Reforestation Helps to Cool Planet

A young American sycamore tree recently planted in Durango, Colorado

Young American sycamore tree grows in a revegetated area in Durango, Colorado

Research into data from satellites and weather stations across the eastern United States has revealed encouraging information. The data stretches from the years 1900-2000. It shows that reforested areas in the eastern U.S. have provided a significant cooling impact.

During the hottest days of summer, the temperatures within 1,300 feet of the trees can be lowered by 3.6 to 9 degrees Fahrenheit. Overall, the added trees cool the entire eastern U.S. by 1.8 to 3.6 degrees Fahrenheit every year.

Mallory Barnes, an environmental scientist at Indiana University led the study. She is quoted in a Feb. 17, 2024 article written by Oliver Milman in The Guardian (U.K.): “The reforestation has been remarkable, and we have shown this has translated into the surrounding air temperatures.”

During early colonial history in the U.S., lots of deforestation occurred when many trees were cut down to provide room for agriculture and housing. But by 1920, tree cutting slowed when more people began to move from rural areas into cities. Trees began to grow again, filling in woodland areas that had earlier been razed.

In addition, the U.S. government began an aggressive tree-planting program. The vast reforested areas helped woodlands in the eastern United States to recover. One of the reasons why is that trees do something called transpiration. That’s similar to human sweating. When humans sweat, the perspiration helps their bodies stay a little cooler.

In transpiration, water is drawn up from the soil through tree roots. The water travels to the leaves. The leaves absorb the water, then release it into the air as water vapor. The result is that the area is cooled around the trees. According to The Guardian (U.K.) article, the vast expanses of reforested areas helped to slow the effects of global heating.

Barnes was quick to point out that reforestation is no substitute for cutting fossil fuel emissions. “Nature-based climate solutions like tree planting won’t get us out of this climate change problem,” she told The Guardian (U.K.). “Reforestation is something that needs to happen in addition to, not instead of, cutting emissions.”

Even so, it is encouraging that data from satellites and weather stations show how helpful reforestation projects can be. On a small scale, we can make a difference every time we plant a tree. And that is heartening to know.

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