Tools to Assess Ecosystem Services and Values
To improve urban forest planning, management and design, managers need the ability to quantify their local urban forest composition and its associated ecosystem services and values. This information can be used to develop better management plans to sustain or enhance environmental quality and human health for current and future generations in urban areas.
Our research unit focuses on field measurements and monitoring of urban vegetation structure (e.g., species composition and distribution, number of trees and tree sizes) and its effects on various ecosystem attributes (e.g., air and water quality, air temperature, soils). To aid in improving urban forest management, various tools have been developed to quantify urban forest structure and its effects on ecosystem services and values. The primary model developed has been the Urban Forest Effects (UFORE) model. This model has been incorporated within a suite of free, technically supported, urban forest software tools called i-Tree. Through i-Tree, UFORE now includes automatic report generation, basic mapping capabilities by linking with National Land Cover Data (NLCD 2001), and a species selection program to help select the most appropriate species based on desired tree functions.
Assessing Urban Forest Structure
The first step in quantifying ecosystem services is to have an accurate measure of the vegetation structure within the area of interest. This measurement is conducted in two ways:
- Aerial assessments
- Ground-based assessments
Aerial Assessments – This approach uses aerial imagery to develop cover maps (e.g., from high-resolution color-infra-red digital images or medium resolution satellite data) or determine percent cover types (e.g., photo-interpretation) within the area of interest. Aerial assessments provide a quick estimate of the tree and other surface cover, but only provide limited two-dimensional information on the vegetation.
Ground-based Assessments – This approach involves random sampling of the area of interest to determine the physical attributes of the vegetation and other surface characteristics. Within i-Tree, several tools are available to aid in locating field sample locations and collect the required data to assess ecosystem services. This ground-based information is necessary to determine many critical forest attributes that can not be obtained from aerial imagery (e.g., number of trees, tree sizes, species composition, leaf area and biomass, tree biomass). This structural information is quantified for the tree population within UFORE to aid in urban forest management (e.g., by providing total tree species distribution by land use; risk to various pests) and in quantifying ecosystem services.
Assessing Ecosystem Services
Based on the structural field data and local hourly air pollution and meteorological data, the following ecosystem services are calculated within UFORE:
- Hourly amount of pollution removed by the urban forest, and its associated percent air quality improvement throughout a year. Pollution removal is calculated for ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide and particulate matter (<10 microns).
- Hourly urban forest volatile organic compound (VOC) emissions and the relative impact of tree species on net ozone and carbon monoxide formation throughout the year.
- Total carbon stored and net carbon annually sequestered by the urban forest.
- Effects of trees on building energy use and consequent effects on carbon dioxide emissions from power plants.
UFORE-Hydro – a new tool to assess urban forest effects on stream flow and water quality has been developed. UFORE-Hydro (Urban Forest Effects Hydrological Model) is a semi-distributed, object-oriented, topographical, physical based watershed scale hydrological model with a graphical user interface (GUI) and auto-model calibration. This model is specifically designed to simulate tree and impervious surface effects on stream flows based on local watershed surface characteristics and weather data, with the model calibrated against measured stream flow data.
Assessing Ecosystem Values
Ecosystem service valuation is based on externality values derived from the literature (for carbon and air pollution) and average state energy values for building energy effects. The model estimates the ecosystem service magnitude (e.g., tons, kWh) and multiplies this amount by the associated value from the literature. Structural value of the forest is based on the Council of Tree and Landscape Appraisers valuation procedures.
Current Tool Development
i-Tree has two main development goals over the next five years:
1) Integration of programs
2) Enhanced spatial analyses
Integration – within i-Tree, there are two main programs: a) UFORE, which assesses ecosystem services and values over any sized area, and b) STRATUM, which assesses ecosystem services and values for street populations. This work is designed to integrate these two programs into one program. Thus, users will be able to sample or inventory areas or streets to quantify ecosystem services and values in one tool. This integration will combine the best parts of both tools within one program. Added capabilities to UFORE will include cost-benefit analyses and property valuation.
Spatial Analyses – spatial integration and mapping within i-Tree has begun, with many projects currently under way. This work merges the field data assessments with the aerial cover maps to help illustrate the distribution of ecosystem services. This work is also integrating field-derived ecosystem service information with several spatial modeling components to help determine how forest cover and ecosystem services will likely change in the future and which forest structures are best to optimize ecosystem services to sustain environmental quality and human health. Various spatial tools in development include programs to determine the highest priority planting areas based on tree and human population distribution, how air pollution concentration may vary based on locations relative pollutant sources in cities (risk to exposure); and how tree and impervious locations can affect local air temperatures. This temperature mapping will be integrated with other programs to help determine how changes in tree cover (and air temperatures) affect air pollution removal and concentrations, volatile organic compound emissions, vehicle emissions, and human comfort. Other programs in development will allow users to alter tree cover within land use categories to illustrate what the new cover would look like in the future and the associated changes in ecosystem services and values due to the cover changes. In addition, tree population projection models have been built and existing land use projections will be incorporated to help determine likely future changes to tree and impervious cover (and ecosystem services) in urban and urbanizing regions. The ultimate goal of these spatial tools is to help planners or managers determine optimal landscape structure to sustain or improve environmental quality and human health at the local to regional scale in urban or urbanizing landscapes.Based on a hybrid multi-layer bigleaf model that calculates hourly tree transpiration and gas exchange using leaf area calculations and local hourly weather and pollution data. Particle pollution removal is based on average measured values of pollutant deposition to leaf surfaces
Based on protocols of the Biogenic Emissions Inventory System that use leaf biomass calculations by species and local hourly weather data
Based on allometric equations to calculate tree biomass that use tree species, diameter and height data; and local growing conditions and tree health to estimate growth rates
Based on research of McPherson and Simpson on tree effects on building energy use nationally. Model uses sampled tree location and height information to determine seasonal energy effects
Improved understanding and appreciation of ecosystem services provided by urban vegetation. Improved urban forest management to enhance environmental quality and human health in urban and urbanizing areas.
Urban forest field data from UFORE exist for numerous areas: Atlanta, GA; Baltimore, MD; Baltimore County, MD; Beijing, China; Boston, MA; Brooklyn, NY; Calgary, Alberta; Casper, WY; Freehold, NJ; Florence, Italy; Fresno, CA; Fuenlabrada, Spain; Gainesville, FL; Gainesville, GA (street trees); Greenville-Spartanburg, SC; Golden, CO; Greenwich, CT (street trees); Halifax, Nova Scotia; Hartford, CT; Houston, TX; Hefei, China; Indiana (state assessment); Jersey City, NJ; Kelowna, British Columbia; Kennedy Meadows, CA; Kent, OH; Little Rock, AR (street trees); Louisville, KY (campus); Milan, Italy, Minneapolis, MN; Moorestown, NJ; Morgantown, WV; Mount Union, OH (campus); Nebraska City, NE; New York, NY; Ningbo, China; Northern KY (3 cities street trees); Oakville, ON; Petrozavodsk, Russia; Philadelphia, PA; Piazzola, Italy (street trees); Porto Alegre, Brazil (parks); Prince Williams Forest, VA; San Francisco, CA; San Juan, PR, Santiago, Chile; Syracuse, NY; Tampa Bay, FL; Toronto, Ontario; Portland, OR (parks); Visalia, CA; Washington, DC; Wilmington, DE; Wisconsin (state assessment); and Woodbridge, NJ. Areas currently or soon to be analyzed are: Baton Rouge, LA; Chicago, IL; Colorado (state assessment); Fredericton, New Brunswick; Los Angeles, CA; Miami, FL; New Jersey (state assessment); Phoenix, AZ; Scranton, PA; Shenzhen, China; Singapore, and Tennessee (state assessment). Many of these cities are analyzed in cooperation with local, state or federal institutions.
UFORE can used to provide necessary information on the urban forest resource and its ecosystem services to improve urban forest management and bolster urban forestry programs. As an example, based in part on UFORE results, Conectiv Electric Utility negotiated to have $1 million of an air pollution fine donated to the New Jersey Tree Foundation (a nonprofit organization working with the Community Forestry Program) for a massive Urban Airshed Reforestation project in the Camden, NJ area. Trained volunteers are planting 3-inch caliper shade trees in the communities most directly affected by the air pollution that led to the fines. In Oakville, Ontario, the Town is using UFORE results to create new programs and policies to sustain tree cover and environmental quality for future generations:
- Oakville's Urban Forest - Our solution to our pollution (pdf)
- Tree Canada helps support UFORE analysis of City of Oakville's forests
Results from UFORE can also be used to help determine the effect of trees on aspects of the environment that are regulated by the U.S. Environmental Protection Agency (US EPA). As the Clean Air and Clean Water Acts impose regulations that affect urban areas, the regulations impact urban development, funding, and management at the local and state levels. As trees affect the environment, the ability to quantify these effects could lead to the incorporation of urban vegetation management strategies (and potential funding) to help meet these environmental regulations. Urban trees can be incorporated as an emerging measure (pdf) with State Implementation Plans to meet clean air regulations. Urban trees could also be used to potentially meet clean water regulations associated with Total Maximum Daily Loads (TMDLs) and storm water programs.
Wang, J., T.A. Endreny, and D.J. Nowak. 2008. Mechanistic simulation of urban tree effects in an urban water balance model. Journal of American Water Resource Association. 44(1):75-85.
Heisler, G.H., J. Walton, I. Yesilonis, D. Nowak, R. Pouyat, R. Grant, S. Grimmond, K. Hyde, and G. Bacon. 2007. Empirical modeling and mapping of below-canopy air temperatures in Baltimore, MD and vicinity. In: Proceedings of Seventh Urban Environment Symposium, sponsored by American Meteorological Society, San Diego, CA. 7 p.
Nowak, D.J., A. Buckelew Cumming, D. Twardus, R. Hoehn, M. Mielke. 2007. National Forest Health Monitoring Program, Monitoring Urban Forests in Indiana: Pilot Study 2002, Part 2: Statewide Estimates Using the UFORE Model. Northeastern Area Report. NA-FR-01-07. 13 p.
Nowak, D.J., R. Hoehn, D.E. Crane, J.C. Stevens and J.T. Walton. 2007. Assessing urban forest effects and values: New York City’s urban forest. USDA Forest Service, Northern Resource Bulletin NRS-9. Newtown Square, PA. 24 p.
Nowak, D.J., R. Hoehn, D.E. Crane, J.C. Stevens and J.T. Walton. 2007. Assessing urban forest effects and values: Philadelphia’s urban forest. USDA Forest Service, Northern Resource Bulletin NRS-7. Newtown Square, PA. 24 p.
Nowak, D.J., R. Hoehn, D.E. Crane, J.C. Stevens and J.T. Walton. 2007. Assessing urban forest effects and values: San Francisco’s urban forest. USDA Forest Service, Northern Resource Bulletin NRS-8. Newtown Square, PA. 24 p.
Nowak, D.J., D.E. Crane and J.C. Stevens. 2006. Air pollution removal by urban trees and shrubs in the United States. Urban Forestry and Urban Greening. 4:115-12.
Nowak, D.J., R. Hoehn, D.E. Crane, J.C. Stevens and J.T. Walton. 2006. Assessing urban forest effects and values: Minneapolis’ urban forest. USDA Forest Service, Northeastern Resource Bulletin, NE-166. 20 p.
Nowak, D.J., R. Hoehn, D.E. Crane, J.C. Stevens and J.T. Walton. 2006. Assessing urban forest effects and values: Casper, WY’s urban forest. USDA Forest Service, Northern Resource Bulletin NRS-4. Newtown Square, PA. 20 p.
Nowak, D.J., R. Hoehn, D.E. Crane, J.C. Stevens and J.T. Walton. 2006. Assessing urban forest effects and values: Washington D.C.’s urban forest. USDA Forest Service, Northern Resource Bulletin NRS-1. Newtown Square, PA. 24 p.
Byun, D., S. Kim, B. Czader, D. Nowak, S. Stetson, and M. Estes. 2005. Estimation of biogenic emissions with satellite-derived land use and land cover data for the air quality modeling of Houston-Galveston ozone nonattainment area. J. Environ. Manage. 75: 285-301.
Davey resource Group. 2007. Environmental Service Report: ί-Tree Benefit Analysis for the Cities of Bellevue, Covington, Florence, Fort Thomas, and Newport, Kentucky.
Nowak, D.J. 2005. The Urban Forest Effects (UFORE) Model: International analyses of urban forest ecosystem structure and functions. Proc. of the National Association of Environmental Professionals 30th Annual Conference. Alexandria, VA. Conference proceedings published on CD. 6 p.
Yang, J., J. McBride, J. Zhou, and Z. Sun. 2005. The urban forest in Beijing and its role in air pollution reduction. Urban Forests and Urban Greening 3(2): 65-78.Buckelew Cumming, A., D.J. Nowak, D.B. Twardus, R. Hoehn, M. Mielke, and R. Rideout. 2007. Urban Forests of Wisconsin 2002: Pilot Monitoring Project 2002. USDA Forest Service, Northeastern Area State and Private Forestry Report, NA-FR-05-07. 33 p.
Lozano, J.V. 2004. Distribucion del arbolado urbano en la ciudad de Fuenlabrada y su contribucion a la calidad del aire. Ciudad y Territorio, Estudios Territoriales 36(140):419-427.
Nowak, D.J. 2004. Assessing environmental functions and values of veteran trees. 2004. Proc. of the International Congress on the Protection and Exploitation of Veteran Trees. Torino, Italy. p. 45-49.
Nowak, D.J., M. Kurodo, and D.E. Crane. 2004. Urban tree mortality rates and tree population projections in Baltimore, Maryland, USA. Urban Forestry and Urban Greening. 2(3):139-147.
Heisler, G.M., R.H. Grant, D.J. Nowak, W. Gao, D.E. Crane, and J.T. Walton. 2003. Inclusion of an ultraviolet radiation transfer component in an urban forest effects model for predicting tree influences on potential below-canopy exposure to UVB radiation. Proceedings of SPIE Vol. 5156 Ultraviolet Ground- and Space based Measurements, Models, and Effects III, edited by James R. Slusser, Jay R. Herman, Wei Gao. SPIE, Bellingham, WA. pp. 228 – 235.
Nowak, D.J., D.E. Crane, J.C. Stevens, and R. Hoehn. 2003. The Urban Forest Effects (UFORE) model: field data collection procedures. USDA Forest Service, Syracuse, NY. 30 p.
Nowak, D.J., D.E. Crane, J.T. Walton, D.B. Twardus, and J.F. Dwyer. 2003. Understanding and quantifying urban forest structure, functions, and value. Proceeding of the 5th Canadian Urban Forest Conference. Oct 7-9, 2002. Markham, Ontario. pp. 27-1 – 27-9.
Nowak, D.J., D.E. Crane, J.T. Walton, J.C. Stevens, F. Escobedo, G. Heisler, R.E. Hoehn, C.J. Luley, J. Bond, G. Ina, M. Binkley, L. Tian, J. Zhou, T. Endreny, J. Wang, C. Post. 2003. A tool for assessing urban forest structure, functions and benefits. Proc. of the 2003 National Urban Forest Conference. San Antonio, TX. p. 37-39.
Escobedo, F., J. Hernandez, C. Luz de la Maza, M. Rodriguez, D.J. Nowak, and D.E. Crane. 2002. Determinando los efectos del arbolado sobre la calidad del aire: Caso Santiago de Chile (Determining the effects of urban forests on air quality: the case of Santiago, Chile). Seminario Internacional “Funciones y Valores del Arbolado Urbano”. University of Chile, Facultad de Ciencias Forestales. Santiago, Chile (published on CD).
Ham, D., C. Post, D. Vanblaricom, D. Lipscomb, D. Hargett, and D.J. Nowak 2003. Analysis of the explosively urbanizing South Carolina Interstate 85 corridor. Proc. of the 2003 National Urban Forest Conference. San Antonio, TX.
Nowak, D.J., D.E. Crane, J.C. Stevens, and M. Ibarra. 2002. Brooklyn’s Urban Forest. USDA Forest Service Gen. Tech. Rep. 290. 107 p.
Nowak, D.J. and D.E. Crane. 2002. Carbon storage and sequestration by urban trees in the United States. Environ. Poll. 116(3): 381-389.
Nowak, D.J., D.E. Crane, and J.F. Dwyer. 2002. Compensatory value of urban trees in the United States. J. Arboric. 28(4): 194-199.
Nowak, D.J. and J.F. Dwyer. 2002. Assessing the value of urban forests in the United States. In: 2001 Society of American Foresters National Conference Proceedings. Denver, CO. p. 237-241.
Nowak, D.J., R.H. Hoehn, and D.E. Crane. 2007. Oxygen production by urban trees in the United States. Arboriculture and Urban Forestry. 33(3):220-226.
Nowak, D.J. and J.F. Dwyer. 2002. Urban forest structure and value at the national scale. Proc. of the National Urban Forest Conference. Washington, DC. p. 24-25.
Nowak, D.J. and P. O’Connor. 2001. Syracuse urban forest master plan: guiding the city’s forest resource in the 21st century. USDA Forest Service General Technical Report. 50 p.
Nowak, D.J., J. Pasek, R. Sequeira, D.E. Crane, and V. Mastro. 2001. Potential effect of Anoplophora glabripennis (Coleoptera: Cerambycidae) on urban trees in the United States. J. Econon. Entomol. 94(1):116-122.
Nowak, D.J., K.L. Civerolo, S.T. Rao, G. Sistla, C.J. Luley, and D.E. Crane. 2000. A modeling study of the impact of urban trees on ozone. Atmos. Environ. 34: 1601-1613.
Nowak, D.J., and D.E. Crane. 2000. The Urban Forest Effects (UFORE) Model: quantifying urban forest structure and functions. In: Hansen, M. and T. Burk (Eds.) Integrated Tools for Natural Resources Inventories in the 21st Century. Proc. of the IUFRO Conference. USDA Forest Service General Technical Report NC-212. North Central Research Station, St. Paul, MN. pp. 714-720.
Nowak, D.J., P.J. McHale, M. Ibarra, D. Crane, J. Stevens, and C. Luley. 1998. Modeling the effects of urban vegetation on air pollution. In: Gryning, S.E. and N. Chaumerliac (eds.) Air Pollution Modeling and Its Application XII. Plenum Press, New York. pp. 399-407.
Principal Investigators and Research Partners
- David J. Nowak, US Forest Service, Northern Research Station Project Leader
- Daniel E. Crane, US Forest Service, Northern Research Station
- Robert Hoehn, US Forest Service, Northern Research Station
- Jack Stevens, US Forest Service, Northern Research Station
- Eric Greenfield, US Forest Service, Northern Research Station
- Lianghu Tian, Davey Tree Expert Co.
- Mike Binkley, Davey Tree Expert Co.
- Greg Ina, Davey Tree Expert Co.
- Scott Maco, Davey Tree Expert Co.
- Jerry Bond
- Ted Endreny, Professor, SUNY College of Environmental Science and Forestry
- Jun Yang
- Andy Lee, SUNY College of Environmental Science and Forestry
- Satoshi Hirabayashi, SUNY College of Environmental Science and Forestry
- Alexis Ellis, SUNY College of Environmental Science and Forestry
Last Modified: 04/13/2009