From our brains to our bowels – 5 ways the climate crisis is affecting our health

The climate crisis is also a health crisis. Higher temperatures, more weather extremes and a greater number of climate-caused natural catastrophes are taking their toll on both our mental and physical health.

Beyond the immediate death toll caused by heat waves, flooding and other extreme events, researchers say there is a broader trend of longer-term health implications as a result of disruption to food systems, closer animal-human contact and an increase in vector-borne diseases. This also includes many diseases and conditions we wouldn’t typically think of as climate-related, such as Alzheimer's and Parkinson’s.

Climate change is expected to cause approximately 250,000 additional deaths per year because of undernutrition, malaria, diarrhoea and heat stress alone, says the World Health Organization. A recent World Economic Forum report – Quantifying the Impact of Climate Change on Human Health – finds that, by 2050, it will cause 14.5 million deaths and over two billion healthy life years lost.

The impact of this growing healthcare burden is likely to be uneven, but it won’t be limited to those countries worst impacted by temperature rises. The pressure is on already stressed healthcare systems around the globe to become more resilient and better prepared.

Here are some of the emerging health risks as a result of the climate crisis.

Climate change and environmental degradation are affecting growing conditions and harvests for many crops, leading to food shortages and failed harvests. By 2050, the risk of hunger and malnutrition could rise by 20% without action to mitigate the effects of climate change, the World Food Programme says.

The impact of malnutrition and hunger is greatest on babies and children. Approaching 150 million children under five around the world are stunted as a result of lack of nutrients. In 2020, 770 million people faced hunger and an additional 98 million people experienced food insecurity compared to the average over 1981-2010.

In recent years, tropical diseases like malaria and dengue have been found over a much wider field. Warmer climates are allowing disease-bearing mosquitos to thrive in new areas and live longer before colder winter snaps kill them off.

Standing water after flooding and heavy downpours exacerbates the problem, as well as contributing to a rise in diarrhoeal diseases. Extreme flooding in Pakistan in 2022 led to a fivefold increase in malaria cases in the country, for example.

This means that in the coming years, these diseases may become common in new areas not previously exposed. However, newly approved malaria vaccines are offering a degree of hope, with millions of at-risk people already vaccinated.

Higher temperatures have also been linked to an increased incidence of neurological diseases including Alzheimer’s, dementia and motor neurone disease. Scientists believe that the warmer temperatures affect biological pathways in the brain and accelerate or cause disruption to crucial proteins. A 1.5-degree rise in mean temperature has been shown to lead to a rise in hospital admissions for Alzheimer’s patients and a worsening of symptoms. Heat-related deaths from neurodegenerative diseases are expected to increase over this century.

Furthering the connection between our environment and neurological health, a link has also been found between air pollution and Alzheimer’s.

Three-quarters of deaths globally each year are caused by non-communicable diseases such as cardiovascular disease, cancer and diabetes, says the WHO. The majority of these occur in low- and middle-income countries.

As well as directly contributing to these diseases – for example, heat waves or air pollution increasing the likelihood of strokes, heart attacks and cancer – there are also less direct impacts. Climate change undermines many of the determinants of good health such as livelihoods, a good diet, access to healthcare and equality.

It is not just physical illnesses that climate change causes – increasing temperatures have been linked to aggression, depression, violent suicides, anxiety and stress.Hospitalizations for mental health disorders also increase with higher temperatures, studies show.

Extreme weather has an impact on the social and economic determinants of good mental health, as it can lead to homelessness, food and water insecurity and unemployment.