Ecology

Spotted-tailed quolls (left) and Tasmanian devils (right) have similar diets and are both active at night.Credit: Bruce Thomson/NPL; Arterra Picture Library/Alamy

Declining numbers of the endangered Tasmanian devil (Sarcophilus harrisii) are affecting the evolutionary genetics of a small predator, the spotted-tailed quoll (Dasyurus maculatus), according to a study published today in Nature Ecology & Evolution1.The findings fit with what scientists would expect — typically, when a top predator’s population dwindles, smaller predators increase in number because there are more resources available and less competition.But little is known about what the effect of a top predator’s decline is on the evolutionary genetics of other species in the food web, says study co-author Andrew Storfer, an evolutionary geneticist at Washington State University in Pullman. “This is one of the first studies to demonstrate that.”Ripple effectsFor the past three decades, Tasmanian devils — carnivorous marsupials native to the island of Tasmania in Australia — have been affected by an infectious type of lethal cancer known as devil facial tumour disease (DFTD). The devil population has declined by nearly 70%, from 53,000 in 1996 to 16,900 in 2020, mainly because of DFTD, which is passed on through biting2.Storfer and his PhD student Marc Beer wanted to study how this decline in devil numbers is affecting another marsupial, the spotted-tailed quoll. Devils and quolls have similar diets and are both active at night, scavenging for food. But devils are larger and more aggressive, so quolls tend to avoid them.The researchers analysed 3,431 genetic variants in the genomes of 345 quolls across 15 generations. They searched for evidence of changes in the variation and selection of genes in quolls that could be associated with the prevalence of DFTD in devils and with the devils’ population density.Evolutionary consequencesThey found that quolls in regions with similar spreading rates of DFTD were genetically more similar to each other compared with those in areas that had different DFTD prevalence and devil population densities. They also found evidence of genetic selection in response to changes in devil numbers, and identified 12 gene variants in quolls that are linked to devil population density and 10 associated with the number of years DFTD has been prevalent for in devils. Among these genes are ones important for movement and muscle development, as well as some linked to feeding behaviour.The study showed that the distribution of genetic variation in quolls is increasing, but that genetic exchange — the movement of genes into or out of populations — is decreasing. This might be because, when few devils are present, quolls do not need to move around as much as they do in areas with a high devil density, thus reducing the chance of animals from different populations encountering each other. “Less genetic exchange among populations will eventually lead to lower genetic diversity within populations. And there are evolutionary consequences of that,” says Storfer. “We really don’t know what they are.” More

RESEARCH HIGHLIGHT
08 January 2024

Young southern pig-tailed macaques, an endangered species, are less likely to reach their first birthday if they spend time on plantations. More

Before I began a PhD in Indigenous knowledge and the biology of invasive species at the University of British Columbia in Vancouver in 2015, I had an existential crisis. I worked for an agency that managed invasive plant species — but despite our efforts, some invasive species would inevitably come back, or a new invader would take over. For me, it was a moment to question the point of eradicating such species without a holistic land-management plan in place.Since then, my scientific journey has been about connecting my Western science to the Indigenous world view I’ve inherited as a Nlaka’pamux woman of mixed ancestry. Now, when I go out into the field as a researcher, I involve archaeologists, elders, soil scientists, plant scientists and historical ecologists so that we can use their knowledge — to understand how this land was managed in the past and how it should be managed in the future. Instead of saying, “How do we get rid of this invasive plant?”, we ask, “What do culturally important local plant species need to flourish?”.
How I use science to protect my people’s birthright
In this image, taken last August, I’m standing on land that’s being restored by the Cowichan Estuary Restoration Project, the largest of its type ever to occur on Vancouver Island. Two kilometres of dikes have been removed from the estuary to reconnect it to wetlands. In 2022, camas, a bright purple flower and an important fibre source for coastal Indigenous peoples, bloomed throughout the estuary. The Cowichan Tribes’ land staff and I then realized that this estuary had been an important food source for the local Indigenous peoples. We had to rethink the restoration project.Now, community-based researchers, elders and knowledge keepers are informing what we do next. Instead of adhering to a post-colonial baseline of restoration, we combine remote-sensing technologies with oral histories to purposefully shape lands, guided by community values and needs. More

Download the Nature Podcast 27 December 2023In this episode:00:54 Franklin’s real roleWhen it comes to the structure of DNA, everyone thinks they know Rosalind Franklin’s role in its discovery. The story goes that her crucial data was taken by James Watson without her knowledge, helping him and Francis Crick solve the structure. However, new evidence has revealed that this wasn’t really the case. Rosalind Franklin was not a ‘wronged heroine’, she was an equal contributor to the discovery.Nature Podcast: 25 April 2023Comment: What Rosalind Franklin truly contributed to the discovery of DNA’s structure14:37 An automated way to monitor wildlife recoveryTo prevent the loss of wildlife, forest restoration is key, but monitoring how well biodiversity actually recovers is incredibly difficult. Now though, a team has collected recordings of animal sounds to determine the extent of the recovery. However, while using these sounds to identify species is an effective way to monitor, it’s also labour intensive. To overcome this, they trained an AI to listen to the sounds, and found that although it was less able to identify species, its findings still correlated well with wildlife recovery, suggesting that it could be a cost-effective and automated way to monitor biodiversity.Nature Podcast: 25 October 2023Research article: Müller et al.27:11 Research HighlightsThe first brain recording from a freely swimming octopus, and how a Seinfeld episode helped scientists to distinguish the brain regions involved in understanding and appreciating humour.Research Highlight: How to measure the brain of an octopusResearch Highlight: One brain area helps you to enjoy a joke — but another helps you to get it30:24 Why multisensory experiences can make stronger memoriesIt’s recognized that multisensory experiences can create strong memories and that later-on, a single sensory experience can trigger memories of the whole event, like a specific smell conjuring a visual memory. But the neural mechanisms behind this are not well understood. Now, a team has shown that rich sensory experiences can create direct neural circuit between the memory regions involved with different senses. This circuit increases memory strength in the flies, and helps explain how sense and memories are interlinked.Nature Podcast: 25 April 2023Research article: Okray et al.38:58 Briefing ChatHow elephant seals catch some shut-eye while diving.New York Times: Elephant Seals Take Power Naps During Deep Ocean DivesSubscribe to Nature Briefing, an unmissable daily round-up of science news, opinion and analysis free in your inbox every weekday.Never miss an episode. Subscribe to the Nature Podcast on Apple Podcasts, Google Podcasts, Spotify or your favourite podcast app. An RSS feed for the Nature Podcast is available too. More

In the heart of the Brazilian Amazon, armed men wearing balaclavas and wielding firearms intimidated me and two other journalists on a remote riverbank near the Colombian border in February. We had ventured into the rainforest to investigate the surge in violence and illegal mining and drug trafficking that the Amazon has witnessed since 2016, and to map the presence of cross-border armed groups. We are part of Amazon Underworld, a media alliance comprising more than 30 professionals.We knew that the region harboured shotgun-carrying gold miners who illegally dredge the river with gargantuan barges, and Colombian guerrillas who cross into Brazil to shake the miners down for gold. But the armed individuals who stopped us were affiliated with the state — a rogue military police unit that oversees and shields illegal mining operations. Working outside the law, they amass millions of dollars in gold payments annually. There, in their shadowy domain, no one who asks questions is welcome.The leader of the armed outfit demanded that we delete all the photos we had taken during two days of observing mining barges, before seizing our memory cards. Fortunately, we had a hidden backup.
Saving the Amazon: how science is helping Indigenous people protect their homelands
Illegal mining is but one part of a complex web of transnational organized crime, corruption and resource extraction that is threatening the Amazon — a crucial climate regulator. Yet improving security in the Amazon was missing from the agenda at COP28, the 2023 United Nations climate summit in Dubai, United Arab Emirates. Addressing this security dilemma is pivotal to safeguarding the Amazon rainforest, the populations it shelters and the global climate.Violence and criminal activity in the Amazon have worsened since the start of the COVID-19 pandemic, when governments and law enforcement prioritized pandemic control over reducing organized crime. The rise in violence coincided with the 2019–22 Brazilian government of then-president Jair Bolsonaro, who openly called for mining Indigenous lands. In 2023, annual deforestation in the Brazilian Amazon decreased sharply. But the year also saw forest fires rage across Brazil and Bolivia, and news articles featuring images of malnourished Indigenous Yanomami children, whose ancestral lands are besieged by gold miners. In Colombia’s southern Putumayo region — a crucial corridor for the cocaine industry — three or more people have been killed on 21 separate occasions since 2020, mainly because of a ruthless territorial struggle between two armed factions.The allure of illicit profits has enticed urban gangs from Brazil, such as Primeiro Comando da Capital from São Paulo and Comando Vermelho from Rio de Janeiro and rural guerrilla outfits from Colombia to the Amazon. Some initially came for the cocaine — its prime ingredient, coca, can be grown there — but stayed for the gold and to launder drug profits. Especially in border areas with minimal state presence, illicit activities intersect with legitimate cattle and agricultural enterprises. Indigenous peoples are often put at risk when these activities overlap with their lands.
The scientists restoring a gold-mining disaster zone in the Peruvian Amazon
One of these populations is the Yuri-Passé, an uncontacted Indigenous group living in a protected national park on the Colombian side of the Puré River, near to where the armed men tried to intimidate us on the Brazilian side. National park rangers abandoned their posts in 2020 after threats from a Colombian guerrilla faction, leaving the Yuri-Passé peoples unprotected. The community, of about 400 people, faces an existential threat from diseases, pollution and attacks by gold miners and armed groups.This Amazonian region on the Colombian–Brazilian border is not an exception. Our investigation found crime groups in 70% of municipalities in the borderlands of Brazil, Peru, Colombia, Ecuador, Bolivia and Venezuela. Often, Indigenous youths are brought into organized crime by force or are enticed by non-governmental armed groups that supplant the state, carry out rudimentary ‘justice’ and levy taxes on the region’s inhabitants and economic activities.Authorities have so far failed to keep up with the increasingly complex criminal networks. Criminal organizations now forge alliances across borders despite cultural and ideological differences. The escalating violence and criminal presence could undermine international backing for conservation projects.Solutions to these multifaceted issues might not be simple, but practical steps exist. Nations must cooperate to guard against this violence. They must support local communities — by increasing the state’s presence in remote areas and promoting health care, education and sustainable economic development — and help them to safeguard the rainforest. For example, Indigenous peoples in Peru and Brazil are using drones and GPS devices to monitor their land and detect threats from violent invaders.Indigenous peoples are the Amazon’s best forest guardians, but they need more legally demarcated lands and protective measures, such as funding for Indigenous guards and rapid response and emergency protocols. In 2022, Colombia and Brazil saw the most deaths of environmental and land defenders worldwide. Developing effective strategies to enhance cooperation between law enforcement and local populations must also be a priority.To prevent irreversible damage to the rainforest and the climate, security in the Amazon must be added to the global climate agenda. More

A fire in Canada in 2023. The country experienced its worst wildfires on record, contributing to record carbon dioxide emissions.Credit: Chine Nouvelle/SIPA/Shutterstock

Global forest fires emitted 33.9 billion tonnes of carbon dioxide (CO2) between 2001 and 2022, according to a report by the Chinese Academy of Sciences (CAS). This makes the CO2 emissions generated by forest fires each year higher than those from burning fossil fuels in Japan — the world’s sixth-largest CO2 emitter. Driving the emissions spike was the growing frequency of “extreme forest-fire events”.Xu Wenru, a co-author and a landscape ecologist at the CAS Institute of Applied Ecology, based in Shenyang, China, says that the term ‘extreme forest fires’ generally refers to blazes that, compared with an average forest fire, burn through a larger area, last for a longer time and leave a bigger impact.Xu and her colleagues found that the growth in emissions had been mostly fuelled by an uptick in infernos on the edge of rainforests between 5 and 20º S and in boreal forests above 45º N.In particular, the emissions from boreal-forest blazes “showed a rapidly growing trend”, she says.The increased numbers of forest fires was partially driven by the frequent heatwaves and droughts caused by climate change, Xu says. “In turn, the CO2 emitted by forest fires contributes to global warming, creating a feedback loop between the two.”Humans also played a part. “Many forest fires were actually caused by humans when they were, for example, building fires to get warm at night, lighting fireworks or discarding cigarette butts,” says Xu.Zhou Tianjun, a meteorologist at the CAS’s Institute of Atmospheric Physics in Beijing, found the report shocking. In particular, he points to a figure showing that, on average, the area of forest burnt by fires between 2001 and 2022 was 11 times the size of the forests planted by humans during that period.“Tree plantation has been regarded as an important way to increase carbon sinks, but this figure shows that humans’ efforts could be offset by natural forest fires,” he says.

Source: Chinese Academy of Sciences

Record-breaking firesThe report singles out ten extreme forest-fire incidents that occurred between 2018 and 2023, each of which sent more than 600 million tonnes of CO2 into the air (see ‘Most-affected countries’). They were concentrated in five countries, all of which have vast forests: Russia, Brazil, Canada, Australia and Indonesia.Topping the emissions list is this year’s record-breaking conflagration that ripped through Canada, home to 28% of the world’s boreal forests. In 2023, more than 6,700 fires have broken out across the country, burning through a total of 18.5 million hectares, almost half the size of Norway.The CAS report found that the forest fires in Canada this year had emitted more than 1.5 billion tonnes of CO2 as of October (see ‘Extreme forest fires’), surpassing the emissions from all forest fires in the country over the previous 22 years combined.

Source: Chinese Academy of Sciences

The effects of forest fires and other types of wildfire are expected to worsen across the world in the decades to come.Wang Yuhang, an atmospheric scientist and professor at the Georgia Institute of Technology in Atlanta, says the report complements his work1 which “indicates a roughly 20% rise in global burnt area by the 2050s compared to the 2000s”.“More surprisingly, global fire carbon emissions are expected to double, highlighting the emergence of fire as a more significant carbon source at short-term timescales in the future,” Wang adds.Wang echoes the report’s suggestion that countries should include carbon emissions from forest fires into their national climate plans and set up a monitoring, reporting and verification system for such emissions.Given the scale of emissions that they generate, forest fires have become a source of CO2 emissions that “cannot be ignored”, Xu says. More

The Hawaiian crow, or ʻalalā (Corvus hawaiiensis), has been pushed to the brink of extinction by waves of human migration through the Pacific. It exists only in captive breeding programmes in 2023.Credit: ZSSD/Minden Pictures via Alamy

Around one in nine bird species has gone extinct in the past 126,000 years, according to a study published today1 in Nature Communications, and humans probably drove most of those extinctions. The findings suggest the rate of bird extinctions is more than double the number estimated previously — and that more than half of the extinct bird species were never documented.The global magnitude of these previously undetected extinctions is likely to “come as a shock to many”, says Jamie Wood, a terrestrial ecologist at the University of Adelaide in Australia. “The sobering thing is that this estimate could actually be conservative,” he says.Over centuries, humans have triggered waves of extinctions among birds and other animals through land clearing, hunting and introducing non-native species. Islands have been particularly badly affected: 90% of known bird extinctions have occurred in these isolated ecosystems. But because birds have lightweight, hollow bones, their remains tend not to be preserved well as fossils. As a result, most analyses of bird extinctions have relied instead on written observational evidence. These records began only around 500 years ago, which makes it difficult to build a picture of species losses over longer periods.Rob Cooke, an ecological modeller at the UK Centre for Ecology & Hydrology in Wallingford, and his colleagues built a model of bird extinctions by combining documented extinctions, fossil records and estimates of undiscovered extinctions across 1,488 islands. The team factored in a number of predictors for species richness — including island size, climate and geographical isolation — when estimating undiscovered extinctions.The model suggested that around 1,300–1,500 bird species — about 12% of the total worldwide — have become extinct since the Late Pleistocene (which was an epoch roughly 126,000–12,000 years ago). Human activities are likely to have caused the vast majority of these extinctions. The researchers also estimated that 55% of these vanished species would not have been discovered by humans or left any trace in the fossil record. The sheer scale of the global loss of birds came as a surprise, says Cooke. “Humans have had a much wider impact on bird diversity than previously thought,” he says.Pacific hardest hitThe authors found that almost two-thirds of all bird extinctions occurred in the Pacific region. Three major extinction waves have occurred since the Late Pleistocene, and the most intense of these waves occurred just over 700 years ago, when people first arrived on islands in the eastern Pacific — particularly Hawaii, the Marquesas Islands and New Zealand. At this time, extinction rates were 80 times higher than would have been expected if humans had not arrived. Cooke says that the introduction of rodents and domestic animals probably led to the loss of species that were well documented during this period, such as the high-billed crow (Corvus impluviatus), which once inhabited Hawaii.Developing an understanding of how many species have been lost over time could help policymakers to set biodiversity targets, says Folmer Bokma, an evolutionary biologist at Karlstad University in Sweden.Cooke says that the findings offer important lessons for tracking and conserving the bird species that remain on the planet today. “Whether or not further bird species will go extinct is up to us,” he adds. More

To lay eggs, Clanwilliam sandfish (Labeo seeberi) swim upstream to gentler, shallower tributaries of the Doring/Olifants river system in the Western Cape and Northern Cape provinces of South Africa. Local people say it was once an epic event: the water seemed to change colour as thousands of sandfish migrated upstream. Now, however, those numbers have shrunk to dangerous levels.That’s where I come in. My PhD at South Africa’s University of Cape Town is a collaboration with the Saving Sandfish project, run by a non-governmental organization called the Freshwater Research Centre in Cape Town — so I am also a conservationist.Human activity, climate change and thirsty invasive plants, are draining the rivers. As newly hatched sandfish try to swim downstream, they now get stuck in shallow pools, making them vulnerable to predators such as bass species introduced into the river system for sport fishing in the 1900s.The sandfish population has declined by more than 90% since we began keeping count in 2013. They’re now classified as endangered by the International Union for the Conservation of Nature.When the river starts to dry up, we scoop out young sandfish and put them into buckets of water, then move them by truck to one of six pre-prepared nurseries donated by local people. In this photo, I’m lifting a fish from one of those reservoirs. The support from local people is amazing.Once the sandfish are large enough to be less threatened by the bass, we return them to the wider ecosystem.We’re at an early stage, but the data so far show the project has been successful. We’ve rescued some 36,000 young sandfish over the past three years and have released almost 3,000. Last year, we got 77 readings from fish coming back from the group we released into the wild. This year, 222 have come back so far. I’m looking forward to adding to those numbers next year. More