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6 Coastal Change and Human Health This chapter provides a summary of a presentation on the role of coastal ecosystems in protecting Gulf Coast communities; the Louisiana Gulf Coast is discussed as an example. The presentation highlights the role that intact coastal ecosystems (barrier islands and wetlands) can play in mitigating flooding and in wave attenuation. These ecosystems play a critical role in mitigating low-magnitude, high-frequency events such as storm surges and flooding that can be disruptive to community life. The summary of the presentation is followed by a summary of the discussion that ensued. THE ROLE OF COASTAL ECOSYSTEMS IN PROTECTING GULF COAST COMMUNITIES Denise J. Reed, Ph.D. Chief Scientist, The Water Institute of the Gulf Denise J. Reed began by stating that her presentation would focus on ecosystem services and coastal protection and the notion that natural systems can protect coastal communities. She went on to explain that coastal areas are dynamic places. They are modified by the changes people make to natural systems, for example, the effect of increased population pressure on ecosystems. Some natural systems remain intact in isolated places in Alaska which experience less population pressure and important ecosystems continue to thrive in those areas. Much can be learned by contrasting modified ecosystems and those that remain in a natural state to determine an appropriate point between the two extremes that could be aimed for, she said. 83
84 ECOSYSTEM SERVICES AND HUMAN HEALTH Louisiana Coastal Ecosystem Reed mentioned that as a Louisiana resident she has directly observed changes in the coastal systems in Louisiana. She noted that since the 1930s, coastal Louisiana has lost 1,880 square miles from land to open water. Currently the coast is losing more than 16 square miles per year. It is estimated that the coast may lose up to an additional 1,750 square miles of land over the next 50 years without any increase in coastal preservation. In Louisianaâs Comprehensive Master Plan for a Sustainable Coast,1 an estimate was developed for the impact of a 100-year storm 50 years into the future. This scenario is for a storm that has a 1-in-100 chance of occurring in any given year. Under this scenario, the whole coast of Louisiana would be in the floodplain (0â5 feet) and some communities would be very deep in the floodplain (20â25 feet). The potential damages of such a storm would reach up to $23.4 billion annually and there would be implications for peopleâs lives, jobs, communities, and the economy (Coastal Protection and Restoration Authority of Louisiana, 2012). The Protective Role of Coastal Ecosystems Reed then posed the question, what if we could reverse land loss trends? An analysis included in the master plan showed that if $25 billion dollars were spent on the best projects, land lost could be curtailed, not returned, but land lost could be stopped or reach equilibrium. What would that do for flooding for coastal communities? What would it mean for coastal communities? What would it mean for the culture of the communities and the lifelines or supporting infrastructure for communities (roads, power lines, and other services and structures essential for sustaining life)? In response to these questions, Reed stated that science provides some answers. Reed discussed a study by Leonard and Croft (2006) that demonstrated that wetlands do change how water flows through them. In this study the water flow velocity, turbulence, and total turbulent kinetic energy were different in land bodies with a Spartina alterniflora marsh canopy compared to those without. Studies also indicate that the coastal 1 Louisianaâs Comprehensive Master Plan for a Sustainable Coast is available at: http://issuu.com/coastalmasterplan/docs/coastal_master_plan-v2?e=3722998/24 47530 (accessed August 14, 2013).
COASTAL CHANGE AND HUMAN HEALTH 85 plant community can affect the way water moves through the wetlands. Plants have individual properties and community properties that affect wave dissipation (Anderson et al., 2011). Seaweed fronds, for example, recline against each other to withstand the high velocity of waves and mangrove density moderates the role of wave breaking on overall wave attenuation. A meta-analysis of studies on the protective role of coastal marshes (Shepard et al., 2011) found that salt marshes or coastal wetlands that are flooded and drained by saltwater brought in by the tides (such as those found along the Gulf Coast) have value for coastal hazard mitigation and climate change adaptation. Factors identified in potentially influencing wave attenuation included marsh species identity or type, density, height, percent cover, and patch size and location. Factors that correlated with shoreline stabilization included species identity, vegetation density, vegetation height, and biomass production. Reed went on to discuss storm surges, an issue of great public concern, and the role of wetlands to mitigate their impacts. He described a study conducted by Loder and colleagues (2009) that employed numerical modeling to determine the effect of the elevation of the marsh (high or low) and storm surge elevation. They found that higher marsh elevation has a protective impact on storm surge elevation. The lower the marsh, the lower the protective effect on storm surge and as the storm surge rises, the protective effect of the marsh is eliminated. Reed said these findings point to where and when this protective ecosystem service can be most effective. The study also highlights the variability in the potential protective effects in ecosystem services because storm surges and marsh elevation are not static. The variability in protective effects of ecosystem services has also been explored in mangroves and wave attenuation, Reed said. Studies have found that wave attenuation is influenced by a number of factors, including the species of mangrove, their location, and age of trees. Studies also indicate that the protective effects of mangroves on wave attenuation are very variable. Ecosystem Restoration and Mitigation of Low-Magnitude, High-Frequency Events Reed went on to discuss how ecosystem restoration can assist coastal communities. She noted that there are many low-magnitude, high- frequency events that affect everyday life that need to be considered and managed. Resilient coastal ecosystems are an ecosystem service that
86 ECOSYSTEM SERVICES AND HUMAN HEALTH could play a role in mitigating these events. Big flood events, she said, will inflict damage even with an âintact coastâ and for these, communities must prepare, adapt, and at times evacuate. She also noted that sea-level rise increases flooding over time even without coastal change; this situation will have to be addressed. Reed emphasized that messaging should not ignore the lower- magnitude, higher-frequency nondisaster events where actions to restore coastal habitats can make the most difference. Road floods are an example of this type of event. When roads flood, school bus and other transportation is disrupted making it a challenge to get children to school and employees to work. Flooding also affects yards and parks and can reduce recreational opportunities. Houses may need to be elevated in flood areas, which can become a significant problem for elderly and disabled individuals who have difficulty navigating stairs. Flood areas are associated with increased mosquitoes and the public health problems they pose. In some rural communities that rely on septic tanks, these do not work when water levels are too high and can pose important sanitation problems. In closing, Reed stated that the important message for coastal protection is the way in which intact, restored barrier islands, and wetlands interact with coastal water movements. It is not about big events such as Katrina, but the protection ecosystem services provide in mitigating the moderate events that happen more frequently. Further, the additional services (recreation, fisheries) and value provided by ecosystems also provide another reason to focus on the natural systems that can protect coastal communities. DISCUSSION Jay Lemery began the discussion by asking Reed about the mindset for preventive action in the Gulf, especially after Katrina. Reed responded that the mindset in the Gulf is âyou pay now or you pay later,â and it is getting more and more difficult to expect people living in the area to start over again. An audience member commented that humans do things to the ecosystem and expect nature to behave differentlyâfor example we build in low-lying areas and expect that the surge will not affect the area. What needs to change is human nature, not nature. Humans need more common sense in how these ecosystems are used.
COASTAL CHANGE AND HUMAN HEALTH 87 Reed responded that we need to make tough decisions regarding how to invest in coast-dependent activities. There are some activities which need to be located near the water such as port activities. Oil and refinery facilities also need to be near water and on flat land; the financial sector on the other hand does not need to be located near water. We need to be more strategic with undertaking water-dependent operations and securing them. Christopher Portier and Linda McCauly both commented on the adverse impact of high-frequency events and ecosystem degradation on communities along the coast. Reed gave an example of a Native American community that has been dwindling over time in response to frequent events and ecosystem degradation. She said that the chief of the community has made a push to relocate the people as a group together to another place where they can still have a sense of community. Reed said that people tend to move individually, leaving the community unviable; ultimately there is a loss of social cohesion and the sense of community is lost. Linda McCauley referred to one of Reedâs slides showing the extent of land that would be underwater and not sustainable. Reed commented that a plan for the future for such areas is needed, but must have reasonable expectations. Building up marshlands or viable wetlands can make a difference but they can only do so much. She reiterated that in the idealized analysis she discussed earlier (that would spend $250 billion over 50 years) would result in a different future but it would never return the ecosystem to its previous state. Reed emphasized that from a ecosystem protection perspective, it is important to communicate to the public about those high-frequency events because people can relate to them and remember them. These events also provide a basis for further communication about more complex choices and longer-term decisions at the household and community level. REFERENCES Anderson, M. E., J. McKee Smith, and S. Kyle McKay. 2011. Wave dissipation by vegetation. ERDC/CHL CHETN-I-82. Vicksburg, MS: U.S. Army Engineer Research and Development Center. Coastal Protection and Restoration Authority of Louisiana. 2012. Louisianaâs comprehensive master plan for a sustainable coast. Baton Rouge, LA: Coastal Protection and Restoration Authority of Louisiana.
88 ECOSYSTEM SERVICES AND HUMAN HEALTH Leonard, L. A., and A. L. Croft. 2006. The effect of standing biomass on flow velocity and turbulence in Spartina alterniflora canopies. Estuarine, Coastal, and Shelf Science 69(3â4):325â336. Loder, N. M., M. A. Cialone, J. L. Irish, and T. V. Wamsley. 2009. Idealized marsh simulations: Sensitivity of storm surge elevation to seabed elevation. ERDC/CHL CHETN-I-78. Vicksburg, MS: U.S. Army Engineer Research and Development Center. Shepard, C. C., C. M. Crain, and M. W. Beck. 2011. The protective role of coastal marshes: A systematic review and meta-analysis. PLoS ONE 6(11): e27374, doi:10.1371/journal.pone.0027374.