Should we change species to save animals?

For tens of millions of years, Australia has been the scene of evolution, and the lands Down Under are home to some of the most remarkable creatures on earth.

It is the birthplace of songbirds, the land of egg-laying mammals and the world capital of pouched marsupials, including koalas and kangaroos. (Look at bilbys and betons!) Almost half of this continent’s bird species and around 90 percent of its mammals, reptiles, and frogs are found nowhere else on Earth.

Australia has also become a case study in what happens when people push biodiversity to the brink. Habitat degradation, invasive species, infectious diseases and climate change are putting many native animals at risk, giving Australia one of the worst species decline rates in the world.

In some cases, the threat is so intractable that scientists say the only way to protect Australia’s native animals is to change them. Scientists are using a variety of techniques, including cross-breeding and gene editing, to modify the genomes of vulnerable animals and give them the traits they need to survive.

“We’re looking at how we can support evolution,” said Anthony Waddle, a conservation biologist at Macquarie University in Sydney.

It’s a bold concept, one that challenges the basic conservation impulse to preserve wildlife as it is. But in this age of human domination, with Australia at the forefront of a global biodiversity crisis, some scientists say traditional conservation strategies may no longer be sufficient.

“We are looking for solutions in an altered world,” said Dan Hurley, senior ecologist at Zoos Victoria. “We need to take risks. We need to be more bold.”

vortex of extinction

The Helmeted Honeyeater is an attention-seeking bird with a patch of electric yellow feathers on its forehead and a habit of making loud calls as it scampers through Victoria’s dense swamp forests. But over the past few centuries, humans and wildfires had damaged or destroyed these forests, and by 1989, only 50 honeyeaters remained, clinging to a small swamp in the Erinbo Nature Reserve. .

Intensive local conservation efforts, including a captive breeding program at Zoos Victoria’s Healesville Sanctuary, have helped the birds survive. But the remaining bird species have little genetic diversity, a problem common to endangered animal populations, and breeding necessarily means inbreeding. “They have very few options to make good mating decisions,” said Paul Sanax, a wildlife geneticist at Monash University in Melbourne.

In small, closed breeding pools, harmful genetic mutations can accumulate over time, negatively impacting animal health and reproductive success, and inbreeding can exacerbate the problem. The honeyeater was a particularly extreme example. Dr. Sanax and his colleagues found that the most inbred birds leave one-tenth as many offspring as the least inbred birds, and females live half as long.

Aleksandra Pavlova, an evolutionary ecologist at Monash University, said that without some intervention, the honeyeater could be drawn into an “extinction vortex”. “It became clear that we needed to do something new.”

Ten years ago, Dr Pavlova, Dr Sanax and several other experts proposed adding the Gippsland yellow-bellied honeyeater and its fresh DNA to the breeding pool, proposing an intervention known as genetic rescue.

Although they belong to the same species, they are genetically distinct subspecies and have evolved apart from each other over approximately the past 56,000 years. The Gippsland bird inhabits drier, open forests and lacks the prominent plumage that gives it its name.

Genetic rescue was not a new idea. One widely cited success story is when scientists revived a small inbred panther population in Florida by importing wild panthers from another population in Texas.

However, this approach violates traditional conservation principles that unique biological populations are sacred and should be kept separate and genetically pure. “This is truly a paradigm shift,” said Sarah Fitzpatrick, an evolutionary ecologist at Michigan State University, who found that genetic rescue is underutilized in the United States.

Crossbreeding the two species of honeycreepers risked destroying the uniqueness of each subspecies and creating hybrids unsuited to either niche. Moving animals between populations can also spread diseases, create new invasive populations, and destabilize ecosystems in unpredictable ways.

Genetic rescue is also a form of active human intervention that violates what some scholars call the “spirit of restraint” of conservation, and is sometimes criticized as a form of god-playing.

“There was a lot of anxiety among government agencies about its implementation,” said Andrew Weeks, an ecogeneticist at the University of Melbourne who started the genetic rescue effort for the endangered mountain pygmy possum in 2010. . I think government agencies encouraged it because the population was on the verge of extinction. ”

Dr. Sanax and his colleagues made similar calculations and argued that the risks associated with gene protection are small. Before the bird’s habitat was cleared and degraded, the two subspecies occasionally interbred in the wild. And it pales in comparison to the risks. Do nothing.

So since 2017, Gippsland birds have been participating in Healesville Nature Reserve’s western honey bee breeding program. In captivity, many mixed pairs produced more independent chicks per nest than pairs consisting of two bees, a real advantage. Currently, dozens of hybrid honeyeaters have been released into the wild. They seem to be doing well, but it’s too early to tell if they have the fitness advantage.

Experts from Monash and Zoos Victoria are also working on genetic rescues of other species, including the endangered leadbeater possum, a small arboreal marsupial known as the woodland fairy. Lowland possum populations share the Erinbo wetland with the honeycreeper. In 2023, there were only 34 western lowland possums left. Last month, the first genetic rescue joey was born at Healesville Sanctuary.

Scientists believe that increasing genetic diversity will make these populations more resilient to any unknown dangers, and that some individuals may have the traits they need to survive. I hope that it will become more sexual. Dr Hurley, from Zoos Victoria, said: “Genetic diversity is the blueprint for how we deal with the future.”

targeted threats

For the northern marsupial predator, an existential threat arrived almost a century ago when the invasive and poisonous cane toad landed in eastern Australia. Since then, the poisonous toads have marched steadily westward, wiping out populations of possums that feed on invasive amphibians.

But some of the surviving possum populations in eastern Australia appear to have evolved an aversion to toads. When scientists bred toad-hating possums with toad-hating possums, the offspring of the hybrids also turned their little pink noses at the poisonous amphibians.

What would happen if scientists were able to move some of the toad-avoiding possums west and spread their identification genes before the cane toads arrive? “This means the problem is completely and permanently solved,” said study leader Ben Phillips, a population biologist at Curtin University in Perth.

However, field tests demonstrated how unpredictable nature is. In 2017, Dr. Phillips and his colleagues A mixed population of northern black rats lives on a small island infested with toads. Some possums did interbreed, and there was preliminary evidence of natural selection for “toad smart” genes.

However, the population has not yet fully adapted to toads, and some quolls have died from eating the amphibians, Dr. Phillips said. A large-scale wildfire also broke out on the island. Then the cyclone hit. “All of these things conspired to wipe out our experimental population,” Dr. Phillips said. Scientists didn’t have enough money to try again, but “all the science was there,” he added.

As science advances, future efforts may become more targeted. In 2015, for example, scientists created more heat-tolerant corals by interbreeding colonies from different latitudes. In a 2020 proof-of-concept study, researchers used a gene editing tool known as CRISPR to directly modify genes involved in heat tolerance.

Australian Institute of Marine Science biologist Lyn Bey, author of both studies, said CRISPR would not become a practical real-world solution any time soon. “It’s really complex to understand the benefits and risks,” she said. “And this idea of ​​interfering with nature is very uncomfortable for people.”

However, there is growing interest in biotechnological approaches. Dr. Waddle hopes to use synthetic biology tools such as CRISPR to create frogs resistant to the chytrid fungus, which causes a deadly disease that has already contributed to the extinction of at least 90 species of amphibians. ing.

This fungus is so difficult to eradicate that some vulnerable species can no longer live in the wild. “So either they live forever in a glass box, or we come up with a solution to get them back into the wild and thrive,” Dr Waddle said.

unintended consequences

However, no matter how advanced technology becomes, living organisms and ecosystems remain complex. Tiffany Kosh, a conservation geneticist at the University of Melbourne who also hopes to create chytrid-resistant frogs, said genetic intervention was “likely to have unintended consequences”.Genetic variations that help frogs survive chytrid fungus may also make them more susceptible to other health problems, she said.

There are many cautionary tales of efforts to redesign nature that backfired spectacularly. In fact, it turns out that the poisonous cane toads were intentionally released in Australia in a highly misguided attempt to control the pest beetle.

But some environmental groups and experts are concerned about genetic approaches for other reasons. “Focusing on intensive interventions for specific species can be distracting,” said Friends of the Earth Australia spokesperson Cam Walker. Avoiding extinction will require broader landscape-level solutions, such as halting habitat loss, he said.

Furthermore, animals are autonomous beings, and interfering with their lives and genomes requires “a very strong ethical and moral justification” that even many traditional conservation projects cannot pass. Deakin University environmental scientist Adam Cardillini said there were no hurdles to overcome. Victoria.

Macquarie University biological philosopher Chris Lean believes in the fundamental conservation goal of “preserving the world as it is, for its heritage value and ability to tell the story of life on Earth.” he said. Still, he said he supports careful and limited use of new genomic tools, which may require a rethinking of long-held environmental values.

In a sense, assisted evolution is an assertion, or perhaps a recognition, that unless humans deeply shape the lives and destinies of wildlife, there will be no retreat and no future.

For Dr. Hurley, it became clear that preventing further extinction would require human intervention, innovation, and effort. “Don’t be intimidated by it, lean into it,” he said. “My thinking is that 50 years from now, biologists and wildlife managers will look back at us and say, ‘Why didn’t they take action when they had the chance?’ .”