A group of researchers published an article in Nature Climate Change on the links between tropical deforestation and heat-related mortality (September 2025).
Human Level’s Take:
- Researchers found that tropical deforestation significantly increases local temperatures, with 1.6 million km² of forest lost between 2001 and 2020 causing an average warming of 0.7°C. This accounts for 64% of total warming in affected areas, especially in regions facing higher deforestation impacts like the Amazon, and Sumatra and Kalimantan in Indonesia.
- Deforestation-linked warming affects millions, with 345 million people exposed and over 28,000 annual heat-related deaths estimated. Areas with higher forest loss, particularly in Southeast Asia, show the highest mortality due to greater population exposure and heat vulnerability.
- Vulnerable populations face the greatest risks, including low-income communities, smallholder farmers and Indigenous groups living near deforested areas. Limited access to healthcare, infrastructure, and adaptive resources heightens their exposure to rising temperatures.
- The impacts go beyond heat, as deforestation also increases health risks from vector-borne diseases like malaria and smoke pollution from forest fires, compounding the burden on already at-risk populations.
- What does all this mean for companies? It could have implications for the workers and local producers in deforested regions across supply chains, who may face increased risk of heat stress and will need increased resources and technology to adapt safely to warming temperatures. This can factor into companies’ assessment of human rights risks and help them to plan proactively to protect workers and producers in these areas.
- It also emphasises the importance for companies of considering environmental and human rights commitments holistically, given the close interlinkages shown between deforestation and impacts to people. For example, companies could consider including deforestation targets that focus on areas where deforestation-related warming and other human rights risks are likeliest to emerge. They can also consider ways to strategically deploy resources so they address both deforestation and increased heat risk at the same time.
Some key takeaways:
- Deforestation can cause localised temperature increases: Tropical deforestation is closely linked to local land warming. The researchers found that, between 2001 and 2020, tropical deforestation caused an average local land surface warming of 0.7°C, which accounted for 64% of the total warming in affected regions. During this period, 1.6 million km² of tropical forest was lost, primarily in Central and South America, Southeast Asia, and Tropical Africa. Areas with the highest deforestation, such as the southern Amazon, Sumatra and Kalimantan, experienced the most intense warming. Similar patterns were observed in parts of Central America, West and Central Africa, and Mainland Southeast Asia, showing that deforestation is a major driver of regional temperature increases.
- Higher deforestation corresponds to higher mortality: The research also indicated that an estimated 345 million people were exposed to warming caused by tropical deforestation between 2001 and 2020, with 33 million experiencing deforestation-driven temperature increases of over 1°C, 8 million experiencing temperature increases of over 2 °C, and 2.6 million experiencing temperatures increases of over 3 °C. Around 76% of people living in deforested tropical regions felt this impact, including in Tropical Africa, Southeast Asia, and Central and South America. This warming is linked to approximately 28,330 additional non-accidental deaths annually. The researchers found that areas with the greatest mortality burden correspond to regions that experienced moderate to high levels of forest loss and deforestation-induced warming. The mortality burden is greatest in Southeast Asia, due to a large exposed population with greater heat vulnerability, especially in Indonesia. Beyond heat, deforestation also contributes to health risks through smoke pollution from forest fires, which worsens air quality.
- The implications for workers and other vulnerable groups: Future climate change is expected to significantly increase heat-related mortality and reduce safe working hours globally, especially for outdoor workers. According to the authors, tropical deforestation will likely worsen these impacts by intensifying local warming. Lower-income and highly vulnerable populations, including the local communities and smallholder farmers living close to deforested areas, are likely to face the greatest risks due to limited access to healthcare, poor infrastructure to protect against heat and limited resources to adapt to higher temperatures. These groups are already experiencing more frequent extreme heat and are projected to suffer disproportionately under future warming. In addition to heat stress, they are also more exposed to other deforestation-related health risks, such as malaria and air pollution from fires.
