8/31/2023 0 Comments Double sided sword after earth![]() ![]() Allochthonous carbon does not remove atmospheric carbon, thus limiting the marsh-climate feedback. This is important because blue carbon policy only counts autochthonous, or locally-produced carbon – in offsetting programs. Corroborating claims from field experiments, we find that allochthonous carbon – or carbon not produced in situ - is a substantial component of total marsh carbon. Our model uniquely tracks both allochthonous (produced somewhere else and transported) and autochthonous (produced in situ) carbon across the ecosystems as part of understanding connectivity, allowing us to separate these different components within marshes. Our findings have direct implications for blue carbon projects globally. However, if sea level rise rates are too great (> 10 mm/yr in our scenario), the marsh is unable to keep pace and the entire marsh system collapses resulting in lower coastal carbon storage. This manifests as marshes expanding their extent into lands that were previously coastal forest and increased vertical accretion rates, as well as increases in bay carbon storage with the increasing accommodation space from sea level rise. The key takeaway is that the coastal system is resilient to climate change and can continue to store increasing amounts of carbon as sea level rises. Here, we took a different approach and coupled both carbon processes and coastal geomorphic processes along a bay-marsh-coastal forest landscape to explore how the entire coast will respond to a changing climate. Even so, when it comes down to modeling the carbon in these systems, the coastal ecosystems are represented individually. These exchanges are well known and well documented in marsh and coastal literature. You often see pieces of marsh slumping into the open bay, marsh vegetation encroaching in coastal forests, and bay sediments accumulating on the marsh surface. The coastal landscape is a mosaic of ecosystems that shift over time, and the ‘individual’ ecosystems – bay, marsh, coastal forest - are woven together. We had noticed in the field that while marshes are very important for coastal morphology and carbon sequestration, they do not exist in isolation. Cartoon of the bay-marsh-forest transect and the geomorphic and carbon processes that drive landscape evolution. We aimed to capture these processes and tie them to how carbon is moved across the landscape and alters the landscape dynamics. With sea level rise, forests become stressed from flooding and salinity, leading to forest die-off and migration of marsh vegetation into this region. The marsh transitions to forest as the land no longer is regularly flooded by seawater. At the marsh-forest boundary, elevation drives the dynamics. These processes are sensitive to the marsh elevation relative to the sea level. Vertical evolution of the marsh is driven by deposition of sediment at high tide, vegetation productivity leading to organic deposition, and decomposition. At the bay-marsh edge, wind waves impact the marsh leading to erosion. Marshes evolve both vertically and laterally. ![]() What’s even more incredible about this landscape is that it is far from static – these ecotones are rapidly shifting in response to rising sea levels. Here, you can walk the rapid transition from an upland forest to salt marsh in only a few minutes. While our model can represent many different coastal morphologies, our time in the field in Virginia helped in developing the model and understanding the driving processes in this system. While this coupled ecosystem is relatively common along the Atlantic coast of the United States, we spend much of our time on the Virginia coast at sites at the Virginia Coastal Reserve Long-Term Ecologic Research site ( VCR LTER). Our team has done a lot of work across this bay-marsh-forest landscape. Alex Smith walking through the marsh at Goodwin Island during field sampling. Here we coupled geomorphic processes and carbon dynamics in a numerical model that spans the a bay-marsh-forest transect to understand the future of the entire coastal zone. Historically, these different environments (bay, marsh, coastal forest) have been studied independently from each other, with intense focus on their future morphodynamic change or carbon processes. While the coastal zone is a relatively short distance, it can span wildly different ecosystems largely dependent on elevation relative to sea level. Coastal ecosystems provide many benefits, ranging from wildlife habitat and flooding protection to enhanced carbon storage. Rapid climate change and sea level rise directly impacts the world’s coastlines, affecting the processes that govern their formation and persistence. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |