SHADY A PLAN
By 2030, Phoenix plans to have 25% tree coverage in its urban areas
Ipreviously wrote an article about Singapore, whose goal is to become a city within a garden. Now I am writing about Phoenix, whose goal is to increase its shade from trees from 10 to 25 percent by 2030. The Tree and Shade Master Plan was adopted in 2010 and came about when Phoenix was studying a variety of ways to decrease summer temperatures within the city.
According to www. phoenix.gov, Phoenix has 92 days each year with temperatures over 100 degrees. The city encompasses 519 square miles and has over 1.5 million residents. Maricopa
County is the fastest-growing county in the United States, which is contributing to the rapid expansion of its urban footprint and increased urban heat.
Studies by Arizona State University showed that increasing Phoenix’s urban tree coverage from 10 to 25 percent could lead to a temperature reduction of 4.3 degrees. If a neighborhood with no trees had a 25 percent tree canopy, its temperatures could drop 7.9 degrees. As summer heat continues to rise, adding more shade within Phoenix would help make the summers more tolerable, provide residents with a more enjoyable environment and be costeffective.
In ASU’s Thrive magazine, fall 2018 issue, ASU professor Nancy Selover explained that natural materials, such as trees, are less dense than concrete and asphalt and don’t conduct heat very deeply. When night comes, heat stored by natural materials is near the surface and quickly dissipates. Within a half-hour, a natural surface will be cool, and you will have less heat storage.
The thought is that increasing the canopy coverage from trees will increase the amount of natural materials available to rapidly dissipate heat at night, leading to cooler daytime temperatures. Twenty-five percent canopy coverage will also increase cooling shade during the daytime.
Other cities that are realizing the benefits of increasing the number of trees in urban areas include Los Angeles, New York, Chicago, Houston and Philadelphia.
The concept of utilizing trees to improve the environment is not new. In 1879, a Phoenix newspaper article stated: “The tree planting season is now at hand, and we expect to see it taken advantage of by almost everyone in the valley. In this city let every person who owns a lot see that shade trees are set out. If nothing better can be obtained, set out cottonwoods. They cost nothing, (are) easy to plant, require no care, and are of quick growth.”
There is always the question of water when cities, especially in Arizona and California, talk about adding landscaping. The continued drought in the Southwest has lowered water levels in Lake Mead and Lake Powell, our two main reservoirs, and may lead to future water shortages. So many states and tribes depend upon the Colorado River for water that increased use of water for landscape purposes could be quite controversial. In order for the Tree and Shade Master Plan to be successful, better water management through improved planting, irrigation and maintenance practices must be employed to significantly lower water consumption.
Another piece of Phoenix’s plan to reduce heat within the city included the Phoenix Cool Roofs initiative passed in 2012. The initiative mandated 70,000 square feet of existing city rooftops be coated with reflective materials to help reduce heat. Private and residential homes were not included in the initiative. To date, this initiative has not been expanded.
As cities in Arizona continue to attract new businesses and more housing
is built to accommodate increased urban growth, hopefully, master plans can be put in place that include planting shade trees and green areas to offset heat generated by buildings, sidewalks and roads.
Creating small oases of trees and other plantings in the midst of “concrete jungles” will not only lower the heat index but will also provide a more calm and tranquil environment for residents to live in. If water is available, increasing the number of trees within Phoenix, as well as within Yuma, is a win-win situation for everyone.
THE SWEET ACACIA IS A BEAUTIFUL TREE IN SPRING WHEN COVERED WITH HUNDREDS OF ROUND, YELLOW BLOOMS. It is a drought-tolerant tree that grows well in the desert Southwest.
A MAN SEEKS RELIEF FROM HEAT IN THE SHADE OF A TREE in the park surrounding Heritage Branch Library in July.
YUMA’S GARDEN CLUBS PLANT TREES IN PUBLIC AREAS each year, including this mesquite tree planted by MGM Garden Club at Crossroads Mission. From left are Elizabeth Moody, Barbara Rochester, Janine Lane, Mary Lou Milstead and Ruth Ann Maguire.
MEMBERS OF FORT YUMA ROTARY HELP STUDENTS at Gary Knox Elementary School plant a citrus tree in the school garden as part of a nationwide campaign by Rotarians to increase the number of trees in U.S. communities.