Why New Zealand is going all out to kill its rats, possums

New Zealand is well-known for harboring hundreds of beautiful native bird species, many of which have called the archipelago home for millennia. Mammalian species, on the other hand, are not native to the island nation — all except two surviving bat species arrived along with humans a mere 700 years ago. Since then, nearly a quarter of the country’s native birds have gone extinct.

Now the government of New Zealand has announced it is adopting a rather extreme conservation strategy to save its birds. It wants to wipe out an entire population of eight mammalian predators, including rats, possums and stoats. But can the country turn back the clock 700 years to before these non-native predators arrived? 

Sarah Dawson, director of the Wohlsen Center for Sustainable Environment at Franklin and Marshall College, thinks it is a possibility. But the effort will not be without some risks.

“This is definitely the largest scale removal ever attempted,” Dawson says. “And when we're talking about things like rats and mice in particular — you have species refuging on private lands and in homes, so there's going to be a lot of public compliance and likely assistance necessary that’s going to be difficult — costs in billions of dollars. And also they're talking about using poisons, which will be effective against the non-native mammals, but there could also be some non-target species like domestic dogs being affected.”

Though there are risks and costs associated with the effort, Dawson says conservation on New Zealand is particularly important. 

“It's not just New Zealand protecting bio diversity, it's critical across the globe because we depend on it for food and housing and medicines both known and almost certainly unknown,” Dawson says. “We're losing thousands of species each year because of impacts from humans. But islands in particular have a disproportionate amount of unique bio diversity because their species have been evolving in isolation for so long. So though islands comprise only about five percent of land area, they do contain about 20 percent of all the species on the globe and so conservation efforts can be more efficient here. But for New Zealand in particular, their unique fauna are also a major economic driver in the form of tourism dollars.”

There is, however, reason to hope that, although extreme, this eradication project will be successful. 

“It does sound ghastly but I do think it's a critical component of a comprehensive conservation plan,” Dawson says. “It's actually been used in some form or another in more than a thousand other places — mostly islands — and sometimes successfully, sometimes not successfully…But it is important to note that New Zealand is not at all new to this sort of strategy. They've actually had success already in removing stoats, possums, rats and also other invasive species from over 100 of their smaller outlying islands, so they're well practiced.” 

This article is based on an interview that aired on PRI's Science Friday.

New Zealand is well-known for harboring hundreds of beautiful native bird species, many of which have called the archipelago home for millennia. Mammalian species, on the other hand, are not native to the island nation — all except two surviving bat species arrived along with humans a mere 700 years ago. Since then, nearly a quarter of the country’s native birds have gone extinct.

Now the government of New Zealand has announced it is adopting a rather extreme conservation strategy to save its birds. It wants to wipe out an entire population of eight mammalian predators, including rats, possums and stoats. But can the country turn back the clock 700 years to before these non-native predators arrived? 

Sarah Dawson, director of the Wohlsen Center for Sustainable Environment at Franklin and Marshall College, thinks it is a possibility. But the effort will not be without some risks.

“This is definitely the largest scale removal ever attempted,” Dawson says. “And when we're talking about things like rats and mice in particular — you have species refuging on private lands and in homes, so there's going to be a lot of public compliance and likely assistance necessary that’s going to be difficult — costs in billions of dollars. And also they're talking about using poisons, which will be effective against the non-native mammals, but there could also be some non-target species like domestic dogs being affected.”

Though there are risks and costs associated with the effort, Dawson says conservation on New Zealand is particularly important. 

“It's not just New Zealand protecting bio diversity, it's critical across the globe because we depend on it for food and housing and medicines both known and almost certainly unknown,” Dawson says. “We're losing thousands of species each year because of impacts from humans. But islands in particular have a disproportionate amount of unique bio diversity because their species have been evolving in isolation for so long. So though islands comprise only about five percent of land area, they do contain about 20 percent of all the species on the globe and so conservation efforts can be more efficient here. But for New Zealand in particular, their unique fauna are also a major economic driver in the form of tourism dollars.”

There is, however, reason to hope that, although extreme, this eradication project will be successful. 

“It does sound ghastly but I do think it's a critical component of a comprehensive conservation plan,” Dawson says. “It's actually been used in some form or another in more than a thousand other places — mostly islands — and sometimes successfully, sometimes not successfully…But it is important to note that New Zealand is not at all new to this sort of strategy. They've actually had success already in removing stoats, possums, rats and also other invasive species from over 100 of their smaller outlying islands, so they're well practiced.” 

This article is based on an interview that aired on PRI's Science Friday.