Climate change is coming for something surprising: the world’s blood supply.
Warming and extreme weather can slow blood donations, disrupt blood transport and risk the safety of transfusions, according to a new study published on Wednesday in The Lancet Planetary Health.
Extreme weather events as a result of climate change can increase demand while also limiting supply, leading to blood shortages when they’re most needed. Avoiding this deadly mismatch of supply and demand is crucial.
“Any major disruptions to the availability and safety of the blood supply puts lives at risk,” said Elvina Viennet, an infectious disease researcher at the University of the Sunshine Coast in Australia and one of the lead authors of the study.
It is the first global assessment of how climate change affects blood supplies.
Dr. Viennet and her collaborators reviewed dozens of studies on how extreme weather events, which are increasing around the world because of climate change, affect physical and mental well-being, the spread of infectious diseases, the safety of blood transfusions and other aspects of public health. They then connected those findings to each stage of the blood supply network.
Weather events such as hurricanes, flooding, heat waves, wildfires and snowstorms can physically keep people from donating. Roads may be impassable and, depending on the disaster, people may have more immediate problems of their own to handle. Mobile donation centers could be unable to deploy where they’re needed.
Blood donations tend to drop during extreme events, at least in the United States. As Hurricane Helene hit the Southeastern United States last year, more than 100 blood drives were canceled. As the Los Angeles fires burned, thousands of donors canceled. By late February this year, the Red Cross in the United States had almost as many donation cancellations as it did in all of 2024, in part because of extreme weather events.
Even if donation centers have blood to deliver, blocked roads can slow down delivery or halt it entirely. Drone deliveries may be an option soon, but technological innovations will be needed, Dr. Viennet said.
Disasters can also increase demand for blood by increasing rates of traumatic injuries or disrupt the care of people who rely on blood for regular treatments, such as cancer patients. Pregnant women, who can face increased risks of complications during climate disasters, are at particular risk if blood is not available and complications arise.
“It’s really critical,” said Margaret Sugg, a climate and health researcher at Appalachian State University who was not involved in the study. “Postpartum hemorrhage, preeclampsia, these are conditions that require blood transfusions.” If the blood supply chain is disrupted, she said, “it can be deadly.”
Rising temperatures are contributing to the spread of infectious diseases that are transmitted through blood, such as West Nile and Zika viruses and dengue fever. The study notes that mass migrations and travel are exposing more people to these diseases and shrinking the pool of potential donors, because people infected with these diseases cannot give blood. And widespread disease outbreaks can shutter donation centers for extended periods, as happened during the coronavirus pandemic. (Infectious diseases may indirectly increase blood demand, too, by increasing need for blood-based treatments.)
With enough planning, the deadly mismatch of low blood supply with high demand can be avoided. To predict blood demand in shifting climates, robust early warning systems for disease outbreaks and severe weather events and disease outbreaks are critical, experts said.
And artificial intelligence tools may be able to help with monitoring disease threats by better harnessing the growing amount of health and climate data available, said Steven Drews, a clinical microbiologist at the University of Alberta who also leads the microbiology team at the Canadian Blood Services.
Variability remains one of the biggest problems for those who want to plan for blood demand. “The challenge is in its unpredictability and how things are shifting,” said Evan Bloch, a pathologist and transfusion specialist at Johns Hopkins University who was not involved in the study. “Climate change introduces these humanitarian crises and natural disasters that can weigh heavily on the blood supply.”
