A Helping Hand?

The helmeted honeyeater is a bird that demands to be noticed. With a patch of electric-yellow feathers on its forehead, it squawks loudly as it zips through the dense swamp forests of the state of Victoria, Australia. But over the past few centuries, humans and wildfires damaged or destroyed these forests, and by 1989, just 50 helmeted honeyeaters remained.

Habitat loss as well as invasive species, infectious diseases, and climate change have put the helmeted honeyeater and many other native animals in peril and given Australia one of the worst rates of species loss in the world.

In some cases, scientists argue, the threat is so great that there’s only one way to save the animals: by changing them. Using a variety of techniques, including crossbreeding and gene editing (see “How Gene Editing Works,” below), scientists are altering the genomes of vulnerable creatures, hoping to give them the traits they need to survive.

The helmeted honeyeater is a bird that lives in the dense swamp forests of the state of Victoria, Australia. The patch of electric-yellow feathers on its forehead and loud squawks make it noticeable. But over the past few centuries, humans and wildfires damaged or destroyed the forests where it lives. By 1989, just 50 helmeted honeyeaters remained.

Habitat loss, invasive species, infectious diseases, and climate change have put the helmeted honeyeater and many other native animals in danger. Australia now has one of the worst rates of species loss in the world.

Scientists argue that, in some cases, the only way to save the animals is by changing them. They hope that by altering the genomes of vulnerable creatures, they will give them the traits they need to survive. Scientist are using a variety of techniques including crossbreeding and gene editing (see “How Gene Editing Works,” below).

“We’re looking at how we can assist evolution,” says Anthony Waddle, a conservation biologist at Macquarie University in Sydney. Evolution is the process that the naturalist Charles Darwin described, by which animals pass on to their offspring the genes and traits that best equip them to survive in their environment.

Changing the genetic makeup of species that no longer have what it takes to survive is an audacious idea, and one that raises thorny ethical questions about whether people should be meddling in the lives and genomes of animals, which critics say amounts to playing God. The idea also challenges a basic impulse of conservationists to preserve wild animals as they are.

But the traditional conservation playbook may no longer be enough, some scientists say.

“We’re searching for solutions in an altered world,” says Dan Harley, a senior ecologist at Zoos Victoria, a zoo-based conservation group. “We need to take risks. We need to be bolder.”

“We’re looking at how we can assist evolution,” says Anthony Waddle, a conservation biologist at Macquarie University in Sydney. Charles Darwin described evolution as the process by which animals pass on to their offspring the genes and traits that best equip them to survive in their environment.

Changing the genetic makeup of species that no longer have what it takes to survive is a bold idea. It raises thorny ethical questions about whether people should be meddling in the lives and genomes of animals. Critics say it amounts to playing God. The idea also challenges a basic belief of conservationists to preserve wild animals as they are.

But the traditional conservation methods may no longer be enough, some scientists say.

“We’re searching for solutions in an altered world,” says Dan Harley, a senior ecologist at Zoos Victoria, a zoo-based conservation group. “We need to take risks. We need to be bolder.”

For tens of millions of years, Australia has been a playground for evolution. It lays claim to some of the most remarkable creatures on Earth, from songbirds and egg-laying mammals to pouch-bearing marsupials, a group that encompasses far more than just koalas and kangaroos. Nearly half of the continent’s birds and roughly 90 percent of its mammals, reptiles, and frogs are found nowhere else on the planet.

But Australia is also a case study in what happens when people push biodiversity to the brink.

The helmeted honeyeater has managed to hold on with the help of conservation efforts. But among the birds that remain, there’s a lack of genetic diversity—the range of traits passed on from parent to offsprin—a problem common in endangered animal populations. Breeding for these birds means inbreeding.

Endangered animals “have very few options for making good mating decisions,” says Paul Sunnucks, a wildlife geneticist at Monash University in Melbourne.

In a small, closed breeding pool, harmful genetic mutations can build up over time, damaging animals’ health and their chances of reproducing. Inbreeding—when close relatives mate—makes the problem worse. The most inbred helmeted honeyeaters left one-tenth as many offspring as the least inbred ones, and the females had lifespans that were half as long, Sunnucks and his colleagues found.

For tens of millions of years, Australia has been a playground for evolution. It lays claim to some of the most remarkable creatures on Earth. These include everything from songbirds and egg-laying mammals to pouch-bearing marsupials, a group that encompasses far more than just koalas and kangaroos. Nearly half of the continent’s birds and roughly 90 percent of its mammals, reptiles, and frogs are found nowhere else on the planet.

But Australia is also a case study in what happens when people push biodiversity to the brink.

The helmeted honeyeater has managed to survive with the help of conservation efforts. But among the birds that remain, there’s a lack of genetic diversity, a problem common in endangered animal populations. (Genetic diversity is the range of traits passed on from parent to offspring). Breeding for these birds means inbreeding.

Endangered animals “have very few options for making good mating decisions,” says Paul Sunnucks, a wildlife geneticist at Monash University in Melbourne.

In a small, closed breeding pool, harmful genetic mutations can build up over time. These mutations damage animals’ health and their chances of reproducing. Inbreeding—when close relatives mate—makes the problem worse. Sunnucks and his colleagues found that the most inbred helmeted honeyeaters left one-tenth as many offspring as the least inbred ones. The females also had lifespans that were half as long.

Without some kind of intervention, the bird could be pulled into an “extinction vortex,” says Alexandra Pavlova, an evolutionary ecologist at Monash University.

A decade ago, Pavlova, Sunnucks, and other experts suggested an intervention known as genetic rescue: They would introduce fresh DNA into the bird’s breeding pool. Enter the Gippsland yellow-tufted honeyeater.

The helmeted and Gippsland honeyeaters belong to the same species, but they have different genes. The Gippsland birds live in drier forests and are missing the pronounced feather crown.

Genetic rescue isn’t a new idea. But it goes against a belief among conservationists that unique biological populations should be kept separate and genetically pure. Crossing the two types of honeyeaters risks muddying what makes each species unique. Moving animals between populations can also spread disease or disrupt ecosystems in unpredictable ways.

Without some kind of intervention, the bird could be pulled into an “extinction vortex,” says Alexandra Pavlova, an evolutionary ecologist at Monash University.

A decade ago, Pavlova, Sunnucks, and other experts suggested an intervention known as genetic rescue. They would introduce fresh DNA into the bird’s breeding pool. Enter the Gippsland yellow-tufted honeyeater.

The helmeted and Gippsland honeyeaters belong to the same species. But they have different genes. The Gippsland birds live in drier forests. They are also missing the pronounced feather crown.

Genetic rescue isn’t a new idea. But it goes against a belief among conservationists that unique biological populations should be kept separate and genetically pure. Crossing the two types of honeyeaters risks changing what makes each species unique. Moving animals between populations can also spread disease or disrupt ecosystems in unpredictable ways.

“There was a lot of angst among government agencies around doing it,” says Andrew Weeks, an ecological geneticist at the University of Melbourne. “It was only really the idea that the population was about to go extinct that I guess gave government agencies the nudge.”

Sunnucks and his colleagues argued that the risks associated with genetic rescue paled in comparison with the risks of doing nothing. And so, since 2017, Gippsland birds have been part of the helmeted honeyeater breeding program at Healesville Sanctuary, a zoo in Victoria.

The intervention seems to have worked. Mixed pairs have produced more independent chicks per nest than pairs of helmeted honeyeaters. Dozens of hybrid honeyeaters have been released into the wild and seem to be faring well, but it’s too soon to say if they have a fitness advantage.

Monash and Zoos Victoria experts are also working on the genetic rescue of other species, including the Leadbeater’s possum, a tree-dwelling marsupial. The scientists hope this will make populations more resilient and increase the odds that some individuals have the traits needed to survive, whatever dangers arise.

“Genetic diversity is your blueprint for how you contend with the future,” Harley of Zoos Victoria says.

“There was a lot of angst among government agencies around doing it,” says Andrew Weeks, an ecological geneticist at the University of Melbourne. “It was only really the idea that the population was about to go extinct that I guess gave government agencies the nudge.”

Sunnucks and his colleagues argued that the risks associated with genetic rescue were small in comparison with the risks of doing nothing. And so, since 2017, Gippsland birds have been part of the helmeted honeyeater breeding program at Healesville Sanctuary, a zoo in Victoria.

The intervention seems to have worked. Mixed pairs have produced more independent chicks per nest than pairs of helmeted honeyeaters. Dozens of hybrid honeyeaters have been released into the wild. They seem to be faring well, but it’s too soon to say if they have a fitness advantage.

Monash and Zoos Victoria experts are also working on the genetic rescue of other species. This includes the Leadbeater’s possum, a tree-dwelling marsupial. The scientists hope this will make populations more resilient and increase the odds that some individuals have the traits needed to survive, even if dangers arise.

“Genetic diversity is your blueprint for how you contend with the future,” Harley of Zoos Victoria says.

By shaping gene pools, scientists are trying to speed up the process of evolution, which can sometimes take thousands or millions of years to take hold in a species.

“You’re essentially using natural selection and evolution to achieve your goals,” says Ben Phillips, a population biologist at Curtin University in Perth.

Advancing science could make future efforts even more targeted. In 2015, for instance, scientists attempted to rescue corals along the Great Barrier Reef—which have been dying because of warming oceans—by crossbreeding colonies from different areas to create a more heat-resistant coral. In a study from 2020, researchers used the gene-editing tool known as CRISPR) to directly alter a gene involved in heat tolerance.

Although the approach is still under development, Waddle, the biologist at Macquarie, hopes to use tools such as CRISPR to engineer frogs that are resistant to the chytrid fungus, which causes a disease that’s contributed to the extinction of at least 90 amphibian species. The fungus is so difficult to eradicate that some vulnerable species can no longer live in the wild.

“So either they live in glass boxes forever,” Waddle says, “or we come up with solutions where we can get them back in nature and thriving.”

By shaping gene pools, scientists are trying to speed up the slow process of evolution. It can sometimes take thousands or millions of years to take hold in a species.

“You’re essentially using natural selection and evolution to achieve your goals,” says Ben Phillips, a population biologist at Curtin University in Perth.

Advancing science could make future efforts even more targeted. In 2015, for instance, scientists attempted to rescue corals along the Great Barrier Reef. The corals have been dying because of warming oceans.  Scientists are trying to crossbreed colonies from different areas to create a more heat-resistant coral. In a study from 2020, researchers used the gene-editing tool known as CRISPR (see “Could We Bring Extinct Animals Back to Life?”) to directly alter a gene involved in heat tolerance.

Although the approach is still under development, Waddle, the biologist at Macquarie, hopes to use tools such as CRISPR to engineer frogs that are resistant to the chytrid fungus. The fungus causes a disease that’s contributed to the extinction of at least 90 amphibian species. It  is so difficult to destroy the fungus that some vulnerable species can no longer live in the wild.

“So either they live in glass boxes forever,” Waddle says, “or we come up with solutions where we can get them back in nature and thriving.”

Still, no matter how sophisticated the technology becomes, genetic interventions are “likely to have some unintended impacts,” says Tiffany Kosch, a geneticist at the University of Melbourne.

Plenty of other efforts to re-engineer nature have backfired. For instance, a breed of toxic toad that scientists deliberately set loose in Australia a century ago in an attempt to control pest beetles has been killing quolls, a marsupial native to Australia. Now the quolls are in need of rescue.

And some environmental groups and experts remain uneasy about genetic approaches for other reasons too.

“Focusing on intensive intervention in specific species can be a distraction,”
says Cam Walker, of Friends of the Earth Australia. Staving off the extinction crisis will require broader solutions, such as halting habitat loss, he says.

Still, no matter how sophisticated the technology becomes, genetic interventions are “likely to have some unintended impacts,” says Tiffany Kosch, a geneticist at the University of Melbourne.

Plenty of other efforts to re-engineer nature have backfired. For instance, a breed of toxic toad that scientists deliberately set loose in Australia a century ago in an attempt to control pest beetles has been killing quolls, a marsupial native to Australia. Now the quolls need help.

And some environmental groups and experts remain uneasy about genetic approaches for other reasons too.

“Focusing on intensive intervention in specific species can be a distraction,” says Cam Walker, of Friends of the Earth Australia. Slowing the extinction crisis will require broader solutions, such as halting habitat loss, he says.

Moreover, animals are self-governing beings, and any intervention into their lives or genomes must have “a very strong ethical and moral justification,” says Adam Cardilini, an environmental scientist at Deakin University in Victoria.

Still, some scientists support a cautious, limited use of tools such as assisted evolution, which may require us to rethink some longstanding environmental values. It’s an acknowledgment, some say, that humans will profoundly shape the future lives and fates of wild creatures.

To Harley, it has become clear that preventing more extinctions will require human intervention.

“Let’s lean into that, not be daunted by it,” he says. “My view is that 50 years from now, biologists and wildlife managers will look back at us and say, ‘Why didn’t they take the steps and the opportunities when they had the chance?’”

Moreover, animals are self-governing beings, and any intervention into their lives or genomes must have “a very strong ethical and moral justification,” says Adam Cardilini, an environmental scientist at Deakin University in Victoria.

Still, some scientists support a cautious, limited use of tools such as assisted evolution. This practice may require us to rethink some longstanding environmental values. It’s an acknowledgment, some say, that humans will profoundly shape the future lives and fates of wild creatures.

To Harley, it has become clear that preventing more extinctions will require human intervention.

“Let’s lean into that, not be daunted by it,” he says. “My view is that 50 years from now, biologists and wildlife managers will look back at us and say, ‘Why didn’t they take the steps and the opportunities when they had the chance?’”

Emily Anthes is a science reporter for The New York Times.

Emily Anthes is a science reporter for The New York Times.