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The Value of Houston's Trees

A new report reveals that the Bayou City has lost a lot of forest to concrete, but the remaining trees provide measurable benefits.

By Wendee Holtcamp

A long-anticipated report by the USDA Forest Service and the Texas Forest Service tells a tale of forest loss and urban expansion, but also puts green to green, quantifying the environmental benefits that Houston’s trees provide in dollar values. The report is just one of many milestones changing the way Houstonians think about their trees.

Houston started getting concerned when national attention focused on its illegal air pollution and unsightly traffic and sprawl. Many realized the city’s image was hurting the economy — companies were choosing not to establish a presence in the city. And with ozone levels dangerously outside of federal Clean Air Act limits, the city has to clean up its air, and trees can help.

A critical milestone was the production of the landmark study released in September 2005, which quantifies not only the canopy loss but also the economic value of trees.

The study examined eight counties around Houston. TFS forester Mickey Merritt and colleagues sampled more than 300 field plots, identifying species, quantifying leaf biomass and measuring tree size. These measures were plugged into the Urban Forest Effects, or UFORE, computer model, which quantifies the structure, function and economic values associated with the existing forest canopy.

Forests encompass about 28 percent of the region’s land matrix and are surprisingly diverse, with nearly 70 species — pines, oaks, elms, ashes and hickories, to name just a few. But the single most common tree in Houston is the invasive Chinese tallow, at 23 percent. Loblolly pine was the most common native tree at 19 percent.

Houston’s trees provide an astonishing $206 billion in structural value to citizens, and an additional $450 million yearly in terms of a quantified value of removing Houston’s toxic air pollutants, sequestering carbon and energy savings to buildings. The present tree canopy removes over 60,000 tons of air pollutants annually, including ozone and particulate matter.

“If we can do a good job of letting the public and policymakers understand the benefits of urban trees, we may be able to influence policy,” stresses Merritt. “We don’t want to stop growth, but to grow smarter.”

For the most part, the urban forests and trees have little protection. From 1992 to 2000, 17 percent of the region’s forest cover got converted to urban and residential areas — 486 square miles — and land development was declared Houston forests’ greatest threat. Developers typically bulldoze every tree because it is the least expensive modus operandi. The study also revealed that small trees provide only a fraction of the benefits that large trees do. To get a copy of the report, visit <www.houstonregion alforest.org>.

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