By Kent F. Kovacs, Robert G. Haight, Suhyun Jung, Dexter H. Locke, and Jarlath O’Neil-Dunne
New York, NY (October 23, 2013) – New research by the University of Arkansas and the U.S. Forest Service, “The marginal cost of carbon abatement from planting street trees in New York City,” gives the London plane tree, trees planted where they shade buildings, and the boroughs of Staten Island and Queens the highest marks for carbon abatement. The study estimated the discounted cost of net carbon reductions associated with planting and caring for street trees in New York City over 50- and 100-year horizons.
Urban trees can store carbon through the growth process and reduce fossil fuel use by lowering cooling and heating energy consumption of buildings through the process of transpiration, shading, and the blocking of wind. However, the planting and maintenance of urban trees come at a cost.
“Because they lower our energy costs, store carbon, and tend to make human beings feel better, we think of urban trees as being priceless,” said research Robert G. Haight. “But in New York City and every city that is spending money to plant and tend trees and remove them when they die, ‘priceless’ comes at a cost.”
The average discounted cost per ton of carbon abated from planting trees near buildings for a 100-year planning horizon ranges from $3,133 per ton of abated carbon for the London plane tree to $8,888 per ton for the Callery pear. That compares to an estimated annual cost per ton of carbon abatement in rural forestry programs of between $117 and $1,407 per ton of abated carbon.
“Cities are more expensive for both trees and people,” said Kent F. Kovacs. “It costs much more to plant and maintain an urban tree than it does a tree in a rural forest. While their location makes them more expensive, it also makes them more effective – street trees are reducing more carbon than rural trees because they provide shade and block wind thereby reducing energy consumption in nearby buildings in addition to sequestering carbon.”
In terms of carbon abatement, Kovacs and Haight found that the long-lived London plane tree is the city’s best bargain, with the cost of carbon abatement varying from $1,553 to $7,396 tons of carbon abated annually depending on the tree’s location.
The study describes planting locations with the lowest average cost of carbon abatement as being 60 feet west of nearby buildings that are more than 60 years-old, one or two-stories tall, entirely residential, and without nearby tree canopy. While New York City’s five boroughs all have locations that fit that description, a spatial examination of the City showed that Staten Island and Queens have more than other boroughs, making them more effective locations for tree plantings.
The study did not address the entire range of benefits associated with urban trees, according to the study’s authors. “In addition to carbon abatement, planting trees in urban areas provides many other benefits, which our study did not attempt to quantify. A comprehensive assessment of all the benefits of urban trees, rather than a focus on carbon alone, is appropriate for deciding how much investment to make in an urban forest,” Haight said.
Sources: “Study Evaluates Costs of Reducing Carbon with Street Trees” (news release); and “The Marginal Cost of Carbon Abatement from Planting Street Trees in New York City” (Journal Ecological Economics)