A new study published in the journal Nature Communications has established a clear causal link between human-driven climate change and the explosion of mouse populations plaguing eastern Australia. The research, led by Dr. Helena Vance of the University of Oxford, shows that warming temperatures and increased rainfall have created ideal breeding conditions for house mice, leading to waves of crop destruction and economic losses exceeding $1 billion since 2020.
The findings come as a team of British rodent control specialists deploys to New South Wales, bringing with them a novel fertility control agent designed to curb population booms without the ecological side effects of poison. The method, developed by the UK’s Animal and Plant Health Agency, targets female mice, rendering them infertile for a breeding season. Initial trials in the UK reduced mouse numbers by 70%.
“The climate signal is unambiguous,” said Vance. “We analysed 50 years of data on mouse plagues in the Australian grain belt. As average winter minimum temperatures rose by 2.3°C and spring rainfall increased by 15%, the interval between plagues shortened from once a decade to once every three years. The pattern matches exactly what greenhouse gas-driven models predict.”
The study uses a metric called ‘thermal breeding days’ to quantify how many days per year exceed the minimum temperature threshold for continuous mouse reproduction. In 2021, parts of New South Wales recorded 280 such days, compared to 180 in the 1970s. Each additional thermal breeding day correlated with a 5% increase in peak mouse density.
This is not just an Australian problem. Rodent outbreaks are intensifying globally. In 2023, the US Midwest saw its worst mouse infestation in 30 years, while parts of Argentina now face annual plagues. The biosphere is responding to the cumulative energy imbalance caused by fossil fuel burning. Warm air holds more moisture, and warm nights prevent the cold that historically capped rodent populations.
Australian farmers have been forced to use broad-spectrum rodenticides like zinc phosphide, which kill non-target species such as birds and snakes. The British fertility control approach offers a more precise solution but raises its own questions about ecological manipulation. Still, with grain silos bursting and fields stripped bare, farmers are desperate.
“The biosphere is a complex system,” Vance adds. “When you change one variable, you get cascading effects. We are seeing an increase in rodent-borne diseases as well. The only durable solution is to decarbonise. Interventions like fertility control are temporary bandages.”
The UK team’s deployment is funded by the British High Commission and will last six months. If successful, it could be scaled across the continent. But Vance warns that without emission reductions, these plagues will become the new normal. “We are in a race against time to stabilise the planet’s energy balance. Every fraction of a degree matters.”
