Millions exposed to deadly heat from deforestation

Tropical forest loss is not just a story about trees. It is a story about people living next to those trees who are now facing hotter days and higher risks.

A new study reports that local warming from tropical deforestation is associated with 28,330 heat-related deaths per year across Central and South America, Africa, and Southeast Asia.

The same analysis estimates that 345 million people were exposed to higher temperatures caused by nearby forest loss between 2001 and 2020.

The research was led by Dr. Carly Reddington and Professor Dominick Spracklen from the University of Leeds’ School of Earth and Environment (UL). The team worked with collaborators in Brazil and Ghana to connect satellite records of forest change and temperature with public health data.

The work adds a direct human health lens to a topic often framed only as a climate or biodiversity problem.

How deforestation raises heat

In simple terms, deforestation means permanent removal of tree cover from an area. The team mapped where tree cover declined and then measured how much land surface temperature rose in those same places.

They compared these deforested pixels to nearby pixels that kept their trees. That method isolates the heat tied to forest loss from broader climate trends.

The researchers overlaid population maps and national data on non-accidental mortality to estimate the share of heat-related mortality linked specifically to the added local heat from deforestation.

The central estimate was 28,330 deaths per year, with the largest numbers in Southeast Asia due to larger exposed populations and higher vulnerability in many districts.

The analysis revealed that deforestation alone added about 0.81 degrees Fahrenheit of warming in deforested areas over 2001 to 2020. In places that lost forest, that local boost accounted for most of the warming people actually experienced.

Trees keep areas cool

Trees cool the air through evapotranspiration, where water moves from leaves to the atmosphere. This process removes heat, while shade further limits surface warming at midday.

A global analysis has shown that when forests are cut, nearby air temperatures rise and daily temperature swings grow larger. When the canopy is lost, the land loses both its source of moisture and its shield from the sun.

The burden is not spread evenly. Regions of Southeast Asia that lost forest had the highest heat-related mortality rates in the new dataset.

Populations working outdoors, living in rural areas, or lacking access to cooling face greater exposure. Health systems with fewer resources also struggle more during heat spikes.

Heat-related deaths from deforestation

Local case studies back up the pan-tropical picture. In Berau Regency, Indonesia, a modeling study showed that deforestation between 2002 and 2018 raised population-weighted mean temperatures by 1.55°F.

The researchers estimated that 7.3 to 8.5 percent of all-cause deaths in 2018 in Berau were linked to the combined warming from deforestation and climate change.

In the current study, the experts estimate that deforestation alone can account for over a third of heat-related deaths where forest loss occurred.

Forest loss and outdoor work

Heat does not just affect mortality. It also limits safe time for labor, especially in agriculture and construction.

Independent research shows that deforestation-driven warming reduced safe outdoor working hours for about 2.8 million workers across the tropics in recent years.

Lost work time means lost income, and it increases health risks for those who continue laboring in dangerous conditions.

Local impact of deforestation

We often talk about forests as carbon stores. That is true, but the cooling services that trees provide to neighboring communities are immediate and local.

The Leeds study shows that in areas with forest losses, local biophysical warming from deforestation explained most of the temperature rise that residents felt.

This explains why people living near cleared land notice sharper heat compared to those located a short distance away near intact forest.

Deforestation adds to global heat

Heat is already a leading environmental risk for health worldwide. A global study estimated that non-optimal temperatures were associated with about 5.08 million deaths per year from 2000 to 2019.

Deforestation adds fuel to that fire by removing local cooling in some of the hottest, most humid places on Earth. It does so alongside rising greenhouse gases that are lifting baseline temperatures.

Actions to protect people 

Stopping further loss of tropical forests can quickly lower local heat stress. Keeping canopy intact restores shade and evapotranspiration, which cools surfaces and the air above them.

At the same time, communities need basic protections, including shade structures, water, rest breaks, and early warning for dangerous heat. Where possible, improving access to efficient cooling can protect health while limiting extra emissions.

The study is published in the journal Nature Climate Change.

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