Deforestation to blame for reduction in rainfall across tropics: study

By James Gamble via SWNS

The destruction of tropical rainforests really does lead to reductions in rainfall,
reveals a new study.

Researchers compared satellite data on deforestation and rainfall across the Amazon, Congo and South East Asian tropics to show that loss of tree cover over the past 14 years has led to drops in rainfall.

Though people living in the tropics have repeatedly attested to the fact that the climate warms and becomes drier after trees are cleared, this new study is the first to identify an empirical link between the two.

Scientists warn that declines in rainfall have negative impacts on biodiversity, increase the risk of forest fires and reduce carbon sequestration - the process by which nature removes carbon from the atmosphere and stores it.

The study's authors predict that if the current rate of deforestation continues in the African Congo, rainfall could fall by up to an eighth by the end of the century - with a devastating potential impact on the biodiversity and agriculture of the forests.

The researchers, from the University of Leeds, used satellite observations over 14 years (2003-2017) to analyze the impact of forest loss in the Amazon rainforest of South America, the Congolese rainforests in central Africa and forests in Southeastern Asia.

All three of these biodiverse tropical areas have experienced rapid changes in land use over recent years.

The research team identified locations across these three regions where forests had been cleared and compared the rainfall data from these deforested areas with nearby locations where trees had not been cleared.

The results revealed that tropical tree loss reduced the amount of rain which fell in these areas all year round.

This included reductions in rainfall during dry seasons, when further drying proves most impactful on plant and animal ecosystems.

It is believed by scientists that loss of tree cover disrupts the process through which moisture in leaves is returned to the atmosphere where it forms rainclouds, in a process called 'evapotranspiration'.

The study's authors predict that by the end of the century, if the rate of deforestation continues unchanged, rainfall in the Congolese rainforests - which are amongst the world's largest stores of carbon - could fall by up to 12 percent.

A reduction this sharp in the next three-quarters of a century would have catastrophic implications for the biodiversity, agriculture and viability of the forests.

The study's lead author, Callum Smith, a doctoral researcher in the School of Earth and Environment at the University of Leeds, says his team's investigation provides 'compelling' evidence to protect forests from unpoliced clearing.

Mr. Smith said: "Tropical forests play a critical role in the hydrological cycle in helping to maintain local and regional rainfall patterns.

"The reduction in rainfall caused by tropical deforestation will impact people living nearby through increased water scarcity and depressed crop yields.

“Tropical forests themselves rely on moisture to survive and remaining areas of forest will be impacted by a drier climate.”

As well as proving damaging to natural ecosystems, reductions in rainfall would also significantly damage agriculture and hydropower plants, which would impact the functioning of these forests and the communities which call them home.

The researchers said crop yields fall by an average of 0.5 percent for every one percent reduction in rainfall.

The study's authors warned that while climate change will lead to increased drought, continued deforestation will exacerbate this risk.

Professor Dominick Spracklen, who supervised the project, added: “Local people living near deforested regions often report a hotter and drier climate after the forests are cleared.

"But until now this effect had not been seen in rainfall observations.

“The study shows the critical importance of tropical forests in sustaining rainfall.

"Although there have been efforts to halt deforestation, the loss of forest cover in the tropics has continued.

"There needs to be renewed efforts to stop forests being lost and to regenerate lost and degraded areas."

The University of Leeds team's research was funded by the European Research Council under the European Union's Horizon 2020 research and innovation program, and the Newton Fund, through the Met Office Climate Science for Service Partnership Brazil.

The crucially important study was published om March 1 in the scientific journal Nature.