Drought likely to kill millions of Houston trees

By Robert Stanton and Carol Christian
Houston, TX (September 2, 2011)- Millions of trees in the Houston area are likely to perish due to the drought gripping the state, potentially worsening air quality problems, destroying wildlife habitat and making the area warmer, experts said.


The most dire prediction came from Barry Ward, executive director of the nonprofit Trees for Houston, who estimated that 66 million trees – about 10 percent of the entire canopy in the eight-county Houston area – would die within two years as a result of the worst drought in Houston’s history.
Houston city workers are removing dead trees from city parks, including Memorial Park, where at least 341 trees have died – some from pine bark beetles but others due to the drought, said Joe Turner, director of the city’s Parks and Recreation Department. Another 200 trees have died in other city parks, and work crews are cutting down trees that could fall on public thoroughfares or injure people.
A Texas Forest Service study in 2001 determined there are 663 million trees in the eight-county region that includes Harris County, said Mickey Merritt, the agency’s bayou region forestry coordinator. About 84 million are in urban areas. “If you lost 1 percent, that’s 6 million trees over the region, or 840,000 in urban areas,” Merritt said. “My gut feeling is that we’re going to lose more than we lost in Hurricane Ike within the eight-county region.”
While there is no universally accepted number of Ike-killed trees, Ward estimated at least 6.6 million trees perished in the September 2008 hurricane. A tree’s chance of survival, Merritt said, depends on the type of soil and its condition before the drought began. “Some weak trees might survive, but they’re so weak that they won’t fully recover and will continue to decline,” he said. “They will be susceptible to insects and diseases.”
Matthew Tejada, executive director of Air Alliance Houston, said the death of many trees would have a mixed effect on air quality because both living and dying trees contribute to harmful ground-level ozone. “If somebody wanted to figure out the net gain or loss of a mass tree die-off, it would be worthy of a Ph.D. in botany,” Tejada said. “But from an overall air-quality standpoint of turning carbon dioxide back into oxygen, dying trees do not help us out in the Houston area.”
Trees are also important on an emotional level, Tejada said. “We need these trees to stay such a big part of our local environment, as they have been in all of Houston’s history,” he said.
Houston Mayor Annise Parker lamented the loss of trees in a message she posted Thursday on Twitter. “I can’t save the trees,” she wrote. “Even when the rain returns it will be too late for so many. Memorial Park just makes me sad.”
Although the drought is statewide and affecting trees of all species, the jury is still out on how catastrophic it will be, said Pete Smith, the forest service’s urban forestry partnership coordinator. “There are lots and lots of trees showing stress, but I hope people don’t overreact and cut them down at the first sign of stress,” Smith said. “Some species may drop some leaves but may not be dead.”
The full impact could take as much as three years to manifest itself, said Smith, who has worked in Texas forestry for 23 years. “Often, drought stress leads to mortality from other causes, such as insect outbreaks,” he said, adding that invasive species can gain a foothold when big shade trees and pines start dying.
Trees are natural air conditioners, Smith said. “When there’s moisture in the soil and they’re transpiring, they are cooling the air,” he said. “We’re going to miss these trees that are dying, especially the ones around our homes.” One of the biggest impacts will be an increase in the number of “heat islands,” or treeless areas where pavement and other development features drive up the temperature, said Mark Bowen, executive director of Urban Harvest, a Houston nonprofit that promotes gardening and farmers’ markets.
Temperatures can be 9 to 10 degrees warmer in heat-island areas than in green belts, said Bowen, a horticulturist and author who operated a landscape design firm for 20 years. The loss of trees makes it difficult to sustain a large and diverse wildlife population, Bowen said. “Houston is a major flyway,” he said. “People come here from all over the world to watch birds and other forms of wildlife. Loss of trees cuts down on shelter, food sources and even the ability to have solitude to reproduce effectively and raise their young.”

Related Resources:

The Houston Chronicle- Drought likely to kill millions of Houston trees
Trees for Houston