A sweeping scientific review published this week in Science argues that forests do far more than absorb carbon dioxide they actively regulate temperature, water and local climate systems in ways that directly protect human health and livelihoods.
The paper, titled “More than mitigation: The role of forests in climate adaptation,” synthesizes decades of research to show that forests function as climate infrastructure, moderating heat extremes, stabilizing rainfall and creating microclimates that support agriculture and daily life.
At local scales, intact forests act as thermal buffers. Tree canopies shade the ground while evapotranspiration the process by which trees release water vapor converts heat into moisture, lowering surrounding air temperatures.
Across nearly 100 field sites reviewed in the study, daytime temperatures inside forests averaged about 4°C lower than in adjacent cleared areas. At night, forests were slightly warmer, effectively narrowing temperature extremes.
In tropical regions, the cooling effect was even stronger often exceeding 6°C compared to deforested land. During heatwaves, apparent temperatures inside forests have been recorded as 6 to 14.5°C lower than outside.
Urban trees also provide measurable relief, reducing air temperatures by roughly 1.5 to 1.7°C on sunny days.
The findings suggest that forest loss does more than reshape landscapes it alters living conditions. A 2025 study in Nature Climate Change estimated that tropical deforestation has exposed hundreds of millions of people to higher temperatures and contributes to tens of thousands of heat-related deaths annually.
Local warming linked to deforestation can rival and sometimes exceed the effects of global climate change over similar time periods.
Water regulation and rainfall
Forests also play a critical role in water systems. They intercept rainfall, enhance groundwater recharge and recycle moisture back into the atmosphere. In humid regions, these processes can reduce flood risks and stabilize streamflows.
However, the review notes that benefits vary by region. In drier areas, expanded tree cover may reduce downstream water availability if more water is retained or returned to the atmosphere before reaching rivers.
Not all tree planting cools
The authors emphasize that forests deliver their greatest climate benefits where they are native. Introducing dense tree cover into ecosystems that historically evolved without it such as tundra or certain savannas can sometimes lead to warming.
Dark forest canopies absorb more sunlight than snow or grasslands, reducing surface reflectivity, or albedo. In high-latitude regions, this effect can offset carbon storage gains. Still, globally, most landscapes capable of sustaining natural forests would experience net cooling when all factors are considered.
Regional evidence from Borneo
Research from Borneo illustrates how forest loss affects climate stability. Studies have linked deforestation there to rising daily temperatures, more frequent heat extremes and declining rainfall, particularly in heavily cleared watersheds. Areas retaining intact forests showed more stable climatic conditions.
The review reframes forests as more than carbon sinks they are adaptive systems that help societies cope with climate change. While climate policy often measures forests in terms of stored carbon, their local cooling, water regulation and health benefits remain underrepresented in adaptation planning.
Protecting and restoring native forests may offer cost-effective climate resilience compared to engineered solutions alone, while also supporting biodiversity and rural livelihoods.
The researchers caution that forests are not a universal solution. Poorly planned afforestation can strain water supplies or disrupt ecosystems. Nor can forests fully shield communities from global warming’s trajectory.
Still, their conclusion is clear: forests do not merely slow climate change they help people survive it. As heatwaves intensify and rainfall patterns grow more erratic, that role is becoming increasingly critical.