Jack C. Stevens

Measuring and analyzing urban tree cover

Measurement of city tree cover can aid in urban vegetation planning, management, and research by revealing characteristics of vegetation across a city. Urban tree cover in the United States ranges from 0.4% in Lancaster, California, to 55% in Baton Rouge, Louisiana. Two important factors that affect the amount of urban tree cover are the natural environment and land use. Urban tree cover is highest in cities that developed in naturally forested areas (31%), followed by grassland cities (19%) and desert cities (10%), but showed wide variation based on individual city characteristics. Tree cover ranged from 15 to 55% for cities in forested areas, 5 to 39% for those in grassland areas, and 0.4 to 26% for cities developed in desert regions. Park and residential lands along with vacant lands in forested areas generally have the highest tree cover among different land uses. Methods of measuring urban tree cover are presented as are planning and management implications of tree-cover data.

Brooklyn's urban forest

An assessment of trees in Brooklyn, New York, reveal that this borough has approximately 610,000 trees with canopies that cover 11.4 percent of the area. The most common trees are estimated to be tree of heaven, white mulberry, black locust, Norway maple and black cherry. Brooklyns trees currently store approximately 172,000 metric tons of carbon with an estimated value of

Modeling the Effects of Urban Vegetation on Air Pollution

3.5 million. In addition, these trees remove about 2,500 tC per year (

Assessing urban forest effects and values, New York City's urban forest

51,000/yr) and about 254 metric tons of air pollution per year (

Assessing urban forest effects and values, Minneapolis' urban forest

1.3 million/yr). The replacement or compensatory value of Brooklyn?s trees is estimated at

Assessing urban forest effects and values, Chicago's urban forest

679 million. Potential damage from an Asian longhorn beetle infestation is

Assessing urban forest effects and values, Washington, D.C.'s urban forest

390 million (51 percent of the population). Management strategies are suggested for maximizing air quality and carbon benefits from urban trees.

Assessing urban forest effects and values, San Francisco's urban forest

Urban vegetation can directly and indirectly affect local and regional air quality by altering the urban atmospheric environment. Trees affect local air temperature by transpiring water through their leaves, by blocking solar radiation (tree shade), which reduces radiation absorption and heat storage by various anthropogenic surfaces (e. g., buildings, roads), and by altering wind characteristics that affect air dispersion. During the summertime, trees predominantly reduce local air temperatures, but may increase within- and below-canopy air temperature due to reduced turbulent exchange with above-canopy air (Heisler et al., 1995). Reduced air temperature due to trees can improve air quality because the emission of many pollutants and/or precursor chemicals are temperature dependent. Decreased air temperature can also reduce ozone (O3) formation (Cardelino and Chameides, 1990).

Assessing urban forest effects and values, Philladelphia's urban forest

An analysis of trees in New York City reveals that this city has about 5.2 million trees with canopies that cover 20.9 percent of the area. The most common tree species are tree of heaven, black cherry, and sweetgum. The urban forest currently stores about 1.35 million tons of carbon valued at

Assessing urban forest effects and values, Scranton's urban forest

24.9 million. In addition, these trees remove about 42,300 tons of carbon per year (