Urban Forest Study Values Shade, Quantifies Privet Problem

Urban forests like this one at Nashville's Lenox Village often marry maintained and unmaintained treelines. (photo by Tim Phelps)

Urban forests like this one at Nashville’s Lenox Village often marry maintained and unmaintained treelines. (photo by Tim Phelps)

Tennessee’s city trees provide environmental benefits valued at $650 million a year. That’s according to the U.S. Forest Service, which has completed its first inventory of the state’s urban forest.

Shade trees save Tennesseans an estimated $66 million annually. The benefit comes primarily in protecting rooftops from the blazing summer sun. But in the winter, trees can also block cold winds.

Tim Phelps of the state Forestry Division says the numbers help make the case for planting and protecting trees.

“Once people realize the impact that a strategically placed tree can have on their energy savings, it affects their pocketbook. And when you affect your pocket book, that’s a resounding influence.”

The state’s urban trees also store and remove from the air more than half-a-billion dollars worth of carbon and other pollutants each year.

Tennessee is just the second state in the country to have it’s urban landscape inventoried by the U.S. Forest Service. The study is meant to set a baseline for measuring future health.

Problem with Privet

Invasive privet is difficult to trim back because it quickly sprouts back from roots and stumps. (image courtesy UT AgResearch)

Invasive privet is difficult to trim back because it quickly sprouts back from roots and stumps. (image courtesy UT AgResearch)

While the state tree – the Tulip Poplar – is the second most common species in Tennessee, it’s number 15 in urban areas. And number one is held by an invasive species known as Chinese privet.

State forestry officials aren’t exactly surprised. But they are concerned with the findings.

Phelps says Chinese privet started as an ornamental plant used in landscaping. Now it accounts for one in every 10 trees found in Tennessee’s urban forests.

“It basically invades a site and completely dominates it. It provides great structure, great food source for birds and things of that nature, but it reduces the regeneration of our native plants.”

Phelps says Chinese privet is choking out native saplings that should replace aging trees as they die off.

Currently, researchers at UT are testing herbicides to help eradicate privet.

A Chinese privet infestation (photo by David J. Moorhead, University of Georgia)

A Chinese privet infestation (photo by David J. Moorhead, University of Georgia)

Here’s a link to the complete 54-page study.

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