The Structural Value of Urban Forests — and What Pests Can Take

Urban forests have two kinds of value:

• Functional — what trees do: removing air pollution, filtering runoff and more (earlier pages in this series).
• Structural — the value of the tree itself.

Structural value

A tree's structural value is roughly the cost of replacing it with a similar tree, calculated from factors such as trunk area and health. This compensatory value can measure the losses from wildfire or pests. A 2002 USDA Forest Service study put the structural value of all urban forests in the continental U.S. at about $2.4 trillion.

A witness tree at Manassas National Battlefield Park. NPS.

Values that can't be replaced

Trees have intrinsic values beyond structure — especially in national parks, where many carry cultural, historical, aesthetic and personal meaning. The "Legacy Trees" at Manassas National Battlefield Park were alive during the First and Second Battles of Manassas; a tree planted today could never recapture that.

The Valuing Trees and Forests StoryMap, made by researchers at Virginia Tech and the Urban Ecology Research Learning Alliance (UERLA), explores notable trees at National Mall and Memorial Parks, Rock Creek Park and Monocacy National Battlefield.

Pests

Insects and diseases can kill trees and cut the health, structural value and sustainability of an urban forest. Pests favor different hosts, so the risk differs by species.

• Climate change raises the risk: stressed trees are weaker, destructive pests survive better, and invasive plants spread. See plants and climate change.
• Recovery: in a healthy, resilient forest, i-Tree Eco and i-Tree Hydro models show a fast rebound — other trees grow into the gap, and within 30 years ecological benefits return to pre-loss levels.

Next: other tree benefits · Previous: avoided runoff

References

• Ferguson, K., 2017, UERLA Resource Brief: Ecobenefits of National Capital Region Park Trees.
• Gallagher, A.M., 2021, Strategic Approaches to Tree Management Can Promote Climate Resiliency and Protect Ecosystem Services.
• Garner, J., 2018, UERLA Resource Brief: Quantifying Ecological Benefits of Trees in the National Capital Region.
• National Park Service, 2018, Witness Trees.
• Nowak, D.J., Crane, D.E., and Dwyer, J.F., 2002, Compensatory value of urban trees in the United States.
• Sherman, H., 2020, UERLA presentation: Forecasting Changes in Population Demographics and Forest Benefits in NCR Parks Using iTree Eco.
• Urban Ecology Research Learning Alliance, 2018, i-Tree Ecosystem Analysis: Urban Forest Effects and Values.

Sources

Based on "Structural Values of Urban Forests," part of Eco-Values of the Urban Forest: i-Tree Analysis, Urban Ecology Research Learning Alliance, National Park Service; a work of the United States government in the public domain.