Atrocity Exhibition: The Anthropocene Extinction Event

Introduction

With all the many and varied matters relating to wildlife or conservation today it is worthwhile taking an global and time-scale view to gain an overall sense of perspective. Popular aphorisms give well-meaning insight on the need to be attentive to scale; “rearranging deckchairs on the Titanic”, “penny-wise but pound foolish”, “being unable to see the wood for the trees” - all examples of what is encapsulated in Parkinson’s Law of Triviality (Parkinson, 1958), the disproportionate emphasis on relatively minor matters when a much larger issue is at stake. Parkinson understood this as a type of the psychology of ambiguity aversion in the face of complexity and scale. Politically, it can occur through a lack of power. As Herodotus (1920, Book 9, Ch 16) wryly observed (with variant translations): "This is the bitterest pain among men, to have much knowledge but no power."

Certainly one could, and must, be sympathetic and in solidarity to those who are doing the absolute best they can with the power, knowledge, and community they at hand have to engage in valiant conservation efforts, especially given the effectiveness of such local efforts. All of this does not take away from grim facts that many conservation scientists are alerting us to the possibility that the planet is facing an atrocity exhibition that is becoming known as the Anthropocene extinction, which affects so many numerous species across all biological domains is being called a mass extinction event. To fend off accusations of histrionic alarmism is is necessary to begin with established definitions and apply the facts available. Recognising there is significant debate over matters of quantity and time, a mass extinction event is defined as a sudden loss of quantity and diversity of life where the rate of extinction far exceeds the background extinction rate (Sudakow et al, 2022).

With this definition in mind, this inquiry first seeks to quantify the extent of the extinction to see if there is similarity with other events that are considered mass extinctions, and reviewing the debate within conversation and ecological research communities exists on whether we are at the verge of this extinction event or in the midst of it. Following this there is a review of the degree that human or natural causes have contributed to biodiversity loss, and finally a discussion of proposals for mitigation or solutions.

Quantification

Palaeontology identifies five mass extinction events in the fossil record (Raup & Sepkoski, 1982) originally based on the geologically sudden loss of marine life, with subsequent calculations used to estimate the loss of species and genera diversity (e.g., Pimm et al, 1995., Simberloff, 1996, Sepkoski, 1996, etc). Whilst the exact quantity of species currently on the planet is unknown, among known species it is possible to calculate extinctions per million species-years (E/MSY) as a more accurate gauge in preference to absolute numbers with the fossil record providing background rates, albeit extremely coarse in time, space, and taxonomic level (Pimm et al, 2014). An alternative is the use of molecular-based phylogenies to calculate average diversification of speciation minus extinctions. Even given incomplete taxonomic knowledge, “extinction rates are likely a thousand times higher than the background rate of 0.1 E/MSY”, primarily the result of changes to biogeography. Further investigations (De Vos, et al 2015) develop median extinction rates of 0.023 to 0.135 E/MSY, with diversification rates of 0.05 to 0.2 per million species per year. Current extinction rates are calculated at 1000 times the natural rate with future rates likely to reach 10000 times higher.

The emphasis on biogeographical changes concurs with Spalding & Hull (2021) who nevertheless, take up the issue of the comparison of a background rate of extinction. They note that extinctions in the fossil record occur as pulses rather than within intervals characterised by the background rate. This makes evaluation of the current rate of species loss difficult to determine whether or not it constitutes an “extinction event”, simply because of the timescale involved with problems in rate determination and magnitude. They therefore propose a new metric that correlates with sedimentary turnover which has predictive value for future modification of ecosystems by human activity. This may seem unusual, but it draws attention to the issue of just background extinction rates as a metric. Their proposal of an alternative for future predictions and strong use of robust statistic methods leads to a conclusion that the Late Pleistocene stage is already highly anomalous in terms of an extremely short duration and high genus extinction and comes with the concluding recommendation to "save the rocks" to save future species; in other words, we are witnessing a transformation to the physical environment that is typically witnessed on a geological timescale and correlates with mass extinction.

Denial, Acceptance, Verge, or Midst?

The estimated rate of loss of the abundance and diversity of life and the biogeographical changes raise the question on whether were are on the verge of the Anthropocene extinction event or on the midst of such an event or, whether the event is occurring at all. One argument is that whilst population sizes for particular species are declining this occurs concurrently with an overall gain in biodiversity (Briggs, 2014); a key element of this argument is that there is evidence of an increased number of documented species whereas the apparent loss of species is based on indirect measures such as loss of habitat which, it is acknowledged, can cause a loss of populations. A further argument against the proposal of a contemporary mass extinction event is that the proposed species loss is overestimated (Briggs, 2016), with evidence of deliberately over-stated values based on estimations, and the conflation of categories in the IUCN Red List (e.g., “extinct in the wild” and “possibly extinct”) . Instead, it is argued, that documentation extinctions of well-known species should be used as a surrogates.

Scepticism over proxy values and conflations are, of course, justifiable but justifications have to be rationally grounded. Extinctions are expressed as probabilities and require proof-positive that a species is not extinct when populations are not found (e.g., Lord Howe Island stick insect, Dryococelus australis, see Mikheyev et al (2017)). Elaboration of well-known documented species to unknown species suffers the problem that unknown species are usually in inaccessible areas or areas that have not been surveyed for species populations. Of great significance is the limitations of using tools like the IUCN Red List when the species samples are extremely biased toward vertebrate species (mammals, birds, amphibians) when the overwhelming majority of species - as high as 97% (Chapman, 2009) - are invertebrates. Not only does this have sheer numerical issues but vertebrate species typically have greater range and, as a result, are less likely to go extinct (Cowie et al, 2022). Definition breakpoints can also be employed to suggest that an extinction event is possible, but not yet occurring, for example that at least 75% of species are lost in a short period (Barnosky et al., 2011), making a mass extinction a potential event that may occur. However, if the trajectory says that we are rapidly heading toward a mass extinction event, it is peculiar luxury to viewing the matter from a geological perspective and debate whether whether we are “on the verge” or “in the midst” of it.

Whilst the debate over precision of loss of populations, species, and definitions are clearly ongoing, the calculated values from proxies do seem to be well-grounded, even if the results of those estimations give discomforting results. A more peculiar position is those authors (e.g., Kareiva, Lalasz & Marvier, 2011; Thomas, 2017)) who who accept the extinction crisis but consider it a new evolutionary trajectory that ought to be embraced for humanity and that it provides an opportunity for neoliberal property rights, a very different approach to denial (it's not happening) or scepticism (it's not as bad as mainstream research suggests). This, of course, steps into the realm of political ecology and consideration of how human stewardship applies in terms of political economy and whether animal agency is given appropriate consideration (Blattner, 2021). As a response to the neoliberal perspective, Cowie et al., (op cit) argue for the "the nurturing of the innate human appreciation of biodiversity" as well as scientific role of "preventative archeology". Advantages in local conservation action in biodiversity hotspots is recognised as a priority, especially given that the prognosis for survival for a number of extant species in not optimistic.

Degree of Human Cause

Whilst under some discussion, the evidence is in favour of rapid loss of biodiversity, in terms of populations, species, and biodiversity. Even if particular breakpoints of losses have not have been reached a precautionary and preventative principle should apply, especially in consideration of the changes to biogeography and the rate of change. It is important to note that all the referenced reviewers here in this debate over quantification and whether or not the change to biodiversity and abundance represents an extinction event recognise the role of human activity in the changes, documented and estimated. Even when limiting extinctions to the background rates of for mammal and other vertebrate extinctions, based on "highly conservative" and "conservative" rates from the International Union of Conservation of Nature, a comparison of rates in the last century (since 1900 CE) and the last few centuries (1500 CE) indicates “an exceptionally rapid loss of biodiversity” (Ceballos et al, 2015).

These accelerated extinction rates closely correspond to the rise of industrial society and the accelerated rate of human development and impact on the environment. Whilst the extinction of species due to the effects of anthropogenic global warming are currently few - the Bramble Cay Melomys (melomys rubicola) is a notable exception (Waller et al, 2017) - human development includes population growth and consumption, changes to land-use (e.g., crop pollination, water purification), industrialisation, economic inequality between humans, and the rise of culturally and aesthetically important associations between humans with their non-human companions. Such developmental changes are readily evident in the geographic changes relevant to species. Making use of detailed classification of anthromes (Ellis, et al, 2010) on a global level it has been determined that in 1700 CE, approximately 50% of the terrestrial biosphere was wild and with an additional 45% in a seminatural state consisting of sparsely populated woodlands, with only 5% consisting of settlements, croplands and pasture. By 2000 CE, 55% had become agricultural and settled anthromes, less than 20% seminatural and only 25% left wild. Needless to say, human development was also in the most ecologically rich areas as well; whilst wild barren land changed moderately (1700CE 17.22%, to 2015CE 12.14%), seminatural land has declined substantially (58.68% to 24.25%) as croplands (2.52% to 14.70%) and pasture have increased (6.87% to 26.48%) (Ellis, Beusen, & Goldewijk, 2020).

Mitigation and Solutions

The documented extent and future trends of biodiversity loss and abundance, including the requirements for biodiversity, e.g., freshwater, the significance of climate disruption and global warming, and ever-increasing and devastating metrics of human consumption, all make for grim prognosis. Already living biomass of terrestrial vertebrates on Earth with only c5% made up of all wild animals (Bar-On et al., 2018) and there is with only a 1/3 chance of the climate not exceeding a 2°C warming (IPCC, 2018). Understanding the extent, however unsettling, and identifying the causes, does give rise to the possibility of solutions.

Based on this knowledge, two main issues of concern are raised by Bradshaw et al, (2021); the failure of international cooperation and targets, and the political impotence of an uninformed and misinformed public against the media power of vested interests and extremist ideologies. As examples of the former, the authors note that none of the Aichi Biodiversity Targets for 2020 were met and most of the nature-related United Nations Sustainable Development Goals are on track to failure. The arrival of the global pandemic occurred despite predictions that biodiversity loss increased the probability of zoonotic disease, with three-quarters of new infectious diseases resulting from human-animal interactions, with ever-increasing rates as human activities such as deforestation and wildlife trade occurs increasingly in regions where pathogen diversity is high, but institutional capacity is weak (Austin, 2020). With regard to the latter, inequalities in wealth, power, and consumption among people and countries weaken attempts to implement global policies.

Further, whilst human ingenuity allows the species to surpass the population limits that would normally be limited by density feedback (Herrando-Pérez et al., 2012) the limits of the tribalistic political system that places resource use above the long-term decisions for environmental sustainability ultimately destroys the very conditions necessary for the survival of the species as part of nature. Fundamental changes to global capitalism are considered requisite, including greater education and equality (especially equality for women), the abolition of perpetual growth, the regulation of markets, the pricing of externalities, and the exit from fossil-fuel use. Finally, they places stress on the "extraordinary responsibility" that scientists carry to inform government, industry, and the public with candour and accuracy, noting again the lack of awareness.

In a similar manner Dirzo et al (2022), identify an intersection of the current extinction crisis between two complex adaptive systems; human culture and ecosystem functioning. Like Bradshaw et al, they recognise that humans are part of that biodiversity and that civilisation and the fate of the species depends on a functional ecosystem, which is being destroyed by human society. Three reasons are for this; the first is a lack of awareness, the second is an incorrect assumption of species extinctions versus population extinctions, and third the lack of individual and collective effort to reduce the scale of the human enterprise by reducing birth-rates and reducing inequitable and wasteful consumption. Regional populations are identified as the priority over the more conclusive and popular global metric of species loss, which occurs a posteriori, noting "an unappreciated network of synergies". The ongoing acceleration of human development in population growth and resource consumption is directly related to these population and species losses. Specific mitigating strategies are suggested, which include public science on the crisis, safeguarding unscathed territories (especially indigenous territories), dietary changes, and ending kakistocracy (the rule of the least capable).

Concluding Remarks

A review of the possibility of an Anthropocene extinction event has been carried out by reviewing matters of quantification, the degree of the extinction, the human contribution, and potential mitigation. Whilst additional precision and research on quantification is clearly necessary, the weight of evidence is in favour of the proposition that we are witnessing a dramatic and increasing loss of populations of species, profound biogeographical changes, all of which can be overwhelmingly attributed to human activity and human consumption, clearly evident in metrics such as land use changes, and also recognised by those studies which recommend a range of mitigating actions starting from raising awareness of the seriousness of the situation, to changes in the global political order and lais land use sez-faire capitalism.

It is perhaps fair to say that none of the authors are deeply versed in political economy or the processes of institutional change. It is all very well to suggest including externalities in price signals, reining in capitalism, empowering women (especially reproductive choices), ending an economic system predicated on perpetual growth, and so forth, but what has is lacking to date is systematic approach that takes these very specific policy objectives and applying robust statistical methods that can show their contribution to population extinctions and the effects that it has on a functioning human society. Insofar that this is a scientific problem related to human action in the environment, the Anthropocene extinction event is a matter worth including in future IPCC publications to spur action on the international stage, at the very least. The opening paragraph spoke of “rearranging deckchairs on the Titanic”; to follow that metaphor more literally what is needed is commitment shown by the crew and passengers of the RMS Carpathia (Butler, 2009) who, in a coordinated fashion and recognising the seriousness of the situation, dedicated every resource that they had at disposal to save the lives of those on a doomed and sinking ship.

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