Brussels (Brussels Morning) Satellite data from the European Space Agency’s (ESA) Climate Change Initiative revealed that afforestation – the creation of new forests —increases the coverture of low-level clouds, leading to stronger evergreen forests and a cooler climate.
Evergreen forests can be so dense that sunlight cannot penetrate the canopy to reach the ground.
Normally, they occur across a wide range of climatic zones, and include trees such as conifers and holly in colder climates. In more temperate zones, eucalyptus, live oak, acacias and banksia are common, with rainforest trees typically found in tropical zones.
The ESA data findings were recently published in Nature Communications, detailing how it used global data records of clouds and land-fractional cover to examine the transition of vegetation levels into deciduous and evergreen forest.
The paper describes how clouds generally built up in the course of the whole year in afforested areas in temperate, tropical and arid regions, sometimes by as much as 15%.
Yet, during the boreal winter and spring across North America, Russia and Eastern Europe, when these regions have prolonged snow cover, the authors found a reduction in cloud cover over forests compared to open land.
The boreal summer has strong and consistent increases in cloud fraction by about 5%, the study found.
Trees and forests
“Earth observations are increasingly showing that trees and forests are impacting climate by affecting biophysical surface properties”, Alessandro Cescatti, one of the co-authors of ESA’s study, noted.
Trees have long been known for their great capacity to sequester carbon dioxide from the atmosphere and convert it into biomass. In particular, forests are widely championed for their role in mitigating climate change.
However, what has been less clear is how forests affect the climate in other ways such as their role in the water cycle and surface energy balance.
“Without global cloud and land-cover type observations from satellites this study would not have been possible on a global scale”, Martin Stengel, who leads the Climate Change Initiative Cloud project, said.
Finally, the authors highlighted that land-based climate mitigation through afforestation, forest restoration and the avoidance of deforestation should not be reasoned purely in terms of carbon capture.
Instead, policies should include the wider climate benefits that forests offer, including increasing cloud cover for localised cooling and generating rainfall, factors that add to the hydrological value of forests per se.
“Studies like this one, based on robust satellite observations, are fundamental to characterise the complexity of the climate system and provide benchmarks for climate model developments”, Cescatti observed.