Summary: Estimation of carbon storage on suburban lands for three southeastern states

The amount of carbon in urban areas is a small but increasingly significant portion of total carbon in all terrestrial ecosystems. To date, current carbon models have not included any estimate for urban carbon storage. This static model estimates the amount of carbon stored in urban environments, including all components of trees, soil, and grass in the states of Virginia, North Carolina, and South Carolina.

The carbon storage calculations for urban trees were based on Forest Service inventories of above-ground biomass for 366 urban sample plots surveyed in the three states. Above-ground tree biomass was converted to total tree biomass including roots and then multiplied by percent carbon to estimate the amount of carbon stored. Carbon percentages were based on estimates of percent carbon in wood, bark, and foliage of specific species. Carbon percentages were weighted by biomass of individual species. Acres of urban lawns were based on urban land-use studies of 14 U.S. cities. Grass carbon was calculated by multiplying the per-acre percent carbon stored by grass biomass, including roots. Grass biomass was estimated using a single biomass study of residential lawns. Soil carbon estimates were based on land-use classes in the same 14-city study. Soil carbon was calculated under four broad categories: bare soil, grass cover, tree cover, and impervious surface.

Total soil carbon was calculated at 27.4 million short tons for Virginia, 37.5 million short tons for North Carolina, and 21 million short tons for South Carolina. Total tree carbon for Virginia was about 13.7 million short tons; for North carolina, 14.9 million short tons; and for South Carolina, 10.3 million short tons. Carbon stored in grass was estimated to be 7.2 million short tons for Virginia, 9.8 million short tons for North Carolina, and 5.9 million short tons for South Carolina.

Estimates of urban carbon storage indicate additional sites of carbon dioxide sinks in terrestrial systems. Intensive urban planting, coupled with reforestation on non-urban land, can mitigate global warming by sequestration of atmospheric carbon dioxide in woody biomass. Estimating carbon in urban areas serves as a basis of tracking net carbon fluxes and may otherwise serve to identify anthropogenic factors in modifying natural carbon dynamics.