Southeast Asia’s tropical forests have long acted as natural climate buffers, sheltering delicate ecosystems beneath dense canopies that keep forest floors cooler and more humid than surrounding landscapes. But new research suggests that this protective shield is weakening as rising temperatures and deforestation reshape the region’s forests.
A recent study published in Geophysical Research Letters warns that by 2050, peak daytime temperatures even in the shaded understory of Southeast Asian forests could rise by 1.4°C to 2.1°C compared with conditions recorded between 1984 and 2014. The projections are based on analyses of ground-level temperature sensors, satellite observations, and future climate scenarios across 46 forests in the region, many of which are experiencing rapid deforestation.
Researchers say the findings reveal a growing vulnerability in forest “microclimates”—the cooler, stable conditions near the ground that many species depend on to survive.
The disappearing forest “cooling system”
In intact tropical forests, thick layers of foliage intercept sunlight and retain moisture, creating microclimates that are often significantly cooler than open air. Studies of tropical forests show that near-ground temperatures inside forests are typically about 1.6°C cooler than surrounding open environments, demonstrating how effectively canopy cover moderates heat.
But the new research indicates that this natural cooling system is increasingly compromised. When trees are removed—whether for logging, agriculture, or infrastructure—the canopy opens and sunlight reaches the forest floor. Without shade and humidity, ground-level temperatures rise sharply.
According to the study, canopy loss in Southeast Asia’s forests is amplifying the warming trend driven by global climate change. The researchers found that as canopy cover declines, heat penetrates deeper into forest interiors, eliminating the cooler microclimates that many plants, insects, amphibians, and other forest-dwelling organisms rely on.
A region under pressure
Southeast Asia contains some of the world’s most biodiverse rainforests, stretching across Indonesia, Malaysia, Thailand, Vietnam, and neighboring countries. But it is also among the fastest-deforesting regions on Earth, with large areas converted to oil-palm plantations, cropland, and infrastructure.
The new study’s projections suggest that warming beneath the canopy could become widespread. In some areas, the authors estimate that more than half of forests could experience understory temperatures outside their historical range by mid-century, especially under higher greenhouse-gas emission scenarios.
For species adapted to stable, narrow temperature ranges, even small shifts can be disruptive. Tropical forest organisms often evolve under relatively constant climate conditions, meaning they may struggle to adapt when temperatures change rapidly.
Previous global analyses have already shown that even modest increases in temperature beneath forest canopies are producing “novel” thermal conditions across much of the tropics, signaling that the buffering effect of forests is weakening. (Nature)
Heat stress for hidden biodiversity
Most rainforest biodiversity lives close to the ground—in leaf litter, understory vegetation, and soil layers. These organisms rarely experience the full heat of the open atmosphere, thanks to the protective canopy above.
As those microclimates warm, the consequences could ripple through ecosystems. Rising temperatures can alter species distributions, disrupt reproduction cycles, and increase stress on plants and animals already facing habitat loss.
Even small canopy gaps can change local temperatures, humidity, and soil processes, showing how sensitive forest microclimates are to structural changes in the forest itself.
The study’s authors warn that species with limited mobility—such as amphibians, insects, and small understory plants—may be particularly vulnerable because they cannot easily migrate to cooler environments.
Mapping climate refuges
Despite the troubling trend, the researchers say not all forests will warm equally. Some areas—due to elevation, dense canopy structure, or local geography—are better able to preserve cooler microclimates.
Identifying these locations could become a key strategy for conservation.
The team recommends prioritizing protection for forests most capable of maintaining stable microclimates, effectively turning them into climate refuges for vulnerable species as regional temperatures rise.
Such targeted conservation, scientists say, may help preserve biodiversity in a warming world—provided that the forests themselves remain standing.
Without stronger efforts to curb deforestation and greenhouse-gas emissions, however, the natural cooling systems of Southeast Asia’s forests may continue to weaken, leaving ecosystems increasingly exposed to the heat they once helped keep at bay.
Reference: [Geophysical Research Letters study]
