University of Hawaii study suggests onslaught of disease amid global warming

As if drought, heat waves, coastal flooding and other extreme weather aren’t enough in a warming world influenced by greenhouse gas emissions, a new study from researchers at the University of Hawaii suggests that humanity also will be threatened by growing incidence of life-threatening disease.

The survey of medical literature of known cases of illness found evidence that more than 58% of human diseases caused by pathogens, such as dengue, hepatitis, pneumonia, malaria and more, already have been aggravated by the kind of climatic hazards that would become more commonplace as the planet heats up.

“For me personally the results were mind-blowing,” said UH Manoa geography professor Camilo Mora, lead author of the research paper published Monday in the journal Nature Climate Change. “That’s the fire we are playing with as we put more greenhouse gases into the atmosphere.”

Researchers reviewed the results of more than 70,000 studies in a systematic search for examples of the impacts of 10 climatic hazards sensitive to the effects of greenhouse gas emissions on all known infections and pathogenic diseases. The climate hazards were warming, drought, heat waves, wildfires, extreme precipitation, floods, storms, sea level rise, ocean biogeochemical change and natural area loss.

The research revealed that climate hazards all were found to influence diseases generated by viruses, bacteria, animals, fungi, protozoans, plants and chromistas. Pathogenic diseases were primarily transmitted by vectors, but there were examples of waterborne, airborne, direct-contact and foodborne transmission.

In the end the research found that more than 58% — 218 out of 375 — known human infectious diseases had been affected at some point by at least one climatic hazard. The study also found 1,006 unique transmission pathways linking climate hazards to illness in people.

Mora said the thought of having to adapt to climate change with the onslaught of disease is overwhelming.

“If you have heat waves, floods, hurricanes, and on top of that you have to deal with diseases? We think we’re going to be able to deal with climate change as it gets worse? I don’t think so,” he said.

Other findings in the paper:

>> Climatic hazards bring pathogens closer to people and people closer to pathogens. Warming and precipitation changes, for instance, were associated with expanded ranges of mosquitoes, ticks and fleas and other creatures responsible for disease outbreaks. Storms, floods and sea level rise also have displaced humans through leptospirosis, cryptosporidiosis, cholera, typhoid and lots of other diseases.

>> Climatic hazards amplify the dangers of pathogens, including making conditions more ideal for reproduction and accelerating the life cycle. For instance, stagnant water from storms, heavy rainfall and floods increase breeding and growing opportunities for mosquitoes and the array of pathogens they transmit.

>> Climatic hazards diminish the capacity for people to cope with pathogens by exposing them to unsafe conditions, damaged infrastructure and reduced access to medical care, among other things. Drought, for instance, can lead to unsanitary conditions responsible for many kinds of nasty diseases.

The researchers also found that some diseases were suppressed by hazards (63 out of 286 diseases). Warming, for example, may have caused conditions that were less likely to spread disease or even lead to stronger immune systems.

However, most diseases that were diminished by at least one hazard were at times aggravated by another and sometimes even the same hazard, according to the study.

“In this paper, what we show is that there are 1,000 ways that you can get attacked by these diseases. And every one of them is just as lethal as the other one,” Mora said in an interview. “There are just too many diseases and pathways of transmission for us to think that we can truly adapt to climate change.

“It really does highlight the urgent need to reduce greenhouse gas emissions globally. We are playing with fire, and we need to take this issue more seriously,” he said.

Dr. Aaron Bernstein, interim director of the Center for Climate, Health, and the Global Environment at Harvard School of Public Health, told The Associated Press that the study is a good warning about climate and health for now and the future, especially as global warming and habitat loss push animals and their diseases closer to humans.

“This study underscores how climate change may load the dice to favor unwelcome infectious surprises,” Bernstein said in an email. “But of course it only reports on what we already know and what’s yet unknown about pathogens may be yet more compelling about how preventing further climate change may prevent future disasters like COVID-19.”

As part of the project, the researchers developed an interactive web page showing each connection between a climatic hazard and a disease case. The tool (camilo- mora.github.io/Diseases) allows users to query specific hazards, pathways and disease groups, and see the available evidence.

The study is the latest project of Mora and the students in his UH Manoa College of Social Sciences class called Methods in Large Scale Ecology.

Conducting methodical and far-reaching surveys of the scientific literature and media online, Mora and his students have generated nine studies, each completed in a semester’s time, that have been published in peer-reviewed science journals, including some papers that have made national news, appearing in The New York Times and other major outlets.

One publication in 2017 concluded that three-quarters of the world’s inhabitants would be exposed to deadly heat waves by the end of the century unless greenhouse gases are not substantially reduced. Another, in 2018, found that some parts of the world could face as many as six climate-related crises at the same time in a world of accelerating warming.

The research has helped to fuel Mora’s enthusiasm for climate action. He is the founder of Carbon Neutrality Challenge, a joint project of UH Manoa and other organizations whose united goal is to test the feasibility of restoring local ecosystems to offset the state’s carbon emissions.

Mora, who is currently on sabbatical, said the project is now gearing up with the aim of being able to plant 1 million trees — in one day — as part of a goal to offset all of Hawaii’s greenhouse gas emissions.