Metropolitan areas tend to be significantly warmer than surrounding rural areas because of human activities, infrastructure, and the lack of vegetation. Asphalt, concrete, and dark rooftops absorb sunlight during the day and slowly release it at night. This raises temperatures by 1 to as much as 7 degrees during the day and 2-5 degrees at night. This is known as the urban heat island effect.
One of best ways to mitigate the urban heat island effect is to plant trees. Trees provide cooling shade, and they cool the air through evapotranspiration, which releases moisture.
A new study by MIT researchers finds that the amount of tree cover varies widely within cities and is generally connected to wealth levels. An examination of cities on four continents and at different latitudes finds a consistent link between wealth and neighborhood tree abundance within a city. Better-off residents usually enjoy much more shade on nearby sidewalks.
Cities vary greatly with respect to the amount of tree shading they enjoy. Stockholm was the most well-shaded city in the study; Belem in Brazil was the least shaded. The study looked at the amount of shade available on sidewalks, both citywide and within specific neighborhoods. Overall, the pattern of disparities with respect to relative affluence was consistent across all the cities.
What was most surprising was that in poor cities and very unequal societies, this disparity was expected, but in rich cities, it was still very much pronounced.
With temperatures on the rise, providing shade is an essential public amenity. It is not just an advantage to be experienced by the well-to-do.
