Final Report: Beach Grass Invasions and Coastal Flood Protection: Forecasting the Effects of Climate Change on Coastal Vulnerability

EPA Grant Number: R833836
Title: Beach Grass Invasions and Coastal Flood Protection: Forecasting the Effects of Climate Change on Coastal Vulnerability
Investigators: Seabloom, Eric , Ruggiero, Peter , Hacker, Sally
Institution: Oregon State University
EPA Project Officer: Packard, Benjamin H
Project Period: July 1, 2008 through June 30, 2012 (Extended to June 30, 2013)
Project Amount: $599,980
RFA: Ecological Impacts from the Interactions of Climate Change, Land Use Change and Invasive Species: A Joint Research Solicitation - EPA, USDA (2007) RFA Text |  Recipients Lists
Research Category: Global Climate Change , Aquatic Ecosystems , Ecosystems , Climate Change

Objective:

Increased storm severity and sea-level rise resulting from climate change have greatly elevated the risk of coastal communities. These risks have been exacerbated by alterations to coastal ecosystems and the introduction of non-native species. In the Pacific Northwest of the US, coastal dunes protect about half of the coastline, and our initial results suggest that increases in wave height and sea level could increase the frequency with which waves overtop and erode dunes. Intentional planting of non-native grasses (Ammophila spp.) may have initially increased coastal protection from flooding by building tall foredunes parallel to the shoreline. However, an unintentional second invasion appears to be decreasing foredune height thereby increasing risk exposure. In addition, many agencies are removing beach grasses to restore habitat for imperiled species. The effects of these conservation actions on flooding risk are unknown. Managers of west coast dune systems are faced with an apparent conundrum. Climate change is increasing the need for the protection services of grass dominated coastal dunes, but conservation mandates the removal of these invasive grasses to favor recovery of threatened and endangered species. Furthermore, the uncontrolled invasion by the second grass, A. breviligulata, is associated with declines in dune height and biodiversity. Despite the conflicting values of coastal protection and conservation, neither invasive species dynamics nor coastal protective values have been quantified under future invasion and climate change scenarios.

Here we proposed research to address three fundamental objectives (1) Determine the relationship between climate change and beach grass invasion, (2) Determine the effects of non-native beach grass invasion on coastal vulnerability, and (3) Determine if conservation management alters coastal vulnerability to flooding under a range of climate change, invasion and management scenarios.

Summary/Accomplishments (Outputs/Outcomes):

We have assembled a large dataset that includes shoreline change, dune geomorphology, and vegetation data necessary to understand the interaction between sand supply, dune grass invader, and the effects on foredune geomorphology from Grays Harbor, Washington, to Bandon, Oregon (Objective 1). Analysis shows that dune geomorphology is the result of both sand supply and dune grass species—sites with high sand supply and Ammophila breviligulata as the dominant invader feature shorter and wider dunes compared to sites that have low sand supply and A. arenaria as the dominant invader (Hacker et al. 2012). Mechanistic experiments have revealed that A. breviligulata captures less sand than A. arenaria (Zarnetske et al. 2012) and it is also competitively dominant over A. arenaria (Zarnetske et al. 2013) raising the possibility that the spread of A. breviligulata could compromise dune protective services.

To assess this vulnerability to storm waves and sea level we applied total water level (TWL) models developed by Ruggiero to our dune geomorphology measurements (Objective 2). Our calculations show that shorter dunes dominated by A. breviligulata are more vulnerable to overtopping than taller dunes dominated by A. arenaria (Seabloom et al. 2013). To further assess vulnerability of dunes to various climate change, invasion, and management scenarios, we developed a number of realistic climate change scenarios relevant to foredune flooding risk (Objective 3). These included sea level rise and increases and decreases in wave heights. We have applied these scenarios to current and projected grass invasion dynamics including one scenario that has A. breviligulata dominate along the Oregon coast (Seabloom et al. 2013). In our models, altered storm intensity was the largest driver of overtopping, however the invasion by A. breviligulata tripled the number of areas vulnerable to overtopping and posed a fourfold larger exposure than sea-level rise over multi-decadal time scales. More recent analyses that involved restoration areas established for Western snowy plover show that removal of beach grass from foredune areas may make them more vulnerable to overtopping under current and stormier conditions (Biel et al. 2013). However, erosion was estimated to be similar to control areas with no Ammophila removal.

Finally, one of us (Hacker) has worked as part of a collaborative group that has considered the functions and services provided by estuarine and coastal ecosystems. The knowledge of dunes gained from this grant has contributed substantially to this broader, international research and we have a number of papers published from this group.

Conclusions:

This study supports the notion that beach grass invasions along the Pacific coast have had large effects on the structure, function, and services provided by these dune ecosystems. Given that nearly half of the Oregon and Washington coasts are beach and dune ecosystems, the potential for coastal protection with current and increased storminess are substantial. However, attention should be paid to the species of beach grass that is managed and the geomorphology and sand supply present at the sites of interest. Finally, although restoration of dune ecosystems to their native state increases vulnerability to storms, if restoration areas are carefully planned in areas that lack coastal development, the conflicting services of coastal protection and preservation of biodiversity are likely be mitigated.   


Journal Articles on this Report : 17 Displayed | Download in RIS Format

Other project views: All 55 publications 19 publications in selected types All 17 journal articles
Type Citation Project Document Sources
Journal Article Barbier EB, Koch EW, Silliman BR, Hacker SD, Wolanski E, Primavera JH, Granek EF, Polasky S, Aswani S, Cramer LA, Stoms DM, Kennedy CJ, Bael D, Kappel C, Perillo GME, Reed DJ. Vegetation's role in coastal protection:response. Science 2008;320:176-177. R833836 (2010)
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  • Journal Article Barbier EB, Koch EW, Silliman BR, Hacker SD, Wolanski E, Primavera J, Granek EF, Polasky S, Aswani S, Cramer LA, Stoms DM, Kennedy CJ, Bael D, Kappel CV, Perillo GME, Reed DJ. Coastal ecosystem-based management with nonlinear ecological functions and values. Science 2008;319(5861):321-323. R833836 (2010)
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  • Journal Article Barbier EB, Hacker SD, Kennedy C, Koch EW, Stier AC, Silliman BR. The value of estuarine and coastal ecosystem services. Ecological Monographs 2011;81(2):169-193. R833836 (2010)
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  • Journal Article David AS, Zarnetske PL, Hacker SD, Ruggiero P, Biel RG, Seabloom EW. Invasive congeners differ in successional impacts across space and time. PLoS One 2015;10(2):e0117283 (15 pp.). R833836 (Final)
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  • Journal Article David AS, Seabloom EW, May G. Plant host species and geographic distance affect the structure of aboveground fungal symbiont communities, and environmental filtering affects belowground communities in a coastal dune ecosystem. Microbial Ecology 2016;71(4):912-926. R833836 (Final)
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  • Journal Article David AS, May G, Schmidt D, Seabloom EW. Beachgrass invasion in coastal dunes is mediated by soil microbes and lack of disturbance dependence. Ecosphere 2016;7(11):e01527 (12 pp.). R833836 (Final)
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  • Journal Article Hacker SD, Zarnetske P, Seabloom E, Ruggiero P, Mull J, Gerrity S, Jones C. Subtle differences in two non-native congeneric beach grasses significantly affect their colonization, spread, and impact. Oikos 2012;121(1):138-148. R833836 (2010)
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  • Journal Article Kaminsky GM, Ruggiero P, Buijsman MC, McCandless D, Gelfenbaum G. Historical evolution of the Columbia River littoral cell. Marine Geology 2010;273(1-4):96-126. R833836 (2009)
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  • Journal Article Koch EW, Barbier EB, Silliman BR, Reed DJ, Perillo GME, Hacker SD, Granek EF, Primavera JH, Muthiga N, Polasky S, Halpern BS, Kennedy CJ, Kappel CV, Wolanski E. Non-linearity in ecosystem services: temporal and spatial variability in coastal protection. Frontiers in Ecology and the Environment 2009;7(1):29-37. R833836 (2010)
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  • Journal Article Mull J, Ruggiero P. Estimating storm-induced dune erosion and overtopping along U.S. West Coast beaches. Journal of Coastal Research 2014;30(6):1173-1187. R833836 (Final)
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  • Journal Article Ruggiero P, Buijsman M, Kaminsky GM, Gelfenbaum G. Modeling the effects of wave climate and sediment supply variability on large-scale shoreline change. Marine Geology 2010;273(1-4):127-140. R833836 (2009)
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  • Journal Article Ruggiero P, Komar PD, Allan JC. Increasing wave heights and extreme value projections:the wave climate of the U.S. Pacific Northwest. Coastal Engineering 2010;57(5):539-552. R833836 (2009)
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  • Journal Article Seabloom EW, Ruggiero P, Hacker SD, Mull J, Zarnetske P. Invasive grasses, climate change, and exposure to storm-wave overtopping in coastal dune ecosystems. Global Change Biology 2013;19(3):824-832. R833836 (2012)
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  • Journal Article Zarnetske PL, Seabloom EW, Hacker SD. Non-target effects of invasive species management:beach grass, birds, and bulldozers in coastal dunes. Ecosphere 2010;1(5):1-20. R833836 (2010)
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  • Journal Article Zarnetske PL, Hacker SD, Seabloom EW, Ruggiero P, Killian JR, Maddux TB, Cox D. Biophysical feedback mediates effects of invasive grasses on coastal dune shape. Ecology 2012;93(6):1439-1450. R833836 (2011)
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  • Journal Article Zarnetske PL, Gouhier TC, Hacker SD, Seabloom EW, Bokil VA. Indirect effects and facilitation among native and non-native species promote invasion success along an environmental stress gradient. Journal of Ecology 2013;101(4):905-915. R833836 (2012)
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  • Journal Article Zarnetske PL, Ruggiero P, Seabloom EW, Hacker SD. Coastal foredune evolution:the relative influence of vegetation and sand supply in the US Pacific Northwest. Journal of The Royal Society Interface 2015;12(106):20150017. R833836 (Final)
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  • Supplemental Keywords:

    Global climate, invasion, dune geomorphology, foredune, coastal protection, risk assessment, beach grasses, Ammophila arenaria, Ammophila breviligulata, community structure, shoreline change, ecosystem services, climate models, total water level models, management, RFA, Scientific Discipline, Air, climate change, Air Pollution Effects, Environmental Monitoring, Ecological Risk Assessment, Atmosphere, anthropogenic stress, biodiversity, environmental stressors, coastal ecosystems, ecosystem impacts, landscape characterization, climate variability, Global Climate Change

    Relevant Websites:

    Sally Hacker:

    http://www.science.oregonstate.edu/~hackers/Site/Homepage.html

    Peter Ruggiero:

    http://geo.oregonstate.edu/people/faculty/Peter_Ruggiero

    Eric Seabloom:

    http://www.tc.umn.edu/~seabloom/index.html

     

    Progress and Final Reports:

    Original Abstract
  • 2009 Progress Report
  • 2010 Progress Report
  • 2011 Progress Report
  • 2012 Progress Report