00 · IN THREE MINUTES
What the new study changes
- 1Landsat imagery identified abrupt and gradual loss of marsh area along the U.S. Atlantic and Gulf coasts.
- 2Combining that loss with eroded-soil depth and carbon estimates yielded gross export of 0.66 Tg C per year and new-marsh burial of 0.22 Tg C per year.
- 3The difference—about 0.38 Tg C per year—is lateral export to the ocean, not an equal, immediate release of carbon dioxide to the air.
01 · WETLANDS STORE CARBON VERTICALLY
Wetlands store carbon vertically
Marsh plants draw carbon dioxide from the air and add organic matter to roots and waterlogged soil. Low-oxygen conditions can slow decomposition, allowing carbon to accumulate through depth. Shoreline retreat cuts across that vertical archive and moves old as well as recent material sideways.
02 · SATELLITES FOLLOWED 37 YEARS OF SHORELINE CHANGE
Satellites followed 37 years of shoreline change
The researchers used Landsat observations from 1985 to 2022 to classify marsh loss and gain along the Atlantic and Gulf coasts. Lidar-derived elevation helped estimate how much soil depth disappeared, while carbon-density information converted eroded volume into mobilized carbon.
03 · GROSS LOSS AND NEW BURIAL MUST BE SEPARATED
Gross loss and new burial must be separated
The estimated erosion flux was 0.66 Tg C per year, with a 68% confidence interval of 0.46–0.91. Newly formed marsh buried about 0.22 Tg C per year, also with wide uncertainty. Subtracting the offset produced a net lateral export near 0.38 Tg C per year.
Wetlands store carbon vertically
Marsh plants draw carbon dioxide from the air and add organic matter to roots and waterlogged soil. Low-oxygen conditions can slow decomposition, allowing carbon to accumulate through depth. Shoreline retreat cuts across that vertical archive and moves old as well as recent material sideways.
soil carbon storeSatellites followed 37 years of shoreline change
The researchers used Landsat observations from 1985 to 2022 to classify marsh loss and gain along the Atlantic and Gulf coasts. Lidar-derived elevation helped estimate how much soil depth disappeared, while carbon-density information converted eroded volume into mobilized carbon.
1985–2022Gross loss and new burial must be separated
The estimated erosion flux was 0.66 Tg C per year, with a 68% confidence interval of 0.46–0.91. Newly formed marsh buried about 0.22 Tg C per year, also with wide uncertainty. Subtracting the offset produced a net lateral export near 0.38 Tg C per year.
0.66 − 0.22Export is not the same as emission
Most displaced material first enters coastal water. Some may be buried again in sediment, some decomposed and returned to the atmosphere, some carried offshore, and some incorporated into food webs. The study quantifies movement out of marsh storage, not the eventual fraction emitted as carbon dioxide or methane.
ocean pathways04 · EXPORT IS NOT THE SAME AS EMISSION
Export is not the same as emission
Most displaced material first enters coastal water. Some may be buried again in sediment, some decomposed and returned to the atmosphere, some carried offshore, and some incorporated into food webs. The study quantifies movement out of marsh storage, not the eventual fraction emitted as carbon dioxide or methane.
05 · STORMS LEAVE REGIONAL SIGNATURES
Storms leave regional signatures
The Mississippi River Delta moved more marsh carbon than the entire Eastern seaboard in the analysis. Abrupt loss increased after hurricanes including Katrina and Ida, while gradual erosion and new wetland growth created different balances elsewhere. One national average therefore hides strong local variation.
06 · SOURCES AND EVIDENCE
Sources and evidence
The news angle is traced back to the primary paper and the institutional record.
- 01Net lateral carbon loss from eroding US Atlantic and Gulf Coast marshesPRIMARY STUDY ↗
Supports a defined observation, inference or evidence boundary in this update.
- 02NASA GISS publication record and abstractINSTITUTIONAL EXPLAINER ↗
Supports a defined observation, inference or evidence boundary in this update.
- 03NASA-Supported Study Tracks Carbon Cost of Coastal ErosionINSTITUTIONAL EXPLAINER ↗
Supports a defined observation, inference or evidence boundary in this update.