Estimating soil subsidence and carbon loss in the Everglades Agricultural Area, Florida using geospatial techniques

Climate change due to elevated carbon dioxide levels in the atmosphere presents a long-term threat to the biosphere. The contribution of soil oxidation to global carbon dioxide levels is of growing concern. Until the past century, for over five millennia, the Everglades has been accreting peat soils and acting as a carbon sink. Anthropogenic drainage of the northernmost one-fourth of the Everglades, one of the largest deposits of organic soils in North America, began in the 1880s. Subsequently, the peat soils of that area began subsiding and releasing carbon dioxide (CO2) into the atmosphere. We quantified subsidence and CO2 evolution at the regional scale by calculating the changes in peat volume using surface maps reconstructed from historical and current data. The estimated peat volume was originally about 7 × 109 m3 and is currently about 3 × 109 m3. The average subsidence was about two meters and the CO2 emitted was 4.9 × 108 metric tons. Assuming a constant CO2 emission rate during the century since drainage, then the regional scale CO2 flux rate from this study (0.2 g CO2 m−2 yr−1) was similar to short-term, small-scale measurements made under controlled conditions (0.2–6 g CO2 m−2 yr−1).