Ecology

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Wildfires are a natural part of forest life that help to shape diverse habitats. But the extreme ‘megafires’ that ravaged California in 2020 (pictured) and 2021 were more severe and about ten times more widespread than the yearly average in the region since records began, as Ayars et al. report in the Proceedings of the National Academy of Sciences (J. Ayars et al. Proc. Natl Acad. Sci. USA 120, e2312909120; 2023).
Competing Interests
The author declares no competing interests. More

Faced with the realities of meeting the United Nations sustainable development goals (SDGs), scientists will need to move beyond rescuing them (see S. Malekpour et al. Nature 621, 250–254; 2023). In my view, modifying those that inherently contradict one another is more likely to secure the protection of the planet’s ecosystems and resources.
Competing Interests
The author declares no competing interests. More

The Aral Sea, on the border between Uzbekistan and Kazakhstan, almost completely dried up between 2000 (left) and 2018 (right).Credit: NASA

Last week, Samarkand in Uzbekistan hosted an important intergovernmental conference on how to halt the creeping spread of degraded land. The country was aptly chosen: only about 800 kilometres from the meeting, the Aral Sea spans the border between Uzbekistan and Kazakhstan. Once the world’s fourth-largest lake, it has almost completely dried up because of excessive extraction of water for irrigation during the twentieth century. Its exposed, highly polluted lake bed is a large source of blinding sandstorms and emits more than 100 million tonnes of dust and toxic chemicals every year.Between 2015 and 2019, the world lost at least 100 million hectares of healthy and productive land a year, according to an analysis for the United Nations Convention to Combat Desertification (UNCCD), which organized the meeting. Human activities — including deforestation and agricultural practices — and climate change are among the main causes.As part of tracking progress towards the 15th UN Sustainable Development Goal, ‘life on land’, 115 countries reported ahead of the meeting on three measures for restoring degraded land and soil (see go.nature.com/3sqzxm2): the area used for agriculture or covered by forests, grassland or wetlands; productivity, the ability of land to support and sustain life; and above- and below-ground stocks of carbon. Reaching the target of ‘land degradation neutrality’ by 2030 means reversing a negative trend. The global share of land that is degraded increased from 14.7% in 2015 to 18.9% in 2019 (see ‘Land loss’), the last year for which comprehensive data were available. In Mexico, more than 71.9% of land was classed as degraded in 2019, up from 56.7% in 2015. During the same period, India’s fraction of degraded land more than doubled to 9.5%. And many countries in Africa reported considerable increases — in Ethiopia, Madagascar, Mauritania, Eritrea and Somalia, the area of degraded land was between two and eight times larger in 2019 than in 2015.

Yet there are some important signs of hope amid a mostly bleak outlook. The analysis enables countries to understand land degradation at a more-granular level than before. And the UNCCD’s science teams did not perform the study: they helped to train researchers in some of the most-affected countries, so that local scientists and policymakers could do the work themselves, including monitoring progress on a continuous basis, using open sources.This work is crucial for altering course. And some countries are moving in the right direction. In Ecuador, for example, the area of land classed as degraded went from 21.9% to 12.8% between 2015 and 2019. During the same period, the degraded area in Botswana decreased from 36.3% to 17.1%, and in Burkina Faso from 34.6% to 8.2%. In Africa, Latin America and the Caribbean, improvements are made mainly by restoring tree cover; in Asia, gains also came from improvements in soil fertility.Land degradation is not a priority on the world’s environmental agenda. Although the UNCCD has the same status as the UN conventions on climate change and biodiversity, unlike them it does not have an autonomous body that provides independent scientific advice. Restoration projects also receive much less international funding — they attracted around US$5 billion between 2015 and 2019 — than do climate projects, which have yearly funds of close to $100 billion, and biodiversity programmes, which attract around $154 billion a year.This funding disparity illustrates just how little priority is given to restoring land and preventing further degradation. Yet the latest analysis shows what can be done even with limited resources. But not all countries are providing data. These nations, especially high-income countries, should start reporting their plans and actions, to raise the profile of land degradation and help reverse the trend. More

RESEARCH BRIEFINGS
15 November 2023

In 2019, Cyclone Idai caused devastating flooding in Mozambique’s Gorongosa National Park when ecological studies of mammals were already under way. Small-bodied species and those in low-lying areas were affected most, suggesting that animals’ sensitivity to extreme weather depends on traits such as body size and habitat use. More

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Conservation of seabirds that congregate on islands to breed seems straightforward: protect the colony and job done. But seabirds spend most of their lives at sea, where safeguarding them is much more challenging.

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doi: https://doi.org/10.1038/d41586-023-03526-0

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Conservation biology More

The manatee in this photo is named Daniel. The picture was taken in Mexico’s Guerrero Lagoon in July this year, as I was assessing a small bump on his head. Thankfully, he was fine. Daniel was rescued about 20 years ago, rehabilitated and released, but he continues to be very attached to people — behaving like a pet — which is really problematic for conservationists and ecologists like me.That’s because locals and tourists offer Daniel food and drinks that aren’t part of his typical diet, or that could harm him by transmitting pathogens. And Daniel is a strong, playful animal, so he could injure people — or even put their lives at risk.My colleagues and I are involved in an intensive campaign to help people understand that Daniel is not a pet. Manatees are such wonderful, intelligent and interesting creatures; we can love them without owning them.There are three species of manatee. All of them are threatened, and one subspecies is endangered. Historically, manatees were hunted by many Indigenous civilizations in the Americas. Now, they face habitat loss, and risk being struck by boats or entangled in fishing nets.I’m working on a project in the Sian Ka’an Biosphere Reserve — an extensive area in Quintana Roo, the Mexican Caribbean state that also contains Guerrero Lagoon. The aim is to assess how boat collisions are affecting manatee populations. In the past ten years, we’ve had six reports of manatees being killed by boats, so we’re concerned that these incidents will become more common as tourism continues to increase in the area.After 25 years working with these animals, it still gives me chills to see a healthy manatee in the wild. We need to act fast to save our endangered wildlife. No matter what happens in terms of legislation, if people don’t make their own decisions to care for these animals, it’s going to be impossible for us to protect manatees and other threatened species. More

Scottish wildcats (Felis silvestris) have varying levels of domestic-cat DNA from decades of interbreeding.Credit: RZSS – Saving Wildcats

In a remote corner of the Scottish Highlands, researchers are about to see what happens when cats go wild.In June, the first captive-bred European wildcats (Felis silvestris) fitted with GPS-tracking collars were released in Cairngorms National Park, UK. If things go according to plan, they will form a sustainable population of an animal that once roamed forests across Britain, but is now all but extinct.“The last hope for Scottish wildcats is the captive wildcat population,” says Jo Howard-McCombe, a conservation geneticist at the Royal Zoological Society of Scotland (RZSS) in Edinburgh, UK, which is leading the wildcat breeding effort.
Genes unleashed: how the Victorians engineered our dogs
There’s just one problem: house cats (Felis catus) or, more precisely, their DNA. All of the captively bred wildcats — and the handful that still live in the wild — bear varying levels of domestic-cat DNA from decades of interbreeding. Researchers worry that interbreeding with roaming pets will further dilute the genome of the wildcat — also known as the Highland tiger — until there’s nothing ‘wild’ left in it.But now, insights from ancient genomics are giving captive breeding efforts a boost1,2. An ancient-genomics study published today found that wildcats have started breeding with their domestic counterparts only relatively recently, in the late twentieth century2. For at least 2,000 years before that — when Romans, Vikings and other ancient cat-loving societies took domesticated felines everywhere they went — the two species rarely mixed, even when living side by side.“That changes the thinking about the prospects for preserving the Scottish wildcat in its ancestral form,” says Jonathan Losos, an evolutionary biologist at Washington University in St. Louis, Missouri, who was not involved in the studies. “It’s not a lost cause.”Wild ancestorsResearchers are still debating the details, but it’s clear that domestic cats mostly descend from a wildcat species (Felis lybica) that is distinct from European wildcats and that lives in what is now North and sub-Saharan Africa and the Middle East. Scientists think that F. lybica cats formed mutually beneficial relationships with early farming communities in the Middle East thousands of years ago. But it might have been ancient Egyptians who transformed these partly domesticated creatures into something more like today’s house cats, says Leslie Lyons, a feline geneticist at the University of Missouri in Columbia. “They mummified thousands of them, tens of thousands. I would say they were the first cat breeders.”

The first cat breeders? The ancient Egyptians lived alongside cats and often mummified them after death.Credit: Lanmas/Alamy

In 2017, an ancient-DNA study found that some ancient cat remains in Europe and the Middle East, which dated to around 800 bc and later, had the same mitochondrial DNA markers as Egyptian mummy cats3. Then, 1,000 years later, the same lineage turns up in feline remains from a Viking port near the Baltic Sea.It makes sense that early Europeans imported their cats, rather than attempting to domesticate the wildcats that roamed their forests. Modern African wildcats are much more tolerant of humans than are their “hellaciously mean” European counterparts, says Losos. “No matter how nicely you treat them, they grow up into being nasty animals that are terrible pets.”Despite their darker dispositions, it can be hard to distinguish European wildcats from their domestic counterparts. Wildcats — which still thrive in larger, less hybridized populations in some parts of Europe and west Asia — tend to be slightly bigger and have bushier tails than house cats. As a result of interbreeding with their domestic counterparts, the wildcats in Scotland now constitute what biologists call a ‘hybrid swarm’ of mixed interbreeding individuals, and wildcat ancestry is at risk of vanishing.Breeding effortsBut all is not lost for truly wild Scottish wildcats. A captive population of around 150 animals lives in more than 35 zoos, wildlife parks and other sites across the United Kingdom. These animals carry varying amounts of domestic-cat DNA — but less than the current ‘wild’ population does, says Helen Senn, head of conservation at RZSS and its Saving Wildcats programme.In 2019, Saving Wildcats won European Union funding for a captive breeding programme, with the aim of revitalizing the wildcat population. Animals are bred in a wildlife park in the Scottish Highlands and raised in large, naturalistic enclosures away from visitors.

The Saving Wildcats breeding programme raises the animals away from people, at a remote wildlife park in the Scottish Highlands.Credit: Saving Wildcats

So far, 19 wildcats have been released into a tract of land of more than 600 square kilometres called the Cairngorms Connect landscape. The goal is to release around 60 wildcats by 2026 to give the animals a decent shot at forming a self-sustaining wild population.For the programme to be successful, preventing further interbreeding with domestic cats will be crucial. The Saving Wildcats team has implored people living near the site to get their house cats spayed and neutered and to take other steps to protect them from wildcats. Senn is hopeful that hybridization can be limited.Researchers say that it’s important to figure out when and why domestic cats and wildcats started mixing in the first place. “We need to understand the factors that led to this to prevent it happening again,” says Howard-McCombe.Ancient specimensTo investigate when cats descended from African wildcats started mixing with European wildcats, an international team of researchers analysed the genomes of dozens of ancient and modern cats, which mostly lived in Europe and included an 8,000-year-old animal from Scotland that is thought to have lived before the arrival of domestic cats there1.

Domestic cats are descended from Felis lybica, a species of wildcat found in North and sub-Saharan Africa and the Middle East.Credit: Owen Jason Kandume/500px via Getty

The ancient domestic-cat genomes, including that of a 2,000-year-old feline found at a Roman palace in West Sussex, UK, contained barely any European wildcat DNA. The 600-year old remains of a wildcat — which might have been tamed — found at a ruined castle in the north of England had no trace of domestic cats in its genome, although other cat remains at the site had mitochondrial DNA commonly found among domestic cats. “They’ve been living side by side for 2,000 years, so it is surprising that they haven’t interbred,” says study co-author Mark Beaumont, a population geneticist at the University of Bristol, UK.
How cats conquered the world (and a few Viking ships)
One explanation could be the stark differences in the two species’ behaviour, says Laurent Frantz, a population geneticist at Ludwig Maximilians University in Munich, Germany, who jointly led the study with Greger Larson, an ancient-DNA researcher at the University of Oxford, UK. Domestic cats are happy living with humans, other cats and even dogs, whereas wildcats prefer a solitary life. “If you go into any town today you can see domestic cats hanging around. In wildcats that doesn’t happen,” Frantz says.In Scotland, this icy coexistence seems to have lasted well into the twentieth century, finds a study that analysed the genomes of living and ancient cats as well as museum specimens of potential wildcats predominantly from the early twentieth century2. The team, led by Howard-McCombe, Beaumont, Senn and population geneticist Daniel Lawson, who is also at the University of Bristol, estimate that domestic cats and wildcats probably didn’t start mixing significantly until the 1970s. “That was a huge surprise,” says Beaumont.Wild againThe current wildcat breeding programme, although it excludes animals with particularly high levels of domestic-cat DNA, chooses breeding pairs with the aim of preserving genetic diversity. Senn’s team, however, is hoping to go further, through an audacious breeding strategy that could see house-cat DNA slowly whittled out of the genomes of wildcats.The process — called de-introgression — involves sequencing the genomes of captive wildcats and pairing up those animals with domestic DNA that mostly occurs in non-overlapping regions of their genomes. By chance, some kittens in the litter would, hopefully, inherit more wild versions of genes than either parent has, and those individuals would be included in future rounds of breeding to further reduce the levels of domestic-cat DNA (see ‘Rewilding a genome’).De-introgression has never been tried before, says Lawson. In a preprint published in July, he, Senn, Howard-McCombe and Beaumont estimated that it would take 10–20 generations to recover the complete Scottish wildcat genome4, and the team has now applied for funding to put this theory into practice.

Source: Ref. 4

Yet getting rid of domestic-cat DNA from the wildcat genome is not without uncertainties. “We don’t know what genes make a wildcat a wildcat,” says Senn. Some house-cat DNA could be helpful: certain gene variants might help populations to resist diseases, for example. The team’s analysis of wildcat genomes found signs of this: domestic-cat genes involved in immunity seem to be under natural selection in Scottish wildcats’ genomes, potentially protecting them from diseases circulating in house cats. “It’s probably the case that wildcats would already be extinct if it wasn’t for hybridization,” says Senn.Early results from the breeding programme are positive. In a 13 October update, RZSS reported that 18 of the released wildcats were still alive, had occupied a suitable habitat and were hunting successfully. But the animals have a hard winter ahead and the success of this year’s release won’t be clear until the breeding season. Senn’s dream is to see wildcats roaming large tracts of Scotland — an outcome that could decades, she concedes. “In conservation, we’re in the business of hope.” More