Here’s a simple solution to the cane toad invasion. And it costs just 66¢ a hectare

A dripping tap in the city is an annoyance. Something too small to fix, often put on hold until something bigger goes bang.

But in the dry season in the outback, a single leak from a bore can keep 1000 cane toads alive until the next big wet.

Stop a drip from an irrigation pipe and cane toads will perish within three days in the dry, says Professor Ben Phillips, a specialist in population biology and invasive species at Curtin University who is leading an $18 million project to stop the spread of cane toads in Western Australia.

Plug leaks in 150 agricultural water points down a long dry strip of land south of Broome bordered by the sea and the Great Sandy Desert, and the cane toad invasion will come to a stop – 90 years and 200 million toads after it began.

Ronald Yanawana leads a group of Karajarri and Nyangumarta rangers as they move through the tall grass, simulating how they would search for cane toads in the area. Credit: Tamati Smith

That’s the promise of the Toad Containment Zone Investment Prospectus released this month by a group Phillips leads that is seeking government and industry support.

“I’m 99 per cent confident it will work,” Phillips said.

The solution comes down to plumbing, fences and understanding the amphibians’ Achilles heel – water.

Map of the Toad Containment Zone. Green dots shows waterpoints (natural and artificial) within the toads’ potential distribution in Australia. The red line shows the approximate current distribution. The cane toad containment zone is exploiting a naturally dry, arid area with far fewer water points than to the south in the Pilbara.Credit: Cane Toad Containment Zone

The waterless barrier would stop the toads from descending on the Pilbara and invading 27 million hectares, threatening six species of national importance, including the northern quoll, and affecting Indigenous homelands. The toads could disrupt Australia’s $136 billion iron ore industry, which accounts for a third of WA’s revenue.

Phillips is racing to implement the program before the toads arrive at the beginning of the 2027-28 wet season.

At 66¢ a hectare, Phillips says it is the best deal in conservation.

It is backed by an alliance of Indigenous landowners: Karajarri, whose land is south of Broome, and Nyangumarta to the south, with six properties. They are working with scientific advisers, including Professor Tim Dempster from Deakin University and Rangelands NRM.

“It’s such a different conservation project,” Phillips said. “We are going to manage this piece of land to deliver a benefit elsewhere.”

Most agricultural infrastructure leaks. Until now, Phillips said, there has been little incentive to fix it.

David Stoate’s family owns Anna Plains cattle station at the narrowest and driest part of the zone, where the sea and desert create a potential bottleneck. Despite their name, Bufo marinus, the toads cannot survive in seawater nor survive on land without water.

“It’s a pretty unique place from that point of view,” he said. “There are no rivers; it is pancake flat, with no natural water sources, and those that here are more ephemeral.”

About 90 agricultural water-points across Stoate’s 300,000-hectare property will need to be made toad-proof, including sprinklers and air-conditioners.

“Where you have people, there’s going to be toads, so you have to secure the homes,” he said.

What’s been a challenge for Anna Plains – its lack of natural water sources – is the key to success.

“A tank overflowing to a soak is like an artificial lake … we wouldn’t worry about it now, but that will be cane toad paradise,” he said.

Dempster said landholders such as Stoate won’t benefit much financially from the project because the upgrades won’t increase the number of cattle they can run.

Standing in the long grass near a dam in the Aboriginal community in Bidyadanga last month, Ronald Yanawana, a ranger from Nyangumarta Warrarn Aboriginal Corporation, said the water attracted goannas and birds.

Karajarri and Nyangumarta rangers had been meeting to discuss the program’s implementation and will be employed to monitor the water-points.

The rangers said they couldn’t stop the toads from arriving in Bidyadanga, about two hours’ drive south of Broome, but they could stop them from destroying country and species further south.

The unstoppable, undefeatable cane toad

Nearly a century ago, the entomologist Walter Froggett warned against introducing South American cane toads to eat the beetles eating Queensland’s sugar cane.

Dr Jodi Rowley, a lead scientist at the Australian Museum and a co-founder of FrogID, said Australians loved to hate cane toads, but the animals were “objectively impressive creatures” that had managed to survive in their new land, adapted to a huge range of terrain, and had been found in the most unlikely of spaces.

This has had devastating consequences for native wildlife.

“It was not their fault that we moved them across the world,” she said.

There are an estimated 200 million in Australia, and females lay as many as 30,000 eggs a year.

Front-line toads are bigger than others, have longer legs, carry more poison in the paratoid glands near their ears and are more determined. “They have a behavioural tendency to go in a straight line,” Phillips said. “These are crazy toads.”

In a wet season, they will move 50 kilometres. “That manifests itself as an invasion front that has moved at an average speed of 43 kilometres a year through the Kimberley.”

If they make it to the Pilbara, its vast natural gorges, gullies and rivers would act as a toad superhighway, allowing them to colonise sensitive habitats, including world heritage area Shark Bay, destroying Indigenous cultural heritage and decimating native wildlife.

Karajarri ranger Frankie Watson during a field exercise preparing for cane toad.Credit: Tamati Smith

An analysis found the toads would badly affect 25 species, and about 10 species would be more at risk of extinction.

Toads wreak the most damage within a year of arrival. “You will regularly see a decline in northern quoll populations of 95 per cent,” Phillips said.

The group is also talking to mining groups in the Pilbara such as Rio Tinto, seeking their support.

“It is the first place where the toad invasion will have a substantial economic impact.”

Rio Tinto Pilbara environment and cultural knowledge manager Kieran Birch said the company was undertaking a feasibility study as an in-kind contribution to the project.

Birch said: “We wanted to help. It’s an infrastructure project, and this is something we can do.

“Invasion of the toads could impact local communities’ livability and tourism. I wouldn’t want toads on my doorstep and taking over local rivers, so we have to do something. This is a real opportunity to protect the Pilbara’s rich biodiversity by stopping toads in their tracks.”

A biodiversity hotspot supported by many natural water bodies, the Pilbara was the opposite of the dry zone to the north. “Based on the data, you may not see species go completely extinct, but you would expect to see species populations decline as the cane toads take over water bodies, food bowls, foraging grounds and kill native species.”

If the environmental status of these species changed, the miners’ licensing conditions would be subject to review and probably become more challenging. This could add delays to significant projects.

Invading cane toad 150 kilometres east of Broome with a boab tree in background.Credit: Ben Phillips

Given these risks, Birch said: “We have a responsibility to do our part and protect the lands in which we operate. My guess is that we wouldn’t be alone as other mining companies and government would want to join the fight.”

A 2019 federal Senate inquiry backed a cane toad containment zone, and the WA government has publicly supported it.

While the solution to the cane toads may lie in plumbing, it is backed by decades of research by Australian scientists. Researchers who tracked toads discovered they died even in the cool of a burrow made by goannas or bilbies if there was no water.

They cannot jump more than 50 centimetres vertically.

A group of Karajarri rangers load equipment for a field expedition.Credit: Tamati Smith

Dempster said the toads were good at detecting water sources and returned to them in the dry.

“They don’t try to hop over or go around [a fence]; they keep pushing. They are not used to finding [something] impenetrable. At some [elevated water holes] where we put temporary fences in the dry season, the toads came every night, piled up near the fence and had died by the morning. That early work sparked the idea we could do something bigger.

“We have people and funders who say ‘what if you get three once-in-5000-year wet seasons in a row?’ We’ve made [the zone] almost twice as big as it needs to be. That gives us more security, and a lot of people say, ‘OK, we can see this will really work’.”

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