Science proposes a new path to fight against animal extinction

For tens of millions of years Australia has been a playing field for evolution. Its land is home to some of the most notable creatures on Earth.

It is the birthplace of songbirds, the birthplace of egg-laying mammals, and the world capital of marsupials with baga group that encompasses much more than koalas and kangaroos.

Almost half of the birds on that continent and approximately 90 percent of its mammals, reptiles and frogs, They are not found anywhere else on the planet.

Australia has also become case study about what happens when people push biodiversity to the limits.

Habitat degradation, invasive species, infectious diseases and climate change have endangered many native animals: The country has one of the worst rates of species loss in the world.

In some cases, according to various researchers, so insurmountable are the threats that the only way to protect animals that only exist in Australia is to modify them.

To achieve this, a variety of techniques are used, including crossing over and gene editing. The researchers are altering the genomes of vulnerable animals hoping to provide them with characteristics they need to survive.

“We seek to help evolution,” summarizes Anthony Waddle, a conservation biologist at Macquarie University in Sydney.

It’s a bold concept that questions the conservationist impulse to preserve wild creatures as they are. “We are looking for solutions in an altered world”clarifies Dan Harley, senior ecologist at Zoos Victoria, a wildlife conservation organization. “You have to take risks, be bold.”

The helmeted honeycreeper is a bird that demands attention, with its patch of electric yellow feathers on its forehead and his habit of squawking loudly as it passes through the dense swampy forests of the state of Victoria.

But in recent centuries, people and forest fires have damaged or destroyed those forests and In 1989 there were only 50 helmeted honeyeaters left.clinging to a small fraction of swamp in the Yellingbo Nature Conservation Reserve.

Intensive local conservation efforts, which included a captive breeding program in Healesville Sanctuaryone of Zoos Victoria’s zoos, helped the birds survive.

But there was very little genetic diversity among the remaining birds (a common problem in endangered animal populations) and inevitably reproduction involved inbreeding.

“They have very few options for making mating decisions suitable,” explains Paul Sunnucks, wildlife geneticist at Monash University in Melbourne.

In any small, closed breeding group, over time harmful genetic mutations can accumulatewhich harm the health and reproductive success of animals, and inbreeding exacerbates the problem.

The helmeted honeycreeper was an especially extreme case. The most inbred birds left one tenth of the offspring than the least inbred, and the longevity of the females was half.

Without some intervention, the helmeted honeycreeper could be drawn into an “extinction vortex,” warns Alexandra Pavlova, an evolutionary ecologist at Monash. “It became clear that it is necessary to do something new.”

A decade ago, Pavlova, Sunnucks, and several other experts suggested an intervention known as genetic rescue and proposed adding some yellow-eared honeyeaters from the Gippsland region with their fresh DNA to the breeding pool.

Genetic rescue was not a new idea at the time. In what was a successful operation widely cited, a team of scientists had already revived Florida’s small inbred panther population by importing wild panthers from a separate population from Texas.

For some experts, this approach violates the traditional conservation principle according to which unique biological populations are sacrosanct and they must be kept separate and genetically pure.

“It’s a paradigm shift,” says Sarah Fitzpatrick, an evolutionary ecologist at Michigan State University in the United States, who has detected that genetic rescue is underutilized in that country.

By crossing the two types of honeyeaters there was a risk of clouding what made each subspecies unique and create hybrids that did not adapt well to either of the two ecological niches.

The movement of animals between populations can also spread diseasescreate new invasive populations or destabilize ecosystems in unpredictable ways.

Furthermore, genetic rescue is a mode of human interference active that violates what some scholars call “ethics of restriction” of conservation and has sometimes been critically described as a way of playing God.

“There was a lot apprehension in government agencies about doing it,” says Andrew Weeks, an ecological geneticist at the University of Melbourne who in 2010 initiated a genetic rescue of the endangered mountain pygmy possum.

Paul Sunnucks and his colleagues made the same calculation, arguing that associated risks with genetic rescue were small and paled in comparison to the risk of doing nothing.

Experts from Monash University and Zoos Victoria have also been working on genetic rescue of other species, such as the Leadbeater’s phalanx or possum. in critical danger of extinction, a small marsupial that lives in trees and is known as a forest fairy.

The possum population of Lowlands shares the Yellingbo swamps with the helmeted honeycreeper; In 2023 there were only 34 of these plains possums left. The first genetically rescued calf was born in Healesville Sanctuary last month.

Scientists hope that accelerating the increase in genetic diversity will make these populations more resilient to any unknown dangers that may arise and increase the odds that some members possess the necessary attributes to survive.

“Genetic diversity is the model for facing the future,” says Harley, from Zoos Victoria.

For the northern quoll, a small marsupial predator, the existential threat arrived almost a century ago, when the invasive poisonous cane toad landed in eastern Australia.

Since then the toxic toads marched steadily westward and They wiped out entire populations of satanels.

But some of the surviving populations of eastern Australia appear to have developed aversion to toads. When scientists crossed toad-averse Satanels with others that didn’t even know them, the hybrid offspring also wrinkled their little pink noses at the toxic species.

What would happen if scientists moved some satanels that toads avoid to the west, allowing them spread your genes discriminators before the cane toads arrived?

“Essentially you would be resorting to natural selection and evolution to achieve the objectives, which means that the problem is resolved in a very comprehensive and permanent way”answers Ben Phillips, a population biologist at Curtin University in Perth who led the research.

However, a field test showed how unpredictable nature can be. In 2017, Phillips and his colleagues released a mixed population of northern satanels in a little island infested with toads. Some satanels mated with each other and there was preliminary evidence of natural selection of “toad-smart” genes.

In 2015, other researchers created more heat-resistant corals by interbreeding colonies from different latitudes. In a proof of concept study In 2020, the gene editing tool known as CRISPR was used to directly alter a gene involved in heat tolerance.

Anthony Waddle hopes to be able to use synthetic biology tools, including CRISPR, to create frogs that are resistant to chytrid funguscausing a fatal disease that has already contributed to the extinction of no less than 90 species of batrachians.

Still, no matter how sophisticated technology becomes, organisms and ecosystems will remain complex universes. Genetic interventions “are likely to have some unintended impacts,” says Tiffany Kosch, a conservation geneticist at the University of Melbourne who also expects create resistant frogs to chytrids, but are not more susceptible to other health problems.

There are many stories of prevention, efforts to redesign nature that failed spectacularly. In fact, toxic cane toads they deliberately let go in Australia in what would turn out to be a misguided attempt to control a certain beetle infestation.

Some environmental groups and experts are uncomfortable with genetic approaches for other reasons as well. “Focus on an intensive intervention in specific species It can be a distraction,” says Cam Walker, spokesperson for Friends of the Earth Australia.

Avoid the extinction crisis will require broader landscape-level solutions, such as halting habitat loss, he estimates.

On the other hand, animals are autonomous beings and any intervention in their lives or genomes must have “a very strong ethical and moral justification”, a bar that not even many traditional conservation projects surpass, highlights Adam Cardilini, environmental scientist from Deakin University, Victoria.

Biological philosopher at Macquarie University, Chris Lean believes in the fundamental goal of conservation to “preserve the world as it is for its heritage value, for its ability to tell the story of life on Earth.” However, he highlights his support for cautious and limited use of new genomic toolswhich may require us to reconsider some long-held environmental values.

In a way, assisted evolution It is an argument – or, perhaps, a recognition – that it is not possible to take a step back, that there is no future in which humans do not profoundly shape the lives and destinies of wild creatures.

For Dan Harley, it is clear that preventing more extinctions is going to take human intervention, innovation and effort. “Let’s lean on that, let’s not be intimidated,” she proposes.

“My vision is that in 50 years, wildlife biologists and managers They will look at us and say, ‘Why didn’t they take action and take advantage of opportunities when they had the chance?’

Translation: Román García Azcárate