In the face of climate change, scientists often focus on the harmful effects of greenhouse gas emissions, but new research shows that tropical deforestation triggers global changes that are just as costly as carbon pollution.
Clearing trees not only releases carbon into the atmosphere, adding to the greenhouse gas effect, but also alters rain patterns and increases temperatures worldwide. This distorts Earth’s normal wind and water systems and puts future agricultural productivity at risk.
“Tropical deforestation delivers a double whammy to the climate – and to farmers,” lead study author Deborah Lawrence said in a statement. “Most people know that climate change is a dangerous global problem, and that it’s caused by pumping carbon into the atmosphere. But it turns out that removing forests alters moisture and air flow, leading to changes – from fluctuating rainfall patterns to rises in temperatures – that are just as hazardous, and happen right away.”
Most people might think that this only impacts tropical places like South America, which is home to the expansive Amazon rainforest. However, researchers say that these findings even apply to the United Kingdom and Hawaii, which could see an increase in rainfall, while less rain would fall in the US Midwest and Southern France.
Overall, there would be 10-15 percent reduced rainfall in the region surrounding where the tree clearing took place. Thailand has already seen less rainfall at the start of its dry season, and the Amazon’s annual rainfall schedule has started to shift as well.
In addition, deforestation in South America, Southeast Asia and Africa may alter growing conditions in agricultural areas in the tropics and as far away as the US Midwest, Europe and China, which is bad news for farmers.
Complete tropical deforestation could lead to a rise in global temperature of 0.7 degrees Celsius (33.3 Fahrenheit), which is on top of the projected impact from greenhouse gases such as carbon dioxide. According to the report, described in the journal Nature Climate Change, temperature increases are guaranteed with deforestation.
“This does not change, no matter what you do – no matter what kind of model you use, temperature increases occur – whether it’s half a degree, a full degree or two degrees,” Lawrence explained.
“That’s a very big deal,” she added. “In the last few centuries, the average global temperature has never varied by more than about one degree. Once we go above one degree – to 1.5 degrees or more – we’re talking about conditions that are very different from anything humanity has ever experienced.”
Tropical forests move more water than any other ecosystem on land and are central to the Earth’s ability to generate moisture, helping to keep the planet cool. But removing large swaths of forests disturbs this natural cycle. What’s more, as more deforestation occurs, the greater its impact worldwide will be.
“While complete deforestation is unlikely to occur, over the course of history, deforestation has continued as countries develop,” Lawrence said. “Further, this study fills gaps in our understanding of deforestation tipping points – and what could happen if we continue down this path.”
According to the research, if 30-50 percent of the Amazon rainforest is cut down, it would put deforestation at the tipping point, meaning any more forest clearing than that would lead to rainfall reductions that could significantly change ecosystems, as well as raise the risk of forest fires.
Lawrence and her colleagues hope that this study can help policy makers and rainforest managers come up with better strategies for combating deforestation.