The magic of trees

Plane trees in Green Park, London.
Source: The Royal Parks

Tree-lined street in Tulsa
Source: Strong Towns.

From ZME Science:

The fact that cities are heat islands has been thoroughly documented in recent years — in all parts of the world, urban areas are considerably hotter than their surroundings. However, trees can help counterbalance that phenomenon, helping to keep our cities cooler. The effect is especially pronounced for a large number of trees.

The list of benefits that trees provide in urban areas is huge. Not only do they help absorb carbon and pollutants from the air, but they help with soil erosion and stability, water absorption and filtration, they provide ecosystems for a number of creatures, and offer shade and protection from wind. Studies have shown that trees inspire children to be more curious and fond of nature, increase property values, and can even help reduce criminality rates.

Another service which trees provide is thermal regulation. That has been suggested by previous studies and is quite intuitive. However, a new study shows that the relationship isn’t linear. When the canopy cover reaches a particular threshold, the effect is much more pronounced.

“We found that to get the most cooling, you have to have about 40 per cent canopy cover, and this was strongest around the scale of a city block,” says Carly Ziter, an assistant professor of biology in the Faculty of Arts and Science, and lead author of the study. “So if your neighbourhood has less than 40 per cent canopy cover, you’ll get a little bit of cooling, but not very much. Once you tip over that threshold, you really see large increases in how much you can cool areas off.”

The effects can be huge. The temperature difference from tree-less area just a few hundred meters away from an area with a heavy canopy cover can be as high as four or five degrees Celsius. It’s not just the shade either. Trees transpire, giving off water vapor, almost like a natural air conditioner.

[Read more here]

There is much you can do, personally, to stop global warming.  You can become a vegetarian; you could put solar panels on your roof; you could get an electric car.  And you can plant trees on your own property, while also persuading your local council to plant trees as well, along streets, next to streets, and next to municipal buildings.