Heat exposure is a major human health risk, especially for people living in low latitude tropical countries where the ability to adapt to higher temperatures (ie, adaptive capacity) can be hindered by inadequate access to water, electricity, and other infrastructure. In the general population, particularly older people, very young children, and those with chronic diseases, heat-related mortality is projected to increase as a result of climate change. These mortality effects are projected to be particularly pronounced in south-east Asia. In working populations, including young and otherwise healthy workers, excess ambient heat exposure, combined with internal heat generated from physical labour, can lead to increased morbidity and mortality, decreased productivity, and increased risks of traumatic injury. A growing body of research indicates that in tropical countries, both climate change and deforestation are increasing temperatures and heat exposure, but the combined risks of these changes have so far been underappreciated. For example, forest clearing in tropical countries can cause immediate increases in local temperatures of up to 8°C and exacerbate diurnal temperature variation. The amount of warming can scale with larger deforested patches (>100 km2), and the effects of warming can extend up to 50 km beyond deforested sites. Yet, little is known about how warming associated with deforestation affects human health at large geographical scales (eg, >10 000 km2), or how these risks are likely to change in the future due to climate change.
Research on the human health risks of climate change has largely focused on urban areas in industrialised settings and on the potential health effects associated with heatwaves, other extreme weather events, and vector-borne diseases. Less research has been done to explore how environmental change that exacerbates climate change—such as deforestation—can have immediate and substantial local and regional effects on heat exposure and human health for rural populations living in tropical countries. These populations are identified as being the least resilient to the effects of climate change and are expected to experience substantial temperature increases, indicating that they are at especially high risk of experiencing substantial adverse health effects. A primary barrier to understanding and addressing how local (ie, deforestation) and global (ie, climate change) factors driving temperature increases impact the health of these populations is the paucity of representative human health data needed to understand the impact of these changes over large temporal and spatial scales. Yet, when considered alongside recommendations such as those from the Intergovernmental Panel on Climate Change, this information could have substantial implications for protecting human health as trade-offs between economic welfare, human health, and the natural environment are considered in the implementation of climate adaptation and mitigation recommendations.
The aim of this study was to estimate the effects of deforestation and climate change on all-cause mortality and unsafe work conditions due to heat exposure in the tropics. We focused our analysis on the Berau regency in Indonesia (hereafter referred to as Berau), which is emblematic of tropical forest conditions in other countries experiencing pressures on forests from expansion of agriculture, palm oil production, mining, and other activities. We used satellite, climate model, and population data to quantify changes in heat exposure resulting from deforestation; estimate the effects of deforestation and climate change on all-cause mortality due to heat exposure; and estimate the effects and implications of deforestation and climate change on unsafe work conditions, assessed as changes in hours of work deemed unsafe by established occupational health guidelines for heat stress.