A significant cause of death in cities is directly related to heat exhaustion, which occurs when either a heat stroke or heart failure overcomes a person and body functions are impaired. A few extra degrees of heat can be the difference between life and death.
That's where trees help. Since the population in most cities is concentrated in their cores, elevated temperatures in those areas affect more individuals.
Infrared measurements show that almost all city centers have heat islands with temperatures from 6 to 15 degrees hotter than the suburbs. Studies have proven the absence of trees is the difference. These heat islands exist in almost every city of any size, and persons living there have a much greater risk of dying of a heat-related problem than others in shady regions.
The Texas Tree Foundation, which has researched this problem, has focused on tree canopies, because heat islands have a direct relationship to them. Not only are city centers hotter, but they have less moisture and consequently more dust, which brings about allergic reactions and more health problems. Trees solve these problems by secreting moisture.
Towns with good tree canopies record much lower temperatures than those without them. Some of the best have a heat-island effect of 6 degrees hotter than a tree-lined suburb, and the worst have plus-15 degrees.
When we have 100-degree days, usually recorded at an airport away from an asphalt-concrete downtown, the actual downtown temperature could be as high as 115 degrees--and that is not the heat index, which will be much higher. If you figure in the heat index, cities with a heat island could easily have downtown temperatures of over 120 degrees.
In 2011, Dallas had temperatures that topped 100 degrees for 40 consecutive days, and 112 people died. Nearly half of those deaths were directly attributed to the heat wave, according to the Foundation's research. An estimated 30,000 people die from heat-related deaths annually in the U.S., twice as many as are killed by gun violence.
Almost all city centers have impermeable surfaces such as concrete and asphalt, which soak up the sun's heat and cause the heat island effect. This increase in temperature can be deadly for those with respiratory problems or childhood asthma. Trees can filter deadly air pollution and protect people from chronic respiratory illness.
The problem is not just in the Southwest where 100-degree days are common, it is now worldwide because of global warming. Paris has just experienced a brutal heat wave, and is responding with a reforestation effort to ensure 50 percent of the city's land is planted by 2030.
Here in the U.S., a recent study indicates replanting trees lost to urban development could reduce between one-sixth and two-thirds of our carbon pollution. There are an estimated 255 million suitable acres available for tree-planting in an area the size of Texas.
How are we coping in Arkansas, the Natural State? We're doing a lousy job, but there are bright spots. The city of Fayetteville is committed to a 40 percent tree canopy and is working to maintain that while having to replace older trees. Little Rock has a City Street Tree Origination that is committed to planting trees that could use help from the city and volunteers.
Just last week on North Washington Avenue in El Dorado, two healthy 100-year old oaks were cut down without good reason. However, we're making some progress. I've gotten over 1,000 trees planted in our downtown. But on ugly north West Avenue and Hillsboro Street I have been stonewalled, even after I offered to buy the trees. I'm not picking on El Dorado. My hometown is just an example of almost every town in the state.
But planting trees in city centers is just a small part of the problem. We need to plant trees in every available spot, and we can't possibly plant too many. Plant them around bus stops, in parking lots, on city sidewalks, and in every green space in your town. Try to pick a recommended street tree with wide leafy foliage. We can easily plant native trees in the late fall and winter, if use a little initiative to find them, or spend a few bucks with a local nursery.
Trees can be anywhere; there's no reason not to plant them in highway medians where we have hundreds of miles of mowed grass.
We were once the Bear State, but we killed off nearly all the bears, so we changed to the Natural State. Will we repeat history by losing so much tree cover that one day we'll be too embarrassed to call ourselves that?
I will speak on "Rewilding Arkansas, or Making Arkansas a Wilder Place" at the Little Rock Sierra Club's meeting at 7 p.m. Tuesday at the Oyster Bar, 3003 W. Markham St. Come by for a Bring Back the Wolf bumper sticker. You don't have to be a Sierra Club member to attend.
Email Richard Mason at [email protected]
Editorial on 09/15/2019
Print Headline: Trees as saviors of cities