionsConsistent convergence in phylogenetic and morphological structure among archipelagic communities arises through a combination of non‐random colonization andin situadaptation. In addition, by including data from extinct taxa, we show that community convergence both precedes and is accentuated by the anthropogenic extinction of endemic lineages. Our results highlight the potential role of non‐random extinction in generating patterns of community convergence and show that convergence existed even before anthropogenic extinctions, owing to deterministic community assembly in similar environmental settings at the global scale.

The Art and Craftivism of Exhibiting Species and Habitat Loss in Natural History Museums

In recent years the presentation of anthropogenic extinction narratives in natural history museums has occurred through temporary exhibitions, curatorial and artistic interventions in permanent collections displays and public engagement events. Such work has enabled institutions to re-orientate historical collections and permanent galleries towards this pressing contemporary issue. This article examines a subset of this wider field of curatorial activity by considering how contemporary handicrafts including knitting and crochet have been displayed to engage visitors with species and habitat loss in natural history museums, situating this work within craftivist practices and the longer history of craft being mobilized for political and ethical ends. While the habitat diorama alerted audiences to disappearing species and threatened ecosystems in the twentieth century through a combination of art, science and craft, I reveal how recent exhibitions and events have reconfigured a similar interdisciplinary mix to raise awareness of species and habitat loss in the twenty-first century.

Conservation paleobiology on Minami-Daito Island, Okinawa, Japan: anthropogenic extinction of cave-dwelling bats on a tropical oceanic island.

BackgroundWith strong environmental and geographic filtration, vertebrates incapable of flying and swimming are often extirpated from island ecosystems. Minami-Daito Island is an oceanic island in Okinawa, Japan that harbors the Daito flying fox (Pteropus dasymallus daitoensis), a subspecies of the fruit bat and the only extant mammal endemic to the island. However, the skeleton of a cave-dwelling bat Rhinolophus sp. and fossil guano were briefly reported in a previous study.MethodsHere, we present evidence for the anthropogenic extirpation of two species of cave-dwelling bats (Miniopterus sp. & Rhinolophus sp.) from Minami-Daito Island. Our goal is to reliably constrain the ages of the extirpated bat species by a multiproxy approach. Because skeletal materials did not preserve sufficient bone collagen for direct radiocarbon dating, we alternatively examined guano-like deposits based on SEM observation and Fourier-transform infrared spectroscopy (FTIR) along with stable carbon and nitrogen isotope analyses for possible indirect dating. We also examined stable carbon isotopes in bone apatite, assuming that an isotopic signal of C4 plants on the bat bones links to sugarcane plantation on the island based on the historical knowledge that early human settlers quickly replaced the island’s native C3 forests with sugarcane (C4 perennial grass) plantation from 1900 onward.ResultsOur cave survey documents the remains of Miniopterus sp. from the island for the first time. Based on the unique taphonomic conditions (unpermineralized bones, disarticulated skeletons closely scattered without sediment cover, various degrees of calcite crystal growth around bones) and a radiocarbon age of a humic sample, we suggest that the maximum age constraint of Miniopterus sp. and Rhinolophus sp. is 4,640 calBP. Based on a series of analyses, we conclude that the guano-like deposits are composed not of bat guano but mainly of humic substances; however, a hydroxyapatite crust associated with bat-lying stalagmites may be derived from bat feces. Stable carbon isotope analysis of bone apatite revealed C4 signals in various degrees, confirming that small populations of cave-dwelling bats persisted on Minami-Daito Island after 1900.ConclusionsThe results of this study indicate that these populations remained rather small and did not leave many generations and that the estimated ages can be bracketed from 4,640 calBP to the post-1900 (perhaps, until the 1950s). They likely faced a continuously high mortality risk due to severe anthropogenic stresses on the island, where most of the forests were turned into sugarcane plantations within a few decades in the early 20th century. A result of hearing surveys to local residents suggests the latest remnants most likely disappeared on the island concurrently with the introduction of chemical pesticides after World War II.

Loss of functional diversity through anthropogenic extinctions of island birds is not offset by biotic invasions.

Human impacts reshape ecological communities through the extinction and introduction of species. The combined impact of these factors depends on whether non-native species fill the functional roles of extinct species, thus buffering the loss of functional diversity. This question has been difficult to address, because comprehensive information about past extinctions and their traits is generally lacking. We combine detailed information about extinct, extant, and established alien birds to quantify historical changes in functional diversity across nine oceanic archipelagos. We found that alien species often equal or exceed the number of anthropogenic extinctions yet apparently perform a narrower set of functional roles as current island assemblages have undergone a substantial and ubiquitous net loss in functional diversity and increased functional similarity among assemblages. Our results reveal that the introduction of alien species has not prevented anthropogenic extinctions from reducing and homogenizing the functional diversity of native bird assemblages on oceanic archipelagos.

Aesthetic Consolation in an Age of Extinction

In light of the environmental pressure humans are currently placing on the biosphere, there is overwhelming evidence to think that we have entered the early stages of a major extinction event. Indeed, some scientists worry this extinction event will be so bad as to constitute Earth’s sixth mass extinction. Our most pressing responsibility as a species is to do everything in our power to prevent such an extinction from occurring. But the question I wish to pursue here is, what should our philosophical response be if we fail? Drawing on George Harris’ account of tragic loss, I argue that, while we should rightly consider an anthropogenic extinction a moral tragedy and cause for grief, we should not consider it cause for despair. The reason is that we can take aesthetic consolation from the knowledge that life will almost certainly recover and re-diversify in new and unpredictable ways. Adam Smith’s insights into the beauty and sublimity of systems is particularly relevant in showing how Earth’s biosphere remains a bearer of aesthetic value, even in the face of the (temporary, though long-term) damage we are causing it.

Nuclear weapons, extinction, and the Anthropocene: Reappraising Jonathan Schell

AbstractIn the Anthropocene, International Relations must confront the possibility of anthropogenic extinction. Recent, insightful attempts to advance new vocabularies of planet politics tend to demote the profound historical and intellectual links between our current predicament and the nuclear age. In contrast, we argue that it is vital to revisit the nuclear-environment nexus of the Cold War to trace genealogies of today's intricate constellation of security problems. We do so by reappraising the work of Jonathan Schell (1943–2014), author of The Fate of the Earth (1982), who came to regard extinction as a defining feature of the nuclear age. We show how a deep engagement with nuclear weapons led Schell to an understanding of the Earth as a complex, delicate ecology and fed into a sophisticated, Arendtian theory of extinction. Despite its limitations and tensions, we argue that Schell's work remains deeply relevant for rethinking human–Earth relations and confronting the Anthropocene.

Dark extinction: the problem of unknown historical extinctions.

The extinction of species before they are discovered and named (dark extinction, DE) is widely inferred as a significant part of species loss in the 'pre-taxonomic' period (approx. 1500-1800 CE) and, to some extent, in the 'taxonomic period' (approx. 1800-present) as well. The discovery of oceanic islands and other pristine habitats by European navigators and the consequent introduction of destructive mammals, such as rats and goats, started a process of anthropogenic extinction. Much ecosystem change happened before systematic scientific recording, so has led to DE. Statistical methods are available to robustly estimate DE in the 'taxonomic period'. For the 'pre-taxonomic period', simple extrapolation can be used. The application of these techniques to world birds, for example, suggests that approximately 56 DEs occurred in the 'taxonomic period' (1800-present) and approximately 180 in the 'pre-taxonomic period' (1500-1800). Targeting collection activities in extinction hotspots, to make sure organisms are represented in collections before their extinction, is one way of reducing the number of extinct species without a physical record (providing that collection efforts do not themselves contribute to species extinction).

Selective extinctions resulting from random habitat destruction lead to under-estimates of local and regional biodiversity loss in a manipulative field experiment.

Land-use change is a significant cause of anthropogenic extinctions, which are likely to continue and accelerate as habitat conversion proceeds in most biomes. One way to understand the effects of habitat loss on biodiversity is through improved tools for predicting the number and identity of species losses in response to habitat loss. There are relatively few methods for predicting extinctions and even fewer opportunities for rigorously assessing the quality of these predictions. In this paper, we address these issues by applying a new method based on rarefaction to predict species losses after random, but aggregated, habitat loss. We compare predictions from three rarefaction models, individual-based, sample-based, and spatially clustered, to those derived from a commonly used extinction estimation method, the species-area relationship (SAR). We apply each method to a mesocosm experiment, in which we aim to predict species richness and extinctions of arthropods immediately following 50% habitat loss. While each model produced strikingly accurate predictions of species richness immediately after the habitat loss disturbance, each model significantly underestimated the number of extinctions occurring at both the local (within-mesocosm) and regional (treatment-wide) scales. Despite the stochastic nature of our small-scale, short-term, and randomly applied habitat loss experiment, we found surprisingly clear evidence for extinction selectivity, for example, when abundant species with low extinction probabilities were extirpated following habitat loss. The important role played by selective extinction even in this contrived experimental system suggests that ecologically driven, trait-based extinctions play an equally important role to stochastic extinction, even when the disturbance itself has no clear selectivity. As a result, neutrally stochastic null models such as the SAR and rarefaction are likely to underestimate extinctions caused by habitat loss. Nevertheless, given the difficulty of predicting extinctions, null models provide useful benchmarks for conservation planning by providing minimum estimates and probabilities of species extinctions.

Anthropogenic extinctions conceal widespread evolution of flightlessness in birds

Human-driven extinctions can affect our understanding of evolution, through the nonrandom loss of certain types of species. Here, we explore how knowledge of a major evolutionary transition-the evolution of flightlessness in birds-is biased by anthropogenic extinctions. Adding data on 581 known anthropogenic extinctions to the extant global avifauna increases the number of species by 5%, but quadruples the number of flightless species. The evolution of flightlessness in birds is a widespread phenomenon, occurring in more than half of bird orders and evolving independently at least 150 times. Thus, we estimate that this evolutionary transition occurred at a rate four times higher than it would appear based solely on extant species. Our analysis of preanthropogenic avian diversity shows how anthropogenic effects can conceal the frequency of major evolutionary transitions in life forms and highlights the fact that macroevolutionary studies with only small amounts of missing data can still be highly biased.