Action

Protect habitat: Sea turtles

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

Study locations

Key messages

  • Four studies evaluated the effects of protecting habitat on sea turtle populations. One study was in each of Costa Rica, the Seychelles, Belize and the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (4 STUDIES)

  • Abundance (3 studies): One before-and-after study in Costa Rica found that after an area was protected, there were fewer nesting female leatherback turtles than before protection. One replicated, randomized, site comparison study off the coast of Belize found that in protected areas there were more hawksbill turtles than outside. One site comparison study in the USA found that differences in the abundance of green, loggerhead and hawksbill turtles in protected and unprotected areas were mixed.
  • Reproductive success (2 studies): One before-and-after study in Costa Rica found that after an area was protected, more leatherback turtle hatchlings were produced than before protection. One before-and-after study in the Seychelles found that nesting activity by green turtles increased following both habitat and species protection.

BEHAVIOUR (0 STUDIES)

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 before-and-after study in 1988–2004 on three beaches in Costa Rica (Santidrián Tomillo et al. 2007) found that six years after a national park was created, numbers of nesting female leatherback turtles Dermochelys coriacea tended to be lower and hatchling numbers tended to be higher than before the park was created. Results were not statistically tested. In the six nesting seasons after a national park was created, 68–1,000 female leatherback turtles nested/year and 15,734–153,547 hatchlings/year were produced, compared to 732–1,504 nesting female leatherback turtles and 30,180–30,788 hatchlings/year in the three years before the park’s creation. The park was declared in 1991 and comprises three beaches. An unspecified number of nests were relocated due to threat of tidal inundation. Nesting female numbers were based on counting depressions left in the sand by nesting turtles.

    Study and other actions tested
  2. A before-and-after study in 1968–1976 and 1981–2008 on sandy beaches on an atoll island, Aldabra Atoll, Seychelles (Mortimer et al. 2011) found that legal protection for green turtles Chelonia mydas, followed by protection of the whole island 15 years later, was associated with an increase in nesting activity. Results were not statistically tested, and the effects of species and habitat protection cannot be separated. Overall nesting activity was estimated to be higher 36–40 years after turtle protection began (2004–2008: 28,200 nesting attempts/year) compared to 13–17 years after turtle protection began (1981–1985: 10,900–16,500 nesting attempts/year). The authors also reported that estimates of nesting activity around the time that turtle protection began ranged from sightings of seven females (11 day survey in 1967), to 2,000–3,000 nests/year (surveys during 1968–1970 and 1975–1976). Protection for turtles began in 1968, with the Green Turtle Protection Regulations 1968, and the atoll became a UNESCO World Heritage Site in 1983. In 1981–2008, up to 68 nesting beaches on the atoll were surveyed for turtle tracks and evidence of nesting. Survey effort varied between different years and beaches, with beaches surveyed 0–37 times/years in 1981–1994, and 4–171 times/month in 1995–2008.

    Study and other actions tested
  3. A replicated, randomized, site comparison study in 2009–2010 on an offshore coral reef atoll with two marine protected areas near Belize (Scales et al. 2011) found that hawksbill turtle Eretmochelys imbricata abundance was greater inside than outside protected areas. Hawksbill turtle abundance was greater inside protected areas (2–3 turtle sightings/hour) than outside protected areas (1 turtle sightings/hour). Hawksbill turtles were surveyed in the vicinity of a coral reef atoll (45 km long and 10 km wide) that contained six small cays and two no-take protected areas. Turtles were monitored on 49 randomly selected transects (1 km long) carried out over 30 days in April–May 2010 by three swimmers (1–20 m depths). In addition, 26 turtles were captured in April–May 2009 and in May 2010. Captured turtles were weighed and measured and a subset (10 individuals in 2009 and 9 individuals in 2010) were radio tracked every 24 hours for 6–25 days. It is unclear whether the captured turtles were included in the abundance estimates.

    Study and other actions tested
  4. A site comparison study in 2003–2012 in shallow coastal and deeper water off the coast of Florida, USA (Herren et al. 2018) found that inside a protected area there were fewer green turtles Chelonia mydas, more loggerhead turtles Caretta caretta and similar numbers of hawksbill turtles Eretmochelys imbricata compared to outside of the protected area. Results were not statistically tested. Inside a protected area, 0.1–0.6 green turtles/km, 0.2–0.5 loggerhead turtles and 0.01–0.2 hawksbill turtles were encountered compared to 1.8 green turtles/km, 0.1 loggerhead turtles/km and 0.01 hawksbill turtles/km outside the protected area. Three sites (15–27 km2) were surveyed in shallow-water habitats (0.2–6 m depths) inside a protected area (a national marine sanctuary covering 835 m2 of open water and 8 km2 on land) and compared to a single unprotected site (36 km2) in deeper waters (3–6 m depths). Surveys were carried out during 27 boat trips in September 2003–September 2012 (139 total survey days) by driving haphazard, non-linear transects on a boat with several observers (129 km2 total area covered by surveys). Turtle sightings were recorded and where possible turtles were captured, individually-marked, weighed and measured.

    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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