One of largest inventories of urban trees in the U.S.
Oaks and hornbeams line a street in Goose Hollow.
Nearly every planted street tree in Portland – almost 220,000 – has been mapped, measured, identified, and its health rated as part of the City’s first comprehensive inventory of street trees. Findings from the inventory, which was completed in September, will be presented at a free public event in Southeast Portland:
What: 2016 Tree Inventory Summit
When: Saturday, Nov. 5th, from 8:30 a.m. – 3:30 p.m.
All of Portland’s 96 neighborhoods were inventoried
More than 1,300 Portland-area volunteers trained by Portland Parks & Recreation Urban Forestry staff participated in the inventory. Beginning in 2010 and ending in September of this year, volunteers and Urban Forestry staff systematically gathered information on street trees in all of Portland’s 96 neighborhoods, compiling the most comprehensive and in-depth look ever at Portland’s street trees.
Reports on the last 11 neighborhoods will be available at the Nov. 5th event, where the public will also get its first look at citywide results. However, detailed reports about street trees in individual neighborhoods have been shared with interested groups as the inventory finished in each area. Those reports are posted and available here.
Volunteers collect data on street trees in Creston-Kenilworth (L) and Irvington (R).
Inventory Key findings
Street trees are providing $28.6 million worth of environmental, real estate value, human health, and other benefits in Portland annually. The overall value of Portland’s street trees is estimated at nearly $753 million.
A large variety of trees in Portland
A huge variety of tree species thrive in our climate. The inventory documented 162 tree types, most identified only to the genus level. This list would be even longer if trees were identified to the species level. Most trees are in good or fair condition.
Most common trees
Maples and trees in the rose family - mainly cherries, plums, hawthorns, and crabapples – dominate streetside plantings at levels well above what is considered healthy in community forestry. Over 50% of all street trees belong to only two families. There are nearly 20,000 Norway maple street trees in Portland, the most common tree, and a species on the nuisance list. Cherries are also common, and one in five is in poor condition. Increasing diversity can reduce risk and expense due to introduction of pests and disease.
These Norway maple (L) and ornamental plum trees (R) in Beaumont-Wilshire
are among Portland’s most common street trees.
Larger trees for more community benefits
Small form trees, which offer a fraction of the environmental and community benefits of large form trees, are increasing within the street tree population. This is true even for planting sites that could accommodate large trees. Dogwoods and snowbells are among the smaller trees showing a sharp rise in popularity in recent years.
More year-round green needed
Broadleaf deciduous trees, which shed their leaves each winter, are the dominant tree in all neighborhoods, particularly east of the Willamette River where they represent between 80% to 98% of street trees. Opportunities to diversify plantings, including more evergreen species to capture winter rains and reduce storm water volume, exist in all areas of the city.
Evergreen silverleaf oaks provide benefits year round (L). Glossy evergreen leaves of a southern magnolia (R).
Setting Urban Forest Policy and Priorities
Preliminary findings from the survey have already been influencing the city’s tree-related policies. For example:
- Seeing how vulnerable Portland is to catastrophic tree losses from pests and diseases as a result of our over abundance of maples, Urban Forestry now requires property owners to plant alternative species as street trees.
- Given the low percentage of evergreen trees being planted, Urban Forestry has increased the number of evergreen trees on its approved planting lists from a handful to more than 20.
Empowering Portlanders and growing forest stewardship
Angie DiSalvo, Urban Forestry Outreach and Science Supervisor, has been involved with the inventory since the beginning. She organized the initial counting of trees in the Concordia neighborhood in Northeast Portland back in 2010. She says the inventory was an opportunity to partner with Portlanders from diverse backgrounds to gain a greater understanding of issues facing the urban forest and their neighborhood street trees in particular.
“Together we were able to quantify the state of street trees everywhere in the city. The data produced is empowering residents to take science-based actions to improve the urban forest right where they live.” Neighborhood Tree Teams were formed by volunteers as part of the inventory process. These volunteers will use the results to prioritize neighborhood-based tree projects. “These can range from helping low-income residents remove and replace dead street trees to conducting educational tree walks and providing pruning and care for young trees,” says DiSalvo.
2016 Street Tree Inventory volunteers at a Brentwood-Darlington inventory work day
To learn more detail about the inventory project results and how they will be used, please join us at the 2016 Tree Inventory Summit on Saturday, Nov. 5th. Pre-registration is appreciated and can be submitted here.