Coastal wetlands offer numerous ecosystem services including protecting coastal regions from storm surge and improving water quality. However, the destruction and degradation of these habitats has been widespread, with about 25 – 50% of the world’s coastal wetlands lost over the last century. In addition, coastal wetlands are among the strongest carbon sinks in the biosphere, removing ~45 to 230 Tg carbon annually. As a result of their high carbon sequestration potential, there is growing interest in financing coastal wetland restoration and conservation using carbon markets. This research project focuses on soil carbon sequestration in restored coastal wetlands in the Sacramento-San Joaquin River Delta, California as a means of mitigating climate change. Specifically, we are interested in the trajectory of peat accretion and carbon storage as the restored wetland matures. We hypothesize that the older the wetland, the more peat and soil carbon stored. The data we collect will test this hypothesis. We will combine soil coring and analysis of soil organic matter and carbon content throughout the peat layer (1-5m) with ground-penetrating radar and seismic surface wave analysis to map peat soil carbon across three islands in the Delta encompassing three wetland sites of different ages (3, 7 and 20 years old) and three agricultural (degraded peatland) sites (alfalfa, rice and corn).
Preliminary analyses from the young wetland (3 year old), mature wetland (20 year old) and alfalfa field show very distinct soil organic matter storage in the peat layer. We found up to 16% organic matter at shallow depths (0-30cm) in the young wetland and 26% organic matter in the mature wetland. At the alfalfa site, we found 18% organic matter at shallow depths. Based on our initial data, we found that organic matter is similar in recently restored wetlands compared to agricultural land. However, the mature wetland had significantly higher organic matter in the shallow peat layer compared to the other sites suggesting that it may take several years to begin restoring soil peat carbon in these systems. Preliminary analyses confirm our hypothesis that carbon is being stored at high rates in restored wetlands in the Delta, however this carbon storage may take several years to establish. This has implications for financing wetland restoration using carbon markets as newly restored wetlands may not accrete peat within the first 3 years of restoration.