More than half of the known human diseases are made worse by climate change, according to new research.

Climate-driven hazards such as warming, floods, and droughts increased the spread and severity of illnesses like Lyme disease, dengue fever, and malaria, researchers from the University of Hawai’i found.

Analysing more than 3000 cases of disease, they found of the 286 diseases involved almost all (277) were aggravated by climate-driven hazards, and the impacts of only nine were diminished.

For instance, global warming has increased the habitable area for disease spreaders such as mosquitoes, meaning more people are vulnerable to malaria infections.

While a few diseases became less common due to a climate hazard, such as droughts reducing the number of certain disease-carrying insects, the researchers found in most cases there was also a rise in a different disease driven by that same hazard.

They concluded that of the 375 recorded pathogenic diseases in the world, 58% have been made worse by climate change.

University of Otago environmental epidemiologist Simon Hales says Aotearoa is also experiencing health impacts driven by climate change, and that these will only get worse.

As temperatures rise, New Zealand will see many serious diseases increase, he says.

Examples include a rise in the number of salmonella contaminations, or even cases of rheumatic fever, which evidence suggests is linked to a skin infection that is more common at warmer temperatures.

Some illnesses will be driven by our changing ecosystems, Hales says, such as ciguatera, or poisoning from eating fish contaminated by toxins from certain types of algae around coral reefs. As sea temperatures increase, Hales says they expect instances of ciguatera to also rise.

Warmer weather may also make New Zealand hospitable to disease-carriers, such as mosquitoes.

“If climate change progressed without mitigating emissions, by mid-century there is a risk of dengue fever in the northern parts of the North Island.”

Indirect changes will also affect health

However he says while there will be these direct health impacts from climate change, the much larger impact on our health will come from indirect changes.

Aotearoa has seen increases in extreme weather, having just experienced the wettest winter on record. Hales says these weather disruptions can bring extreme events such as heatwaves and cyclones which can cause injury or death.

This will also cause systems disruptions such as reduced access to fresh water, Hales says. There are short term health concerns when this happens, such as reduced cleanliness, but it also may ultimately impact our food supplies as water-dependent crops and agriculture are disrupted.

On top of this will be the added health pressures caused by societal change, Hales says. 

“Our societies will change profoundly in the coming decades because we haven't managed climate change. The impacts will be quite severe.”

Pacific Islands will become less habitable leading to a rise in refugees; economies will be disrupted, leading to higher socio-economic strain for New Zealand families; and food and fresh water may be more scarce, Hales says.

“Socio-economic situations underpin all health issues. I think this will be one of the biggest issues,” Hales says.

“My hope is that we do respond to this climate emergency, and that our plans transform societies for the better.

“We can’t fix this problem without that.”

Top Image: Mosquito sucking blood on human skin. Credit: auimeesri / iStock

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