People around the world are living longer, healthier lives than they did half a century ago.
Climate change threatens to undo that progress.
Across the planet, animals—and the diseases they carry—are shifting to inhabit the globe on the fritz. And they are not alone: Ticks, mosquitoes, bacteria, algae, even fungi are moving, shifting or expanding their historical ranges to adapt to climate conditions that are developing like never before. that speed.
These changes did not happen in a vacuum. Deforestation, mining, agriculture, and urban sprawl are taking bites out of the world’s remaining wild areas, contributing to biodiversity loss occurring at a rate unprecedented in human history. Populations of species that humans rely on for sustenance are shrinking and being pushed into smaller habitat patches, creating new zoonotic-disease hotspots. Meanwhile, the number of people experiencing severe effects of a warming planet continues to grow. Climate change is displacing about 20 million people each year—people who need housing, medical care, food, and other necessities that strain already fragile systems even more. which is more stressed.
All these factors create conditions ripe for human disease. Old and new diseases are becoming more widespread and even growing in places where they have not been found before. Researchers are beginning to piece together a patchwork of evidence that illuminates the dire threat climate-driven diseases now pose to human health—and the scope of the risks to come.
“It’s not just something in the future,” Neil Vora, a doctor at the nonprofit Conservation International, said. “Climate change is here. People are suffering and dying now.”
Research shows that climate change is influencing the spread of disease in some major ways.
To escape the rising temperatures of their native ranges, the animals began to move to higher, colder places, bringing diseases with them. This poses a threat to the people living in the areas, and it also leads to dangerous mixing between new animals and species. Bird flu, for example, spreads quickly among wild animals because sea level rise and other factors push bird species to nest on land, where they are more likely to run into other species. Diseases that jump between species tend to have an easier time eventually making the jump 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. Extended active seasons mean busier mating seasons and fewer casualties in the winter months. The Northeastern United States has seen a large increase in Lyme disease-carrying black-legged ticks over the past decade, with warmer winters playing a significant role in that trend.
Adverse weather patterns, such as periods of extreme drought and flooding, create conditions for the spread of diseases. Cholera, a water-borne bacteria, thrives during the rainy season in South Asian countries when flooding contaminates drinking water, especially in areas that lack quality sanitation infrastructure. Valley fever, a fungal-borne pathogen that grows in the soil of the Western US, thrives during the rainy season. The extreme drought that tends to follow rain in that part of the world dries out the fungal spores, making it easier for them to disperse into the air over the slightest disturbance—a hiker’s boot, say, or a garden rake—and find their way into the human respiratory system.
These climate-driven impacts harm human health. Disease cases linked to mosquitoes, ticks, and fleas tripled in the US between 2004 and 2016, according to the Centers for Disease Prevention and Control. The threat extends beyond the commonly recognized vector-borne diseases. Research shows that more than half of all pathogens known to cause disease in humans may worsen with climate change. The problem increases over time. The World Health Organization estimates that between 2030 and 2050, climate-related threats alone, such as malaria and water insecurity, will kill a quarter of a million more lives each year.
“I think we’re underestimating not only how much climate change is already changing disease risks, but how many kinds of risks are changing,” said Colin Carlson, a global change biologist at Georgetown University.
He noted that while connecting the dots between tick-borne diseases and climate change, for example, is a relatively straightforward scientific endeavor, the scientific community and the general public should be aware that the The effects of global warming on disease can also be seen widely. other, less obvious ways. The COVID-19 pandemic is an example of how quickly disease can progress in global populations and how complex the public health response to such threats can be.
“I think there’s still a lot to worry about in terms of epidemic and pandemic threats,” he said.
The world has the tools it needs—wildlife monitoring networks, vaccines, early warning systems—to mitigate the effects of climate-induced disease. Some of these tools have already been deployed on a local scale to great effect. What remains to be seen is how quickly governments, NGOs, medical providers, doctors, and the public can work across borders to develop and implement a global plan of action.
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