Every year, the upper Zambesi River breaks its banks and spreads across the wide Barotse floodplains in Zambia.
These seasonal wetlands are famed for their exceptional richness of species, from birds to unique cichlid fish.
But there are signs of profound upheaval. Native fish and invertebrate populations have fallen, river plants are being devoured and river banks hollowed out from within.
Every Australian knows common myna birds are bad, rabbits are worse and feral cats kill native animals unchecked.
But how do we decide what makes an introduced species “good” or “bad” – and will we ever concede that some species are here to stay?
The culprit will be familiar. As the flood eases and the dry season begins, the shallow muddy pools left behind teem with redclaw crayfish (Cherax quadricarinatus), a freshwater crayfish native to the tropics in northern Australia and Papua New Guinea. Many Australians call these “yabbies”, as they do other medium-sized Cherax crayfish.
It might seem bizarre that an Australian species has become an invasive pest overseas. The flow of introduced species usually goes the other way. But these yabbies were forged in the intense crucible of the Australian climate. Unfortunately, they may be all but unstoppable in the Zambesi – and many other water bodies around the world.
Built for a harsh landscape
Over 100 species of freshwater crayfish are found in Australia. Many are remarkable. The giant Tasmanian crayfish (Astacopsis gouldi) is the largest crayfish in the world across both fresh and salt water, while burrowing crayfish species spend most of their lives in burrows, marked by chimneys of clay.
Of Australia’s ten freshwater crayfish genera (groups of species), the Cherax species are arguably the toughest.
They evolved to survive in Australian billabongs, ephemeral lakes left behind when a river changes course. These lakes can dry up and refill at times, causing a brutal wet-dry cycle.
Cherax species became adapted to survive in deeply inhospitable habitats, such as water with virtually no dissolved oxygen. They can burrow deeply and enter a dormant state for months to years before better weather arrives. A single female can produce several broods a year, with up to 1000 eggs in each brood.
They are aggressive generalists, eating everything from detritus and aquatic plants to fish, invertebrates and even each other.
As climate change brings more extreme weather, tough species such as the redclaw are better equipped to survive than local species who may have evolved in a kinder climate.
Australia has over 100 species of freshwater crayfish, including the striking Lamington spiny crayfish.Ken Griffiths/Getty
How did redclaws get to southern Africa?
Throughout the 1980s and 1990s, redclaws were exported to aquaculture facilities across Africa, Europe, Asia and South America. Farmers liked them for their hardiness, adaptability and rapid growth.
Their striking blues and reds made them popular in the global aquarium trade, creating a second major pathway for their spread.
In the wild, the humble redclaw multiplied. Soon, there were signs of devastating shifts in local waterways.
We don’t know exactly how redclaws got into the Zambesi. During the 1990s, redclaws began to be spotted in the river. Their numbers soon surged – and native plant, fish and invertebrate species suffered.
Redclaws are now on the doorstep of pristine, highly sensitive ecosystems such as Botswana’s famous Okavango Delta. They are already present in South Africa’s famous Kruger National Park. Fishers in Zambia report significant falls in their catch. They can spread 6 kilometres in an average year – and up to 49km/year during flooding seasons.
Many Australians think fondly of yabbies (likely derived from “yabidj/yapitj”, the name used by several First Nations groups in southern Australia). How could they become pests?
Australia’s long geographic isolation meant its unique species evolved in a closed system. They often lack the competitive edge to survive against aggressive invaders from other continents. As a result, it’s rare for Australian wildlife to become invasive pests overseas.
But as our freshwater crustaceans show, there are exceptions.
Common yabbies pose another threat
The redclaw isn’t alone. Australia’s common yabby (Cherax destructor) has also escaped aquariums and aquaculture farms to quietly colonise rivers and lakes in parts of Europe and Southeast Asia. Endemic to the rivers of the Murray-Darling basin, it can tolerate water temperatures between 1°C and 35°C and survive in many habitats. This helps it outcompete many native crayfish.
Worse, Cherax destructor is susceptible to and can carry strains of lethal crayfish plague, meaning it can spread the pathogen to highly susceptible species in Europe. The plague is an aquatic mould native to North America, which infects the host’s cuticle (shell) and can cause mass deaths.
In Australia, Cherax species co-evolved with native predators such as Murray cod, platypus and rakali who naturally keep their populations in check.
Overseas, local predators are not always able to provide these checks and balances. Australian yabbies find it easy to bully and outcompete smaller, less aggressive native crustaceans and fish. They do particularly well in degraded rivers or lakes where native species are already struggling.
What can be done?
It’s nearly impossible to eradicate redclaws and yabbies once they are breeding in a major river system.
Traps often catch the larger adults, which can inadvertently trigger a population boom by freeing up food and territory for juveniles left behind.
In response, ecologists and conservationists are shifting tactics. In southern Africa, community harvesting programs train locals to catch and sell “redclaws” for food, suppressing numbers while generating income.
In Europe, aquaculture hatcheries are deploying more effective physical barriers to halt escapes, alongside biological controls such as stocking waterways with large, predatory native fish.
Efforts like these, may keep redclaw numbers down in the Zambesi. But the yabbies are likely there to stay.
What the story of Australia’s pest yabbies tells us is that an organism that seems harmless or even struggling in its home habitat can sometimes become an environmental super-weapon when dropped into an ecosystem unequipped to fight it.
Moving species across borders has long been done for short-term economic gain. But as the plague of yabbies in the Zambesi shows, it’s ecological roulette.
Rachael King does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
A rapidly warming world means more frequent and intense bushfires. And in Australia, the strengthening El Niño could create the conditions for fierce fires this summer.
To protect our communities, Australia must take a proactive approach to bushfire preparedness, response and recovery. But this doesn’t just depend on firefighters or equipment. Reliable, accessible and consistent data is vital to keeping communities safe.
Fire agencies across Australia are increasingly adopting new technologies that track where fires start and how they spread. However, much of this data is spread across different databases, organisations and jurisdictions, making it difficult to access when bushfires break out.
Our recent research interrogates why Australia needs a national bushfire database and maps out what it could look like.
Reliable, accessible and consistent data is vital for bushfire resilience.NSW Rural Fire Service
Bushfires do not respect borders
Bushfires burn across borders, impacting countless communities far beyond where they first ignite. Australia’s current approach to collecting bushfire data fails to reflect this.
Bushfire data is recorded and managed by different organisations – including state emergency and land management services – each with their own systems, processes, standards and technical terms. With siloed databases, agencies and communities struggle to coordinate during bushfires.
During the 2019–20 Black Summer bushfires, residents on the border of two jurisdictions witnessed a devastating bushfire sweep through their communities. However, conflicting state guidelines around labelling fires meant locals couldn’t tell whether incoming warnings were about a new blaze or the one they were already watching.
The Australian government has since acknowledged just how dangerous data fragmentation can be. The 2020 Royal Commission into National Natural Disaster Arrangements and the 2020 New South Wales Independent Bushfire Inquiry both spotlighted the lack of centralised, accessible bushfire data as a major challenge. These findings have prompted initiatives such as the CSIRO’s National Bushfire Intelligence Capability.
Our latest research makes a case for a national database, built on trustworthy, standards-based AI technologies like knowledge graphs.
To understand how such a database might work, we looked abroad. We systematically reviewed national bushfire databases, including Europe’s Forest Fire Information System. Under this system, European Union countries and neighbouring nations each collect specific types of information – including data on fire danger, burnt areas and weather forecasts – using a set of shared definitions. This allows authorities to compare fire activity and risk across national borders.
In the United States, the National Emergency Response Information System brings together data from multiple existing systems on a shared digital platform. State-based agencies – including the National Interagency Fire Center and National Weather Service – still own their information but share additional data with the national system.
These examples show national coordination doesn’t require bushfire databases to be completely centralised. Instead, it relies on interoperability – the capacity for different systems to communicate and exchange information effectively.
Technical infrastructure is key to making an Australian bushfire database work. This includes metadata that sets out rules that govern the database and a controlled vocabulary that contains a standardised list of terms and definitions. Both ensure data is collected and interpreted in a consistent way.
Our research suggests data ownership, privacy, governance, funding and ongoing maintenance are among the main obstacles to establishing an Australian bushfire database.
We spoke to a range of experts from the emergency sector. They advocated for a national bushfire database, saying it would improve risk management, strengthen coordination and help agencies get resources to where they are most needed.
However, many raised data discoverability as a key concern. Vast amounts of valuable bushfire data already exist, but emergency responders may not know where to find it or who maintains it. They also expressed concerns about who would oversee the system and how responsibilities would be distributed.
Other agencies worry strict national standards could limit what practical actions they can take in local contexts. Any national system must be built on trust and collaboration between different agencies and jurisdictions. Relying on shared technology is simply not enough.
Bushfire management involves a range of agencies with their own databases.NSW Rural Fire Service
From national to local
Beyond coordination, a national database could help Australia more fairly distribute bushfire management resources and facilitate the sharing of expertise, equipment and systems. Some agencies or jurisdictions may struggle to fund or develop these systems by themselves.
Local knowledge is crucial to making any national database work. Local communities can often identify at-risk landscapes and vulnerable groups that are not reflected in formal databases. First Nations peoples have used fire to care for Country over millenia. A national database informed by local and Indigenous knowledge systems would offer invaluable insights about fire behaviour, local ecosystems and cultural burning practices.
As the next bushfire season nears, the need for a national bushfire database grows ever more urgent. Collaboration and long-term federal funding are key to making it a reality.
Nader Naderpajouh received research funding for this project from Natural Hazard Research Australia (NHRA).
Matt Duckham received funding for this research from Natural Hazards Research Australia (NHRA). Matt also co-leads the Victoria Disaster Research Alliance (VDRA).
Raghad Emran and Soniya Rijal do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.
A new study shows one species of sea cucumber lives much longer than previously thought, putting it at even more risk of being eaten to death by humans.
Government says ambition for 2036 will be good for food and climate resilience, but concerns remain over funding
The government has set an ambition to increase the share of English land farmed organically to 10% by 2036, but concerns remain over how the transition will be funded.
Currently, just 3.4% of England’s agricultural land is farmed organically, one of the smallest shares in Europe. France, for example, farms 10.4% of its land organically, and aims to increase this to 18% by 2027.
The Coalition has come up with the perfect solution to deal with the climate pollution from when Australian fossil fuels are burned overseas.
We should either just pretend they don’t exist, or ignore the reason why people are concerned about them, even if those people include a majority of high court judges or the international court of justice.
