What is the sixth extinction?
Since its formation roughly 4.5 billion years ago, the Earth has continued to evolve. Its continents have shifted, its atmospheric composition has altered and its temperatures have risen and decreased. Change on Earth is inevitable and in order to survive here, adaptation is necessary. Organisms have evolved alongside these changing conditions since life began, diversifying into the complex forms we see today (Turvey and Crees).
There have been five occasions, however, where conditions have changed so drastically that large numbers of species have been eradicated. We refer to these events as mass extinctions, or the big five. The most commonly known case, and the last to of occurred, is that of the dinosaurs (the end-Cretaceous extinction). This event took place sixty-five million years ago and saw three-quarters of life on earth become extinct (Turvey and Crees).
It is hard to imagine three-quarters of all species vanishing. It’s a hugely significant reduction in biodiversity. If predictions are correct though, this could once again become a reality. We are now thought to be in the midst of a sixth event. One that differs slightly from its predecessors, however, in that it is caused by a species (yes, us!) rather than a natural catastrophe. Not only are we experiencing one of the rarest occurrences in history, we are actually causing it (Turvey and Crees).
How are we causing this event?
When humans arrived on Earth approximately two hundred thousand years ago, we were not a particularly strong or fertile group. Our ability to be incredibly resourceful made up for this though. We were able to cross oceans and inhabit new lands, develop tools and hunt wide varieties of prey. With the development of agriculture, we created more reliable food sources and were able to grow in numbers (Kolbert). We were also set apart from other animals in that we were able to cooperate both flexibly and on a large scale. We communicated through language, created sophisticated systems of cooperation, and were able to invent and theorize (Kolbert).
As we became increasingly dominant, our impacts on the environment also increased. We disrupted ecological communities, exploited resources, left pollution, and began to change the composition of the atmosphere and oceans by burning fossil fuels (Kolbert). In addition to these factors, blame may also be placed on our desire for economic growth. As we have pursued wealth and profits, we have consumed and appropriated more resources (Cafaro).
This is not the first time that the Earth’s temperatures or atmospheric composition have changed. It is the rate at which these processes are taking place that is causing the issue. Global warming, for example, is thought to be occurring at least ten times faster today than it was at the end of the last glaciation period (Kolbert). Survival will therefore require organisms to migrate or to adapt, at least ten times more quickly than in the past. Whilst some will be able to do this, many others will not.
How do we know this?
We use the ‘background extinction rate’ to estimate the number of species we would expect to disappear over a period of time. It is generally expressed as ‘extinctions per million species-years’ and is calculated using fossil records (Ceballos et al.). Mammals, for example, are thought to have a background extinction rate of 0.25 per million species-years. As there are roughly five-thousand five-hundred species in this group today, the background extinction rate would predict one species to disappear every seven hundred years (Kolbert).
During a mass extinction event, however, rates of disappearance drastically increase. We are seeing evidence of this today. It is thought that a quarter of all mammals, third of all reef-building corals, a fifth of all reptiles, and a sixth of all birds are heading towards extinction (Kolbert). Perhaps one of the most significant examples is that of the amphibians. Modern forms of these animals, such as frogs and toads, have been in existence for two-hundred and fifty million years. They roamed the Earth long before the dinosaurs and are therefore one of the planet’s best survivors. Despite this, their extinction rate is now thought to be forty-five thousand times higher than their background rate (Wake & Vredenburg).
The case of the golden frog
The golden frog, a species endemic to Panama, was once abundant in central America. Following the introduction of a foreign fungus, however, the frog became extinct in the wild. The frog’s disappearance initially baffled scientists but when cultures were taken from a group of infected frogs, at the National Zoo in Washington DC, the fungal theory was formed.
Since its discovery, the fungus has been detected across South America, Australia, New Zealand, Europe, and the United States (Wake & Vredenburg). It is not known how exactly the fungus was spread. One idea is that it was distributed with shipments of African Claw Frogs, which were once used in pregnancy tests. Another possible explanation is that it was spread by North American Bullfrogs, which are exported for human consumption. Both species are infected with the fungus but are not threatened by it. Regardless of the origin, all theories point towards the human movement of animals around the world (Wake & Vredenburg). This example highlights how our interference with the natural environment can have devastating impacts.
How should we view this issue?
As a waste or a mistake?
It’s hard to disagree that this reduction in biodiversity is a waste. Healthy ecological communities enable our ecosystems to flourish and in turn, they provide us with food, medicine, water, protection, and countless other services. They contribute to our well-being and provide an invaluable cultural, educational and aesthetic resource. Through extinction, we are limiting our future possibilities (Cabellos et al.).
By approaching the issue as one of waste though, we may not capture its full meaning. We risk focusing a little too largely on human wants and needs and present the loss of biodiversity as a failure to meet them. This approach also presents biodiversity as a resource and in turn, ignores important moral aspects. It commoditizes organisms and ignores their histories and intrinsic values, serving to justify the extinction of those who have little use to us (Cafaro).
This approach recognizes mass extinction as an immoral event. An injustice caused by us towards other species. Whilst it may not be the result of intentional spite, there was no planning to wipe out the golden frogs for example, we do continue to take over both land and resources. The global population has risen by over three hundred percent in the last one hundred years and in this same period, the global economy has also increased by at least one-thousand five-hundred percent. We continue to pursue economic growth despite the impacts it is having on our biodiversity (Cafaro).
This has led to the division and destruction of natural habitats, reduction of animal populations, and greater bio-homogeneity . We reduce ocean life to food and by-catch, rainforests are destroyed for the sake of meat production, temperate forests are cut down for timber and freshwater channels are dammed, overfished and polluted. Given humanity’s refusal to stop practices that are causing significant harm, and to take the necessary steps to protect other species, it is hard to claim that this loss is completely inadvertent (Cafaro).
So we must answer this question – are other species worth our consideration? Cafaro provides an eloquent summary, ‘The organisms comprising a species often show incredible functional, organizational, or behavioral complexity. Every species, like every person, is unique, with its own history and destiny. Every species is an ongoing achievement. These empirical truths support the moral claim that species possess great intrinsic value and that people should appreciate and defend that value—not destroy it.’ (Cafaro).
As natural beings we must use nature as a resource for our own survival but as conscious and moral beings we should be able to limit our impacts. We should be able to recognize the rights of other species and live alongside them, sharing territory and resources. What if this is not the case though? If we recognize economic and demographic growth as the key factors in biodiversity loss, do we, our leaders or institutions really have the ability to limit this growth – even if desired? If anything the problem appears to be getting increasingly out of control, as technological advances enable us to push beyond constraints that would of traditionally limited us (Cafaro).
Can we limit growth?
The Intergovernmental Panel on Climate Change’s fourth and fifth assessment reports (2007 and 2014) provide a prime example (Intergovernmental Panel on Climate Change). They identified population growth and increased per capita wealth as the main drivers of increased global greenhouse gas emissions. Neither report, however, considers stabilizing our population size or reducing economic growth as a means to slowing emissions. Both focus on improvements to efficiency, despite both the proven failure of such strategies. If we fail to consider these things an option in order to save human lives, which will become threatened if catastrophic climate change occurs, it is unlikely that we will do so in order to protect other species.
Some argue that we can in fact limit growth. There are cases whereby land/waters have been designated protected status in order to preserve their ecosystems and species, for example, or instances where policymakers have chosen social causes over economic growth. Whilst these cases do provide hope, these efforts are somewhat weak in a global context. Protecting areas of land, for example, is of little use if climate change means that the biodiversity in the region is lost anyway. If we are to create significant change, it will be necessary to limit growth on a much larger scale – something that is currently not under consideration (Cafaro).
To believe the sixth extinction is inevitable though, is to accept there is no other outcome for life on earth. This is a bleak outlook and one that is unconstructive. It is important that we believe in our capability of creating a better future for ourselves and for the planet. If we are to maintain the natural world’s diversity, we must cultivate better relationships with our environment and create policies and institutions that make these relationships a reality.
Significance in Anthropology: So what does this mean for the future of humanity?
We are currently at a crossroads, whereby we must decide the future of life on Earth. If we choose to accept moral responsibility for the event we are causing, we may be able to take the necessary steps to end this extinction (Bjaerke). If not, one possibility is that humans may eventually make the planet uninhabitable for themselves. Their dependence on the natural world and their drastic transformation of it, means it will no longer support their survival. Another possibility is that the ingenuity of humans will overcome this transformation. We will use technology to counteract the disruption we have caused to natural systems. Humans are at a point where they will decide which pathways will remain possible (Kolbert).
Bjaerke, M. (2021). The sixth extinction: Naming time in a new way. In K. Kyrre, M. Bjaerke, & A. Eriksen (Eds.), Climate Change Temporalities: Explorations in Vernacular, Popular, and Scientific Discourse (178-215). Routledge.
Ceballos, G., Ehrlich, P., Barnosky, A., Garcia, A., Pringle, R., & Palmer, T. (2015). Accelerated modern human-induced species losses: entering the sixth mass extinction. Science Advances. 1(5).
Ceballos, G., Ehrlich, P., & Dirzo, R. (2017). Biological annihilation via the ongoing sixth mass extinction singled by vertebrate population losses and declines. Proceedings of the National Academy of Sciences. 114(30).
Cafaro, P. (2015). Three ways to think about the sixth mass extinction. Biological Conservation. 192. 387-393.
Intergovernmental Panel on Climate Change. (2007) .Summary for Policymakers. Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. CambridgeUniversity Press, Cambridge.
Intergovernmental Panel on Climate Change. (2014). Summary for Policymakers. Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge.
Kolbert, Elizabeth. (2014). The sixth extinction: an unnatural history. London: Bloomsbury.
Turvey, S., & Crees, J. (2019). Extinction in the Anthropocene. Current Biology. 29. 982-986.
Wake, D., & Vredenburg, V. (2008). Are we in the midst of the sixth mass extinction? A view from the world of amphibians. Proceedings of the National Academy of Sciences. 105(1). 11466-11473.