2023-07-20 13:43:20
Around the world, people are living longer and healthier lives than even half a century ago.
Climate change threatens to undo this progress. All over the planet, animals ― and the diseases they carry ― are moving to adapt to a boiling globe. And they’re not alone: ticks, mosquitoes, bacteria, algae and even fungi are on the move, shifting or expanding their historic range to adapt to climatic conditions that are changing at an unprecedented rate. .
These changes do not happen in a vacuum.
Deforestation, mining, agriculture and urban sprawl are eating away at the planet’s last wild areas, contributing to biodiversity loss that is occurring at a rate unprecedented in human history. Populations of species on which humans depend for their livelihoods are shrinking and being pushed into smaller and smaller areas of habitat, creating new outbreaks of zoonotic diseases.
Meanwhile, the number of people experiencing the extreme impacts of global warming continues to rise. Climate change displaces some 20 million people each year, in need of shelter, medical care, food and other basic necessities, putting strain on already fragile systems and increasingly in demand.
All of these factors create conditions conducive to human disease. Diseases, old and new, are becoming more prevalent and appearing even in places where they have never been seen before. Researchers have begun to assemble a body of evidence that sheds light on the formidable threat that climate-related diseases currently pose to human health, as well as the scale of the dangers ahead. “This is not a future phenomenon,” warned Dr. Neil Vora of the non-profit organization Conservation International. Climate change is here. People are suffering and dying right now. Research shows that climate change affects the spread of disease in several ways.
To escape the rising temperatures in their natural range, the animals begin to move to higher and cooler altitudes, bringing disease with them. This poses a threat to the people who live in these areas and also leads to a dangerous mix between newcomers and existing species. Avian flu, for example, spreads more easily among wildlife, as rising waters and other factors push breeding bird species inland, where they are more likely to encounter other species. Diseases that cross from one species to another tend to spread more easily to humans.
Warmer winters and milder autumns and springs allow carriers of pathogens ― ticks, mosquitoes and fleas, for example ― to remain active for longer periods of the year. Longer periods of activity mean more active breeding seasons and fewer casualties during the cold winter months. The northeastern United States has seen a massive proliferation of blacklegged ticks carrying Lyme disease over the past decade, with warmer winters playing a major role in this trend. Irregular weather patterns, such as periods of extreme drought and flooding, create conditions conducive to the spread of disease.
Cholera, a water-borne bacterium, thrives during the monsoon in South Asian countries when floods contaminate drinking water, especially in places without good sanitation infrastructure. Valley fever, a pathogenic fungus that thrives in soil in the western United States, thrives during periods of rain. The severe drought that usually follows rains in this part of the world dries out fungal spores, allowing them to more easily disperse through the air at the slightest disturbance―a hiker’s boot, for example, or a garden rake― and work its way into the human respiratory system.
These climate-induced effects weigh heavily on human health. Cases of mosquito-, tick- and flea-related illnesses tripled in the United States between 2004 and 2016, according to the Centers for Disease Control and Prevention. The threat extends beyond commonly recognized vector-borne diseases. Research shows that more than half of the pathogens known to cause disease in humans can be made worse by climate change. The problem gets worse over time. The World Health Organization estimates that between 2030 and 2050, a handful of climate-related threats, such as malaria and water insecurity, will claim a quarter of a million additional lives each year.
“I think we have dramatically underestimated not only the magnitude of climate change that is already changing disease risk, but also the number of types of risk that are changing,” said Colin Carlson, a global change biologist at Georgetown University. He pointed out that while the link between tick-borne diseases and climate change, for example, is a relatively simple scientific undertaking, the scientific community and the general public should be aware that the effects of global warming on diseases can also manifest in many other, less obvious ways.
The COVID-19 pandemic is an example of how quickly a disease can spread through global populations and the complexity of the public health response to such threats. “I think there are a lot more reasons to worry in terms of epidemic and pandemic threats,” he warned. The world has the necessary tools―wildlife surveillance networks, vaccines, early warning systems―to mitigate the effects of climate-related diseases. Some of these tools have already been deployed at the local level with great effect. It remains to be seen how quickly governments, NGOs, medical providers, doctors and the public can work across borders to develop and roll out a global plan of action.
Photo credit: Archive.
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