Forests do far more than store carbon or shelter wildlife. They actively regulate temperature, humidity and rainfall and when they disappear, the climate shifts almost immediately.
A recent study published in Communications Earth & Environment provides striking quantitative evidence of this effect. According to the research, when forest cover drops below 60 percent, local weather patterns begin to change significantly: surface temperatures rise, evapotranspiration declines, and rainfall becomes less frequent.
The Hidden Cooling System of Forests
Forests function as natural climate stabilisers. Through evapotranspiration the combined process of water evaporating from soil and transpiring from plant leaves vegetation releases moisture into the atmosphere. This moisture contributes to cloud formation and precipitation.
When trees are removed, this feedback loop weakens. Less moisture enters the air, cloud formation declines, and rainfall drops. At the same time, exposed soil absorbs more solar radiation, intensifying surface heat.
Up to 4°C Hotter in Heavily Cleared Areas
The data reveal a clear threshold effect:
Below 60% forest cover:
• Temperatures increase by up to 3°C during the dry season
• Evapotranspiration drops by 12%
• Rainfall declines by 25%
Below 40% forest cover:
• Temperatures rise by as much as 4°C
• An average of 11 fewer rainy days per year
This is not merely a matter of lighter rainfall. Researchers found that both the intensity and frequency of rain events decline, indicating a structural shift in atmospheric dynamics rather than short-term variability.
The long-term consequences can be profound. As rainfall diminishes and heat intensifies, remaining trees struggle to survive. Over time, once-humid rainforest conditions begin to resemble a savanna-like climate a transformation that can become self-reinforcing.
Satellite data between 1985 and 2024 show that the Amazon rainforest has lost approximately 13 percent of its vegetation around 520,000 square kilometres, an area larger than Spain. Much of the cleared land has been converted into pasture, agricultural fields and mining sites.
While deforestation rates have slowed in recent years, scientists warn that the cumulative loss may already be pushing some regions toward ecological tipping points, where recovery becomes increasingly difficult.
The findings reinforce a crucial reality: forests are not passive landscapes. They are dynamic systems that directly shape regional climate stability.
In a world already warming due to greenhouse gas emissions, deforestation compounds the problem by altering local hydrological cycles and amplifying heat. The climate response is not delayed or abstract it is measurable, immediate and regionally intense.
Protecting forests, therefore, is not only about conserving biodiversity or reducing carbon emissions. It is about preserving the environmental processes that keep temperatures moderated, rainfall patterns balanced and ecosystems resilient.
Once that balance is disrupted, nature does not simply reset. The consequences can echo for decades or longer.