When it comes to saving animals, humans have a long history of making ‘very bad decisions’

The third-to-last male northern white rhinoceros on Earth was in his late 20s — middle-aged by rhino standards — when a team of scientists carefully anesthetised him, inserted a probe into his rectum, and administered a mild electric shock to nerves near the prostate, causing the rhino to ejaculate in his sleep. The sperm was then separated out and frozen.

That rhino — named Suni — grew old and eventually died. So did the other remaining males.

Today, the only surviving members of the species are two females — Najin, and Fatu. In the wild, that would mean the species would, inevitably, go extinct.

But Thomas Hildebrandt, a senior biologist at the Leibniz Institute for Zoo and Wildlife Research and a pioneer of assisted reproduction in large mammals, has a different idea.

Mr. Hildebrandt, who led the team that collected Suni’s sperm, plans to use it (and that of another of the last males) to perform a miracle: bringing a species back from the brink of extinction when one sex is already gone.

To do this, he would use the sperm to fertilize an egg collected from one of the remaining females, which would be implanted in a surrogate mother of a different kind of rhino (Najin and Fatu both have problems with their uteruses and can’t carry offspring).

After spending a few years carefully crafting a stockpile of embryos, Mr. Hildebrandt now feels that he has enough to try for a pregnancy by the end of this year. Rhino pregnancies last 16 months. So by spring 2024, Najin and Fatu could be a little less lonely. The plan to rescue the northern white rhino is unique, but its existential predicament is not.

Between poaching, the bulldozing of natural habitats for farms or shopping malls, and the mounting pressure of climate change, up to one million species are currently at risk of extinction, according to a 2019 United Nations report. We are living through one of only half a dozen periods in Earth’s history with such a devastating rate of species loss, even without the help of an asteroid or mega-volcano.

But this time, we do have the help of science. And as threats to biodiversity escalate, and more and more species face extinction, scientists are responding with ever more creative, hands-on and potentially risky interventions to try to save them.

They are — as with Suni — cryogenically banking reproductive cells collected via electroejaculation and using them to perform assisted pregnancies. They are physically relocating animals to safer habitats by truck and airplane. They are transporting animals over special bridges shooting them through cannons and dangling them upside-down from helicopters.

To study shy animals, they’re dispatching robots and dressing in costumes. They’re concocting love potions and personally mimicking mating rituals. To knock out invasive predators, they’re chucking poisoned sausages and mice out of airplanes and dispatching more robots weaponised to kill invasive starfish).

Most controversial, they’re studying how they might alter the genes of wild animals to either confer resistance to climate shocks or — if the animal in question is an invasive predator — deliberately cause its population to collapse.

These increasingly inventive initiatives signal a shift toward a new era in the science of conservation — one that could prove vital for preserving certain ecosystems, but that also poses some serious ethical questions.

Traditionally, conservation was a game of isolating land and leveraging cash and local laws to place vulnerable areas out of the reach of developers and poachers. As the name implies, it was a field of science primarily concerned with protecting and maintaining wild habitats as they already were — a science that postured itself in opposition to the capitalist pressures of development and change.

“The problem is, you can’t protect enough,” says Rebecca Shaw, chief scientist at the World Wildlife Fund. Over the past few decades, as the rate of global development has increased to a dizzying speed, traditional conservation has struggled — and failed — to keep up. “As the more tried-and-true prevention activities aren’t addressing the problem adequately at scale, you start getting more and more far-fetched examples of how to handle little pieces of it.”

In short, conservationists are being forced to think outside the box. And given the multitude and urgency of threats wild flora and fauna face, the stakes of their initiatives have never been higher. But neither has the risk of error.

A chief lesson of the last century of ecological research and public policy is that well-intentioned interventions can easily, disastrously backfire — with consequences borne by people and animals left out of the decision-making process. As conservation technology becomes more advanced, the scale of potential adverse consequences rises.

“There’s a long history,” Ms. Shaw says, “of very bad decisions by people who were very passionate about their solutions.”

One infamous example of conservation gone wrong is the case of the rosy wolfsnail. The four-inch snail was introduced to Hawaii in the 1950s from Florida under the theory that it would eat and control the spread of invasive African land snails. Instead, the rosy wolfsnail developed an appetite for native snails and other gastropods, and drove one-third of native species to extinction.

If that can happen simply by introducing a new species to a sensitive ecosystem, what might happen if scientists introduced — as some have suggested — a new gene? Some researchers are currently exploring the possibility of employing the cutting-edge bioengineering technology CRISPR — which allows scientists to edit DNA with pinpoint accuracy, most often in the pursuit of treatments for disease — to help achieve conservation goals.

“Gene drive” is an application of CRISPR in which genes are modified to spread a bespoke mutation quickly through successive generations in a population.

The most promising application for gene drive is destructive ends: an edit that renders offspring infertile or causes them all to be born female, eventually driving the population to collapse.

Target Malaria, an international research consortium backed by the Bill and Melinda Gates Foundation, is investigating how this approach could be used to eliminate malaria-carrying mosquitoes, a potentially world-changing benefit for public health.

For conservation purposes, gene drives could be used to target invasive species that are harmful to endangered native ones. Federal biologists recently considered a mosquito-focused gene drive, this one aimed at eradicating avian malaria, which is responsible for crashing populations of endangered birds in Hawaii. But for now the idea is on the back burner, says Eben Paxton, a biologist with the U.S. Geological Survey, because it can’t be ready for a field trial soon enough and would most likely face “an intense backlash” from the public.

In December, computational biologists at Cornell published the results of a complex computer simulation of a gene drive targeting rats on a hypothetical island. Depending on how efficiently the altered genes were passed from parents to offspring, among other factors, the simulation proved highly effective — capable of wiping out a population of tens of thousands of rats within 20-30 years.

If that sounds brutal, it at least entails no physical pain for any individual rats, unlike poison, traps, or other conventional methods of population control, said Philipp Messer, who designed the study. The research was funded by Predator Free 2050, a conservation group in New Zealand that is working to protect critically endangered species there — some of which are threatened by invasive rodents — and is “pretty desperate at the moment,” Mr. Messer said.

Still, he is adamant that, if anything, his research only showed how ill-prepared the world is for a real-life gene drive.

The biggest risk is that the alteration escapes its intended setting: One gene-edited rat stows away from the island on a cruise ship and within years the entire global rat population is decimated, with incalculable consequences. Although scientists are tinkering with genetic techniques that could limit a gene drive’s ability to spread unchecked, a decision today by any single conservationist to initiate a gene drive could endanger countless global ecosystems.

“It’s of the utmost importance to look at these things,” Messer said, “but at the moment we’re nowhere close.”

To Kevin Esvelt, a biologist at the Massachusetts Institute of Technology who helped pioneer gene drives, another major risk is that a misuse of the technology, even if it stops short of ecological catastrophe, would spook the public and lawmakers enough to throw the brakes on research, like that on malaria, that he believes is on the cusp of saving millions of human lives.

“A high-profile disaster,” he said, “can set a field back by 10 years.”

Genetics is contributing to conservation efforts in other ways, too.

An ambitious project of more than 100 scientists led by biologist Brad Shaffer at UCLA is currently working to catalogue the genomes of about 230 animal and plant species across California. The goal is to create a map of the state’s genetic diversity and identify hot spots: Areas of high diversity that should be prioritised for protection, or of low diversity that might need a boost from assisted breeding programs. Marine biologists at the Carnegie Institute for Science are taking a similar approach to coral in the Great Barrier Reef, identifying genes that seem to make some corals more resistant to rising ocean temperatures with the idea that populations with these genes could be prioritised for conservation.

Phillip Cleves, who leads the coral project, said he doesn’t see this type of work as playing God. Instead, it’s more like taking the process of natural selection off autopilot. As species face a host of “unnatural” obstacles, Cleve said his goal is to leverage existing genetic variation to raise the odds that as many as possible can survive whatever the climate of the coming century will throw at them.

“Our role as biologists, as stewards of ecosystems, is to predict how life will find its way, and make sure we do everything we can to facilitate that,” he said.

For Mr. Shaffer, the efficient use of resources could also mean inviting wild species into closer contact with humans. Cities already host many thriving, non-native wild species, from endangered Mexican parrots that now flock around Los Angeles to dozens of non-native reptile species slithering around Miami.

“You might argue there’s no such thing as a natural system anymore,” he said. “I’m looking out my window on an urban forest, and I don’t think a single tree is native.”