Greening Landscape helps

Categorie(s): Climate, Ecology, News, Trees

For at least a century, air, ocean, and land temperatures on Earth have been steadily rising. For at least the past forty years, the planet has been growing a bit greener. Now researchers have found that the greening of the planet can offset at least some warming. Essentially, global warming would be even worse were it not for extra greenery changing how and where heat builds up across the landscape.

In 2019 scientists used satellite observations to show that vegetation cover globally had increased by 5 percent since the early 2000s. In 2020, the research group linked that increase in greenness to a slight slowing of global warming.

Now using satellite data and advanced computer models, they found that increased vegetation has a cooling effect coming from an increased efficiency in the vertical movement of heat and water vapor between the land surface and atmosphere.

There are several ways vegetation can alter temperatures at the surface. Changing leaf area can change albedo  (how much sunlight is absorbed or reflected by a landscape). More greenery can also change how well water can penetrate and be retained by soil and leaves. And it can change how the surface emits or reflects longwave radiation.

But the new study shows that the strongest cooling effect comes from the way increasing leaf cover leads to less aerodynamic resistance (how features on the ground increase or decrease drag and turbulence in the air above). Extra leaves can enhance the efficiency of vertical air mixing, allowing more heat and water vapor to rise into the atmosphere. Extra leaves may also increase the amount of water transpired (exhaled) by plants, allowing even more water to be transferred. That extra moisture can carry away a significant amount of heat from the ground level and lead to cooler surfaces.

Most vegetated areas on Earth (about 93%) see their land surfaces cool when leaf area increases. Since 2000, at least 30% of areas with more leaf coverage have been cooled by it, but 5% have grown warmer.

The map shows the trends in the “leaf area index” around the world from 2000 to 2014. Leaf area index (LAI) is a measure of the amount of leaf area relative to ground area during the growing season.Note that the map does not show overall greenness, but how greenness has changed since 2000.

The second map shows global changes in land surface temperatures over the same period due to the increased leaf area. Note that the map land surface temperatures (LSTs), not air temperatures. LSTs reflect how hot the surface of the Earth would feel to the touch in a particular location, and they can sometimes be significantly hotter or cooler than air temperatures.

“In the fight against climate change, plants are the lonely-only defenders,” said Chen, one of the researchers. “Stopping deforestation and ecologically sensible large-scale tree-planting could be one simple, but not sufficient, defence against climate change.”

The study authors noted, however, that the cooling effect from extra vegetation is large from an energy dissipation perspective, but it is small compared to the pace and intensity of global warming.

 Read here the complete article 

Greening the city helps even more to keep them livable! Read here about greening the cities