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.
Beginning as a grassroots movement, Predator-Free 2050 has picked up huge public support and official government backing. Former Minister for Conservation Maggie Barry once described the initiative as “the most important conservation project in the history of our country.” If it works, Zealandia’s fence would be irrelevant; the entire nation would be a song-filled sanctuary where kiwis trundle unthreatened and kakapos once again boom through the night.
By coincidence, the rise of the Predator-Free 2050 conceit took place alongside the birth of a tool that could help make it a reality—CRISPR, the revolutionary technique that allows scientists to edit genes with precision and ease. In its raw power, some conservationists see a way of achieving impossible-sounding feats like exterminating an island’s rats by spreading genes through the wild population that make it difficult for the animals to reproduce. Think Children of Men, but for rats. Other scientists, including at least one gene-editing pioneer, see the potential for ecological catastrophe, beginning in an island nation with good intentions but eventually enveloping the globe. (...)
In 2014, kevin Esvelt, a biologist at MIT, drew a Venn diagram that troubles him to this day. In it, he and his colleagues laid out several possible uses for gene drives—a nascent technology for spreading designer genes through groups of wild animals. Typically, a given gene has a 50-50 chance of being passed to the next generation. But gene drives turn that coin toss into a guarantee, allowing traits to zoom through populations in just a few generations. There are a few natural examples, but with CRISPR, scientists can deliberately engineer such drives.
Suppose you have a population of rats, roughly half of which are brown, and the other half white. Now, imagine there is a gene that affects each rat's color. It comes in two forms, one leading to brown fur, and the other leading to white fur. A male with two brown copies mates with a female with two white copies, and all their offspring inherit one of each. Those offspring breed themselves, and the brown and white genes continue cascading through the generations in a 50-50 split. This is the usual story of inheritance. But you can subvert it with CRISPR, by programming the brown gene to cut its counterpart and replace it with another copy of itself. Now, the rats’ children are all brown-furred, as are their grandchildren, and soon the whole population is brown.
Forget fur. The same technique could spread an antimalarial gene through a mosquito population, or drought-resistance through crop plants. The applications are vast, but so are the risks. In theory, gene drives spread so quickly and relentlessly that they could rewrite an entire wild population, and once released, they would be hard to contain. If the concept of modifying the genes of organisms is already distasteful to some, gene drives magnify that distaste across national, continental, and perhaps even global scales.
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.
Together with Neil Gemmell from the University of Otago, who is advising Predator-Free 2050, Esvelt has written an opinion piece explicitly asking conservationists to steer clear of standard gene drives. “We want to really drive home—ha ha—that this is a technology that isn’t suitable for the vast majority of potential applications that people imagine for it,” he says. (The only possible exceptions, he says, are eliminating certain diseases like malaria and schistosomiasis, which affect hundreds of millions of lives and have proven hard to control.)
It’s not ready yet, either. Even if gene drives were given a green light today, Gemmell says it would take at least 2 to 3 years to develop carrier animals, another 2 years to test those individuals in a lab, and several years more to set up a small field trial. And these technical hurdles pale in comparison to the political ones. Rats are vermin to many cultures, but they’re also holy to some, and they’re likely to be crucial parts of many ecosystems around the world. Eradicating them is not something that any single nation could do unilaterally. It would have to be a global decision—and that’s unlikely. Consider how much effort it has taken to reach international agreements about climate change—another crisis in which the actions of certain nations have disproportionately reshaped the ecosystems of the entire world. Genetic tools have now become so powerful that they could trigger similar changes, but faster and perhaps more irreversibly.
“In a global society, we can’t act in isolation,” says Gemmell. “Some of these tools we’re thinking about developing will cross international borders. New Zealand is an island nation relatively isolated from everyone else, but what if this was a conversation happening in the United States about eradicating rodents? What if Canadians and Mexicans had a different view? This is something that should be addressed.”
[ed. See also: Mail Order CRISPR Kits Allow Absolutely Anyone to Hack DNA.]
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.
Beginning as a grassroots movement, Predator-Free 2050 has picked up huge public support and official government backing. Former Minister for Conservation Maggie Barry once described the initiative as “the most important conservation project in the history of our country.” If it works, Zealandia’s fence would be irrelevant; the entire nation would be a song-filled sanctuary where kiwis trundle unthreatened and kakapos once again boom through the night.
By coincidence, the rise of the Predator-Free 2050 conceit took place alongside the birth of a tool that could help make it a reality—CRISPR, the revolutionary technique that allows scientists to edit genes with precision and ease. In its raw power, some conservationists see a way of achieving impossible-sounding feats like exterminating an island’s rats by spreading genes through the wild population that make it difficult for the animals to reproduce. Think Children of Men, but for rats. Other scientists, including at least one gene-editing pioneer, see the potential for ecological catastrophe, beginning in an island nation with good intentions but eventually enveloping the globe. (...)
In 2014, kevin Esvelt, a biologist at MIT, drew a Venn diagram that troubles him to this day. In it, he and his colleagues laid out several possible uses for gene drives—a nascent technology for spreading designer genes through groups of wild animals. Typically, a given gene has a 50-50 chance of being passed to the next generation. But gene drives turn that coin toss into a guarantee, allowing traits to zoom through populations in just a few generations. There are a few natural examples, but with CRISPR, scientists can deliberately engineer such drives.
Suppose you have a population of rats, roughly half of which are brown, and the other half white. Now, imagine there is a gene that affects each rat's color. It comes in two forms, one leading to brown fur, and the other leading to white fur. A male with two brown copies mates with a female with two white copies, and all their offspring inherit one of each. Those offspring breed themselves, and the brown and white genes continue cascading through the generations in a 50-50 split. This is the usual story of inheritance. But you can subvert it with CRISPR, by programming the brown gene to cut its counterpart and replace it with another copy of itself. Now, the rats’ children are all brown-furred, as are their grandchildren, and soon the whole population is brown.
Forget fur. The same technique could spread an antimalarial gene through a mosquito population, or drought-resistance through crop plants. The applications are vast, but so are the risks. In theory, gene drives spread so quickly and relentlessly that they could rewrite an entire wild population, and once released, they would be hard to contain. If the concept of modifying the genes of organisms is already distasteful to some, gene drives magnify that distaste across national, continental, and perhaps even global scales.
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.
Together with Neil Gemmell from the University of Otago, who is advising Predator-Free 2050, Esvelt has written an opinion piece explicitly asking conservationists to steer clear of standard gene drives. “We want to really drive home—ha ha—that this is a technology that isn’t suitable for the vast majority of potential applications that people imagine for it,” he says. (The only possible exceptions, he says, are eliminating certain diseases like malaria and schistosomiasis, which affect hundreds of millions of lives and have proven hard to control.)
It’s not ready yet, either. Even if gene drives were given a green light today, Gemmell says it would take at least 2 to 3 years to develop carrier animals, another 2 years to test those individuals in a lab, and several years more to set up a small field trial. And these technical hurdles pale in comparison to the political ones. Rats are vermin to many cultures, but they’re also holy to some, and they’re likely to be crucial parts of many ecosystems around the world. Eradicating them is not something that any single nation could do unilaterally. It would have to be a global decision—and that’s unlikely. Consider how much effort it has taken to reach international agreements about climate change—another crisis in which the actions of certain nations have disproportionately reshaped the ecosystems of the entire world. Genetic tools have now become so powerful that they could trigger similar changes, but faster and perhaps more irreversibly.
“In a global society, we can’t act in isolation,” says Gemmell. “Some of these tools we’re thinking about developing will cross international borders. New Zealand is an island nation relatively isolated from everyone else, but what if this was a conversation happening in the United States about eradicating rodents? What if Canadians and Mexicans had a different view? This is something that should be addressed.”
by Ed Yong, The Atlantic | Read more:
Image: Stas Kulesh/Getty Images[ed. See also: Mail Order CRISPR Kits Allow Absolutely Anyone to Hack DNA.]
