The nation wants to eradicate all invasive mammal predators by 2050. Gene-editing technology could help—or it could trigger an ecological disaster of global proportions.
The Atlantic said:The first thing that hit me about Zealandia was the noise.
I was a 15-minute drive from the center of Wellington, New Zealand’s capital city, but instead of the honks of horns or the bustle of passersby, all I could hear was birdsong. It came in every flavor—resonant coos, high-pitched cheeps, and alien notes that seemed to come from otherworldly instruments.
Much of New Zealand, including national parks that supposedly epitomize the concept of wilderness, has been so denuded of birds that their melodies feel like a rare gift—a fleeting thing to make note of before it disappears. But Zealandia is a unique 225-hectare urban sanctuary into which many of the nation’s most critically endangered species have been relocated. There, they are thriving—and singing. There, their tunes are not a scarce treasure, but part of the world’s background hum. There, I realized how the nation must have sounded before it was invaded by mammals.
Until the 13th century, the only land mammals in New Zealand were bats. In this furless world, local birds evolved a docile temperament. Many of them, like the iconic kiwi and the giant kakapo parrot, lost their powers of flight. Gentle and grounded, they were easy prey for the rats, dogs, cats, stoats, weasels, and possums that were later introduced by humans. Between them, these predators devour more than 26 million chicks and eggs every year. They have already driven a quarter of the nation’s unique birds to extinction.
Many species now persist only in offshore islands where rats and their ilk have been successfully eradicated, or in small mainland sites like Zealandia where they are encircled by predator-proof fences. The songs in those sanctuaries are echoes of the New Zealand that was.
But perhaps, they also represent the New Zealand that could be.
In recent years, many of the country’s conservationists and residents have rallied behind Predator-Free 2050, an extraordinarily ambitious plan to save the country’s birds by eradicating its invasive predators. Native birds of prey will be unharmed, but Predator-Free 2050’s research strategy, which is released today, spells doom for rats, possums, and stoats (a large weasel). They are to die, every last one of them. No country, anywhere in the world, has managed such a task in an area that big. The largest island ever cleared of rats, Australia’s Macquarie Island, is just 50 square miles in size. New Zealand is 2,000 times bigger. But, the country has committed to fulfilling its ecological moonshot within three decades.
...
Esvelt understood that from the beginning. In an early paper discussing gene drives, he and his colleagues discussed the risks, and suggested several safeguards. But they also included a pretty Venn diagram that outlined several possible applications, including using gene drives to control invasive species—like rats. That was exactly the kind of innovation that New Zealand was after. You could spread a gene that messes with the rodent’s fertility, or that biases them toward one sex or the other. Without need for poisons or traps, their population would eventually crash.
Please don’t do it, says Esvelt. “It was profoundly wrong of me to even suggest it, because I badly misled many conservationists who are desperately in need of hope. It was an embarrassing mistake.”
Through mathematical simulations conducted with colleagues at Harvard, he has now shown that gene drives are even more invasive than he expected. Even the weakest CRISPR-based gene drives would thoroughly invade wild populations, if just a few carriers were released. They’re so powerful that Esvelt says they shouldn’t be tested on a small scale. If conservationists tried to eliminate rats on a remote island using gene drives, it would only take a few strongly swimming rodents to spread the drive to the mainland—and beyond. “You cannot simply sequester them and wall them off from the wider world,” Esvelt says. They’ll eventually spread throughout the full range of the species they target. And if that species is the brown rat, you’re talking about the entire planet.
...