Biodiversity loss, the introduction of invasive species, the climate emergency, and chemical pollution all increase the risk of infectious disease, a first-of-its-kind analysis has found.
The paper, published in
Nature Wednesday, reviewed 972 studies and 2,938 observations on how human-driven environmental change had impacted the spread of disease, looking specifically at 1,497 host-parasite relationships.
“New study in Nature confirms that if we want to avoid the next pandemic—we should stop destroying biodiversity, heating, and polluting the planet,” Diarmid Campbell-Lendrum, who leads the World Health Organization’s climate change unit and was not involved with the study,
wrote on social media. “Just one more reason to go for a greener, healthier future.”
“This adds to a very long list of reasons we should be rapidly moving away from fossil fuels and trying to mitigate the impacts of climate change.”
The Covid-19 pandemic, which some scientists believe passed from bats to humans, has led to increased interest in how diseases emerge and spread. At the same time, research research has pointed to a larger range for pathogens and their hosts as one of the health dangers of the climate emergency. For example, The Lancet’s most recent report on climate change and health predicted that, if temperatures rise by 2°C above preindustrial levels by 2100, the ideal conditions for Vibrio would expand by 17-25% and the risk of catching dengue fever would go up by 36-37%.
While previous studies had considered how certain types of environmental change—like deforestation or global heating—impacted disease spread, no study had considered the risk for plants, animals, and humans across the different ways that industrial society has altered the environment.
“This literature gap is critical to fill because resources for infectious disease management will always be limited and could be poorly targeted without knowledge of which global change drivers most affect infectious disease risk,” the study authors write.
The researchers looked at four major drivers of change: biodiversity loss, the introduction of new species, the climate crisis, and habitat loss or alteration. They found that human-driven biodiversity loss increased illness and death by almost nine times compared with areas where biodiversity remained intact. The next most impactful changes were the introduction of new species, global heating and increased carbon dioxide levels, and chemical pollution such as pesticides and fertilizers, which can put additional pressure on plants’ and animals’ immune systems.
“It could mean that by modifying the environment, we increase the risks of future pandemics,” study co-author Jason Rohr, a University of Notre Dame biology professor, told The Washington Post of the results.
One way that the loss of species can increase disease is by eliminating rare species, Rohr explained to The New York Times. As parasites and pathogens tend to evolve to infect more common species, when these species are all that remain, the risk of infection goes up. One example is the rise of white-footed mice, who host Lyme disease. One theory is that as these mice have proliferated in comparison with other, rarer mammals, the rates of Lyme disease in the U.S. have gone up. Of course, the spread of Lyme disease has also been linked to the expansion of the range of ticks due to warming temperatures, in an example of how different environmental alterations can interact to increase illness.
“This adds to a very long list of reasons we should be rapidly moving away from fossil fuels and trying to mitigate the impacts of climate change,” Bard College professor Felicia Keesing, who was not a part of the study, told the Post in response to its findings.
One of the study’s more surprising discoveries was that habitat loss actually decreased disease. The authors think this is due to the rise and expansion of cities, as urban areas tend to have better public health and fewer opportunities for humans and animals to mix and exchange germs.
“In urban areas with lots of concrete, there is a much smaller number of species that can thrive in that environment,” Rohr told The Guardian. “From a human disease perspective, there is often greater sanitation and health infrastructure than in rural environments.”
Colin Carlson, a Georgetown University biologist who was not part of the research team, told the Times that the lack of urban biodiversity was “not a good thing.”
Next, the researchers hope to explore more about the connections between the different drivers of change.
“Importantly, greater effort is needed to identify win-win solutions that address multiple societal stressors, such as disease, food, energy, water, sustainability, and poverty challenges,” they write.
However, the study already points the way toward some recommendations: “Specifically, reducing greenhouse gas emissions, managing ecosystem health, and preventing biological invasions and biodiversity loss could help to reduce the burden of plant, animal, and human diseases, especially when coupled with improvements to social and economic determinants of health,” the researchers advise.
Carlson told the Times that the study was “a big step forward in the science.”
“This paper is one of the strongest pieces of evidence that I think has been published that shows how important it is health systems start getting ready to exist in a world with climate change, with biodiversity loss,” Carlson said.
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