Eric J. Greenfield

Evaluating The National Land Cover Database Tree Canopy and Impervious Cover Estimates Across the Conterminous United States: A Comparison with Photo-Interpreted Estimates

The 2001 National Land Cover Database (NLCD) provides 30-m resolution estimates of percentage tree canopy and percentage impervious cover for the conterminous United States. Previous estimates that compared NLCD tree canopy and impervious cover estimates with photo-interpreted cover estimates within selected counties and places revealed that NLCD underestimates tree and impervious cover. Based on these previous results, a wall-to-wall comprehensive national analysis was conducted to determine if and how NLCD derived estimates of tree and impervious cover varies from photo-interpreted values across the conterminous United States. Results of this analysis reveal that NLCD significantly underestimates tree cover in 64 of the 65 zones used to create the NCLD cover maps, with a national average underestimation of 9.7% (standard error (SE)xa0=xa01.0%) and a maximum underestimation of 28.4% in mapping zone 3. Impervious cover was also underestimated in 44 zones with an average underestimation of 1.4% (SExa0=xa00.4%) and a maximum underestimation of 5.7% in mapping zone 56. Understanding the degree of underestimation by mapping zone can lead to better estimates of tree and impervious cover and a better understanding of the potential limitations associated with NLCD cover estimates.

Assessment of 2001 NLCD Percent Tree and Impervious Cover Estimates

The 2001 National Land Cover Database (NLCD) tree and impervious cover maps provide an opportunity to extract basic land-cover information helpful for natural resource assessments. To determine the potential utility and limitations of the 2001 NLCD data, this exploratory study compared 2001 NLCD-derived values of overall percent tree and impervious cover within geopolitical boundaries with aerial photo interpretation-derived values for the same areas. Results of the comparison reveal that NLCD underestimates tree cover and to a lesser extent, underestimates impervious cover. The underestimate appears to be consistent across the conterminous United States with no statistical differences among regions. However, there were statistical differences in the degree of underestimation of tree cover among mapping zones and of impervious cover by population density class.

Assessing urban forest effects and values: Toronto's urban forest

An analysis of trees in Toronto, Ontario, reveals that this city has about 10.2 million trees with a tree and shrub canopy that covers approximately 26.6 percent of the city. The most common tree species are eastern white-cedar, sugar maple, and Norway maple. The urban forest currently stores an estimated 1.1 million metric tons of carbon valued at CAD

Urban and community forests of the Southern Atlantic region: Delaware, District of Columbia, Florida, Georgia, Maryland, North Carolina, South Carolina, Virginia, West Virginia

25.0 million. In addition, these trees remove about 46,700 metric tons of carbon per year (CAD

Urban and community forests of New England: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont

1.1 million per year) and about 1,905 metric tons of air pollution per year (CAD

Urban and community forests of the North Central West region: Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota, South Dakota

16.9 million per year). Trees in Toronto are estimated to reduce annual residential energy costs by CAD

Urban and community forests of the Pacific region: California, Oregon, Washington

9.7 million per year. The compensatory value is estimated at CAD

Urban and community forests of the North Central East region: Illinois, Indiana, Michigan, Ohio, Wisconsin

7.1 billion. Information on the structure and functions of the urban forest can be used to improve and augment support for urban forest management programs and to integrate urban forests within plans to improve environmental quality in the Toronto area.

Urban and community forests of the Mountain region: Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, Wyoming

This report details how land cover and urbanization vary within the states of Delaware, Florida, Georgia, Maryland, North Carolina, South Carolina, Virginia, and West Virginia; and the District of Columbia by community (incorporated and census designated places), county subdivision, and county. Specifically this report provides critical urban and community forestry information for each state including human population characteristics and trends, changes in urban and community lands, tree canopy and impervious surface cover characteristics, distribution of land-cover classes, a relative comparison of urban and community forests among local government types, determination of priority areas for tree planting, and a summary of urban tree benefits. Report information can improve the understanding, management, and planning of urban and community forests. This data is reported for each state on the CD provided in the back of this book and may be accessed by state at: http://www.nrs.fs.fed.us/data/urban.

Assessing Urban Forest Canopy Cover Using Airborne or Satellite Imagery

This report details how land cover and urbanization vary within the states of Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont by community (incorporated and census designated places), county subdivision, and county. Specifically this report provides critical urban and community forestry information for each state including human population characteristics and trends, changes in urban and community lands, tree canopy and impervious surface cover characteristics, distribution of land-cover classes, a relative comparison of urban and community forests among local government types, determination of priority areas for tree planting, and a summary of urban tree benefits. Report information can improve the understanding, management, and planning of urban and community forests. The data from this report is reported for each state on the CD provided in the back of this book, and it may be accessed by state at: http://www.nrs.fs.fed.us/data/urban.