NASA Satellites Reveal Vegetation is Essential for Cooling City Hotspots

It turns out that when it comes to cities, vegetation is essential. Trees and plants actually limit urban heat, which is crucial when it comes to lowering the temperatures for these urban hotspots.

Scientists have long known of the urban heat island effect, which can raise the temperature of big cities by almost 6 degrees Fahrenheit in some cases. This rise is due to the presence of asphalt, concrete, buildings, and other so-called impervious surfaces disrupting the natural cooling effect provided by vegetation.

In this latest study, the researchers used multiple satellite observations of urban areas and their surroundings, and then combined these data into a model. The scientists also quantified how plants within existing urban areas, along roads, in parks, and in wooded neighborhoods, regulate the urban heating effect.

"This has nothing to do with greenhouse gas emissions, it's an addition to the greenhouse gas effect," said Lahouari Bounoua, research scientists and lead author of the new study, in a news release. "This is the land use component only."

Impervious surfaces' biggest effect is caused by a difference in surface temperature between an urban area and surrounding vegetation. The researchers actually found that averaged over the continental United States, areas covered in part by impervious surfaces had a summer temperature 1.9 degrees Celsius higher than the surrounding rural areas. In winter, the difference was 1.5 degrees Celsius higher.

The scientists also used a model to find out what the temperature would be for a city if all the impervious surfaces were replaced with vegetation. Then, they began reintroducing impervious surfaces one percentage point at the time. They found that the temperature differences actually held steady at about 1.3 degrees Celsius, as impervious surfaces increased to 35 percent.

"Urbanization is a good thing," said Bounoua, one of the researchers. "It brings a lot of people together in a small area. Share the road, share the work, share the building. But we could probably do it a little bit better."

The findings are published in the journal Environmental Research Letters.

Related Stories

Nature Helps Older Men Sleep Better

Scientists Capture CO2 and Transform it into Carbon Nanofibers Used for Industry

For more great science stories and general news, please visit our sister site, Headlines and Global News (HNGN).