Quantifying The Environmental Role of Roadside Trees

One way to value roadsides is the scenic views they provide, a window into the soul of the places through which they pass and a pivotal factor in facilitating 1.9 billion tourism person-trips and a trillion dollars of economic impact each year.

Another way to quantify the value of roadside vegetation is by its ability to sequester or capture and hold carbon emissions from escaping into the atmosphere.

According to a pilot study of the National Highway System (NHS) by the Federal Highway Administration, the 3.4 million acres of roadside vegetation including trees, grasses and shrubs in the unpaved right of way along 163,000 miles of Interstates and U.S. Highways is able to clean the air of the equivalent of the emissions from 2.6 million passenger cars each year.

If the voluntary Chicago Climate Exchange hadn’t been torpedoed by members of a particular party in Congress, at the hypothetical carbon price of $20 per metric ton, the sequestration by vegetation along just 4% of the nation’s roadsides would equate to a potential value of $8.5 to $14 billion.

Nonetheless, the value to our planet Earth remains priceless.

Nationwide, including all of the areas where they are so difficult to grow, trees (deciduous, conifer and mixed,) make up 25% of all roadside vegetation along the NHS or about 827,000 acres total.

Roadside trees alone, growing in the right of way of major highways, sequester half of the carbon emissions captured by vegetation or nearly 2 million tons of carbon emissions every year.

In part, because North Carolina precariously clings to 60% of its tree cover, a good deal of the roadside sequestration occurs in this state, where I live. But while other states from Oregon to Maryland are using transportation enhancement grants to plant millions of trees, two North Carolina State Senators, Harry Brown of Jacksonville and Bob Rucho of Mathews, did their best during the recent session of the General Assembly to win back North Carolina’s reputation for being backward.

Working on behalf the outdoor billboard industry, Brown and Rucho pushed through a bill that will soon enable the clear-cutting of 575 miles of publicly-owned roadside trees or enough to go from one end of the state to the other. This is on top of what had already been generously permitted so the 8,000 private outdoor billboards mooching off the North Carolina public right of ways could be visible and purposely distracting to drivers even though they are utilized by fewer than 1 in 10 North Carolinians.

Most of the clear-cutting in North Carolina will occur along major highways that are part of the National Highway System. While representing only 4% of the nation’s roads, the NHS carries 40% of its traffic including 90% of all tourism traffic nationwide, 81% of business travel and the 37 million visitor person trips taken in North Carolina.

It is impossible to speculate on the motives of these two senators but before you deem all North Carolinians as deserving of the epitaph, “backward,” remember the scientific polls showing that 7 out of 10 North Carolinians consider outdoor billboards to be a “desecration” on our state.

As home to programs such as the Green Plus Certification and the Center for Sustainable Tourism at ECU, North Carolinians do understand the triple-bottom-line of social, environmental and financial responsibility and that the outdoor billboard legislation fails miserably on all three measures.

It may not be long before North Carolinians rise up and reclaim control of our roadsides, but it will be decades before the damage from outdoor billboards is repaired and before the state optimizes the far greater value of its roadsides instead for the source of scenic beauty and a cleaner environment.