Climate change is also a health crisis — these 3 graphics explain why - Nature.com

Climate change is also a health crisis - these 3 graphics explain why
Water sprays can keep the elderly cool during heatwaves - an example of climate adaptation measures that contribute to better health outcomes.Credit: Fred Dufour/AFP via Getty

Climate change is worsening health and costing lives, according to the 2023 report of The Lancet Countdown on health and climate change. On 3 December, the United Nations COP28 climate summit in Dubai will host a day dedicated to tackling the health impacts of climate change, the first for a COP. More than 50 health ministers will be attending the talks, in which countries are expected to announce their financial commitments that prioritize health. Ahead of the meeting, Nature outlines three major ways that climate is harming human health.

Heatwaves kill

“People are dying from heatwaves caused by climate change every year,” says climate and health researcher Wenjia Cai, at Tsinghua University in Beijing. High temperatures increase the risk of cardiovascular disease and heat stroke, which is when the body can no longer regulate its temperature through sweating. This can lead to multi-organ failure and death.

Among those most vulnerable to extreme heat are people over the age of 65. Older people struggle to cool themselves down because their sweat glands are less sensitive to chemical signals from the brain. They are also more likely to have cardiovascular diseases.
Source: 2023 report of The Lancet Countdown

The Lancet report, which was published on 14 November, estimates that, in Africa, 11% more people over 65 years old died of extreme heat during 2017–22 compared with a baseline period of 2000–05 — when measured as a fraction of deaths per 100,000 people. The equivalent increase for Europe was 8.8% and 7% for South and Central America during the same time period.

Infants under one year old are also highly vulnerable to the dangers of extreme heat, because the systems that regulate their body temperature are not yet fully developed, Cai adds.

A home for malaria

Global warming is contributing to infectious diseases expanding into newer regions. Take malaria, which is caused by the parasites Plasmodium falciparum and P. vivax — transmitted to people when parasite-carrying Anopheles mosquitoes bite humans. Mosquitoes thrive in warmer temperatures and lay their eggs in still water.

Source: 2023 report of The Lancet Countdown

Climate and health scientists Rachel Lowe and Martin Lotto Batista at the Barcelona Supercomputing Centre in Spain estimated that nearly 10% of the world's land area that was once too dry or too cold for transmission of P. falciparum malaria during 1951–60 became suitable for malaria transmission from 2013–22. Over the same period, around 17% of land previously unsuitable for P. vivax malaria transmission became suitable. Regions were considered suitable for malaria transmission if they had precipitation, humidity and temperature levels in which malaria could spread for at least one month per year, on average, over a decade.

Warmer conditions are also increasing the rate of spread of viral diseases such as dengue, zika and chikungunya, and expanding the range of harmful Vibrio bacteria.

Increased drought, rising sea levels, reduced access to clean water and migration also create larger breeding grounds for pathogens, especially in low- and middle-income countries, says Lowe who is also at the Catalan Institution for Research and Advanced Studies, in Barcelona. “A combination of climate change, land-use change and agricultural practices can increase the risk of disease spillover from animals to humans which can, of course, lead to pandemics”, they say.

Heat and hunger

As the world heats up, more people are losing access to safe and nutritious food. High temperatures and droughts kill crops and extreme weather events mean that outdoor workers can’t work, so they lose their income and struggle to afford enough food. “It’s a vicious cycle. Food insecurity makes people more vulnerable to disease, which reduces how much they can work, so then they earn less income to pay for food,” says Shouro Dasgupta, an environmental economist at the Euro-Mediterranean Center on Climate Change in Venice, Italy.

Source: 2023 report of The Lancet Countdown

Dasgupta and another environmental economist, Elizabeth Robinson at the Grantham Research Institute on Climate Change and the Environment in London built a mathematical model using past data on how more frequent heatwaves and droughts impact food insecurity. Using this model, they estimated that 127 million more people will have experienced moderate-to-severe food insecurity as a result of climate change in 2021 compared with a scenario without global warming. Severe food insecurity means things such as running out of food or going an entire day without any meals.

Adapt to survive

If countries can be helped to become more resilient to climate change, health benefits will follow, researchers say.

Dominic Kniveton, a climate scientist at Sussex University, UK, found that deaths caused by storms and flooding events decreased from an average of 86 deaths per event during 1990–99, to 16 deaths during 2013–22 in countries that are classed as ‘highly developed’, according to the Human Development Index, a measure built on a country’s profile in education, health and standard of living. This decline could be attributed to adaptation efforts, such as the limiting of construction in high-risk coastal areas and the building of defensive structures that protect against flash flooding, says Kniveton.