Conservation: terrestrial buffer zones for freshwater turtles

      During the school year, our class at the College of Charleston discussed an article regarding conservation biology. It was a study done in 1995 by Burke and Gibbons, reported in the journal, Conservation Biology. The article looked into the idea of adding buffer zones to protected wetland areas. It appeared that with federal regulations, the areas covered in the protected wetland area did not include enough terrestrial land to protect the hibernation and nesting sites of amphibians which are crucial for maintaining populations. It specifically looked at three freshwater turtle species in an inland wetland area in South Carolina. It concluded that if there was a buffer zone of 73 meters around wetlands, 90% of the sites would be protected. A 273 meter buffer zone would cover 100% of the sites. The conservation of wetland species was dependent on a buffer zone for access to safe terrestrial habitat in order to hibernate and reproduce.

      After looking more into the idea of conservation biology I found that there have been many studies done similar to the one previously mentioned.  One article I found is a compilation of studies throughout the United States and Canada and includes more than a staggering 8,000 sites. The study was done by Steen, Gibbs, Buhlmann, et al. and published by the journal, Biological Conservation, in June of 2012. The compilation included data for hibernation sites, nesting sites, and the tracking of females that were known to be returning from a nesting site.  Another important piece of information they looked at was distance traveled by turtle hatchlings moving to new wetland areas (dispersal). The goal of the study was to provide an idea as to how much terrestrial area was used for nesting by various freshwater turtle species. Also, by compiling the data, which consisted of 31 species of turtles, they hoped to understand what else needs to be learned in regards to the terrestrial space traveled by nesting turtles.

       The article that we had read and discussed for class only focused on three freshwater turtle species. It is clear from reading the article that compiled data from around the U.S. and Canada that some turtle species need much more terrestrial habitat than others.  Terrestrial distance from the wetland to protect 50% was as follows: “ <10 m for Malaclemys, Sternotherus, and Macrochelys;  17–34 m   for Clemmys, Apalone, Graptemys, Chelydra, Glyptemys, Actinemys, and Chrysemys; 60 m for Pseudemys; 100–120 m for Emydoidea, Kinosternon, and Deirochelys; and 816 m for Trachemys.” To Include 95% of nest sites terrestrial distance needed was: “<100 m for Malaclemys, Sternotherus, and Macrochelys; 100–200 m for Actinemys, Chelydra, Apalone, Clemmys, Pseudemys, Chrysemys,Graptemys, and Glyptemys; 200–300 m for Kinosternon and Deirochelys; 408 m for Emydoidea; and 1396 m for Trachemys.” Overall, average distances necessary to protect all species was “50% included = 93 m, 75% = 154 m, 90% = 198 m, 95% = 232 m, and 100% = 942 m.”

       The compiled data suggests that in order to protect the conservation of aquatic and semi-aquatic turtles terrestrial buffer zones around protected wetland areas need to be larger. The article reports that most protected wetland areas include a terrestrial buffer of 30-120 m. It is problematic that these zones may protect the nesting, hibernation, and migration of possibly only 50% of the turtle species.Decent increases in the protected terrestrial zone could largely increase the percentage of turtles’ sites covered.  The conservation of these turtle species revolves around their ability to safely be able to nest and migrate to and from their wetland area. Due to human encroachment of the wetland area, nesting turtles, hatchlings, and migrating turtles may be put at risk. Turtles eggs may be destroyed, turtles may be in danger while crossing roads, as well as other problems that result from human interaction and habitat fragmentation. Not only would this kind of buffer apply to freshwater turtles species. It would also help protect other aquatic and semi-aquatic animals. This study can help conservationists and spatial planners to understand, and most importantly, to plan for larger terrestrial areas surrounding wetlands if we want to preserve biodiversity. 

Article: Terrestrial habitat requirements of nesting freshwater turtles:

http://www.harding.edu/plummer/pdf/steenetal2012.pdf