The destruction of tropical forests is often framed as a carbon issue, but it has more immediate consequences for people living nearby. One of the most tangible effects is local temperature. Deforestation in Borneo, for instance, has left the island significantly hotter and drier, with severe consequences for both the environment and local communities.
A piece by Jeremy Hance provides valuable background on this issue, drawing on a study from Environmental Research Letters that found deforested areas in Borneo are, on average, 1.7°C warmer than those with intact forests. In oil palm plantations, the difference is even starker, with temperatures 2.8 to 6.5°C higher than in primary forests.
“Sit under a forest or in a big clearing on a sunny day and you will feel the difference. Forests are cool and clearings are hot,” Douglas Sheil, a co-author of the study, told Hance. “Trees act as sun-shades protecting those beneath from the direct heat of the sun — like a parasol.”
Sheil and his colleagues found that areas losing 40 to 75 percent of their forest cover “experienced extreme temperatures above 31 degrees Celsius with greater frequency than other forested regions.” This is significant because the combination of heat and humidity can limit local people’s ability to work outdoors when they otherwise would be productive.
As Hance writes: “When Erik Meijaard, co-author and research scientist with Borneo Futures, interviewed 7,000 people in Borneo in 2008 about how deforestation was impacting their well-being, he found ‘The common answer was that deforestation makes their world so much hotter.’”
Forests also moderate temperature by converting solar energy into water vapor through evaporation. This vapor helps form clouds, which provide shade and reflect sunlight back into space, cooling the planet. Forest loss disrupts this balance, altering local rainfall patterns.
The study found that rainfall in Borneo has decreased by about 20% over the past six decades. With less precipitation and higher temperatures, conditions have become harsher for farmers, many of whom now struggle to grow crops in the escalating heat. Shifting weather patterns also increase the likelihood of fires, such as those in 2015, which burned 2.1 million hectares of land and caused widespread health and economic damage.
The implications for the region’s most controversial export, palm oil, are concerning. “Oil palm is most productive if humidity is maintained year-round,” says Sheil. As conditions become hotter and drier, yields may drop, potentially prompting further plantation expansion, exacerbating the cycle of destruction.
Borneo’s story serves as a cautionary tale for other tropical regions. As Sheil notes, “If Borneo is considered a microcosm for the effects of forest loss, I would expect the impacts to be markedly greater in the interior of the Congo and Amazon regions.” The long-term consequences of forest loss will stretch far beyond Borneo.
