Rusty A. Feagin

Coastal erosion, global sea‐level rise, and the loss of sand dune plant habitats

Much of Americas coastline is threatened by overdevelopment and coastal erosion, driven by global sea-level rise, a problem that is attracting the attention of researchers around the world. Although we have now acknowledged the impending risks, little is known about the response of spatially dependent dune plant communities to the loss or restriction of their habitat. In order to study this development, a spatially explicit model of sand dune plant succession on Galveston Island, Texas, was created, using sea-level rise as the primary mechanism causing local erosion. Simulations of sea-level rise scenarios developed by the Intergovernmental Panel on Climate Change demonstrated that beach erosion constrained plants to a narrow area, resulting in a breakdown of the successional process. The loss of late-succession plants along coastlines, their dependent faunal species, and possible solutions are discussed. This model and example serves as a harbinger of the future for many of the USs sandy beaches and co...

Does vegetation prevent wave erosion of salt marsh edges

This study challenges the paradigm that salt marsh plants prevent lateral wave-induced erosion along wetland edges by binding soil with live roots and clarifies the role of vegetation in protecting the coast. In both laboratory flume studies and controlled field experiments, we show that common salt marsh plants do not significantly mitigate the total amount of erosion along a wetland edge. We found that the soil type is the primary variable that influences the lateral erosion rate and although plants do not directly reduce wetland edge erosion, they may do so indirectly via modification of soil parameters. We conclude that coastal vegetation is best-suited to modify and control sedimentary dynamics in response to gradual phenomena like sea-level rise or tidal forces, but is less well-suited to resist punctuated disturbances at the seaward margin of salt marshes, specifically breaking waves.

Going with the flow or against the grain? The promise of vegetation for protecting beaches, dunes, and barrier islands from erosion

Coastlines have traditionally been engineered to maintain structural stability and to protect property from storm-related damage, but their ability to endure will be challenged over the next century. The use of vegetation to reduce erosion on ocean-facing mainland and barrier island shorelines – including the sand dunes and beaches on these islands – could be part of a more flexible strategy. Although there is growing enthusiasm for using vegetation for this purpose, empirical data supporting this approach are lacking. Here, we identify the potential roles of vegetation in coastal protection, including the capture of sediment, ecological succession, and the building of islands, dunes, and beaches; the development of wave-resistant soils by increasing effective grain size and sedimentary cohesion; the ability of aboveground architecture to attenuate waves and impede through-flow; the capability of roots to bind sediments subjected to wave action; and the alteration of coastline resiliency by plant structur...

Vegetation's role in coastal protection.

We are concerned about the assertion in the Report by E. B. Barbier et al. that vegetation reduces coastal damage during extreme events (“Coastal ecosystem-based management with nonlinear ecological functions and values,” 18 January, p. [321][1]). Although the intended point was that ecosystem

Barrier Islands: Coupling Anthropogenic Stability with Ecological Sustainability

Abstract Barrier islands provide a host of critical ecosystem services to heavily populated coastal regions of the world, yet they are quite vulnerable to ongoing sea level rise and a potential increase in the frequency and intensity of oceanic storms. These islands are being degraded at an alarming rate, in part because of anthropogenic attempts at stabilization. In this article, we outline a possible sustainability strategy that incorporates the natural degree of substrate instability on these sedimentary landscapes. We recommend placing the focus for managing barrier islands on maintaining ecosystem function and process development rather than emphasizing barrier islands as structural impediments to wave and storm energy.

Artificial modifications of the coast in response to the Deepwater Horizon oil spill: Quick solutions or long-term liabilities?

The Deepwater Horizon oil spill threatened many coastal ecosystems in the Gulf of Mexico during the spring and summer of 2010. Mitigation strategies included the construction of barrier sand berms, the restriction or blocking of inlets, and the diversion of freshwater from rivers to the coastal marshes and into the ocean, in order to flush away the oil, on the premise that these measures could reduce the quantity of oil reaching sensitive coastal environments such as wetlands or estuaries. These projects result in changes to the ecosystems that they were intended to protect. Long-term effects include alterations of the hydrological and ecological characteristics of estuaries, changes in sediment transport along the coastal barrier islands, the loss of sand resources, and adverse impacts to benthic and pelagic organisms. Although there are no easy solutions for minimizing the impacts of the Deepwater Horizon disaster on coastal ecosystems, we recommend that federal, state, and local agencies return to the ...

Sargassum as a Natural Solution to Enhance Dune Plant Growth

Many beach management practices focus on creating an attractive environment for tourists, but can detrimentally affect long-term dune integrity. One such practice is mechanical beach raking in which the wrack line is removed from the beach front. In Texas, Sargassum fluitans and natans, types of brown alga, are the main components of wrack and may provide a subsidy to the ecosystem. In this study, we used greenhouse studies to test the hypothesis that the addition of sargassum can increase soil nutrients and produce increased growth in dune plants. We also conducted an analysis of the nutrients in the sargassum to determine the mechanisms responsible for any growth enhancement. Panicum amarum showed significant enhancement of growth with the addition of sargassum, and while Helianthus debilis, Ipomoea stolonifera, Sporobolus virginicus, and Uniola paniculata responded slightly differently to the specific treatments, none were impaired by the addition of sargassum. In general, plants seemed to respond well to unwashed sargassum and multiple additions of sargassum, indicating that plants may have adapted to capitalize on the subsidy in its natural state directly from the ocean. For coastal managers, the use of sargassum as a fertilizer could be a positive, natural, and efficient method of dealing with the accumulation of wrack on the beach.

The Use of Terrestrial Laser Scanning (TLS) in Dune Ecosystems: The Lessons Learned

ABSTRACT Feagin, R.A.; Williams, A.M.; Popescu, S.; Stukey, J., and Washington-Allen, R.A., 2014. The use of terrestrial laser scanning (TLS) in dune ecosystems: the lessons learned. This paper presents a methodology for using terrestrial laser scanning (TLS) to quantify sand dune geomorphology. As an example of the use of TLS, we present methods that were used to investigate changes in sediment and vegetation volumes after Hurricane Ike. We collected TLS data within a 100 m × 100 m plot on the East Matagorda Peninsula, Texas, from early September 2008 (before landfall) to early October 2009 (a year after landfall). Terrestrial laser scanning-collected laser point clouds were then interpolated into several grid sizes. From several interpolated grid sizes, 0.50 m × 0.50 m grids were determined best for analysis as they were able to compromise two competing resolution-related issues: gaps caused by vegetation shadows and the natural contours of the dune. We outline several additional lessons to aid coastal researchers in strengthening their own future work: the use of reference survey stakes in an unstable environment, the development of a novel method to test for errors in point cloud registration among multiple dates, how best to interpret sediment and vegetation change analysis as derived from interpolated grids, and suggestions for incorporating mass-based sedimentary and biomass-based vegetation field studies within the volumetric context of TLS analysis.

SPATIAL PATTERN AND EDGE CHARACTERISTICS IN RESTORED TERRACE VERSUS REFERENCE SALT MARSHES IN GALVESTON BAY

Terraced salt marsh restoration projects have been designed to maximize edge because the edges between habitat types have been shown to be the most productive locations in Spartina alterniflora salt marshes for nekton and benthic infauna. We compared terraced plots with reference plots to see how much edge was created. We also quantified the differences in the spatial patterns of the habitat in the plots. We found that reference marshes had significantly more habitat diversity and more total low marsh area. We also found that reference marshes had a greater absolute amount of low marsh edge. Yet, we found little difference between terraced restoration marshes and nearby reference marshes in Galveston Bay, Texas, USA in terms of the percent of all habitat-to-habitat edge-type combinations that were aquatic edge (water- or seagrass-to-low marsh interface), and much of the reference marshes’ area was in core marsh areas that were not suitable for high fisheries production value. Terracing appears an efficient strategy for the sole purpose of creating aquatic edge for fisheries production but does not appear to match other aspects of reference marshes in terms of their habitat composition or spatial configuration. This study shows the potential for using spatial pattern analysis to monitor restoration projects in the future.

Foredune Restoration Before and After Hurricanes: Inevitable Destruction, Certain Reconstruction

In many parts of the world where shorelines are eroding, hurricanes or other storms destroy foredunes every few years. Moreover, in highly urbanized locations, there may be so little habitat space available that a dune ecosystem is unable to sustain itself. So why do people restore dunes in these contexts, only to see their hard work subsequently destroyed by the next hurricane? People restore them, even if only for their short-term benefits, because: they effectively demarcate the public beach from private property, protecting homeowners’ properties from wandering tourists; they are aesthetically-pleasing, providing a sense of nature and wildness to homeowners and tourists alike; they protect housing and infrastructure from the impacts of future storms. These three incentives drive large sand-moving and re-vegetation projects, even though they are ultimately futile against the forces of nature. Using three foredune restoration projects on Galveston Island, Texas as examples, these incentives and the storms that instigated or subsequently destroyed the projects are examined. This is not a cynical story—rather, it shows that small pockets of the natural world can co-exist within a largely urban matrix, simply because it is in people’s financial interest to maintain them.