PNAS

EXPERT REACTION: More than 500 species on the brink of extinction

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Peer-reviewed: This work was reviewed and scrutinised by relevant independent experts.

Human activity in biodiversity hot-spots has brought more than 500 vertebrate species to the brink of extinction, according to international researchers who say the world is experiencing its sixth mass extinction, which harms ecosystem function and endangers human wellbeing. The researchers looked at 29,400 species on the Red List of Threatened Species and from Birdlife International and found that 1.7 per cent, or 515 of them, are on the brink of extinction. They also say 84 per cent of the 388 terrestrial vertebrate species that have fewer than 5,000 remaining individuals are located in the same geographical regions as species on the brink and may therefore soon face a similar risk due to the human-driven collapse of regional biodiversity. Additional analyses suggest that terrestrial vertebrate species on the brink have collectively lost approximately 237,000 populations since 1900. According to the authors, the findings underscore the need for global action to prevent further loss of terrestrial vertebrate species. Below Australian experts comment on the research.

Journal/conference: PNAS

DOI: 10.1073/pnas.1922686117

Organisation/s: Australian Science Media Centre, Griffith University, James Cook University, University of Tasmania, Deakin University, Monash University, Charles Darwin University, Instituto de Ecología

Funder: The work of G.C. was partially supported by the Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica (PAPIIT) Project IN208017 and a sabbatical scholarship from Dirección General Asuntos del Personal Académico (DGAPA) of the Universidad Nacional Autonóma de México.

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Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Associate Professor Diana Fisher is from the School of Biological Sciences at the University of Queensland, and the Co-Chair of the IUCN Marsupial & Monotreme Species Specialist Group and Vice President of the Australian Mammal Society

Gerado Ceballos, Paul Ehrlich and Peter Raven want to draw your attention to the global extinction crisis by highlighting where in the world species of mammals, birds, amphibians and reptiles are on the brink of extinction (fewer than a thousand individuals left). Using International Union for the Conservation of Nature (IUCN) Red List of threatened species data (and Birdlife - the bird authority for the IUCN), they find at least 515 species on the brink. These are on every continent but Antarctica, most in the tropics and subtropics, about half on continents and half on islands, in places highly impacted by humans.

This is an important study that deserves attention, because so many people do not realise how much of the world’s wildlife faces impending extinction. I agree with the authors that this extinction crisis needs to be elevated to an emergency equal to climate change.

This study is very relevant to Australia. Ceballos and colleagues show that our region has the second-highest number of land vertebrates on the brink of extinction, despite being the smallest continent (we are about the size of Brazil). Only South America has more species on the brink, because of the many critically endangered frogs there. 

We continue to lose our wildlife; of the over 400 modern extinctions of land vertebrates, about fifty are Australian, and several have happened in the last decade. Ceballos and colleagues highlight the wildlife trade, but in Australia, habitat loss and invasive predators and diseases are particularly serious threats. Ceballos and colleagues chose the threshold of 1000 for species ‘on the brink of extinction’ because it is relevant to some IUCN criteria for assessing the highest extinction risk (Critically Endangered).

Evidence of decline rates and risks predicts how many extinctions are coming; there are many good ways to find this. For example, I was part of a recent study looking at several types of data – we found that up to 42 Australian mammals and birds (up to 6 per cent of all species) are expected to be eliminated in the next 20 years if our efforts to save them don’t improve. Ceballos and colleagues are worried that all of the ‘species on the brink’ might go extinct by 2050, and they are calling on the IUCN to immediately classify all species with populations under 5000 to be classified as Critically Endangered. It is possible that the highest extinction risk threshold could change as the global situation for wildlife continues to deteriorate, but the current IUCN Red List criteria are based on rigorous data, and they are not only about absolute numbers in the population. I don’t see a reason to change this well-supported threshold unless we find that the risk of losing populations of 1000-5000 really has shot up, for example.

Also, I think we should not give up. Conservation efforts do work, and every population can be saved if we want to save them. Dozens of birds and mammals have recovered from tiny populations due to intense conservation effort. It is affordable to avoid more species extinctions in Australia - we just need to get our priorities right (an estimate of the recovery cost for threatened species in 2019 was $1.69 billion per year - half of the amount spent on pet cat care

Last updated: 01 Jun 2020 2:26pm
Declared conflicts of interest:
None declared.
Dr Amy Coetsee is a Threatened Species Biologist at Zoos Victoria

Globally, humans are driving many species towards extinction at an accelerated rate. The PNAS paper is a wake-up call to take urgent action on a global scale, to reverse the extinction crisis. If we don’t, civilization is at risk. Australia has the worst mammal extinction record in the world. Many of our unique species are on the brink of extinction due to habitat destruction, introduced species, such as cats, foxes, cane toads, and climate change. We can already see the evidence of what happens when we lose species. Since European settlement, our once fertile soils have become degraded as our digging mammals such as bandicoots, potoroos and bettongs have disappeared across most of their range. These diggers perform an important role when they turn over the soil every night looking for food, as their digging action improves soil health.

Whilst we are currently on a devastating trajectory, there is hope, we can reverse the extinction crisis. With strong environmental laws that protect native wildlife, long term investment into threatened species recovery and a renewable energy future, we will save species from extinction. The mainland Eastern Barred Bandicoot is one species that is making a comeback. Once listed as extinct in the wild it has now been returned to live in the wild on Victorian islands. 

Zoos Victoria work with 27 species on the brink of extinction, including mammals, birds, reptiles, amphibians and invertebrates. We have made a commitment that no threatened vertebrate species will go extinct on our watch.

Last updated: 01 Jun 2020 2:23pm
Declared conflicts of interest:
None declared.

Professor Chris Johnson is a Professor of Wildlife Conservation & ARC Australian Professorial Fellow in the School of Zoology at the University of Tasmania

The current rate of extinction of species is higher than at any time since 65 million years ago, when the collision of a space-rock with the Earth killed off dinosaurs and many other species. Threats to species in today’s world - things like habitat destruction and climate change - are growing rapidly. This suggests that the rate of extinction may be about to increase further. The significance of this study is that it provides evidence for that impending rise in extinctions. The authors do this by tallying all of the land vertebrates on the planet that are down to 1,000 or fewer individuals. There are 515 of these. That’s roughly the same as the number of all vertebrates that have gone extinct in the last century. Most of these species currently on the brink have far fewer than 1,000 individuals left, and are likely to be gone very soon. 

The analysis shows that Australia is one of the world’s hotspots of species on the verge of extinction. Things are especially bad in southeastern Australia, and of course this study was not able to take account of the bushfires of last summer, which have made matters in the southeast even worse.

The tragedy of all of this is that we have the knowledge to save species from extinction, and doing that is cheap in a global context. But this task is just not given enough priority by society and governments.

Last updated: 01 Jun 2020 1:59pm
Declared conflicts of interest:
None declared.
Professor Ralf Buckley is Director of the International Centre for Ecotourism Research at Griffith University

Ceballos, Ehrlich and Raven are very well known conservation scientists. Here they show that the most critically endangered vertebrate species occur in geographical clumps. Where there is one, there are likely to be many. For example, they show that some regions of Australia support the last remaining populations of critically endangered endemic bird species, and that these species occur together in the same habitat remnants. 

This clumping is both bad and good. Bad, since where one species is driven to extinction, others are likely to go with it. Good, since if one species and its habitat can be protected, others will survive with it. In addition, funding to protect many endangered species now relies largely on ecotourism. So, if one species is charismatic and attracts tourists, this can also help less well known species in the same area. 

But tourism depends on safety. This study shows that northwestern Colombia is a super hotspot, an overlap zone for endangered mammals, birds, reptiles and amphibians, all at once. Tourism to Colombia is still small. This new analysis shows, for example, that if conservation efforts could focus on boosting tourism to Colombia, there would be a high payoff.  The same applies for other overlap zones.

These authors rightly point to the enormous losses in biodiversity to date, and continuing threats to many species. But they also give us a set of priorities, places to focus efforts.

Last updated: 01 Jun 2020 1:52pm
Declared conflicts of interest:
None declared.
Dr Noel Preece is a University Fellow at the Research Institute for the Environment and Livelihoods at Charles Darwin University, an Adjunct Associate Professor at James Cook University and Director at Biome5 Pty Ltd - an environmental management and consultancy for Northern Australian businesses.

On the brink: Ceballos, Ehrlich and Raven have rightly raised the alarm on extinctions, but they seriously underestimate the plight of native species. Their estimates of species ‘on the brink’ are serious underestimates because most species are not monitored. For instance, the only long-term monitoring of mammal species across the whole of the northern savanna and northern desert regions, more than 2 million square kilometres, is on three national parks in the Northern Territory, some 200 sites. For half the savanna region, in north Queensland, there are zero monitoring sites. Scientists really don’t know the status of even the most iconic species. 

There are no Recovery Plans for most threatened species, and no money to research and manage them. Radical cuts to environment, research and national park budgets by all governments over decades, the period of greatest increases of species extinctions, have trashed any efforts at saving species. 

This sad situation is compounded by Federal and State governments establishing, with Indigenous people, Indigenous Protected Areas, that now cover 44 per cent of Australia, but they underfund the estate by 95 per cent compared with government conservation estate. Australia claims Indigenous Protected Areas as part of its national estate where many threatened species live but does not provide the resources to manage that estate.

Last updated: 01 Jun 2020 1:51pm
Declared conflicts of interest:
None declared.
Associate Professor Euan Ritchie is Director of the Media Working Group at the Ecological Society of Australia and an Associate Professor in Wildlife Ecology and Conservation at Deakin University

This recent study by Ceballos and colleagues is yet more dire confirmation that we are destroying life at a horrific pace and scale. As they note, the 400 vertebrate species that have gone extinct in the previous one hundred years, would normally take 10,000 years under a normal ‘background’ rate of extinction. This work and that of many other conservationists is demonstrating that there is a gross failure of governance and duty of care for this planet’s inhabitants, which we share Earth with and are enriched by and utterly dependent upon.

Australia is indeed one of the world’s worst conservation performers, despite the fact we are a relatively wealthy nation and our remarkable plants and animals are largely irreplaceable, being found nowhere else. Crucially, there is still time to stop the extinction crisis worsening, and COVID-19 has taught us that we can make big and rapid changes that benefit the environment. We simply cannot afford any further delay to a transition to a more sustainable way of life.

Last updated: 01 Jun 2020 1:49pm
Declared conflicts of interest:
None declared.
Dr Rohan Clarke is a lecturer in the School of Biological Sciences at Monash University

This new research is an important contribution to our understanding of extinction rates for the world’s fauna. Much previous work has focussed on known extinctions in recent centuries, and used that to project future extinctions. Here, the focus is on species that ‘hang by a thread’ but are not yet extinct; specifically species whose global populations now total fewer than 1000 individuals. Using these new data, their projections are that already grim extinction rates are likely to get much worse. Indeed, they estimate extinction rates in the coming decades may be more than 100 times greater than background extinction rates. 

The links between human health and wellbeing, and the health of our planet are well known. This research highlights the fragility of the earth’s support systems and the urgent need to act. The call for the conservation of endangered species to be elevated to a national and global emergency is both warranted and urgent. 

In Australia, amongst other actions, this means the halting of native vegetation clearance, effective management of invasive pests, best practice management of our existing conservation reserve system for the benefit of nature, and efforts to restore landscapes beyond reserve boundaries.

Last updated: 01 Jun 2020 1:48pm
Declared conflicts of interest:
None declared.

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