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Urban forest beneficial to city
By Richard A. Marini : December 19, 2013 : Updated: December 20, 2013 12:16pm
SAN ANTONIO — A few years ago, we were working away here at the Express-News when there was a loud BAM! from outside. We all ran to the window to look at the street below and saw that a car had crashed into one of a series of live oaks that line the street.
I don't recall anyone being seriously hurt, but after they towed the car away, I noticed that the bark where the tree had been hit had been broken by the impact. The tree still stood, but I wondered if it would survive being rammed by a 2-ton vehicle.
Years later, the tree still stands proudly alongside its compadres, the only sign of the accident, the exposed heartwood where the bark had been peeled back like on an orange.
One tough tree, eh? But that's the primary requirement for arboreal survival in the big city.
“City trees have to be tough to survive,” city arborist Mark Bird said. “They've got to contend with limited planting space, overhead signage and light fixtures, and the occasional car running into them.”
I asked Bird if we could take a tour of downtown to talk about the city's greenery. He readily accepted the chance to promote the many benefits of city trees and to discuss the equally numerous challenges they face.
On most every block we drove, Bird was able to point out young trees planted during the city initiative completed two years ago that saw 10,000 trees planted across the city, including 1,000 in the downtown area.
According to Bird, a survey done one year later found that 98 percent of the newbies were still alive.
“We worked with quality nurseries and made sure the trees hadn't been in their containers too long,” he said, explaining this success rate.
The city also learned the best way to plant a tree.
“Most people think you've got to dig this huge hole,” he said. “But we've learned it's better to dig a shallow-but-wider hole. Roots grow at a certain horizon in the soil. Plant the tree too deep and they have to expend energy regenerating a new layer of roots.”
When I asked Bird about the benefits of urban trees he listed many of the usual suspects; trees create shade that helps reduce the “heat island” impact. That is, the build-up of heat because of all that concrete and asphalt. They also help clean the air and help reduce flooding by absorbing water during heavy rains.
But did you know that asphalt used in streets and parking lots lasts longer when shaded by trees?
Or that trees also make roadways safer?
“Trees lining the street act as visual friction,” he said. “They make you instinctively slow down because you see them near you as you drive.”
He also argued against companies that want to level every piece of vegetation taller than waist level so as not to impede the view of their business.
“Trees serve are landmarks,” Bird explained. “You may not know what, exactly, a building looks like, but you know it's near the huge sycamore where people picnic. People can find anything they're looking for even without seeing it.”
I ask Bird to direct me to some of his favorite downtown trees and he takes me to what he called a “really nice anaqua,” a native affectionately known as the Aggie Toilet Paper Tree for its sandpaper-rough leaves.
“In spring, it's covered with clusters of white flowers,” he said. “It looks like a huge snowball. Just a beautiful tree.”
Bird said several city organizations are in the process of tracking down notable, or significant trees throughout the city. The resulting index, which will list trees based on their location, species and character, will help make us aware of the city's arboreal treasures.
If you're interested in helping create this index, or would like to nominate a tree for consideration, contact Bird at 210-207-0278.
At one point during our leisurely drive, I took Bird by the Express-News building and showed him the live oak that survived the crash.
He laughed and said he wasn't surprised that the tree was still standing.
“It's called a live oak for a reason,” he said. “If it were any other species it would surprise me that it survived. It might live another 100 years.”
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