The Houston Chronicle
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Houston’s tree canopy thinning rapidly

By Bill Dawson
Thursday, December 14, 2000

Houston's urban forest declined significantly from 1972 to 1999, depriving the area of $55 million annually in benefits such as reduced air pollution and enhanced flood control.

The findings are part of a study that recommends adopting policies to reverse the deforestation trend.

"It's an opportunity people ought to go for," said Gary Moll, an official of American Forests, a 125-year-old conservation group that conducted the study for the Houston Green coalition.

"It's an opportunity to set a standard — a goal of some kind, with a certain percentage of tree canopy — and to find a way to reach that standard, no matter how they do it," he said.

In recent years, there have been a number of major public and private efforts to plant large numbers of trees around the Houston area.

Along with an overall decline in tree cover, the study found localized increases in the forest canopy, said Dewayne Huckabay, an official in the Houston Finance and Administration Department, part of the Houston Green coalition.

These instances of greater tree cover typify "the direction all development should be moving," said Huckabay, who heads Mayor Lee Brown's multiple-agency Clean Air Team.

The study used satellite images of 3.2 million acres within a 50-mile radius of Houston, tracking changes during the 27-year period. Among the key conclusions:

· Land with "heavy tree canopy" (defined as having tree cover of 50 percent or more) declined to 26 percent of the region, from 31 percent. Areas with "light tree canopy" (less than 20 percent cover) increased to 71 percent from 63 percent.

· The lost tree canopy would have removed 15.3 million pounds of pollutants from the air annually, reducing health expenditures and other costs by $38 million a year.

· Tree loss reduced the urban forest's ability to slow stormwater runoff, with the change equal to a new stormwater-detention system costing $237 million.

· The shade from Houston's remaining trees reduces air-conditioning use enough to save residents $26 million a year in electricity costs — about $72 for an average home.

The study concluded that the average tree canopy across the Houston area is now about 30 percent.

Expanding tree cover to a 40 percent average would increase stormwater-collection benefits by 163 percent and increase the removal of conventional air pollutants by 25 percent, the American Forests researchers calculated.

Increasing the local canopy to 40 percent would also mean 55 percent more removal of carbon dioxide — the principal gas implicated in global warming, they said.

To create a larger urban forest, the study recommends several actions — including tree-cover data in decisions about public works, transportation and development; encouraging tree-planting as one way to improve air quality and reduce flooding; and considering tree issues in "land-use planning and growth management."

Moll acknowledged that Houston's absence of zoning means public policies will have to be "less direct" than in other cities.

He stressed that American Forests, which calls itself "the oldest national nonprofit citizen conservation organization," refrains from pushing specific policies. Instead, the group encourages local citizens and officials to expand tree canopy by whatever means they prefer.

"It's not good business to sacrifice trees," he said.

The study did not identify and quantify specific trends that have contributed to Houston's tree loss, but Moll said it is partly attributable to the urban growth pattern known as sprawl.

The Houston Green coalition, which sponsored the study with the U.S. Forest Service, includes several prominent groups that have participated in tree-planting campaigns, such as the private Trees for Houston.

The coalition's other members include the Bayou Preservation Association, the Houston-Galveston Area Council, the Park People, the University of Texas Health Science Center at Houston, the Texas Forest Service and the Galveston-Houston Association for Smog Prevention.