Feeling the heat in Indonesia’s forests: new research suggests a link between people’s health and forest clearing

The dense tropical Wehea forest in the Kalimantan region of Borneo, Indonesia.

The health of rural people in Indonesia may be at risk from local temperature increases as a direct result of widespread forest clearing, a study by The Nature Conservancy (TNC) and the University of Queensland has shown. Published today in Global Environmental Change, the study surveyed nearly 500 villages throughout Kalimantan (Indonesian Borneo) and finds a significant and under-recognized link between deforestation, temperature rise, and experiences of hotter temperatures in rural farming communities.

The study, Impacts of tropical deforestation on local temperature and human well-being perceptions, used extensive social surveys to identify villagers who believed forests are important for their health. An open-ended question asked, “What is the reason for this importance of the forest for health?” Of the 4,634 villagers from 477 villages who answered, the most frequent answer (expressed independently by nearly a third of respondents) was that forests kept the environment cool. Since the responses were unprompted, this gives strong evidence for the widespread perception of forests as important for temperature regulation. Indeed, recent evidence suggests that forests can cool the local environment by over 4°C. To put this in perspective, converting forests to open landscapes, something that can occur in a single season, can have the same temperature effect as nearly a century of warming under high emissions scenarios.

Dr. Nicholas Wolff, lead author from The Nature Conservancy, said, “We found the frequency of the response, that forest cooling was such an important health benefit to the villagers, surprising. We wanted to dig deeper into what might be driving these perceptions.” The study used statistical techniques to evaluate how village perceptions were influenced by deforestation, land use change and local temperature.

“We found that that villagers were more likely to notice the cooling effect of forests if they were from villages with highly fragmented forests due to deforestation, particularly if the villages were in hotter locations,” Dr. Wolff said.

He added that these results make intuitive sense; the villagers will notice the cooling effect of forests if they experience the contrast of cool forest patches and hot open patches in their daily lives.

More highlights of the study

Dr. Wolff said, “A more worrying result was we also found villagers from recently cleared forests were more likely to notice the cooling effect of forests than villagers from locations that had experienced longer-term, more extensive deforestation.” This suggests some villagers may be suffering from shifting baseline syndrome which occurs when traditional relationships with the natural world are lost, due to human’s short life-spans and faulty memories. The danger for Borneo and other tropical forest regions is that as deforestation expands and awareness of its effects fade, its contribution to heat stress and heat illness may be underappreciated until these consequences are already extreme.

Dr. Yuta Masuda, co-author from The Nature Conservancy, said, “Our concern is our results may be indicative of widespread, underlying heat-related health issues. These health issues could be underappreciated and, as global temperature rise and forest clearing continues in the coming decades, could become a larger issue. We need more studies to examine how less resilient rural populations are affected by and adapting to heat from deforestation and climate change.”

Dr. Eddie Game, co-author from The Nature Conservancy, said, “Our study points towards an opportunity to strengthen the case for forest conservation. To date, arguments for conserving tropical forests based on urgent biodiversity threats or mitigation of carbon emissions have failed to halt deforestation trends. The connection between forest health and human health offers an additional, perhaps more locally resonant and more immediately relevant argument for avoiding forest loss.”


The social and health challenges ahead

This study raises several questions about how people living in rural areas of developing countries might adapt to temperature increases driven by deforestation and climate change. Deforestation may be a social challenge with serious human health implications. As villages that were once encompassed by vast tracts of intact forest become surrounded by open, deforested landscapes, their inhabitants will become increasingly vulnerable to heat illness. This is especially true for those involved in agriculture, often the poorest sections of these communities.

The benefits of the cooling effects of forests should not be underestimated as their conversion to open landscapes will have negative consequences, especially for rural communities that may lack infrastructure to be more resilient to sudden temperature increases. In the worst case, heat stress can lead to death, but it also has a range of other effects including compromised immune systems, impaired decision-making and a reduced productivity, possibly jeopardizing livelihoods. Already, physical labor in the hot, humid tropics approaches the thermal thresholds that humans can withstand. The additional temperature increase caused by deforestation may push that boundary — a recipe for significant negative economic and human health impacts.

The effects of increasing temperatures are not limited to human health. Recent estimates suggest increased heat-related illness over the last few decades has already reduced current global labor capacity to 90%, with projected declines to 80% by 2050.


Why more research is needed

 The impacts of heat stress on health have primarily been quantified for urban environments, particularly in developed countries. Far less is known about other settings, including the effects of ongoing tropical deforestation on local temperatures and its consequences for people living in these rapidly changing landscapes. Borneo is also at the epicentre of global deforestation and a region particularly vulnerable to climate change impacts. Continued deforestation not only affects global climate, but increases local temperatures well beyond what is expected from climate change alone.

Previous research led by The Nature Conservancy has shown that protection and restoration of land sector solutions, such as avoiding deforestation, could offer up to 37 percent of the mitigation needed between now and 2030 to keep global temperature rise below 2°C. As this current study points out, maintaining tropical forest is not only important for emission mitigation and biodiversity, but may also be critical for helping vulnerable people adapt to climate change.

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