Portland's urban trees are the soul of a city known for its progressive land-use planning and extensive green infrastructure. Trees are a crucial part of the cityscape, softening and beautifying the built environment, improving neighborhood safety and livability, and providing vital ecosystem services such as air purification, temperature mitigation, and stormwater interception. Effective and efficient management of the urban forest relies on an understanding of the structure and function of the resource, as well as the benefits it provides.
Canopy cover has been identified as an important measure of urban forest health by the City of Portland. Canopy cover is a measure of Portland Parks & Recreation's bureau-wide performance, and is also cited as an important indicator in the Portland Urban Forest Management Plan (2004), Urban Forest Action Plan (2007), Climate Action Plan (2009), and the Portland Plan (2012). Monitoring Portland's tree canopy is important in order to understand how canopy may be changing, and understanding canopy trends will allow managers to make important decisions regarding management strategies.
To monitor trends in Portland's urban forest canopy, PP&R established a protocol for measuring canopy change using point interpretation of aerial photos. Canopy cover was measured for 2000, 2005, and 2010
In 2007, PP&R released its first canopy report, where it identified the replacement value of Portland’s public tree resource as over $2.3 billion and the structural value of the entire urban forest canopy as nearly $5 billion