It was a sight more common than usual this past summer: a tree too thirsty to live became another casualty to the drought. City workers would either remove the tree, or, if they were too late, it would fall, possibly on power lines, cars or a house.
Texas Forest Service researchers said the current drought claimed the lives of about 5.6 million trees in cities, or roughly 10 percent of the state's urban forests, in the agency's first attempt at counting urban tree loss.
Those trees will cost at least $560 million to remove and provided about $280 million annually in environmental and economic benefits, a study released Wednesday said.
Austin officials said the impact hasn't been as bad here, with about 1,200 trees lost on city ground during a year of drought, because of more drought-resistant trees and less development than other urban areas.
The death toll is likely to continue to tick upward as already-dead trees become more obvious when they don't grow leaves in the spring and more trees die from diseases, said the study's leader, Pete Smith.
"The damage is widespread, but it varies widely from really heavy amounts of loss to not really heavy amounts of loss," Smith said.
The state's urban areas, including large metropolitan areas like Houston or Austin, as well as smaller cities like Killeen, have a total of about 60 million trees, Smith said. One of the most dramatic changes came in Houston's Memorial Park, where thousands of pine trees were lost.
Smith said he was uncomfortable with drawing regional conclusions of urban tree loss for any of the places where samples were taken, including Austin.
Researchers took satellite images from 3.9 million acres in 15 metropolitan areas from 2010 and compared them with images of the same places in early October 2011 and counted the number of trees that were lost, Smith said.
"Fortunately, Austin hasn't been hit as hard as other areas," said Walter Passmore, a urban forester for the city's Parks and Recreation Department. "However, if we have another drought this summer, we're likely to see some significant impacts."
Passmore said that from October 2010 to September 2011, one of the driest periods of the drought, the city removed about 1,200 dead trees from public areas, compared with a typical annual loss of about 800 trees. However, there are about 300,000 trees on city lands, so the loss is less than half a percent, Passmore said.
Some trees found in the Austin area, such as the Texas live oak, are more attuned to droughts and have natural reserves to make it through a hot and dry year like 2011, Passmore said. But with so many trees already having gone through their reserves, another year of drought may kill off at least double the number of trees, he said.
Since the fall, the city has shifted to planting smaller, less-water dependent trees because of the drought, said city arborist Michael Embesi.
"Everyone thinks that the recent rains might let their trees perk back up, but it may be too little, too late," Smith said, adding that people should be careful planting new trees as they may have an especially tough time making it through another hot and dry summer.
The city is expecting a higher mortality rate for the infant trees being planted, Embesi said, but they are hoping to plant at least some new trees during the drought.
Urban trees are important because they shade buildings to reduce cooling costs, slow down runoff that can cause flooding and create a distinct sense of place, Embesi said.
Those factors are used in determining the $280 million estimated value of losing 5.6 million urban trees, computed by the National Tree Benefit Calculator, a website that researchers used to value trees by their typical species, size and location. The calculator was developed by a nonprofit group that protects urban trees and a tree and lawn company.
If the drought continues, the Forest Service researchers said they may do another survey in October.
The study released Feb. 15 shows similar tree losses in urban areas as a December study showed for forests. The December preliminary report said the drought killed as much as 10 percent of the state's forest cover — as many as 500 million trees in outlying areas.