What do urbanized regions contribute to the global C balance?
Abstract
Urbanized land (i.e. "developed" land) covers 98.3 million acres in the United States, and the acreage in this category increased by 25% between 1982 and 1997, based on statistics from the 1997 USDA Natural Resource Inventory (this "developed" category includes "large urban built-up areas," "small urban built-up areas," and "rural transportation land"). Despite this large and growing land base, studies using land-based approaches to quantify land-atmosphere C exchange in the US have overlooked urbanized areas as potential contributors to national and global C cycles. From an inventory of vegetation on "nonforest" (predominantly urbanized) land in and around Baltimore, MD conducted in 1999 by the USDA Forest Service Forest Inventory and Analysis (FIA) program, we found that annual wood production and tree biomass values on nonforest land were approximately 22% and 25%, respectively, of corresponding values on land classified as forest. We estimate that vegetation on nonforest land in Maryland currently stores 25.9 x 106 Mg C, while urban soils in Maryland store an additional 119 x 106 Mg C. Annual gross C sequestration in vegetation on nonforest land in Maryland is approximately 0.6 x 106 Mg C yr-1. Extrapolating this result to the northeastern US, we estimate that vegetation on developed land in the northeastern US currently stores 280.2 x 106 Mg C, with an additional 1372 x 106 Mg C stored in developed soils. Vegetation on developed land in the northeastern US sequesters 14.5 x 106 Mg C annually. Extrapolating further to the rest of the United States, we suggest that vegetation on developed land could store an additional 0.03 to 0.04 Pg C yr-1 in the US, which could be as much as 10% of the existing "missing" North American terrestrial sink of 0.35 to 0.90 Pg C yr-1. We recognize, of course, that substantial regional variability is likely to exist in ratios of nonforest: forest wood production and nonforest: forest land area. Additional research on the dynamics of C stocks and fluxes in nonforest areas across the United States will provide enhanced accuracy in this sector of the global C budget.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2001
- Bibcode:
- 2001AGUSM...B42A11J
- Keywords:
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- 1615 Biogeochemical processes (4805);
- 4805 Biogeochemical cycles (1615);
- 4806 Carbon cycling