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Texas A&M University at Galveston researchers use space technology along with historical plant and soil data to address impact of land use and climate change on coastal ecosystems.
A healthy Texas coastline is not only important for recreation, fishing and shipping, but it could also be essential in adapting to the threat of climate change.
According to the National Oceanic and Atmospheric Administration, salt marshes, mangroves, and sea-grass beds absorb large quantities of the greenhouse gas, carbon dioxide, from the atmosphere and store it, thus decreasing the rate of global warming. Now, some scientists are concerned that these natural carbon-storage banks are at risk.
“Nature’s ability to absorb carbon in coastal marshes, mangroves or sea grass beds is like depositing money in a bank account,” said Dr. Patrick Louchouarn, head of the Department of Marine Science at Texas A&M University at Galveston. “Coastal ecosystems have immense values beyond recreation, fisheries and shipping. It is only recently that we started to recognize that managing these systems for their carbon sequestration (storage) potential, can also help us balance the human influences to the global carbon cycle, and in turn the climate.”
Louchouarn is principle investigator, along with a team of Texas A&M University at Galveston researchers who recently completed the first in a three-year study to learn more about the long-term storage of carbon in tidal marshes and mangroves along the Texas coastline. The $400,000 grant for the study was supported by NASA and the U.S. Department of Agriculture.
Louchouarn said the specific focus of this funded research examines how land development in wetland areas, other wetland losses, and shifts in vegetation affect carbon storage along the Texas coast of the Gulf of Mexico.
“Our team’s research is an ideal fit for the carbon cycle science investigations within the NASA Earth Science Program. It will improve understanding of global carbon cycle and quantify changes in carbon storage at the interface between the land and the sea. And, it will show the impact of land use, land cover change, and other human activities and natural events on ecosystem carbon storage,” he said.
“By investigating interactions between land use and land cover change and the carbon cycle, we believe we will develop applications that directly inform future resource management, policy development and decision-making.”
Combining field research and laboratory studies with analyses from NASA’s remote sensing imagery, TAMUG researchers are gaining information to better understand the potential changes in carbon sequestration driven by climate change and alterations in the types of wetland vegetation over the past decade.
Project researchers are Dr. Wesley Highfield, an assistant professor of Marine Sciences; Dr. Anna Armitage, associate professor of Marine Biology; and Dr. Samuel D. Brody, who is professor of both Marine Sciences (TAMUG) and Landscape Architecture & Urban Planning (TAMU), as well as director of the Institute for Sustainable Coastal Communities and the Center for Texas Beaches and Shores. Brody is also holder of TAMUG’s George P. Mitchell ’40 Chair in Sustainable Coasts.
Ultimately, the TAMUG scientists working on this grant agree that the aim of their integrated research is to characterize the storage of carbon within diverse estuarine wetland ecosystems, while they determine what influence development in coastal wetlands as well as climate-induced shifts may have on pools and carbon exchanges in these systems.
Louchouarn says that analyses of a time series of remote sensing images is playing a significant role in determining past and recent changes in wetland types, sizes and locations.
According to Armitage, early research results from analyses of NASA Landsat imagery indicate that forests of black mangroves have expanded in size over the last 20 years, especially on the central Texas coast around San Antonio Bay and near the Aransas National Wildlife Refuge. As areas of mangroves expand, they are displacing the smaller plants in salt marshes – this converts marshes of cordgrass to forests of mangroves.
“Analyses of the carbon content in soils from marsh and mangrove habitats suggest that there is a greater potential for carbon sequestration in salt marsh soils than in mangroves,” Armitage said. She says the shift from salt marshes to mangroves is significant, “because salt marshes may be able to store more soil carbon than mangroves.”
Armitage emphasized the importance of this finding, when she said, “These preliminary results may indicate a general loss of carbon sequestration potential in wetlands on the Texas coast”.
However, Armitage cautions “that ongoing field and laboratory work on the amount of plant material above- and below-ground will help better define the carbon pools in both marsh and mangrove ecosystems and establish more precise carbon budgets for each habitat type.”
Armitage says initial data received from the study will be linked to the NASA imagery classification work to generate regional scale carbon stocks. This data will be integrated in the Texas Coastal Communities Planning Atlas to illustrate historical and future changes due to climate change and land use. The Coastal Communities Planning Atlas is an ongoing project of the CTBS that helps local jurisdictions in Texas understand the implications of development decisions and plan appropriately for the future.
Louchouarn explained, “Continued analyses of a time series of remote sensing images from NASA will permit to put constraints on past and recent changes in wetland types, sizes and locations. Then, the next step will involve focusing on the extent to which climatic changes and population growth ― as well as development along the coast ― are affecting coastal wetland ecosystems”.
After they quantify carbon sequestration in specific study sites on the central Texas coast, the TAMUG researchers will be able to scale up to estimate the carbon storage potential in wetland areas along the entire Texas coast region.