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US urban trees store carbon, provide billions in economic value

From New York City’s Central Park to Golden Gate Park in San Francisco, America’s urban forests store an estimated 708 million tons of carbon, an environmental service with an estimated value of $50 billion, according to a recent U.S. Forest Service study.

Annual net carbon uptake by these trees is estimated at 21 million tons and $1.5 billion in economic benefit.

In the study published recently in the journal Environmental Pollution, Dave Nowak, a research forester with the U.S. Forest Service’s Northern Research Station, and his colleagues used urban tree field data from 28 cities and six states and national tree cover data to estimate total carbon storage in the nation’s urban areas.

“With expanding urbanization, city trees and forests are becoming increasingly important to sustain the health and well-being of our environment and our communities,” said U.S. Forest Service Chief Tom Tidwell. “Carbon storage is just one of the many benefits provided by the hardest working trees in America. I hope this study will encourage people to look at their neighborhood trees a little differently, and start thinking about ways they can help care for their own urban forests.”

Tens of thousands of people volunteered to plant and care for trees for Earth Day and Arbor Day this year, but there are opportunities all year long. To learn about volunteer opportunities near your home, visit the Arbor Day Foundation.

The Forest Service partners with organizations like the Arbor Day Foundation and participates in programs like Tree City USA to recognize and inspire cities in their efforts to improve their urban forests. Additionally the Forest Service is active in more than 7,000 communities across the U.S., helping them to better plan and manage their urban forests.

Nationally, carbon storage by trees in forestlands was estimated at 22.3 billion tons in a 2008 Forest Service study; additional carbon storage by urban trees bumps that to an estimated 22.7 billion tons.
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 Storage by Urban Trees

State

Carbon Stored (tons)

Texas

49,800,000

Florida

47,300,000

Georgia

42,400,000

Massachusetts

39,600,000

North Carolina

37,500,000

New York

35,400,000

California

34,600,000

Pennsylvania

31,700,000

New Jersey

30,900,000

Connecticut

25,700,000

Ohio

25,300,000

Michigan

25,200,000

Tennessee

20,800,000

Alabama

20,600,000

Illinois

20,600,000

South Carolina

19,100,000

Virginia

18,300,000

Washington

15,200,000

Maryland

13,100,000

Missouri

12,400,000

Louisiana

11,600,000

Indiana

10,700,000

Wisconsin

10,400,000

Minnesota

10,200,000

Oregon

8,900,000

Arkansas

8,500,000

Mississippi

8,200,000

New Hampshire

7,900,000

Kentucky

7,100,000

Arizona

6,000,000

West Virginia

5,700,000

Kansas

5,300,000

Colorado

4,800,000

Oklahoma

4,800,000

Rhode Island

4,600,000

Maine

4,200,000

Iowa

4,100,000

Delaware

2,500,000

Hawaii

2,400,000

Utah

2,300,000

Alaska

2,200,000

New Mexico

2,000,000

Nebraska

1,800,000

Vermont

1,700,000

Nevada

1,400,000

Idaho

1,200,000

South Dakota

800,000

Montana

500,000

North Dakota

500,000

Wyoming

300,000

Total

708,100,000

trees in dcThe mission of the U.S. Forest Service is to sustain the health, diversity, and productivity of the nation’s forests and grasslands to meet the needs of present and future generations. The agency has either a direct or indirect role in stewardship of about 80 percent of our nation’s forests; 850 million acres including 100 million acres of urban forests where most Americans live. The mission of the Forest Service’s Northern Research Station is to improve people’s lives and help sustain the natural resources in the Northeast and Midwest through leading-edge science and effective information delivery.

USDA has made a concerted effort to deliver results for the American people, even as USDA implements sequestration – the across-the-board budget reductions mandated under terms of the Budget Control Act. USDA has already undertaken historic efforts since 2009 to save more than $828 million in taxpayer funds through targeted, common-sense budget reductions. These reductions have put USDA in a better position to carry out its mission, while implementing sequester budget reductions in a fair manner that causes as little disruption as possible.




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