Scientists highlight growing risks from humid heat to ~1 billion outdoor workers in the tropics

Humid heat is a feature of daily life in the tropics. But for the ~1 billion outdoor workers in these regions, hot conditions can exact a significant toll on health and labor productivity. As climate change threatens to bring more extreme heat and adverse impacts for these workers, a new study published today in the journal One Earth examines the scale of this threat and explores pathways to boost workers’ resiliency to warming.

The paper – a global collaboration led by the Paul G. Allen Family Foundation alongside scientists from The Nature Conservancy (TNC) and numerous other global institutions – explores the major drivers of increased heat exposure – global warming, local deforestation, and urbanization – and discusses the environmental and physiological factors that increase the danger of heat exposure in workers, such as their general health and the intensity of their work.

The study also estimates how many people are exposed to unsafe heat for outdoor labor now and under future global warming, noting that at 1°C of additional global warming, heat and humidity will inhibit the ability of one in eight people living in the tropics (~13% of the total tropical population) to safely conduct heavy manual labor outside during most daylight hours, highlighting the need to slow warming and protect workers.                   

Commenting on the significance of this study, co-lead author Luke Parsons – a climate scientist with The Nature Conservancy – said: “In many of the countries in the tropics, most of the working-age population participates in outdoor-centric sectors like construction, agriculture, fisheries, and forestry. Some of the world’s highest population growth rates are also projected to occur in these regions, hence the number of people potentially exposed to future high heat and humidity who also work outdoors will probably rise alongside global temperatures, putting them at even greater risk. In addition to slowing global warming, we also need more research around adaptation to guide governments, communities, and individuals toward implementation of effective measures to mitigate this threat as soon as possible.”

While this paper is not the first to review the health and economic impacts global warming could have on worker well-being in the tropics, it also introduces an exploration of ‘modifiable factors’ that could help tropical workers to better adapt and protect their health in the face of climate change. These interventions include nature-based interventions to reduce heat exposure in built environments (e.g. urban greening); government-level heat action plans; adaptive administrative actions (e.g. periodic rest breaks, heat-adjusted pacing, etc), and land-use planning (e.g. avoiding deforestation).

“More research is needed to understand how maladaptation, compounding environmental threats, or non-heat-related external factors fit into the story, either driving or constraining strategies for worker adaptation in the tropics,” adds co-lead author Yuta Masuda from the Seattle-based Paul G. Allen Family Foundation. “But this multidisciplinary paper completes a critical missing piece of the puzzle, illuminating various approaches that can reduce worker vulnerability, while also helping to reorient action-focused discussions around heat mitigation and adaptation.”

This adaptation and resiliency component is critical because one of the primary factors compounding heat exposure risk for outdoor workers in tropical countries is limited capacity to adapt due to constraints like inadequate infrastructure development; absence of the robust labor regulations commonly observed in high-income countries; and the disproportionate number of workers that participate in informal industries in these regions.

To learn more about how The Nature Conservancy’s scientists are informing solutions to some of the world’s biggest challenges, visit: https://www.nature.org/en-us/about-us/who-we-are/our-science/

Masuda Y.J., Parsons L.A., Spector J.T., Battisti D.S., Castro B., Erbaugh J.T., Game E.T., Garg T., Kalmus P., Kroeger T., Mishra V., Shindell D., Tigchelaar M., Wolff N.H., Vargas Zeppetello L.R. Impacts of warming on outdoor worker well-being in the tropics and adaptation options. One Earth. https://doi.org/10.1016/j.oneear.2024.02.001