The United States Forest Service estimates that tree cover in urban parts of the United States is declining at four million trees per year. That’s the same amount of iPhones 4S that sold over a single weekend when they debuted in 2011.  While an iPhone owner could argue Apple and their products are an important facet of technology and urban living, can they prove smartphones are necessary to a city’s landscape?

“Trees are an important part of the urban landscape,” according to Michael T. Rains, Director of the Forest Service’s Northern Research Station. “They play a role in improving air and water quality and provide so many environmental and social benefits. As our Forest Service Chief says, ‘…urban trees are the hardest working trees in America.’

Twenty cities, all designated Arbor Day Foundation Tree Cities- a program that works closely with the Forest Service -were included in the study with slightly over half of the cities having been Tree Cities for over twenty years.

Seventeen of the cities had tree cover decline and sixteen saw increases of impervious cover -pavement and rooftops.

Cities that saw the biggest annual loss of tree cover were Houston,  Albuquerque, and New Orleans.  New Orleans’ loss of trees was expected and is likely due to Hurricane Katrina. 

Atlanta had the highest percentage of tree cover at 53.9% and Denver had the lowest at 9.6%. New York City predictably had the highest percentage of impervious cover and Nashville had the lowest at 17.7%  Houston and Albuquerque both saw large percentages of annual tree loss and increase of impervious cover.

Using a program called “i-Tree Canopy” researchers were able to compare digital satellite images taken recently to images  taken approximately five years ago to determine the rate of tree cover loss, changes in cover types and measurements.

It’s no secret that trees are important to ecosystems and the Forest Service estimates that urban trees provide benefits “three times greater than tree care costs, as much as $2,500 in environmental services such as reduced heating and cooling costs during a tree’s lifetime.”

“Our urban forests are under stress, and it will take all of us working together to improve the health of these crucial green spaces,” said U.S. Forest Service Chief Tom Tidwell.  “Community organizations and municipal planners can use i-Tree to analyze their own tree cover, and determine the best species and planting spots in their neighborhoods. It’s not too late to restore our urban forests – the time is now to turn this around.”