Association between work in deforested, compared to forested, areas and human heat strain: an experimental study in a rural tropical environment

Abstract

Background: With climate change, adverse human health effects caused by heat exposure are of increasing public health concern. Forests provide beneficial ecosystem services for human health, including local cooling. Few studies have assessed the relationship between deforestation and heat-related health effects in tropical, rural populations. We sought to determine whether deforested compared to forested landscapes are associated with increased physiological heat strain in a rural, tropical environment. Methods: We analyzed data from 363 healthy adult participants from ten villages who participated in a two-by-two factorial, randomized study in East Kalimantan, Indonesia from 10/1/17 to 11/6/17. Using simple randomization, field staff allocated participants equally to different conditions to conduct a 90-minute outdoor activity, representative of typical work. Core body temperature was estimated at each minute during the activity using a validated algorithm from baseline oral temperatures and sequential heart rate data, measured using chest band monitors. We used linear regression models, clustered by village and with a sandwich variance estimator, to assess the association between deforested versus forested conditions and the number of minutes each participant spent above an estimated core body temperature threshold of 38.5°C. Results: Compared to those in the forested condition (n=172), participants in the deforested condition (n=159) spent an average of 3.08 (95% CI 0.57, 5.60) additional minutes with an estimated core body temperature exceeding 38.5°C, after adjustment for age, sex, body mass index, and experiment start time, with a larger difference among those who began the experiment after 12 noon (5.17 [95% CI 2.20, 8.15]). Conclusions: In this experimental study in a tropical, rural setting, activity in a deforested versus a forested setting was associated with increased objectively measured heat strain. Longer durations of hyperthermia can increase the risk of serious health outcomes. Land use decisions should consider the implications of deforestation on local heat exposure and health as well as on forest services, including carbon storage functions that impact climate change mitigation.

Tropical deforestation accelerates local warming and loss of safe outdoor working hours

“…In addition to heat exposure impacts on work productivity, 57,58 heat exposure can cause numerous downstream health impacts. Work in deforested versus forested settings in Indonesia is associated with heat strain, lower cognitive performance, and declines in labor productivity 10,20,31 as well as an increase in all-cause mortality. 32 Individuals working under heat stress are also more likely to experience occupational heat strain and kidney disease or acute kidney injury.…”

“…[21][22][23][24][25][26]27 Studies on deforestation and temperature changes have focused on quantifying warming from tropical deforestation at regional scales, 13,28 and the relationship between deforestation and increasing temperatures in the tropics is well established. 4,[7][8][9][10][11]29,30 However, only a few small-scale studies have evaluated deforestation effects on heat exposure and the wellbeing of nearby populations in rural communities, 8,31,32 limiting our understanding of whether these effects extend globally in similar settings across low-latitude countries.…”

Warming from tropical deforestation reduces worker productivity in rural communities

“…The focus on rural communities in tropical countries is important for a few reasons. While studies have long argued for the importance of tropical forests for combating global climate change and biodiversity conservation 14,15 , researchers have more recently started highlighting how tropical deforestation can have significant adverse local human health and well-being impacts [16][17][18][19] . At the same time, the adverse effects of exposure to hotter temperatures are increasingly seen as an area of concern [20][21][22][23][24][25] .…”

The effect of deforestation and climate change on all-cause mortality and unsafe work conditions due to heat exposure in Berau, Indonesia: a modelling study

“…48,49 For populations with low adaptive capacity, the relationship between temperature increases and all-cause mortality might be more pronounced, as shown by Lee and colleagues. 35 Recent studies in Berau have found that even under favourable work conditions, working in deforested versus forested areas for just 90 min can result in elevated core body temperatures exceeding 38•5°C 50 and decreased cognitive performance. 51 For outdoor workers engaged in heavy physical activities in the tropics, where heat and humidity are already high, productivity declines can occur with increasing heat stress, as the human body naturally responds to heat stress by triggering reductions in physical work intensity and internal heat generation.…”