Imagine the Earth's eager lungs, the tropical rainforests, being ruthlessly torn apart. They lose not only their trees, but also their life-giving essence, releasing an invisible, creeping threat: deadly heat. Between 2001 and 2020, this relentless devastation was coupled with an additional 28,000 deaths per year heat-related illnesses, a terrifying toll that often goes unrecognized.

Deforestation is not just causing the distant problems of global warming; it is causing local overheating of enormous scaleThis immediate, intense warming in areas of deforestation could be as great as or even greater than what is expected from a full century of global climate change under a high-emissions scenario. It's like taking away the cooling heart of a rainforest and leaving those who live there to suffer the scorching heat. Analysis satellite data revealed that between 2001 and 2020, 345 million people in the tropics exposed to this local warming caused by deforestation, with the average daily warming of the earth's surface, weighted by population, reaching 0.27 °C.

The consequences are dire. Exposure to elevated temperatures is main risk to human healthHeat stress can negatively impact mood and mental health, impair physical performance, and reduce work productivity. But worst of all, it is associated with increased risk of morbidity and mortality to cardiovascular disease and other causes. For millions of people in the tropics who depend on outdoor work, deforestation has already caused loss of safe thermal working conditions.

Regionally, heat-related mortality rates are highest in Southeast Asia, where an estimated 8 to 11 deaths per 100,000 people living in deforested areas are estimated, followed by tropical regions of Africa and the Americas. Southeast Asia alone bears the brunt of the estimated 15,680 annual deaths related to deforestation. These numbers are frightening. In areas of forest loss, local warming caused by deforestation can be more than one third of total mortality related to heat waves in the context of climate change.

But heat isn't the only specter lurking. Deforestation is also linked to smoke pollution from fires, which can lead to adverse health impacts. Deforestation is also linked to increased risk of malaria in some contexts, especially for children in poor households.

In poorer countries with limited adaptive capacity, including many in the tropics, these populations are already disproportionately affected by rising temperatures and face limited access to resources and infrastructure needed to cope with this combination of rising temperatures and environmental changes. Future climate change will only will amplify these impacts, with deforestation expected to further exacerbate them.

The shadow cast by deforested areas is long and deadly. Sources emphasize the urgent need for targeted policy interventions to reduce tropical forest loss, along with improved adaptation strategies and access to health care, to protect vulnerable populations in the tropics from these growing health risks. If we do not act, these silent deaths will pile up, adding thousands each year, in a relentless heat dance that portends a bleak future. JRi

The study is published in the journal Nature Climate Change .