As Cities Grow, So Does the Need for Urban Trees

It's easy to rattle off the necessary and wide-ranging tasks that trees perform in urban areas. They're unarguably invaluable.

Trees are air-scrubbing, temperature-cooling, mood-improving, flood-mitigating machines. And as a new study published in Lancet Planetary Health points out, they can even save lives. Just look at Philadelphia, where researchers calculated that 403 premature deaths could be prevented in that city alone, simply by meeting the city's goal to improve its urban canopy by 30%.

Urban trees are obviously worth a lot. But how much?

According to a comprehensive study from U.S. Forest Service's Northern Research Station, the nation's urban canopies, which are home to an estimated 5.5 billion trees, provide roughly $18 billion in annual benefits to society through the removal of pollution from the air ($5.4 billion), carbon sequestration ($4.8 billion), reduced emissions ($2.7 billion) and improved energy efficiency in buildings ($5.4 billion). That's a lot.

Five states are particularly bankable when it comes to the economic perks associated with urban trees, per the Forest Service's findings. Florida leads the way with roughly $2 billion in annual savings while California, Pennsylvania, New York and Ohio follow in the ballpark of $1 billion of value per year. This doesn't mean, however, that these states necessarily have the most urban trees. Georgia, for example, has more urban trees (372 million) than California (343 million) while North Carolina (320 million) and Texas (309 million) both have more urban trees than Pennsylvania, New York and Ohio. Florida, which indeed has the most urban trees with an estimated 407 million leafy specimens, remains the most valuable.

Wait ... swampy, flat, hot and golf course-riddled Florida?

It's true. Florida has more urban trees than any other state. Florida's life-bettering verdant splendor is especially on full display in the northern half of the state. In fact, Tallahassee is among America's most tree-blessed cities with 55 percent total tree coverage — that's the highest percentage of any comparable city. (Interestingly, Tallahassee's arboreal claim to fame sprung from tragedy: In 1843, a catastrophic fire leveled large swaths of Florida's capital city. In addition to fire safety, one of the top imperatives when rebuilding Tallahassee was not only replacing the urban canopy that was lost but adding to it.)

Tree coverage crucial in expanding urban areas

The Sunshine State's hugely beneficial — not to mention somewhat surprising — urban lushness aside, the Forest Service study stresses the importance of preserving, protecting and planting city-dwelling trees in states where the amount of urban land area is expected to grow exponentially.

Between 2010 and 2060, the total urban land area of the U.S. is estimated to increase from 95.5 million acres to 163 million acres — a jump that would claim an area roughly the size of Montana or 8.6 percent of land area in the Lower 48. States with the greatest projected amount of urban land growth include California (9 million acres), Texas (7 million acres) and good old Florida at 6 million acres. Over a 50-year period, the spread of urban land in these three states, joined by North Carolina and Pennsylvania, will comprise an area the size larger than Connecticut.

States with the highest percentage of urban land overall consist of the nation's densest and most diminutive states, all of them located in the Mid-Atlantic and Northeast: Rhode Island (35 percent), Delaware (29 percent), Connecticut (28 percent), Massachusetts (23 percent) and New Jersey (23 percent). It's in these highly urbanized locales where the Forest Service notes that the "impact of current urban forests is likely greatest due to the relatively large proportion of urban land."

"Urbanization and urban forests are likely to be one of the most important forest influences and influential forests of the 21st century," says the study's lead author David Nowak, who works with the Forest Service's Inventory and Analysis Program. "A healthy and well-managed urban forest can help reduce some of the environmental issues associated with urbanization such as increased air temperatures and energy use, reduced air and water quality, and increased human stress, and ultimately help people living within and around urban areas."

Previous studies conducted within a 10-year period (2000 to 2010) found that the amount of urban land jumped from 2.6 percent (57.9 million acres) to 3 percent (68 million acres). States that experienced the highest amount of urbanization during this time were largely limited to the South and Southeast.

Not surprisingly, the states with the lowest value of urban trees are the ones where cities are small or far and few between, even though the states in question might be impressively forested: North Dakota, South Dakota, Wyoming, Montana and Idaho. For example, the value of North Dakota's urban trees when it comes to sequestering carbon, removing pollution, curbing emissions and reducing energy use was $7.3 million annually compared to the $1 billion-plus figures claimed by the top five states. Still, not too shabby for a sparsely populated state that's largest city, Fargo, boasts a population just north of 100,000.

States with large and heavily urbanized metro areas that are often thought of as being "woodsy" like Washington, Oregon and Colorado have urban trees that provide annual benefits amounting to $328 million, $136 million and $40 million, respectively. (I would have figured the amounts to be higher for these states.)

Unrelated to urban growth and the value of city-bound greenery per state detailed by Nowak, the Arbor Day Foundation, in cooperation with the Forest Service's Urban & Community Forestry Program and the National Association of State Foresters, oversees the Tree City USA program, which brings together more than 3,000 communities that have made a similar four-pronged commitment to protecting and expanding their urban canopies. Ohio has the most Tree City USA communities (243) following by Wisconsin (193), Illinois (181) and, you guessed it, Florida (179.) California, New Jersey, Georgia and Pennsylvania also have a healthy number of cities looking out for their urban canopies while communities in states such as Nevada, New Mexico, Louisiana and Vermont have some serious work to do.

Published in the Journal of Forestry, you can read the study in full — US Urban Forest Statistics, Values and Projections — to find out the life-bettering monetary value of urban trees in your state. You can also discover if your state is poised to experience rapid urban land growth and, in turn, requires larger urban canopies to allow for trees to do what they do best: improve air quality, mitigate climate change, boost energy efficiency and make our cities safer, healthier and more attractive places to live.