Action

Restore or maintain beaches (‘beach nourishment’)

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages

  • Three studies evaluated the effects of restoring or maintaining beaches on reptile populations. All three studies were in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (3 STUDIES)

  • Abundance (1 study): One replicated, site comparison study in the USA found that gopher tortoise densities were higher and numbers occupying burrows similar on constructed sand dunes compared to natural dunes.
  • Reproductive success (2 studies): Two controlled, before-and-after studies in the USA found that one year after adding sand to beaches, nesting activity decreased more for loggerhead turtles, and loggerhead and green turtles compared to on unmodified beaches. Two years after nourishment, both studies found that loggerhead nesting activity had increased, and in one study nesting had returned to pre-nourishment levels.

BEHAVIOUR (2 STUDIES)

  • Use (1 study): One replicated, site comparison study in the USA found that burrows on a constructed dune were discovered by gopher tortoises after three months.
  • Behaviour change (1 study): One controlled, before-and-after study in the USA found that one year after adding sand to beaches, loggerhead turtles made more non-nesting crawls than on unmodified beaches, but the difference was smaller two years after nourishment.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A controlled, before-and-after study in 1992–1996 of a beach in Florida, USA (Rumbold et al. 2001) found that raising the height of a beach ridge (‘beach nourishment’) decreased loggerhead turtle Caretta caretta nesting frequency and increased the frequency of non-nesting crawls, although the effect reduced in the second year after implementation. In the first year after nourishment took place, sea turtle nesting frequency declined more, and non-nesting crawl frequency increased more on the nourished beach compared to unmodified beaches (nesting frequency declined by 4–5 nests/km/day more and non-nesting crawls increased by 5–6 crawls/km/day more on nourished beaches). In the second year, the reduction in nesting was again greater and the increase in non-nesting crawls higher on nourished compared to unmodified beaches, but the size of the effects were smaller and only statistically significant compared to one of the two unmodified beaches (nesting frequency declined by 1–2 nests/km/day more and non-nesting crawls increased by 1 crawl/km/day more on nourished beaches). In March and April 1995, a 1.6 km stretch of beach was nourished with additional sand, increasing the height of the beach ridge from an average of 32 m to 81 m. Sea turtle nesting activity was recorded daily from May to August from 1992 to 1996 at the nourished and two natural beaches three seasons prior to and two seasons immediately following beach nourishment.

    Study and other actions tested
  2. A controlled, before-and-after study in 2000–2003 on a sandy beach in Florida, USA (Brock et al. 2009) found that nesting success for loggerhead Caretta caretta and green turtles Chelonia mydas declined in the year following beach nourishment, but returned to pre-nourishment levels for loggerheads in the second year following nourishment. Nesting success declined following nourishment for loggerheads (1 year post-nourishment: 30% success; 1 year pre-nourishment: 60% success) and green turtles (1 year post-nourishment: 29%; 2 years pre-nourishment: 64%). Declines in nourished areas were larger than those seen in non-nourished areas over the same period (loggerheads: 63% vs 50%; green turtles: 55% vs 51%). In the second year following nourishment, loggerhead nesting success returned to around pre-nourishment levels (54% success). In 2002, a 5 km stretch of a 40 km beach was artificially nourished with 917,000 m3 of sand just prior to the start of the nesting season.  In May–August 2000–2003, nesting activity was monitored by counting turtle emergence tracks on the beach, and nesting success was defined as the percentage of emergences that resulted in nests. 

    Study and other actions tested
  3. A replicated, site comparison study in 2012–2016 on four sand dunes in Florida, USA (Martin et al. 2017) found that gopher tortoises Gopherus polyphemus colonized man-made sand dunes within three months of their construction, and densities were higher but occupancy of burrows similar compared to natural dunes. Overall, gopher tortoise density was higher on constructed sand dunes (2012 dune: 21 tortoises/ha; 2014 dune: 2–3) than natural dunes (0–8 tortoises/ha, see statistical model results in paper for more details). The first burrow on the dune built in 2014 was discovered three months after construction. Burrow occupancy rates were similar between dunes (2012 dune: 0.6 tortoises/burrow; 2014 dune: 0.4; natural dunes: 0.3). Gopher tortoise use of two natural and two constructed sand dunes (built in 2012 and 2014) was evaluated by surveying a 3 km long stretch of beach for tortoise burrows in May–August 2014 and 2015 (twice/year) and January 2015 and 2016 (once/year). Gopher tortoise burrow occupancy was assessed using cameras in 20 randomly selected burrows each January (one–two surveys/burrow). Resident tortoises were relocated during dune construction.

    Study and other actions tested
Please cite as:

Sainsbury K.A., Morgan W.H., Watson M., Rotem G., Bouskila A., Smith R.K. & Sutherland W.J. (2021) Reptile Conservation: Global Evidence for the Effects of Interventions for reptiles. Conservation Evidence Series Synopsis. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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Reptile Conservation

This Action forms part of the Action Synopsis:

Reptile Conservation
Reptile Conservation

Reptile Conservation - Published 2021

Reptile synopsis

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