Amazon deforestation makes local climate hotter and drier, study finds

A new study has confirmed, with measurements from space, what many scientists have suspected for years: clearing extensive parts of the Amazon alters the climate locally.

The change is substantial rather than marginal. Areas experiencing extensive deforestation are warmer and drier, with rain falling less often than in neighbouring places where much of the forest is still intact.

Using satellite observations, researchers compared Amazon areas with varying amounts of forest cover and found a clear, recurring trend.

After forest loss exceeds a particular threshold, local conditions begin to resemble those found in transition zones between rainforest and savanna.

What happens after the trees go

The team compared areas retaining over 80% forest cover with those where under 60% was left. In the dry season, surface temperatures in the most deforested areas averaged roughly 3°C higher.

Rainfall was affected too. These locations received around 25% less rain and had approximately 11 fewer rainy days.

Meanwhile, evapotranspiration – the process by which trees release water vapour into the atmosphere – fell by about 12%.

In everyday terms, the land receives less rain and it arrives less frequently. Dry periods become longer, heat accumulates more readily, and the atmosphere contains less moisture.

The Amazon shapes its own climate

This occurs partly because the Amazon is not simply a passive landscape exposed to climate conditions. The rainforest plays an active role in producing its own climate.

Trees draw water from the ground before releasing it into the air through evapotranspiration. That moisture ultimately helps form clouds and generate rainfall.

Removing trees weakens this moisture cycle. With less water vapour rising into the atmosphere, less rain is returned to the region.

This creates a feedback loop that concerns researchers. Warmer, drier conditions may place trees under stress, raise the risk of fire and leave forests more susceptible to additional degradation. In time, this can drive the system towards still drier conditions.

Why this matters beyond conservation

The study’s authors emphasise that the implications extend beyond biodiversity and environmental protection – important though both are. Climate shifts associated with deforestation may influence agriculture, water supplies and economic stability.

“The study shows that tropical forests have a huge impact on the climate, with consequences for various sectors of society, both for the well-being of populations and for economic activities,” said Luiz Aragão, a researcher from Brazil’s National Institute for Space Research (INPE).

“Therefore, the debate on the importance of forests must take a more comprehensive view, beyond the environmental issue.”

“We need to work with a vision of national development, with coordinated and integrated action between different sectors of society.”

This view treats forests as part of a country’s infrastructure. Where forest loss changes rainfall patterns, crops, livestock and dependable water supplies can be directly affected far beyond the forest itself.

Forests and agriculture are connected

Marcus Silveira, the study’s lead author and an INPE researcher, says the results reinforce the principle behind Brazil’s Forest Code, which obliges rural properties in the Amazon to retain a significant share of native vegetation.

“Deforested regions suffer from drier and hotter conditions, which also end up affecting agricultural production. The Food and Agriculture Organization of the United Nations [FAO] itself released a document at COP30 showing that forests are allies of agribusiness, not enemies,” he said.

“Through an extensive review of the scientific literature, it highlights the various climate benefits that forests promote, contributing to agricultural productivity and resilience. Our work is very much in line with that.”

The central point is straightforward: preserving standing forests need not conflict with agriculture – it could help ensure farming remains viable.

Deforestation rates in the Amazon

The study comes amid extensive changes in land use across the Brazilian Amazon.

From 1985 to 2024, the area lost around 13% of its native vegetation – approximately 520,000 square kilometres, an area greater than Spain.

Over that same period, pasture expanded sharply, agriculture grew and mining increased.

Although Amazon deforestation rates have declined in recent years, scientists stress that the total scale of loss is still high.

Official monitoring shows that more than 6,300 square kilometres of native vegetation were cleared in the Legal Amazon in 2024 alone.

Global warming is also becoming more severe. The article notes that 2024 was the warmest year ever recorded and the first year to exceed 1.5°C of warming above pre-industrial levels.

Aragão maintains that cutting deforestation will not be sufficient if fossil-fuel emissions continue to increase.

“It’s essential that we chart paths to reduce deforestation, as discussed at COP30, but it’s also necessary to move forward with the process of replacing the use of fossil fuels to curb global warming, which is already a cause for concern,” he said.

Measuring the effects of deforestation

To isolate the impact of deforestation, scientists split the Amazon into large grid cells measuring about 55 by 55 kilometres.

They then grouped these cells according to forest-cover levels and compared them with adjacent reference areas that retained over 80% forest cover.

The researchers assessed 11 climate variables, including temperature, rainfall, evapotranspiration and rainy-day numbers. Comparing nearby locations, rather than distant ones, reduced the likelihood that geography alone accounted for the findings.

The greatest impacts were seen where deforestation was most extreme. In areas with no more than 40% forest cover remaining, dry-season surface temperatures reached up to 4°C above those in nearby heavily forested areas. Evapotranspiration also declined considerably.

Can the trend be reversed?

Despite the concerning figures, the researchers say restoration provides a route forwards. Restoring forest structure may recover some of the lost cooling and moisture-cycling functions.

“Our study indicates that if we manage to restore the forest structure, it’s also possible to bring back ecosystem services, such as temperature reduction, increased water cycling, and carbon stocks, thus ensuring greater water, food, and economic security for the country,” Aragão explained.

The broader conclusion is that the Amazon does not merely respond to climate change – it also helps regulate the climate.

As too much forest is lost, the region begins to forfeit that capacity. Once the balance changes sufficiently, restoring previous conditions may become progressively harder.