About 6-7 million years ago, common rosefinches – which are today found across a vast expanse of northern Eurasia and are even occasional winter visitors to the British Isles – island-hopped their way from the Russian Far East across the Pacific Ocean and arrived in the newly formed, volcanic land masses of Hawaii.
There, a single species evolved into an extended family of 56 Hawaiian honeycreepers, many of which only barely resemble their pioneering ancestor.
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Take, for example, the gorgeous scarlet honeycreeper or i’iwi, with its huge downward curving bill that is perfectly adapted for extracting nectar from endemic Hawaiian flowers. At first glance, it looks nothing like a finch.
It’s an amazing story, but also a tragic one, because according to the US Fish & Wildlife Service, 39 of Hawaii’s honeycreepers are extinct, and 11 of the remaining 17 are threatened.
One of the biggest factors in this natural history catastrophe is avian malaria. Neither the single-celled organism that causes malaria, nor the mosquito that transmits it, are native to Hawaii, so honeycreepers and other endemic birds have almost no immunity to it. All conservationists agree that something needs to be done – and quickly – if we are to save those that remain.
Tackling avian malaria
Step forward scientists such as Tim Harvey-Samuel, an expert in arthropod genetics at the University of Keele. Harvey-Samuel and his team are seeing whether they can “modify the mosquito population in Hawaii such that it’s no longer able to transmit avian malaria.”
The idea is to insert a gene into the mosquito (Culex quinquefasciatus) so that it doesn’t allow the Plasmodium protozoan that causes malaria to complete its life-cycle. It’s called a gene drive – a type of genetic modification (GM) – and this is where the clever bit comes in.
“A normal gene gets passed on to 50 per cent of the offspring,” says Harvey-Samuel. “With a gene drive, the idea is you change it in such a way that it’s passed to more than 50 per cent of your kids. It doesn’t necessarily need to get to 100 per cent to be effective, but the closer you are to 100, the faster it will spread through the population.”
Another scientist compares it to creating a coin with two heads. A gene drive beats the normal odds.
Other non-GM approaches are being considered to deal with the malaria issue. For example, scientists have infected male mosquitoes with the Wolbachia bacterium, making the females they mate with infertile. Millions have been released on Hawaii.
But Harvey-Samuel believes no one single method will save Hawaii’s native birds. His work is at a very early stage, and it could be many years before there are any genetically modified mosquitoes ready to be released. Even then, the team would have to pass numerous regulatory hurdles in Hawaii.
The GM debate
That doesn’t stop scientists opposed to GM organisms being alarmed. At a recent conference of the IUCN (International Union for Conservation of Nature), they proposed there should be a moratorium on any releases into the wild.
The motion failed, and instead delegates agreed one that creates the first global framework on whether, and how, what the IUCN calls ‘synthetic biology’ should be researched for the benefit of nature conservation.
“The policy should not be interpreted as supporting or opposing synthetic biology,” the IUCN says.
“It provides a framework for case-by-case decision-making, establishing a mechanism to guide how, when, and under what conditions synthetic biology applications might be approved and introduced.”
Nevertheless, many conservationists are unhappy about the current direction. “There is no evidence that these technologies will help protect or restore nature,” says Franziska Achterberg, head of policy at Save Our Seeds, one of a number of organisations that supported the moratorium proposal.
She says there are only two examples where wild species have been successfully genetically modified, and neither have provided conservation benefits. One is the creation of what biotech company Colossal calls a dire wolf – in reality, a grey wolf with some genes that have been tweaked, Achterberg points out.
“Look at what IUCN experts say about this,” she says. “It is an engineered grey wolf that could threaten wild wolves if it got out.”
The other example Achterberg highlights is the American chestnut. The species is Critically Endangered in North America, where scientists have attempted to create a tree resistant to blight.
“Initially, the American Chestnut Foundation supported this work, but by 2023, they felt it wasn’t going anywhere,” she says.
The argument of ‘Frankenstein’ creatures getting out into the wider environment is understandable.
Eradicating invasive species
But Harvey-Samuel is developing GM mosquitoes for an island situation, and the same is true of Paul Thomas at the University of Adelaide – his work is looking at creating a gene drive that inactivates female fertility in mice. Why mice?
Because where they – and other rodents, especially rats – have been released onto remote islands, they have caused conservation havoc, feeding on ground-nesting seabird eggs and even the chicks, literally eating them alive.
Of course, conservationists have successfully eradicated invasive rodents using poison baits on large islands such as South Georgia and small ones like Lundy in the Bristol Channel, but this has never been a completely satisfactory method.
“It’s expensive, labour-intensive and involves the release of toxins that result in secondary poisonings,” says Thomas. His laboratory work is at least five to 10 years away from producing anything that could result in an animal that could be used in the field, and he doesn’t have any specific islands in mind where it could have practical applications.
But there are obvious examples: Socorro and San José off the coast of Mexico; Gough Island in the South Atlantic; and Floreana in the Galápagos archipelago are just four of many. Thomas also believes that genetic modification can be done in such a way that limits, or even eliminates, broader concerns.
“We are actively trying to develop the technology so that it’s specific for a particular target population,” he says. Invasive rodents on a small island tend to have all come from a small number of founder individuals, and are therefore genetically homogenous.
“The idea is to find a genetic predisposition on the island population that’s not in those on the mainland,” he says. Another idea would be to create an in-built obsolescence within the gene drive – “forming it in such a way that it breaks down over time.”
A “paradigm shift” in conservation
None of this satisfies the sceptics. Joann Sy, scientific advisor at Pollinis, which was the moratorium proposal’s main sponsor, says it all represents an unwelcome and unnecessary “paradigm shift” in the way conservation is carried out worldwide.
As Sy says: “It is very dangerous because we see this as reshaping how we intervene in nature and reframing the purpose of what we do. We would like to refocus the conversation on protecting nature and how we do that.”
Some 30 years on from the height of fears about GM crops, today they’re grown over some two million km², an area nearly four times the size of France. They are grown in 27 countries, with the US, Brazil and India the three biggest adopters of the technology.
Many groups, such as Greenpeace, which made headlines around the world when activists destroyed a field of GM maize in Norfolk in 1999, no longer actively campaign on the issue. But there is still criticism.
GM crops have failed to deliver on the original promises made by biotech firms, it is argued, with some conservationists saying they are a distraction from truly sustainable farming. In short, they haven’t destroyed the world – but they haven’t saved it either.
Paul Thomas understands the concerns of people about GM animals negatively impacting nature conservation: “Responsible development of what we’ve got is important.”
But time is running out for Hawaii’s honeycreepers. At some point, the state authorities must decide either that the use of GM technology can be their saviour, or that adopting such a policy is taking playing God too far.
