Perhaps we could make destroying grass, plants, and trees a little easier.
(Sarah Diggins | Tribune Feature) July 16, 2021 An unshaded sidewalk in Poplar Grove.
In Utah, we seem to find a strange sense of security in the pavement. At the moment, we are witnessing many examples of lawns and plantations being converted to cement, asphalt, gravel, or artificial turf that can become as hot in the sun as pavement.
These projects seem to be inspired by the false belief that paving and other hard landscaping conserves water and that plants “waste” water. There should be no difference from the truth.
The big paradox of the current drought situation is that there may be more water in the skies above Utah than at any time in human history. As polar ice melts, more water on Earth becomes available in liquid and vapor form, which can precipitate as rain and fill rivers and aquifers.
A frustrating problem with Utah’s drought is that in hot summers, rain can evaporate before it hits the ground (a phenomenon called varga). Heat radiation from the pavement facilitates this and speeds up drying. Hard, hot groundcovers repel surface water rather than “save” it. This is true no matter the size, whether you’re paving acres of vegetation, adding a patio, or simply extending the driveway of a suburban home.
Our drought is not about too little water falling from the sky. Our droughts are caused by excessive heat. Satellite and surface measurements confirm that the Earth’s surface is heating up more than ever before, according to a study recently presented at the Utah Museum of Natural History by a committee that included Utah’s climate scientists. The same satellite images also revealed that Salt Lake City is one of the most overpaved cities in America.
Few of us would recommend Kentucky bluegrass as a mainstay in climate-smart landscaping. But in reality, on a sunny summer day, a mixed plant and grass surface can be 30 to 50 degrees (F) cooler than a paved surface. This is quickly noticed by anyone who simply attempts to walk on the sidewalk.
The bottom line is that pavement and hard urban surfaces are something we don’t really need. Instead, we need more plants, grass, and trees. An unfortunate current example of getting this wrong is the renovation of the Central 9th Precinct. There, five lanes of new pavement and hard landscaping have made roads and sidewalks too hot to walk or even visit during the summer day.
As the EPA explains, it is also wise to consider more water-friendly pavement options, or to limit new pavement and encourage pavement removal to allow for revegetation.
The most water-friendly landscape approach for land of any size is to cover as much of the land as possible with plants, including the roofs of buildings. Installation on a hot, hard surface can result in more water loss than the amount of water needed to maintain the ground level with the planting surface.
Perhaps we could choose to destroy grass, plants, and trees a little more easily, and be more conservative with pavement, which is no friend to urban climates.
If more pavement could save our city and the Great Salt Lake, we could keep doing what we’re doing and just watch the lake fill.
Dr. Thomas Weed, He is a longtime local physician and supporter of Utah’s healthy environment.
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