NZ a world leader in pest eradication techniques

Damage to an egg caused by an invasive rat species (Supplied / Island Conservation)
Damage to an egg caused by an invasive rat species (Supplied / Island Conservation)

New Zealand is a world leader when it comes to protecting native and endangered species, a global study has found.

The study's co-author, Don Croll, says humans have "accidentally or intentionally" introduced invasive mammals to 90 percent of the world's islands -- threatening native species who have developed with no defences against animals like feral cats and rodents.

More than 100 islands in New Zealand are pest-free, allowing biodiversity to flourish.

The security of islands like this is crucial to conservation success -- 37 percent of the world's endangered species live on islands.

Examining 596 populations of 236 native species on 181 islands, the researchers found the eradication of pest species had a number of benefits, including increases in native populations and success when reintroducing a native species.

New Zealand's own titi (Cook's petrel) is one of the big success stories. The species is now at a lower risk of extinction thanks to pest control on Little Barrier Island and Great Barrier Island -- two of the main homes for the titi.

And the study's authors say New Zealand is setting the gold standard when it comes to pest eradication.

"Many eradication techniques were first developed in New Zealand, so much so that it's been commonplace to 'call the Kiwis' if you want to eradicate mammals," says lead author Holly Jones.

Dr Jones, an assistant professor in biological sciences at Northern Illinois University, says more conservation organisations around the world are following New Zealand's lead.

While there's no way to bring back extinct species, Dr Jones says the results of the study could show an easier way to protect the species that still remain.

"Our analysis shows that removing invasive mammals can help us undo some of the damage we've caused."

Environmental Defence Society senior policy analyst Dr Marie Brown says there's a lot to take into account when it comes to preserving native animal species.

"It is important to note however, that pest control is the removal of just one pressure," Dr Brown said.

"Habitat loss presents an equal or greater threat, and we must do very much better at curtailing that -- so that when populations rebound as set out in the article, they have somewhere to live."

Professor Bruce Clarkson, Director of the University of Waikato's Environmental Research Institute, agrees with that sentiment.

"Congratulations to the authors for pulling this together -- but they are one silver bullet with others needed," Prof Clarkson said.

"Offshore islands can never save all of New Zealand's indigenous biodiversity as they are unrepresentative of the full range of ecosystems and habitats of the New Zealand archipelago."

The study was published in the Proceedings of the National Academy of Science today.

In an accompanying editorial, co-author James Russell, an Auckland University senior lecturer in biology and statistics, discusses the ethical implications of pest eradication schemes.

He says lethal control is justified in cases where they can reverse the negative impacts the introduced species had on the natives.

"The principle of 'do no harm' should always underpin any comparison of possible conservation interventions. However, deciding to do nothing is in itself an action, and like the decision to implement lethal control, it determines which animals will die, how many will die, and how they will die."