Study finds that trees cool the planet by one-third of a degree through biophysical mechanisms such as humidifying the air.
As tropical forests disappear from Earth at an alarming rate, scientists clamor to define their essential roles in mitigating global warming. A new study finds that in addition to absorbing CO2, the biophysical aspects of tropical forests, such as humidification, cloud production and organic chemical release, produce massive atmospheric effects. Scientists say people should regard such forests as centerpieces of climate policy, protecting their surrounding communities and the planet as a whole.
- Tropical forests play a critical role in reducing global warming.
- The new analysis underscores increasing worries about extreme tropic deforestation.
- Besides providing shade, tropical trees act as humidifiers, soaking up groundwater and releasing it from leaves.
- As rainforests disappear, surrounding communities suffer negative effects.
Tropical forests play a critical role in reducing global warming.
Scientists know that tropical forests extract and store carbon dioxide from the air, but a recent study found that those biological actions only account for about two-thirds of their cooling ability. The remaining third lies in their cloud creation function, which humidifies air, and their release of chemicals that further cool the atmosphere. The study shows that these ecosystems have more effects on climate than previously thought.
“For a while now, we’ve assumed that carbon dioxide alone is telling us essentially all we need to know about forest–climate interactions.” (Bronson Griscom, forest climate scientist, Conservation International)
The study, published in Frontiers in Forests and Global Change, may allow scientists to construct more accurate climate models, helping governments to implement stronger conservation strategies.
The new analysis underscores increasing worries about extreme tropic deforestation.
Climatologists say that a third of the planet’s tropical forests disappeared in past decades, and another third has been decimated by human activities such as development and logging. With climate change added on to that destruction, many forests may transform into savannas.
“This study gives us even more reasons why tropical deforestation is bad for the climate.” (Nancy Harris, forest-research director at the World Resources Institute, Washington, DC)
Forests play a major role in Earth’s carbon cycle because they remove significant amounts of CO2 from the atmosphere. Tropical forests, in particular, store about a quarter of all terrestrial carbon. They are considered “centerpieces for climate policy,” according to Bronson Griscom.
University of Virginia environmental scientist Deborah Lawrence co-authored the latest study, which collected data on the total cooling ability of the planet’s forests. The team found that, considering both biophysical effects and carbon storage capacities, tropical forests cool Earth by 1°C [1.8°F] and significantly mitigate global warming.
Besides providing shade, tropical trees act as humidifiers, soaking up groundwater and releasing it from leaves.
This action cools the surrounding region in a way similar to a human body producing sweat. As the water evaporates, clouds form, which reflect sunlight to further cool the area. Further, trees release compounds such as organic terpenes that effect more cooling by reacting with atmospheric chemicals.
“If you go into a forest, it immediately is a considerably cooler environment.” (Bronson Griscom, forest climate scientist, Conservation International)
Lawrence’s team studied the cooling effects of forests all over the world, “breaking down their contributions in bands of 10 degrees of latitude.” Counting only biophysical effects, collective forest cooling amounted to about 0.5°C [0.9°F] – with tropical forests most responsible for lowered temperatures.
Unfortunately, tropical forests across Southeast Asia, Central Africa and Latin America are currently experiencing increased deforestation and negative climate change effects. Christopher Boulton, a geographer at the University of Exeter, UK, recently published an analysis of about three decades of satellite images of the Amazon rainforest. By examining the region’s biomass over time, he concluded that three-quarters of the world’s largest rainforest is losing the ability to withstand extreme weather events such as drought.
As rainforests disappear, surrounding communities suffer negative effects.
Rainforests shield human populations from heat waves, and protect valuable crops.
“Every tenth of a degree matters in limiting extreme weather. And where you have forests, the extremes are minimized.” (Deborah Lawrence, environmental scientist, University of Virginia)
Governments in tropical regions struggle to save forests despite wide-ranging campaigns to stop deforestation, halt climate change and encourage sustainable development. Lawrence maintains that protecting forests runs deeper than conservation concerns; the trees produce significant benefits for people who live in these regions.
About the Author
Freda Kreier is a science journalist whose work has appeared in Nature, Science News, The Mercury News and Mongabay.