An isolated archipelago, New Zealand once hosted almost 200 bird species, many of them, like the iconic kiwi, having become flightless over generations because of a lack of natural predators. But several recently introduced species, such as rats, possums, and weasellike carnivores called stoats, now kill about 25 million of these native birds every year. Yesterday, the country’s prime minister, John Key, announced a $20 million commitment of seed money to set up Predator Free New Zealand Ltd., a company that would lead the charge in ridding the nation of the three mammals and five other foreign predators by 2050. Until now, similar eradication efforts by the country have focused on small islands; those efforts boast a 90% success rate in eliminating rodents, says James Russell, a conservation biologist at the University of Auckland in New Zealand. The new goal, Russell says, is “the modern equivalent to landing someone on Mars” and will ultimately require new technologies and billions of dollars to succeed. But he is optimistic because local communities and organizations, which could foot a large portion of the total bill, are on board.
Other areas of the world have become or stayed rat-free or close to it, says Phil Merrill, a conservation biologist with the Alberta Agriculture and Forestry ministry in Lethbridge, Canada. In the 1950s, this western province organized a rat surveillance program that has prevented rodents from neighboring provinces and the United States from settling in, allowing it to boast of a rat-free status. Rats invaded the neighboring Saskatchewan in the 1930s, and for the past 50 years, that province has been trying to get rid of them, recently with increasing success, Merrill says. Farmers in this northern, colder region have a higher standard of living than in the past, enabling them to keep their livestock indoors and build barns, silos, and other structures out of steel and cement instead of wood. As a result, there’s much less ideal rat habitat, he notes, and Saskatchewan “is finally winning” against these invaders.
Tony Martin, a conservation biologist at the University of Dundee in the United Kingdom, is on the verge of calling South Georgia Island, a 100,000-hectare U.K. territory rat-free as well. Working for the South Georgia Heritage Trust, he led a team that used helicopters to drop 300 tons of poisoned rat bait onto the island over 5 years to make the island safe for the many seabirds and other bird species that nest there. Completed in 2015, the program produced little evidence that other wildlife were poisoned and Martin believes the island will be declared rat-free in 2 years. It helped, Martin says, that the rats could live only in small pockets of land isolated from each other by glaciers, enabling targeted drops of the bait. “Our South Georgia campaign demonstrated that it pays to be ambitious and to think big.”
Still, New Zealand could be a tougher challenge, Martin notes. Effective rat control over the country’s many contrasting topographies and habitats will be hard enough, but New Zealand’s human population of millions complicates the process even more. “Finding a way to eliminate every single bad guy (rat, stoat, or possum) while leaving all the good guys untouched is going to be the greatest challenge,” he wrote in an email.
Also, once eliminated, rats will likely keep coming back in, Merrill notes. “They can do it if they can prevent the rats from jumping off the boats,” he predicts. Russell says that’s doable. “We are currently close to a 100% success rate in intercepting new mammal arrivals on the islands.” New Zealand’s track record on its smaller islands bodes well, Martin says. “This challenge is of mind-blowing proportions, but if anyone can do it, the New Zealanders can.”