The climate crisis is accelerating a global increase in antibiotic resistance that poses a serious and growing threat to human health, experts have warned, as new research reveals a direct link between rising temperatures, changing rainfall and the spread of resistance genes in one of the world’s most common bacterial diseases.
While the misuse and overuse of antibiotics remain the primary drivers of antimicrobial resistance (AMR), a first-of-its-kind study published in The Lancet Planetary Health provides what the authors call “robust evidence” that climate change acts as an accelerating force. The research analysed more than 480,000 genomes of Salmonella bacteria collected from 139 countries between 1940 and 2023, and found a 10% global increase in Salmonella antibiotic resistance genes (ARGs) associated with climate change over that period.
Rising temperatures and altered precipitation patterns are thought to be driving this increase through several biological mechanisms. Warmer conditions can accelerate bacterial growth and the exchange of genetic material, including resistance genes, between microbes. Heat stress triggers bacterial survival responses such as reinforced cell walls and superior DNA repair systems – the same tools bacteria use to resist antibiotics. A 1°C rise in environmental temperature above 5°C could lead to a 5%–10% increase in Salmonellosis cases, while a 2018 study found that a 10°C local temperature increase was associated with a 2.2% to 4.2% rise in resistance in common pathogens like E. coli and S. aureus.
Changes in rainfall patterns also play a crucial role. Floods can accelerate the spread of ARGs through waterways, while droughts concentrate antibiotic residues and resistant bacteria in dwindling water sources. Together, these environmental shifts disrupt microbial ecological stability and speed up the evolution of resistance across human, animal and environmental reservoirs, the researchers said. Bacteria can evolve rapidly in response to climate change – sometimes in as little as 18 months – meaning that by warming the planet, humans are inadvertently “training” pathogens to become tougher and harder to treat.
The study found that 82% of the countries examined recorded increases in Salmonella ARGs. The strongest climate-associated rises were seen in the Middle East and north Africa, followed by south Asia and sub-Saharan Africa – regions that already face a double burden of high climate vulnerability and weaker health systems. The model used by the researchers showed that the relationship between temperature, rainfall and resistance genes is non-linear; resistance does not simply increase steadily as the mercury rises, but changes over time in a more complex fashion depending on both climatic factors.
Antimicrobial resistance already kills more than one million people a year globally, according to estimates, and was directly responsible for 1.27 million deaths in 2019, with a further 4.95 million deaths associated with it. Without intervention, deaths directly attributable to AMR could reach nearly two million by 2050. The economic toll is also severe: antibiotic-resistant infections led to an estimated US$693 billion in global hospital costs in 2019 and US$194 billion in productivity losses. Projections suggest uncontrolled AMR could result in $412 billion in annual treatment costs and $443 billion in lost productivity by 2035, potentially shaving 3.8% off global GDP by mid-century.
The study authors stressed that their work does not prove climate change directly causes the increase in resistance genes – it demonstrates an association. But they said the findings highlight the urgent need to consider climate change when designing global strategies to tackle AMR. “The accumulated evidence suggests that climate change is an accelerating force behind the global spread of antimicrobial resistance,” they wrote. “Urgent integration of climate change-mitigation policies, particularly those aligned with the Paris agreement – with enhanced antimicrobial stewardship and One Health surveillance – is essential to curtail the future burden of antimicrobial resistance.”
Urgent action needed to curb future spread
The researchers’ model offers a clear incentive for action: if countries meet low-emission climate targets and strengthen responsible antibiotic use, Salmonella ARG levels could be 24% lower by 2100 compared with a highest-emission scenario. The study underscores the need for a “One Health” approach that recognises the interconnectedness of human health, animal health, agriculture and the environment – a framework already adopted by the UK government in its five-year national action plan, “Confronting antimicrobial resistance 2024 to 2029”. That plan aims to optimise antimicrobial use, reduce the need for antibiotics and support the development of new drugs.
Previous studies had linked higher temperatures to greater levels of resistant bacteria, but until now global quantitative studies on the link have been limited. The authors called climate change a “threat multiplier” for infectious diseases, expanding vector ranges, increasing breeding sites for pathogens and accelerating human displacement. “Our findings provide supporting evidence that rising temperatures and altered precipitation patterns non-linearly amplify the abundance and dissemination of antimicrobial resistance genes in bacterial pathogens such as salmonella,” they wrote. “These findings reinforce the idea that climate change alters microbial ecological stability and accelerates resistance evolution across human, animal, and environmental reservoirs.”