City of Delaware tree inventory update
The Delaware street tree inventory is in full swing again as the weather has warmed up and the leaves have emerged, making tree identification much easier. The census is an ongoing project that began in 2010 with a key goal of aiding the city in maintaining the tree lawn, the grassy area between the sidewalk and the street. According to David Carey, a member of the City’s Shade Tree Commission, “the tree inventory raises public awareness, helps keep tabs on the trees, and helps with planning.”
The data is being collected by the Delaware County Master Gardeners at no cost to the city. The information being gathered for each tree includes the street address location, its GPS coordinates, the species, trunk diameter, significant health issues, and the presence of overhead wires.
As of October 2011, Master Gardeners had spent 400 hours and inventoried 3,039 trees in central Delaware. More than half (51 percent) of these trees are maples, including many silver, sugar, Norway, and red maples. The other most common tree species are flowering crabapple (7 percent), callery pear (6 percent), Japanese tree lilac (5 percent), oak (5 percent), and linden (4 percent).
Studies have shown that a wide diversity of street tree species is a critical component in helping protect against the severe penetration of pests, such as the emerald ash borer or the Longhorned Asian Beetle. Pests generally are not limited to one cultivar or species, but attack all the trees in the same genus, or family. There were 1,546 ash trees in Delaware in 2006, when the Emerald Ash Borer (EAB) was first identified in the city. Over the past 6 years, this pest has killed or infested nearly all of the city’s ash trees and caused an estimated loss in value of the urban forest of $1 million. Due to a paucity of funds, only 186 of these ash trees have been replaced. The Asian Longhorned Beetle (ALB) has been found near Cincinnati and is known to attack maple trees. It has not spread to Delaware County, but it is important that this pest be controlled or it could have a major impact on the street trees in central Delaware.
The City of Delaware is proud of its urban forest. Every year since 1981, it has been recognized as a Tree City USA by the National Arbor Foundation. Central Delaware has many large, stately trees, some of which are found in the tree lawns. Twenty-two trees in central Delaware have massive trunks that are greater than 40” in diameter, including 15 silver maples.
The data that is collected is being shared with the City of Delaware and The Ohio State University’s School of Environment and Natural Resources (SENR). The university researchers use i-Tree software to quantify the benefits of urban forests. According to Sakthi Subburayalu, a research scientist at SENR Urban Forestry, the trees that have been inventoried provide Delaware with $82,484 (average $27.14 per tree) in energy savings (as trees cool in summer and lessen heat loss in winter), $86,468 (average $28.45 per tree) in storm water mitigation, $13,131 (average $4.32 per tree) in air quality benefits, $71,837 (average $23.64) in stored carbon and $91,298 (average $30.14 per tree) in property value enhancement. In total, central Delaware’s street trees contribute $284,388 (average $93.58 per tree in environmental benefits. Bigger trees provide greater environmental impact.
There are about 9,000 more trees in the City of Delaware to inventory before the census is complete. Susan Logan, the project leader for the Master Gardeners believes this work can be done in a couple of years, largely due to the increased collaboration between the City, OSU, and the Master Gardeners. Most of the remaining trees are in the new developments. Chuck Rexrode, the city’s contract forester, has documented all the trees that have been planted in the developments since 1991. Maureen Grener, Delaware’s GIS coordinator, has been able to generate GIS maps of these developments, including the trees. This information will be provided to the data collectors, whose main tasks will be to identify, measure, and comment on the health of the trees. OSU continues to provide the project with PDAs and custom software to use in collecting the data.
National Tree Benefits Calculator is a free online tool that is available at treebenefits.com/calculator. It can be used to estimate the environmental and economic value of any tree in the United States, given its location (ZIP code), species, and size. This calculator, which was conceived and developed by Casey Trees and Davey Tree Expert Co., is also based on i-Tree’s street tree assessment tool.
Nancy F. Traub is an OSU Extension Master Gardener volunteer.