Defining and Assessing Urban Forests to Inform Management and Policy

Not all trees in the city are the same, yet current definitions of the urban forest include all trees growing in the urban environment. Such broad assessments may aggregate types of urban forest that differ significantly in usage and management needs. For example, street trees occur in highly developed environments, and are planted and cared for on an individual basis, whereas forested natural areas often occur in parkland, are managed at the stand level, and are primarily sustained by natural processes such as regeneration. We use multiple datasets for New York City to compare the outcomes from assessments of the entire urban forest, street trees, and forested natural areas. We find that non-stratified assessments of the entire urban forest are biased towards abundant canopy types in cities (e.g. street trees) and underestimate the condition of forested natural areas due to the uneven spatial arrangement of forested natural areas. These natural areas account for one quarter of the city’s tree canopy, but represent the majority of trees both numerically and in terms of biomass. Non-stratified assessments of urban forest canopy must be modified to accurately represent the true composition of different urban forest types to inform effective policy and management.

In a nutshell, this resource offers:

• Explanations of how urban forested natural areas are different than other types of trees found within cities.
• An argument for why urban forested natural areas should be measured differently than other types of trees in cities.
• Examples of how different measurement approaches yield very different estimates of species composition and forest structure.

How to use this resource:

• As a peer-reviewed citation to make the case for a natural-areas specific forest inventory in your city.
• As a resource to explain why urban forested natural areas are different than other types of trees within cities.

Author: Clara Pregitzer

Date published: July 2019

Point of contact: Clara Pregitzer, Deputy Director of Conservation Science, Natural Areas Conservancy, clara.pregitzer@naturalareasnyc.org 

Citation: Pregitzer, C. C.; Ashton, M. S.; Charlop-Powers, S. A.; D'Amato, A. W.; Frey B. R.; Gunther, B.; Hallett, R. A.; Pregitzer, K. S.; Woodall, C. W.; Bradford, M. A. 2019. Defining and assessing urban forests to inform management and policy. Environmental Restoration Letters. Vol 14.

Resource is available online here.