Rodents take nature away, how do we get it back?

About 1000 years ago, the island where New Zealand is located is still a wild land. Birds, reptiles and invertebrates still thrive in this dense forest hundreds of kilometers away from other continents. But in the 13th century, when the Maori migrated to New Zealand, they also brought Polynesian rats (Polynesian rats) as food. Since then, humans and rodents have begun to change the ecological balance of New Zealand, while native species have begun to become extinct.

Ships from Europe are carrying new predators: including more aggressive, larger rats, as well as smaller mice and ferrets. New Zealand wildlife originally only needed to deal with predators such as falcons flying in the air, so they only evolved the corresponding ability to survive. But these new land predators have different predation methods, making it easy for native birds sleeping in burrows to become prey for these predators. In the end, with the surge in the number of invasive predators, local wildlife suffered devastating persecution.

Since then, ecologists in New Zealand have been successful in eliminating invasive harmful species. Today, about 2/3 of New Zealand's smaller islands, as well as 27 forest areas on major islands that have been fenced in, are "zero pests". Fortunately, native creatures surrounded by fences or oceans are "rejuvenating". In 2016, the Prime Minister of New Zealand announced plans to completely eliminate invading predators by 2050, an unprecedented national goal.

The goal of this initiative is to completely eliminate rats, ferrets and possums from more than 600 New Zealand islands by 2050. "it is these three predators that are eating the wildlife around us." Said Brent Beaven, the project manager.

Killing ferrets and possums may come as a shock to some nature lovers, but James Russell, an ecologist at the University of Auckland in New Zealand, describes the choice as an ecological "trolley problem": "if we choose not to kill these rats, then we are essentially choosing to let birds die."

Russell also described the 2016 initiative as a broad social movement. "this is not a government proposal," he said. As a matter of fact, the Government has only followed the rapid upsurge of voices in the community. " In order to achieve this initiative, the Government has joined forces with universities, non-profit organizations, wildlife reserves, habitat restoration project teams and ordinary citizens. In addition to putting bait in their backyard, these groups are also trying something else. For example, they are developing more targeted poisons, repairing native plants, reintroducing native species, and inventing new ways to eliminate predators.

Tame Malcom, who works for an environmental non-profit group called Te Tira Whakam ataki, says the initiative also depends on Maori. Because the Maori have been catching mice for centuries, their participation will help to improve the effectiveness of the project implementation and reduce the operating costs of the project. Malcolm added: "our language also plays a very important role in restoring ecosystems. Because place names can provide clues about what the place looked like in the past. " For example, the place name "Paekyogk birds" comes from the word "horizon" and a kind of parrot, indicating that this kind of parrot was once abundant in this place.

Cost is also a problem. "at present, the standard eradication budget is about 2,5904,320 yuan per hectare, but our country cannot maintain this level all the time," Biwen said. " Therefore, they hope that technology can help reduce costs. Last year, biologists sequenced the genomes of all target species, which could lead to more targeted bait, or gene editing techniques. But the problem is that at the beginning of the 21st century, many New Zealanders were committed to banning genetically modified organisms, so they are still debating whether to use gene editing. In addition, engineers are developing traps to identify species by footprints, and researchers are building drones that can not only distribute bait but also monitor large areas for signs of another invasion. It is worth mentioning that these technological innovations have also "gone" to the world, Armstrong said. New Zealanders are in charge of a large part of the international program to eradicate alien invasive species.

But while these researchers are actively responding to the national challenges posed in 2016, some ecologists have questioned the premise of the initiative. They believe that even in geographically isolated places like New Zealand, it is impossible to completely eliminate invading predators. Wayne Linklater, an environmental scientist at California State University in Sacramento, thinks so, and he advocates mitigation measures, such as protecting feeding areas or forming a network of animal and plant reserves, to protect threatened species more effectively.

In this regard, Biwen believes that these expedient measures require continuous human intervention. But if these exotic predators can be eradicated, local animals and plants can really flourish. This is also the result that project field investigator Scott Sembair (Scott Sambell) expects to see. Every year, Sembel monitors cleaned islands several times through a dog that can smell rats, including places that have been free of harmful rodents for 50 years, such as Maria. "after entering these areas, you will feel like an outsider, because this is the world of birds," he said. It feels so good! "