Carbon storage and sequestration rates vary among states based on the amount of urban tree cover and growing conditions. States in forested regions typically have the highest percentage of urban tree cover. States with the greatest amount of carbon stored by trees in urban areas are Texas (49.8 million tons), Florida (47.3 million tons), Georgia (42.4 million tons), Massachusetts (39.6 million tons) and North Carolina (37.5 million tons).
The total amount of carbon stored and sequestered in urban areas could increase in the future as urban land expands. Urban areas in the continental U.S. increased from 2.5 percent of land area in 1990 to 3.1 percent in 2000, an increase equivalent to the area of Vermont and New Hampshire combined. If that growth pattern continues, U.S. urban land could expand by an area greater than the state of Montana by 2050.
The study is not the first to estimate carbon storage and sequestration by U.S. urban forests, however it provides more refined statistical analyses for national carbon estimates that can be used to assess the actual and potential role of urban forests in reducing atmospheric carbon dioxide.
More urbanization does not necessarily translate to more urban trees. Last year, Nowak and Eric Greenfield, a forester with the Northern Research Station and another study co-author, found that urban tree cover is declining nationwide at a rate of about 20,000 acres per year, or 4 million trees per year.
Carbon Stored (tons)
|Contact: Jane Hodgins|
USDA Forest Service - Northern Research Station