Literature Summary #4 Ed Pritchard
Rizkalla, Carol E. and Savage, Anne 2011. Impact of Seawalls on Loggerhead Sea Turtle
(Caretta caretta) Nesting and Hatching Success. Journal of Coastal Research (2011) Vol. 27,
166-173.
Both authors, Carol E. Rizkalla and Anne Savage are with the Department of Education &
Science at Disney’s Animal Kingdom in Lake Buena Vista, FL.
1) Research problem or question: The particular interest of this study is to investigate the impact of seawalls and beach armoring to sea turtle nesting in Florida. This study expands on previous research by examining the effects of two seawalls using 7 years of nesting and hatching success data.
2) Background knowledge leading up to study: The southeastern United States hosts the largest assemblage of loggerhead sea turtles (Caretta caretta) in the western hemisphere, with approximately 90% of nesting occurring on Florida beaches. Approximately onequarter of beaches along Florida’s east coast are armored with some type of hard structure placed parallel to the shoreline, with bulkheads and seawalls being the most common form of armoring.
3) Methods used by investigators: Nesting activity was recorded between March and
October 2003-2009 along a 1.7-km stretch of beach in Indian River County, Florida. The beach was divided into zones which included a seaward wall zone (max of 5 m of dry beach in front of wall), a landward wall zone (20 m of dry beach in front of wall), and a control zone which was made up of 511 m of undeveloped beach which contained dune escarpments during much of the study period. Nest monitoring took place throughout the three zones and paired t-tests were used on the data from 2003-2009 to compare emergence, nest density, and nesting success between the seaward wall and the unarmored beach. Chi-square tests were also used for paired comparisons between the seaward wall, landward wall, and unarmored beach for data collected from 2007-2009.
Finally, the researchers tested the relative impact of the seawalls in association with other factors on nest site selection using classification and regression trees.
4) Results: The data presented here indicate that seawalls impact loggerhead sea turtle nesting by reducing nesting success and increasing the likelihood of nests being washed away during storm events. Fewer animals emerged in front of the seaward wall and there were fewer nests, but it remains unclear by what mechanism turtles detect appropriate

nesting habitat.
Proportion of marked nests that washed away, and average hatching success for loggerhead nests remaining at seawalls and unarmored beach. Note that no nests were marked for excavation at the landward wall in 2007. Asterisk indicates a statistical difference between the density at a given wall and unarmored beach.
5) Weakness of study: This study was only focused on one species of sea turtle, the
Loggerhead. Future studies are needed to examine the effects of seawalls on nesting of other species, as each species has their own nesting requirements. Furthermore, the impact of storm on nesting and erosion was a variable that was studied in very little detail as most of the strong and powerful storms that affected the test site developed later in the nesting season. But with an increase in number and intensity of storms projected in the coming decades, it is crucial that this factor be studied in greater detail in relation to sea turtle nesting.
6) What was learned: Sea walls prevent turtles from nesting by destroying nesting habitat and also contribute to further beach erosion, causing beach loss for people as well as turtles. Beach erosion often puts coastal counties and the state in the difficult position of having to protect private property while also complying with the rules and regulations designed to protect sea turtles and their habitats. This conflict is evident in Indian River
County on Florida’s east coast. Hurricanes underscore the need to protect as much nesting habitat as possible from development. Ultimately, sea levels will rise, buildings will continue to be threatened by the sea, and in response, armoring will continue to be put in place so sea turtle nesting beaches will continue to shrink.