Scientists declare gene-editing war on pests

Killer critters: Plague is a rat-borne disease which still kills hundreds of people each year.

Should all pests be wiped out? New Zealand’s government plans to kill all rats and invasive predators by 2050. Some want to use genetic modification, but others warn of ecological disaster.

The world is home to an estimated seven billion rats. However, their population could be about to take a large dent — and may even be wiped out entirely.

That is because the New Zealand government wants to kill every single invasive predator in the country by 2050. This includes rats, weasels and stoats.

These pests are not native New Zealanders. About 800 years ago, the only land mammals in the country were bats. This lack of predators made it a paradise for birds — many of which gradually lost the power of flight to scurry harmlessly along the ground.

That all changed when humans introduced rats and other predators to the islands. Between them, they eat over 26 million chicks and eggs every year, and have helped drive 42% of the nation’s birds to extinction.

A radical solution has been proposed. Rather than traditional poisons and traps, some want to use cutting-edge genetic modification to wipe out the rat population.

A technique called “gene drives” allows scientists to edit the DNA of animals, guaranteeing that certain genes are transmitted. For example, rats could be genetically modified to only pass on male sex genes. This would ensure that all future generations were male, making reproduction impossible and leading to extinction.

But some are horrified by the idea. Biologist Kevin Esvelt claims the technique is “uncontrollable” and that the rat-killing gene could escape New Zealand to spread across the globe. Journalist Peter Franklin called it “the genetic equivalent of a nuclear bomb”.

Despite these worries, scientists think “gene drives” could be used to tackle other deadly pests. For example, 10,000 genetically modified mosquitoes are being released in Burkina Faso over the next year to see whether this can eradicate malaria in the area. If it works, the idea could save hundreds of thousands of lives.

Another bug in the crosshairs is the tsetse fly. Native to tropical Africa, it transmits a fatal disease called “sleeping sickness”.

But should we genetically engineer animal extinction?

Pest control

Playing God will lead to misery, some say. Ecosystems are finely balanced. While rats seem like pests, they provide food for countless other animals. Annihilating a whole species could have perilous, unseen consequences. Furthermore, we must not forget that these creatures are still animals. It is immoral to kill living things on such a scale.

The benefits outweigh the risks, reply others. These creatures cause pain and death to thousands of people. The human cost trumps the suffering of insects and pests. What is more, genetic modification is painless and humane compared to killing with traps and poison. We must be bold and embrace the technology.

You Decide

  1. Is it right to make rats extinct?
  2. Should we genetically modify animals?


  1. Define the term “pest” in your own words. Compare your definition with that of others in your class. Do you think rats qualify as “pests” under your definition?
  2. Watch the second video from Fw:Thinking in Become An Expert. Give yourself 10 minutes to write a response to this statement: “Gene drives will immensely benefit humanity. Discuss.”

Some People Say...

“If a mosquito has a soul, it is mostly evil.”

Douglas Hofstadter, US Professor of Cognitive Science

What do you think?

Q & A

What do we know?
There are no definite plans to use gene drives to exterminate rats in New Zealand. There are a number of technological and political obstacles to overcome before the research can begin. A survey of 8,000 New Zealanders found that 32% of people were in favour of using genetic modification to kill pests, and 18% were against. Meanwhile, the mosquitoes that will be released in Burkina Faso are part of an experiment by the research consortium Target Malaria.
What do we not know?
We do not fully know the consequences of the technology. And it is unclear if authorities could contain all genetically modified rats within New Zealand. Furthermore, the gene drive process itself may have unintended consequences (for example, it could cause unexpected mutations in subject animals).

Word Watch

Power of flight
A famous example is the Kiwi. The bird is the national symbol of New Zealand.
Poisons and traps
These methods have led to successful rat eradication in some places. The largest island cleared of rats is Australia’s Macquarie Island. However, New Zealand is 2,000 times bigger.
Gene drives
The process can occur in nature as well as being engineered by humans. Bill Gates has donated $75 million to gene drive research, principally for its disease-defeating potential.
Hundreds of thousands
According to the World Health Organisation (WHO) there were 438,000 malaria deaths in 2015.
Sleeping sickness
The scientific name of the condition is Trypanosomiasis. According to the WHO, there were 2,804 recorded cases of the disease in 2015. The organization aims to eliminate the disease as a public health problem by 2020.


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