Global human population pushing Earth past breaking point

23 04 2026

A few weeks ago we published a paper that was in the works for a long time, so long in fact that one of my co-authors died before it was published online.

That co-author was none other than the legendary Paul Ehrlich of Stanford University, and of The Population Bomb fame (and infamy). More importantly, but often overlooked, Paul wrote more than 700 scientific articles and 30 books during his career.

Paul Ehrlich died on 13 March 2026 at the ripe old age of 93, exactly two weeks before our article appeared online. Paul had a good innings no doubt, but I wish he had survived long enough to see what might very well be his last co-authored paper.

I first met Paul back in the mid-2000s during a trip through San Francisco. I had organised to come chat with Professor Gretchen Daily at Stanford, and Paul came along for lunch. I remember vividly how we clicked almost immediately.

We clicked so well in fact, that we wrote a book together, co-authored several high-impact papers (e.g., ‘ghastly future‘), spent a month in Bellagio as Rockefeller Foundation writing residents, participated in various public and parliamentary presentations, and generally just got on like a house on fire. Paul and his wife Ann became like family, so much so that they were de facto grandparents to my daughter who grew up with them in near-annual contact.

This post isn’t about Paul per se, but I cannot ignore the profound influence Paul had on my career, my personality, and my life view. I miss him. I am therefore dedicating this paper and post to his memory. So long, and thanks for all the fish.

Back to the paper in question.

The paper (Global human population has surpassed Earth’s sustainable carrying capacity) has already been downloaded nearly 23,000 times since it was published less than a month ago. It has an Altmetric score of 543, and is currently the top-trending paper in Environmental Research Letters.

Nothing like writing about human population to get the punters engaged.

We show empirically that the Earth has already exceeded its ability to support the global human population sustainably, with dire implications for increasing pressure on food security, climate stability, and human wellbeing. However, slowing population growth and raising global awareness could still offer us some hope.

Our study shows that humans have pushed well beyond the planet’s long-term carrying capacity and that continued growth under current patterns of consumption will intensify environmental and social challenges for communities worldwide.

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Categories : agriculture, anthropocene, biodiversity, carbon, celebrity, climate change, co-author, conservation, conservation biology, conservation scholars, demography, development, ecology, economics, education, Endarkenment, environmental policy, environmental science, evolution, extinction, food, human overpopulation, modelling, population dynamics, science, sustainability

Protecting the biodiversity brand through sport

15 04 2026

Using animals as sport symbols reflects the integration of biodiversity into cultural identity and the transmission of collective values. This raises the possibility that the economic muscle of the sport industry could translate its symbolic capital into tangible commitments to biodiversity conservation.

Those who have had the privilege of travelling in remote areas might have come across an unexpected scene: a football pitch in the middle of the Amazon rain forest or on the slopes of the Andes, a basketball court on the side of a Buddhist temple, or an ice hockey rink on a snow-ploughed lake in remote northern Canada.

Sport is a global industry that generates identity, belonging, education, and shared emotions for both athletes and their avid spectators (1). Sporting affinities now rival the sense of nationhood once shared by citizens during warfare (2).

Now in our heavily monetised world, sport clubs rely on their fans through tickets and merchandising, and indirectly through television rights and advertising. In this both emotional and commercial relationship, expressions such as being true to the badge reflect the central role of corporate symbols in building bonds between a club and its supporters (3).

Sport club logos with animal iconography. Top row: examples of the grey wolf (Canis lupus) in Neftekhimik Nizhnekamsk (ice hockey, Russia), Warrington Wolves (rugby, England), Wolverhampton Wanderers (football, England), and Roma (football, Italy). Second row: bald eagle (Haliaeetus leucocephalus) in Essex Eagles (cricket, England), Adler Mannheim (handball, Germany), and Philadelphia Eagles (American football, USA). Third row: Free State Cheetahs (represented by the cheetah Acinonyx jubatus; rugby, South Africa), Toronto Blue Jays (blue jay Cyanocitta cristata; baseball, Canada), Memphis Grizzlies (grizzly bear Ursus arctos horribilis; basketball, USA) and Hisamitsu Springs (Japanese white-eye Zosterops japonicas; volleyball, Japan). Fourth row: six Spanish football clubs. Clubs featuring wolves and eagles are often associated with the symbolic qualities of these species (e.g., intelligence, prowess, fealty, bravery, strength). In football, animals reflect represent the history and heraldry of cities and regions, as seen in the crests of in Atlético de Madrid (brown bear Ursus arctos), AS Roma and Athletic Club (wolf), Cultural Deportiva Leonesa and Atlético Osasuna (lion Panthera leo), CD Castellón (raptor) and Levante UD (bat). Photos: Gary Kramer (wolf) and Andy Morffew (eagle).

In professional sport such as football, clubs increasingly function as brands (4) where even traditional logos are modified to enhance a team’s commercial value and strengthen audience loyalty (5). In this process, biodiversity becomes relevant because the iconography of many sport organisations incorporates representations of plants and animals.

Sport fauna

To quantify this phenomenon, Ugo Arbieu and collaborators analysed the presence of animals in club names, crests, and fan nicknames among 10 professional team sports across 50 countries (6). They found that 727 teams use 161 different animal species in their corporate imagery. Football and basketball lead in the number of species represented due to the large number of clubs worldwide, but American football, rugby and baseball display greater symbolic fauna diversity per club. Mammals and birds are the most common, particularly carnivores and raptors.

Animal symbols in club iconography (names, logos, fan nicknames) for the sports with the largest audiences (6): basketball, handball, baseball, cricket, football, American football, ice hockey and volleyball. The sample excludes 106 teams that use domesticated species as identity symbols, includes 163 men’s leagues and 67 women’s leagues, respectively, and the animal species depicted in the emblems of 48 teams could be identified. Horizontal bars above show the most represented animal groups (top panel), and the 15 species most frequently featured (middle panel). Bottom panel: percentage of symbols according to the IUCN’s conservation status of the species, where ‘threatened’ includes the categories Near Threatened, Endangered and Extinct. The trend indicates that sport clubs prefer to identify themselves with large mammal species that are threatened.

This pattern is not coincidental, for it reflects the historical bias of science and conservation towards large, charismatic vertebrates (7), but also the uneven availability of biological information and our social preferences for certain species (8). These preferences are even reflected in the animal emojis we share regularly on social media (9).

Arbieu’s study also revealed that clubs tend to favour images of threatened fauna (6), possibly due to their higher symbolic impact and media visibility (10). Moreover, although clubs in Europe and the Americas more often depict exotic animals, native species dominate in Africa, Asia, and Oceania (6). This suggests that the choice of an animal as an emblem is the product of not only aesthetic or symbolic criteria, but also of cultural roots and the historical relationship of societies with their local fauna.

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Categories : Africa, alien species, biodiversity, birds, conservation, conservation biology, ecological literacy, ecosystem services, education, environmental policy, Europe, extinction, fish, invasive species, mammal, media, research, sustainability, threatened species

Our pets are predators

21 01 2026

Those of us living with cats share our homes with an ancestral predator, one adapted for hunting and the frequent, exclusive consumption of meat. These instincts become fully activated outside the domestic environment, where cats pose a global threat to wildlife.

Pets are family. We celebrate their arrival with the same joy as a grand homecoming, and their absence leaves a grief as deep as losing a loved one. In bonding with cats and dogs, we often attribute human abilities and emotions to them.

But beyond this affection, domestic animals still carry the instincts and genetic legacy of their wild ancestors(1, 2). My cats — Caruso, Muesli, and Plata — have been calm and loving, but they have always enjoyed a real hunt (3). When a moth comes in through a window, they seem possessed: their mouths chitter and make clicking sounds, they leap from one piece of furniture to another, and their heads snap sharply between the insect’s position and other points in the room, calculating the best spot from which to pounce on their prey. That is why when they become feral, cats and dogs integrate into food chains like any other species: they compete for ecosystem resources, hunt and are hunted, and hybridise and exchange diseases with other carnivores (4, 5).

Top: cat eating an Eurasian blue tit (Cyanistes caeruleus), a common visitor to home gardens in Nijmegen (Netherlands). Bottom, domestic cat after hunting an Eastern cottontail rabbit (Sylvilagus floridanus) in a residential neighbourhood of Stratford (Connecticut, USA). Photos courtesy of Jelger Herder (Nijmegen) and Scott Kruitbosch (Stratford). Scott is a photographer and conservationist. Near sunset on 30/09/2020, while intently observing local wildlife, he witnessed a neighbourhood cat sneak up from behind on a cottontail feeding in open grass and grab it. For years, Scott has had extremely negative interactions, both in person and online, with local residents over these issues. These exchanges have revealed that many people show little concern for wildlife or for the dangers their outdoor cats face, and believe that their cats would not, or could not, harm wildlife.

Domestic cats are highly skilled hunters, and their predatory interactions with a wide range of prey are widely documented in social media and documentaries. Some examples include cats catching: bats and birds on the wing, butterflies, chipmunks, dragons, fishes, grasshoppers, frogs, lizards, mice, owls, rabbits, seagulls, snakes, squirrels, and wallabies. See an award-winning photo depicting wildlife with fatal injuries caused by cats recorded in 2019 at a single animal hospital in the USA, and a video showing domestic cats mimicking bird calls and some cat owners explaining that their pets reject commercial cat food after experiencing the thrill of hunting real prey. The documentary Secret Life of Cats contextualises the ecological challenges posed by free-roaming cats.

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Categories : alien species, animal welfare, Australia, behaviour, biodiversity, birds, cat, conservation, conservation biology, decline, disease, ecology, environmental policy, Europe, exploitation, extinction, frog, impact, invasive species, mammal, management, predation, predator, research, threatened species

A long life can be a disadvantage

12 06 2025

Deep-sea sharks include some of the longest-lived vertebrates known. The record holder is the Greenland shark, with a recently estimated maximum age of nearly 400 years. Their slow life cycle makes them vulnerable to fisheries.

Humans rarely live longer than 100 years. But many other animals and plants can live for several centuries or even millennia, particularly in the ocean.

In the Arctic, there are whales that have survived since the time of Napoleon’s Empire; in the Atlantic, there are molluscs that were contemporary with Christopher Columbus’ voyages; and in Antarctica, there are sponges born before the Holocene when humans were still an insignificant species of hunter-gatherers (see video on lifespan variation in wildlife).

Long-lived species grow slowly and reproduce at later ages (1, 2). As a result, these animals require a long time to form abundant populations and to recover from fishing-related mortality.

Among cartilaginous fish (chimaeras, rays, sharks, and skates), the risk of extinction due to overfishing is twice as high for deep-sea species compared to coastal species, because the former have longer and slower life cycles (3).

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Categories : Arctic, biodiversity, conservation, decline, exploitation, extinction, fish, fisheries, food, IUCN, management, marine, predator, research, shark

Genetics to the rescue

27 05 2025

Procreating with a relative is taboo in most human societies for many reasons, but they all stem from avoiding one thing in particular — inbreeding increases the risk of genetic disorders that can seriously compromise a child’s health, life prospects, and survival.

While we all inherit potentially harmful mutations from our parents, the effects of these mutations are often partially or completed masked if we possess two alternative variants of a gene — one from each parent. However, the children of closely related parents are more likely to inherit the same copies of harmful mutations. This is known as ‘inbreeding depression’. 

But inbreeding depression can happen in any species, with the risk increasing as populations become smaller. Because many species are rapidly declining in abundance and becoming isolated from one another predominantly due to habitat destruction, invasive species, and climate change, the chances of inbreeding are also increasing.

Not only are such populations more susceptible to random disturbances, they are also victim of reduced population growth rates arising from inbreeding depression. This produces what is generally known as the ‘extinction vortex‘ — the smaller your population, the more you inbreed and produce sub-optimal offspring, leading to even more population decline and eventually extinction.

One emergency intervention that can ‘rescue’ such inbred populations from extinction (at least in the short term) is to introduce unrelated individuals from other populations in an attempt to increase genetic diversity, and therefore, the rate of population growth. While somewhat controversial because some fear introducing diseases or eroding local-area specialisation (so-called ‘outbreeding depression’), the risk-benefit ratio of this ‘genetic rescue’ is now widely considered to be worth it. 

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Categories : Australia, conservation, demography, extinction, extinction debt, extinction vortex, genetic diversity, genetics, inbreeding depression, mammal, threatened species

Trapped in the light

31 03 2025

Night is the peak activity period for many animal species. In the Western Andes of Ecuador, the Chocó golden scarab flies between forest patches during the night, but urban lighting interferes with their paths and jeopardises populations already struggling to persist in fragmented native forests.

Urban development has created a network of illuminated infrastructure that allows our society to function day and night without interruption. It is no surprise that with so much artificial light, we increasingly have to move farther away from towns and cities to see a sky full of stars.

Light pollution poses a challenge for nocturnal species that have adapted to living in the dimness of night (1, 2) — see documentaries about the impacts of artificial light on wildlife and insects, and a related scientific talk. This problem might be one of the causes of the global decline in insects (3, 4), in turn negatively affecting their role in maintaining agricultural systems through pest control, pollination, and soil quality (5). These concepts are featured by the documentaries The Insect Apocalypse and The Great Death of Insects.

Chocó golden scarab (Chrysina argenteola) walking on forest litter in La Maná (Cotopaxi, Ecuador). Growing to up to 4 cm in length, this species inhabits the tropical rainforest of the Chocó region in the Western Andes (10), where it is frequently attracted to artificial lights at night. The striking colour of this ‘jewel scarab’ is an optical illusion. The exoskeleton is covered with overlapping layers of chitin that polarise light and reflect hues of blue, gold, green, silver, or reddish tones, depending on the species (16). The metallic sheen appears to deter bird predation (17) and might serve as camouflage as well as aid in individual recognition (11). The eyes of insects are ‘compound’ — composed of 100s to 1000s of tubular eyelets (‘ommatidia’), each with its own cornea and lens (18), and all collectively contributing to insect vision. In nocturnal species like the golden scarab, the photoreceptor cells (at the base of each ommatidium) respond more slowly to light compared to diurnal species, allowing the former to collect more nocturnal light per unit of time before forming an image (19). However, just as staring at the sun blinds us, eyes adapted for night vision become overwhelmed by excessive artificial light, disrupting the behaviour of these species. Below the scarab image are two photographs contrasting the day and night landscapes of the same location in Pedro Vicente Maldonado (Pichincha, Ecuador) within the species’ distribution range. Photos courtesy of Martín Bustamante (animal) and Luis Camacho (city).

When flying, nocturnal insects orient their backs toward the sky, using the light of the moon and stars as a reference (6) (explained here and here). However, when they encounter artificial lights, they can no longer distinguish up from down, and so they can become disoriented, flying erratically, like a moth circling a streetlight.

It is estimated that a third of the insects attracted to artificial light die from collisions, burn injuries, exhaustion, and/or predation (7). In the tropics, finding countless dead insects at the base of urban lights is a common scene. Equally important is that artificial light also hinders migration, foraging, and the search for mates in many nocturnal species (1, 8, 9).

Nocturnal jewels

Camacho and collaborators evaluated the effect of artificial lighting at night on the Chocó golden scarab (Chrysina argenteola) (10). This species inhabits the tropical rainforests of the Western Andes from Ecuador to Colombia, and is a member of the group known as ‘jewel scarabs‘ due to their metallic body coloration (11). Because of its nocturnal habits and the larvae’s dependence on wood for food (12), the golden scarab has been increasingly affected by the loss of native forest in combination with light pollution from rural and urban expansion.

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Categories : agriculture, behaviour, conservation, decline, deforestation, ecology, extinction, fragmentation, habitat loss, rain forests, research, South America, tropical

The (new) birds and the bees

20 01 2025

‘Nuff said


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Categories : agriculture, algae, anthropocene, biodiversity, birds, bottom-up ecology, conservation, ecology, ecosystem services, extinction, pollination

Small populations of Stone Age people drove dwarf hippos and elephants to extinction on Cyprus

18 09 2024

Corey J. A. Bradshaw, Flinders University; Christian Reepmeyer, Deutsches Archäologisches Institut – German Archaeological Institute, and Theodora Moutsiou, University of Cyprus

Imagine growing up beside the eastern Mediterranean Sea 14,000 years ago. You’re an accomplished sailor of the small watercraft you and your fellow villagers make, and you live off both the sea and the land.

But times have been difficult — there just isn’t the same amount of game or fish around as when you were a child. Maybe it’s time to look elsewhere for food.

Now imagine going farther than ever before in your little boat, accompanied maybe by a few others, when suddenly you spot something on the horizon. Is that an island?

The western coast of Cyprus. CJA Bradshaw / Flinders University

An island of tiny elephants and hippos

Welcome to Cyprus as the world emerges from the last ice age. You are the first human to set your eyes on this huge, heavily forested island teeming with food.

When you beach your boat to have a look around, you can’t believe what you’re seeing — tiny boar-sized hippos and horse-sized elephants that look like babies to your eyes. There are so many of them, and you’re hungry after the long journey.

The diminutive beasts don’t seem to show any fear. You easily kill a few and preserve the meat as best you can for the long journey back.

When you get home, you are excited to let everyone in the village know what you’ve found. Soon enough, you organise a major expedition back to the island.

Of course, we’ll never know if this kind of scenario took place, but it’s a plausible story of how and when the first humans managed to get to Cyprus. It also illustrates how they might have quickly brought about the demise of the tiny hippopotamus Phanourios minor, as well as the dwarf elephant Palaeoloxodon cypriotes.

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Categories : anthropocene, decline, demography, ecology, endemic, Europe, exploitation, extinction, food, harvest, mammal, mathematics, palaeo-ecology, population dynamics, population viability analysis, predation, predator, research, science, stochasticity

Human impact, extinctions, and the biodiversity crisis

22 08 2024

Human overpopulation is often depicted in the media in one of two ways: as either a catastrophic disaster or an overly-exaggerated concern. Yet the data understood by scientists and researchers is clear. So what is the actual state of our overshoot, and, despite our growing numbers, are we already seeing the signs that the sixth mass extinction is underway?

In a recent episode of The Great Simplification podcast, Nate Hagens was joined by global ecologist Corey Bradshaw to discuss his recent research on the rapid decline in biodiversity, how population and demographics will change in the coming decades, and what both of these will mean for complex global economies currently reliant on a stable environment.

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Categories : agriculture, alien species, anthropocene, Australia, biodiversity, carbon, climate change, climate shift, conservation, conservation biology, corruption, decline, deforestation, demography, development, economics, Endarkenment, environmental policy, exploitation, extinction, extremism, food, gender, governance, habitat loss, harvest, human overpopulation, invasive species, population dynamics, sustainability, threatened species, trophic cascades

New ecosystems, unprecedented climates: more Australian species than ever are struggling to survive

21 02 2024

Australia is home to about one in 12 of the world’s species of animals, birds, plants and insects – between 600,000 and 700,000 species. More than 80% of Australian plants and mammals and just under 50% of our birds are found nowhere else.

But habitat destruction, climate change, and invasive species are wreaking havoc on Earth’s rich biodiversity, and Australia is no exception.

In 2023, the federal government added another 144 plants, animals and ecological communities to the threatened species list – including iconic species such as the pink cockatoo, spiny crayfish and earless dragons.

More and more species stand on the edge of oblivion. That’s just the ones we know enough about to list formally as threatened. Many more are in trouble, especially in the oceans. Change is the new constant. As the world heats up and ecosystems warp, new combinations of species can emerge without an evolutionary connection, creating novel communities.

It is still possible to stop species from dying out. But it will take an unprecedented effort.

The vulnerable southern bell (growling grass) frog (Litoria raniformis). Rupert Mathwin/Flinders University
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Categories : alien species, anthropocene, Australia, biodiversity, climate change, conservation, conservation biology, decline, ecosystem, environmental policy, extinction, genetic diversity, habitat loss, mammal, management, recovery, threatened species

Rextinct: a new tool to estimate when a species went extinct

18 12 2023

If several fossils of an extinct population or species are dated, we can estimate how long ago the extinction event took place. In our new paper, we describe CRIWM, a new method to estimate extinction time using times series of fossils whose ages have been measured by radiocarbon dating. And yes, there’s an R package — Rextinct — to go with that!

While the Earth seems to gather all the conditions for life to thrive, over 99.9% of all species that ever lived are extinct today. From a distance, pristine landscapes might look similar today and millennia ago: blue seas with rocky and sandy coasts and grasslands and mountain ranges watered by rivers and lakes and covered in grass, bush and trees.

But zooming in, the picture is quite different because species identities have never stopped changing — with ‘old’ species being slowly replaced by ‘new’ ones. Fortunately, much like the collection of books in the library summarises the history of literature, the fossilised remnants of extinct organisms represent an archive of the kinds of creatures that have ever lived. This fossil record can be used to determine when and why species disappear. In that context, measuring the age of fossils is a useful task for studying the history of biodiversity and its connections to the planet’s present.

In our new paper published in the journal Quaternary Geochronology (1), we describe CRIWM (calibration-resampled inverse-weighted McInerny), a statistical method to estimate extinction time using times series of fossils that have been dated using radiocarbon dating.

Why radiocarbon dating? Easy. It is the most accurate and precise chronometric method to date fossils younger than 50,000 to 55,000 years old (2, 3). This period covers the Holocene (last 11,700 years or so), and the last stretch of the late Pleistocene (~ 130,000 years ago to the Holocene), a crucial window of time witnessing the demise of Quaternary megafauna at a planetary scale (4) (see videos here, here and here), and the global spread of anatomically modern humans (us) ‘out of Africa’ (see here and here).

Why do we need a statistical method? Fossilisation (the process of body remains being preserved in the rock record) is rare and finding a fossil is so improbable that we need maths to control for the incompleteness of the fossil record and how this fossil record relates to the period of survival of an extinct species.

A brief introduction to radiocarbon dating

First, let’s revise the basics of radiocarbon dating (also explained here and here). This chronometric technique measures the age of carbon-rich organic materials — from shells and bones to the plant and animal components used to write an ancient Koran, make a wine vintage and paint La Mona Lisa and Neanderthal caves. 

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Categories : carbon, conservation, decline, ecology, extinction, mathematics, modelling, New Zealand, research, software, statistics

Assessing the massive costs of biological invasions to Australia and the world

6 09 2023

A global database set up by scientists to assemble data on the economic cost of biological invasions in support of effective government management strategies has grown to include all known invasive species.

Now involving 145 researchers from 44 countries — the current version of InvaCost has 13,553 entries in 22 languages and enables scientists to develop a clear picture about the major threats globally of invasive species to ecosystems, biodiversity, and human well-being.

Biological invasions are caused by species introduced on purpose or accidentally by humans to areas outside of their natural ranges. From cats and weeds, to crop pests and diseases, invasive species are a worldwide scourge. 

Invasive species have cost over US$2 trillion globally since the 1970s by damaging goods and services, and through the costs of managing them, and these economic costs are only increasing.

A new synthesis published in the journal BioScience documents the progress of the InvaCost endeavour. The study provides a timeline of the state of invasion costs, starting with prior flaws and shortcomings in the scientific literature, then how InvaCost has helped to alleviate and address these issues, and what the future potentially holds for research and policymakers.  

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Categories : agriculture, alien species, Australia, biodiversity, climate change, conservation, environmental economics, environmental policy, extinction, invasive species, management

Intricate dance of nature — predicting extinction risks in terrestrial ecosystems

30 06 2023

Have you ever watched a nature documentary and marvelled at the intricate dance of life unfolding on screen? From the smallest insect to the largest predator, every creature plays a role in the grand performance of our planet’s biosphere. But what happens when one of these performers disappears? 

In this post, we delve into our recent article Estimating co-extinction risks in terrestrial ecosystems just published in Global Change Biology, in which we discuss the cascading effects of species loss and the risks of ‘co-extinction’.

But what does ‘co-extinction’ really mean?

Imagine an ecosystem as a giant web of interconnected species. Each thread represents a relationship between two species — for example, a bird that eats a certain type of insect, or a plant that relies on a specific species of bee for pollination. Now, what happens if one of these species in the pair disappears? The thread breaks and the remaining species loses an interaction. This could potentially lead to its co-extinction, which is essentially the domino effect of multiple species losses in an ecosystem. 

A famous example of this effect can be seen with the invasion of the cane toad (Rhinella marina) across mainland Australia, which have caused trophic cascades and species compositional changes in these communities. 

The direct extinction of one species, caused by effects such as global warming for example, has the potential to cause other species also to become extinct indirectly. 
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Categories : alien species, biogeography, bottom-up ecology, climate change, climate shift, community ecology, conservation, conservation biology, decline, demography, ecology, ecosystem, environmental policy, extinction, mathematics, modelling, predation, predator, top-down ecology

What we know we don’t know about animal tolerances to high temperatures

30 01 2023

Each organism has a limit of tolerance to cold and hot temperatures. So, the closer it lives to those limits, the higher the chances of experiencing thermal stress and potentially dying. In our recent paper, we revise gaps in the knowledge of tolerance to high temperatures in cold-blooded animals (ectotherms), a diverse group mostly including amphibians and reptiles (> 16,000 species), fish (> 34,000 species), and invertebrates (> 1,200,000 species).

As a scientist, little is more self-realising than to write and publish a conceptual paper that frames the findings of your own previous applied-research papers. This is the case with an opinion piece we have just published in Basic and Applied Ecology1 — 10 years, 4 research papers2-5 [see related blog posts here, here, here and here], and 1 popular-science article6 after I joined the Department of Biogeography and Global Change (Spanish National Research Council) to study the thermal physiology of Iberian lizards under the supervision of Miguel Araújo and David Vieites.

Iberian lizards for which heat tolerance is known (varying from 40 to 45 °C)
 
[left, top to bottom] Iberian emerald lizard (Lacerta schreiberi, from Alameda del Valle/Madrid) and Geniez’s wall lizard (Podarcis virescens, Fuertescusa/Cuenca), and [right, top to bottom] Algerian sand racer (Psammodromus algirus, Navacerrada/Madrid), Andalusian wall lizard (Podarcis vaucheri, La Barrosa/Cádiz), Valverde’s lizard (Algyroides marchi, Riópar/Albacete), and Cyren’s rock lizard (Iberolacerta cyreni, Valdesquí/Madrid). Heat-tolerance data deposited here and used to evaluate instraspecific variation of heat tolerance3,4. Photos: Salvador Herrando-Pérez.

In our new paper, we examine how much we know and what areas of research require further development to advance our understanding of how and why the tolerance of ectotherm fauna to high environmental temperature (‘heat tolerance’ hereafter) varies within and across the Earth’s biomes. We focus on data gaps using the global database GlobTherm as a reference template (see Box 1 below).

Our three main tenets

1. Population versus species data: Most large-scale ecophysiological research is based on modelling one measurement of heat tolerance per species (typically representing one population and/or physiological assay) over hundreds to thousands of species covering broad geographical, phylogenetic, and climatic gradients.

But there is ample evidence that heat tolerance changes a lot among populations occupying different areas of the distribution of a species, and such variation must be taken into account to improve our predictions of how species might respond to environmental change and face extinction.

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Categories : biodiversity, climate change, climate shift, conservation, conservation ecology, ecology, ecosystem services, extinction, research, science, threatened species

Interrupted flows in the Murray River endanger frogs

17 01 2023

Flooding in the Murray-Darling Basin is creating ideal breeding conditions for many native species that have evolved to take advantage of temporary flood conditions. Led by PhD candidate Rupert Mathwin, our team developed virtual models of the Murray River to reveal a crucial link between natural flooding and the extinction risk of endangered southern bell frogs (Litoria raniformis; also known as growling grass frogs).

Southern bell frogs are one of Australia’s 100 Priority Threatened Species. This endangered frog breeds during spring and summer when water levels increase in their wetlands. However, the natural flooding patterns in Australia’s largest river system have been negatively impacted by expansive river regulation that some years, sees up to 60% of river water extracted for human use.

Our latest paper describes how we built computer simulations of Murray-Darling Basin wetlands filled with simulated southern bell frogs. By changing the simulation from natural to regulated conditions, we showed that modern conditions dramatically increase the extinction risk of these beloved frogs.

The data clearly indicate that successive dry years raise the probability of local extinction, and these effects are strongest in smaller wetlands. Larger wetlands and those with more frequent inundation are less prone to these effects, although they are not immune to them entirely. The models present a warning — we have greatly modified the way the river behaves, and the modern river cannot support the long-term survival of southern bell frogs.’

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Categories : Australia, biodiversity, climate change, connectivity, conservation, demography, drought, ecology, environmental policy, extinction, flood, frog, management, metapopulation, minimum viable population, modelling, Murray River, Murray-Darling, population dynamics, population viability analysis, PVA, River Murray, South Australia, southern Australia, stochasticity, threatened species, water, weir gates

Influential conservation papers of 2022

3 01 2023

Following my annual tradition, I present the retrospective list of the ‘top’ 20 influential papers of 2022 as assessed by experts in Faculty Opinions (formerly known as F1000). These are in no particular order. See previous years’ lists here: 2021, 2020, 2019, 2018, 2017, 2016, 2015, 2014, and 2013.

Genetic variance in fitness indicates rapid contemporary adaptive evolution in wild animals — “… this paper adds a much-needed perspective to the status of genetic diversity and adaptive potential in contemporary populations.“

Habitat, geophysical, and eco-social connectivity: benefits of resilient socio-ecological landscapes — “… distinguishes four distinct but interrelated types of connectivity: landscape, habitat, geophysical, and eco-social connectivity, of which the fourth type is new. The authors discuss how these different types of connectivity are related to ecosystem services and disservices, and how they interact with each other to influence landscape sustainability issues.“

Glyphosate impairs collective thermoregulation in bumblebees — “… low-dose glyphosate, combined with global increases in temperature, converge to disrupt homeostatic regulation in bee colonies. This is a crucial revelation for understanding the loss of bees across the globe, as they serve as major pollinators in nature and agriculture.“

Human disturbances affect the topology of food webs — “… provides great opportunities for the study of food web structures, their dynamics and stability under different human influences.“

A comprehensive database of amphibian heat tolerance — “… provides estimates of amphibian upper thermal limits – a relevant trait for assessing the vulnerability of this highly-threatened group of ectotherms to rising temperatures – derived from thousands of experimental studies.”

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Categories : alien species, biodiversity, birds, climate change, climate shift, community ecology, connectivity, conservation, conservation biology, conservation ecology, coral reefs, deforestation, disease, ecology, ecosystem, ecosystem services, environmental policy, extinction, fish, fragmentation, frog, genetic diversity, genetics, habitat loss, invasive species, management, marine, marine protected area, modelling, monitoring, Murray-Darling, ocean, population dynamics, predator, protected area, recovery, research, restoration, science, seagrass, sustainability, synergies, threatened species, top-down ecology, trophic cascades, tropical, vegetation

Children born today will see literally thousands of animals disappear in their lifetime, as global food webs collapse

17 12 2022
Frida Lannerstrom/Unsplash, CC BY

Corey J. A. Bradshaw, Flinders University and Giovanni Strona, University of Helsinki

Climate change is one of the main drivers of species loss globally. We know more plants and animals will die as heatwaves, bushfires, droughts and other natural disasters worsen.

But to date, science has vastly underestimated the true toll climate change and habitat destruction will have on biodiversity. That’s because it has largely neglected to consider the extent of “co-extinctions”: when species go extinct because other species on which they depend die out.

Our new research shows 10% of land animals could disappear from particular geographic areas by 2050, and almost 30% by 2100. This is more than double previous predictions. It means children born today who live to their 70s will witness literally thousands of animals disappear in their lifetime, from lizards and frogs to iconic mammals such as elephants and koalas.

But if we manage to dramatically reduce carbon emissions globally, we could save thousands of species from local extinction this century alone.

Ravages of drought will only worsen in coming decades.
CJA Bradshaw

An extinction crisis unfolding

Every species depends on others in some way. So when a species dies out, the repercussions can ripple through an ecosystem.

For example, consider what happens when a species goes extinct due to a disturbance such as habitat loss. This is known as a “primary” extinction. It can then mean a predator loses its prey, a parasite loses its host or a flowering plant loses its pollinators.

A real-life example of a co-extinction that could occur soon is the potential loss of the critically endangered mountain pygmy possum (Burramys parvus) in Australia. Drought, habitat loss, and other pressures have caused the rapid decline of its primary prey, the bogong moth (Agrotis infusa).

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Categories : anthropocene, biodiversity, bottom-up ecology, climate change, community ecology, connectivity, conservation, conservation biology, deforestation, ecology, ecosystem, endemism, environmental policy, extinction, habitat loss, mathematics, modelling, predation, research, science, top-down ecology, trophic cascades

Cartoon guide to biodiversity loss LXXIV

5 09 2022

Welcome to the fourth set of 7 cartoons for 2022. See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.

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Categories : climate change, extinction, pollution

What does ‘collapse’ mean, and should we continue using the term?

30 08 2022

The conservation, environment, and sustainability literature is rife with the term ‘collapse’, applied to concepts as diverse as species extinction to the complete breakdown of civilisation. I have also struggled with its various meanings and implications, so I’m going to attempt to provide some clarity on collapse for my own and hopefully some others’ benefit.

State transitions (Fig. 2 from Keith et al. (2015))

From a strictly ecological perspective, ‘collapse’ could be described in the following (paraphrased) ways:

But there is still nor formal definition of ‘collapse’ in ecology, as identified by several researchers (Keith et al. 2013; Boitani et al. 2015; Keith et al. 2015; Sato and Lindenmayer 2017; Bland et al. 2018). While this oversight has been discussed extensively with respect to quantifying changes, I can find nothing in the literature that attempts a generalisable definition of what collapse should mean. Perhaps this is because it is not possible to identify a definition that is sufficiently generalisable, something that Boitani et al. (2015) described with this statement:

“The definition of collapse is so vague that in practice it will be possible (and often necessary) to define collapse separately for each ecosystem, using a variety of attributes and threshold values

Boitani et al. 2015

Despite all the work that has occurred since then, I fear we haven’t moved much beyond that conclusion.

Hell, cutting down the trees in the bush block next to my property constitutes a wholesale ‘collapse’ of the microcommunity of species using that patch of bush. An asteroid hitting the Earth and causing a mass extinction is also collapse. And everything in-between.

But at least ecologists have made some attempts to define and quantify collapse, even if an acceptable definition has not been forthcoming. The sustainability and broader environment literature has not even done that.

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Categories : anthropocene, biodiversity, climate change, community ecology, conservation biology, decline, economics, ecosystem, ecosystem function, ecosystem services, Endarkenment, environmental policy, exploitation, extinction, famine, function, societies, sustainability

Should we bring back the thylacine? We asked 5 experts

17 08 2022
Tasmanian Museum and Art Gallery

Signe Dean, The Conversation

In a newly announced partnership with Texas biotech company Colossal Biosciences, Australian researchers are hoping their dream to bring back the extinct thylacine is a “giant leap” closer to fruition.

Scientists at University of Melbourne’s TIGRR Lab (Thylacine Integrated Genetic Restoration Research) believe the new partnership, which brings Colossal’s expertise in CRISPR gene editing on board, could result in the first baby thylacine within a decade.

The genetic engineering firm made headlines in 2021 with the announcement of an ambitious plan to bring back something akin to the woolly mammoth, by producing elephant-mammoth hybrids or “mammophants”.

But de-extinction, as this type of research is known, is a highly controversial field. It’s often criticised for attempts at “playing God” or drawing attention away from the conservation of living species. So, should we bring back the thylacine? We asked five experts.

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Categories : Australia, biodiversity, climate change, cloning, conservation, conservation biology, conservation ecology, deforestation, ecology, ethics, extinction, genetic diversity, genetics, habitat loss, inbreeding depression, livestock, living dead, mammal, population viability analysis, science

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