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Tropical forest areas that have been deforested through a process of slash and burn
Slash and Burn Tropical forest areas that have been deforested through a process of slash and burn to open areas for agriculture and subsistence farming in the Kalimantan region of Borneo, Indonesia. © Bridget Besaw


Deforestation and global warming increase deaths and unsafe work conditions in rural Indonesia

As international negotiators work to accelerate humanity’s response to the climate emergency at COP26 in Glasgow, a pioneering study led by The Nature Conservancy (TNC) has, for the first time, highlighted how rising local temperatures – driven by tropical deforestation and exacerbated by global warming – are increasing heat stress-related deaths and unsafe working conditions for vulnerable communities in lower-latitude countries such as Indonesia.

Published in the journal Lancet Planetary Health, the research – conducted in collaboration with scientists from the University of Washington and Indonesia’s Mulawaran University – used publicly-available data to calculate that deforestation increased mean daily temperatures in Borneo’s Berau Regency by +0.95°C from 2002-2018. This contributed to an 8% increase in deaths and almost 20 extra minutes per day where conditions were too hot for humans to work safely outdoors.

“Having spent the past five years exploring the impacts of global warming on human health, we believe this latest study represents one of the first-ever to highlight how deforestation and climate change are increasing mortality among low- and middle-income communities in lower-latitude countries – while also contributing to a potentially even more serious increase in unsafe working hours,” commented senior co-author Yuta Masuda of The Nature Conservancy. “Previous research into the health implications of climate change has tended to focus on city-dwellers and the Global North. We sincerely hope our study’s findings will prompt greater awareness and support for those front-line rural communities in latitudes where temperatures and humidity levels are already so close to human heat-stress thresholds.” 

Comparing data from an array of secondary sources – including satellite monitoring of forest cover, temperatures, and population distributions, alongside intelligence from The Lancet’s Global Burden of Disease reports – the study also projects that, under a conservative scenario of +3°C of global warming against pre-industrial levels (or +2°C against 2018 levels), the region could ultimately experience an estimated 17-20% increase in deaths, and up to five unsafe work hours per day, compared with 2018.

Expanding further on the paper’s implications, lead author Dr Nicholas Wolff of The Nature Conservancy said: “When you consider it has taken the wider world 150 years to warm by +0.95°C, compared with just 16 years in Berau Regency, the dramatic impacts of deforestation on this region’s climate become clear. While +0.95°C may not sound like much in isolation – extrapolated across whole populations and coupled with a rise in unsafe working conditions in rural communities where many people have no choice but to work outdoors, the wider implications for human health and livelihoods are worrying and definitely justify further research to find solutions.”

Co-author June Spector, Associate Professor of Environmental and Occupational Health Sciences at the University of Washington, added: “This work reflects a broad collaboration across disciplines, institutions and sectors to synthesize existing information in a new way, providing insights into how climate change and deforestation affect people’s health. This approach is important to address complex, pressing global challenges and inform decision-making, particularly in areas where data are limited.”


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Notes for Editors

Wolff N.H., Zeppetello L.R.V., Parsons L.A., Aggraeni I., Battisti D.S., Ebi K.L., Game E.T., Kroeger T., Masuda Y.J., Spector J.T. The effect of deforestation and climate change on all-cause mortality and unsafe work conditions due to heat exposure in Berau, Indonesia: a modeling study. The Lancet Planetary Health.


The Nature Conservancy is a global conservation organization dedicated to conserving the lands and waters on which all life depends. Guided by science, we create innovative, on-the-ground solutions to our world's toughest challenges so that nature and people can thrive together. We are tackling climate change, conserving lands, waters and oceans at an unprecedented scale, providing food and water sustainably and helping make cities more sustainable. Working in 76 countries and territories: 37 by direct conservation impact and 39 through partners, we use a collaborative approach that engages local communities, governments, the private sector, and other partners. To learn more, visit or follow @nature_press on Twitter.