The city of Ann Arbor conducted its first tree census last year and is making plans on how to manage one of its most important populations with a new Urban Forest Management Plan.
The plan will serve to guide city officials on how to shape and manage one of its principal assets, which they claim provides $4.6 million in benefits annually to local residents and business owners. The idea is to maintain a sustainable urban forest that maximizes these benefits.
The city will hold two public information meetings at Tappan Middle School (May 20) and Forsythe Middle School (June 1) on the Urban Forest Management Plan. Kerry Gray, an urban forest & natural resource planning coordinator with the city, will host the meeting. She can be contacted at kgray@a2gov.org and (734) 794-6430 ext. 43703. She agreed to answer a few questions over email about the Urban Forest Management Plan and how it will impact the city's urban forest.
Ann Arbor has been know for its trees, both big and small but always plentiful, for decades. How will its first Urban Forest Management Plan help it maintain and improve this valuable asset?
The Urban Forest Management Plan will provide the city with a framework to effectively manage the urban forest resource as a community asset, consistent with the values and needs of Ann Arbor residents. It will provide focus and direction to our urban forestry program and will ultimately help us to create a healthy and sustainable urban forest within the city.
The city claims that its urban canopy provides $4.6 million in benefits annually. How did the city come up with that number and could you provide some specific examples of those benefits?
When the city completed its comprehensive GIS tree inventory in 2009, it also had its contractor, Davey Resource Group, conduct an i-Tree analysis of the city's public trees. i-Tree is a peer reviewed software developed by the USDA Forest Service that quantifies the environmental services trees provide.
Some of the benefits that the i-Tree analysis found:
- Ann Arbor's public trees intercept 65 million gallons of stormwater annually. The total value of this benefit to the city is $519,895 per year or $10.98 per tree.
- The city's trees also reduce energy and natural gas use in Ann Arbor through shading and climate effects for an annual savings of $2.25 million.
The city finished its first comprehensive geographic information system-based street and park tree inventory last year. Could you explain what this type of inventory is and how it will help effectively manage the city's trees better than just the institutional memory of its staff?
In 2009, the city completed a comprehensive inventory of all of its street trees and park trees in mowed areas of parks. The inventory arborists collected data on each tree including the species, size, location, condition and maintenance needs. The inventory was added as a layer in the city's geographic information system (GIS), where it is monitored and updated. From the inventory, the city creates work orders for any maintenance (trimming, removals) or planting that occurs. The work order is attached to a tree so we have a history of all of the work that was performed on that tree. This system allows for both more consistent management over time and universal access by city staff to the information. Relying solely on institutional memory has its drawbacks because it is only good while the staff person who has it is working for the city, once they leave so does that knowledge.
Using the tree inventory, the city has begun the process of removing all trees that were listed as Priority 1 Removals (or the most hazardous trees). Once these are completed the city will finish the other priority removal categories and then move on to priority trimming.
The Emerald Ash Borer struck a big blow to the city's urban forest stock. Could you explain how significant of an impact this invasive species of insect had on Ann Arbor's urban forests, how the city's canopy is recovering and how long it will take to regain all of those lost trees?
The city removed 10,000 publicly managed ash trees -- 7,000 along streets and 3,000 in parks. In some neighborhoods, ash trees were the only street trees planted. These neighborhoods were impacted significantly when the ash trees were removed. Emerald Ash Borer reminded us that having a city tree population that has a diversity of tree species is key to maintaining a healthy and vibrant urban forest; an important lesson that we did not fully learn when we lost American Elms to Dutch Elm Disease. The importance of planting a diverse variety of tree species is a practice that we are applying to our tree planting programs today. The city has a goal of replanting 1,000 street trees per year, and since 2004 we have planted over 4,500 trees along streets and in parks.
Source: Kerry Gray, urban forestry & natural resources planner for the city of Ann Arbor
Writer: Jon Zemke
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