Houston’s Urban Forests

Houston urban forest
More than 33 million trees grow in Houston, according to a new FIA survey. Photo by Sarah Worthy.

Urban forests offer a wide range of environmental services, such as stormwater management, air pollution mitigation, reduced air temperatures (Urban Heat Island mitigation), wildlife habitat, aesthetic appeal and visual barriers. Since 1930, the U.S. Forest Service, Forest Inventory and Analysis (FIA) program has provided information on the amount, status, and character of forest land across the country.

In 2015 the Texas A&M Forest Service and Southern Research Station (SRS) FIA staff and researchers implemented the FIA urban protocol in Houston, Texas. A national reporting team led by SRS science delivery technology coordinator Dudley Hartel recently completed a summary of the findings of this analysis. Data were collected from 209 field plots within the city limits of Houston between March and September 2015. Texas A&M Forest Service inventory crews identified tree species, measured tree diameter and height, described tree status, health and damages, as well as taking other measurements.

“The Urban FIA protocol combines the well-established FIA data collection, quality control, and a data analysis system with the Forest Service’s i-Tree research that has a long tradition of conducting urban forest inventories and delivering data about urban forests and ecosystems services,” said Hartel. “This partnership offers an opportunity to use the strengths of each partner, and to build a consistent national inventory of urban forests.”

Prior to the development of the Urban FIA protocol, FIA collected data about trees within FIA-defined forest land excluding urban trees. Recognizing the importance of urban forests, and with direction from the 2014 U.S. Farm Bill, FIA initiated an annual urban forest inventory program.

Houston is the second city to complete a full inventory cycle under the UFIA. Like Austin, the first to complete a full UFIA inventory, Houston is ideal because of the Forest Service’s established relationships with the State of Texas and the Texas A&M Forest Service, and their willingness to collaborate and support the program. San Antonio is the third southern city to participate in the UFIA inventory program having begun data collection in 2017.

To establish a baseline for future monitoring, the field data were processed using FIA methodologies and i-Tree Eco modeling software that uses tree measurements and other data to estimate ecosystem services and structural characteristics of urban or rural forests.

live oak
Live oak shades a park near downtown Houston. Live oak is one of the most environmentally important tree species in the city. Photo by Pinke, courtesy of Flickr.

The Houston urban forest contributes significantly to the environment, the economy, and residents’ well-being. Throughout the city, an estimated 33.3 million trees, representing more than 63 species, provide a canopy cover of 18.4 percent. The canopy provides a wide range of environmental benefits including air pollution removal, reduced carbon emissions, carbon storage and sequestration, reduced energy use for buildings, stormwater capture, and many others.

The study also reveals that roughly 19.2 million (58%) of the city’s trees are located on private lands, and the tree species of most environmental importance are yaupon, Chinese tallowtree, sugarberry, live oak, water oak, and loblolly pine.

Change drivers that will threaten or negatively impact Houston’s forest structure, health, and environmental benefits include insect and disease infestations, non-native invasive plants, aging and loss of larger trees, changes in the management and use of the forest, and human population growth.

“This analysis captures the current urban forest resource, the ecosystem services, and values provided by it,” said Hartel. “The UFIA program provides for future monitoring with annual re-measurement and updates which is necessary to identify how the forest changes over time.”

Data from this inventory and report can be used by city managers, planners, elected officials, and local NGOs to inform long-term management plans and policies to sustain a healthy urban tree population and ecosystem services for future generations.

Interactive access to the Houston (and Austin) data is available at My City’s Trees, an application developed by the Texas A&M Forest Service.

Read the full text of the article.

For more information, contact Dudley Hartel at dhartel@fs.fed.us.

Access the latest publications by SRS scientists.