The status of green sea turtles (East Pacific) can be measured in several ways. These subsections highlight a few of the measures of the species’ status.
Threat & Demography
A species’ conservation status consists of two components: the status of threats to the species and the species’ demographic status. Neither component alone is sufficient for evaluating “how a species is doing”; both must be considered. Defenders of Wildlife has developed a simple method for scoring the threat and demographic status of imperiled species (Malcom et al. 2016), which we illustrate here. Note that the data shown are not real data.
5-year review (2007)
THREATENED BREEDING POPULATIONS
Current nesting abundance trends were determined for 23 threatened nesting concentrations among 11 ocean regions around the world. They included both large and small rookeries and are believed to be representative of the overall trends for their respective regions. Of these 23 sites for which data enable an assessment of current trends, 10 nesting populations are increasing, 9 are stable, and 4 are decreasing. Long-term continuous datasets ≥20 years are available for 9 threatened population sites, all of which are either increasing or stable. These include Ascension Island, Hawaii, Heron Island, Ogasawara Islands, Philippine Turtle Islands, Sabah Turtle Islands, Sarawak, Terengganu, and Tortuguero. Despite the apparent global increase in numbers, the positive overall trend should be viewed cautiously because trend data are available for just over half of all sites examined. With respect to regional trends, data from index sites suggest that some regions are doing better than others based on available trend data. Nesting populations are doing relatively well (# increasing sites > # decreasing sites) in the Pacific, Western Atlantic, and Central Atlantic Ocean. In contrast, populations are doing relatively poorly in Southeast Asia, Eastern Indian Ocean, and perhaps the Mediterranean.
Threats to nesting and marine habitats continue to affect threatened green turtle populations. Continuing human population expansion into coastal areas is expected to increase the severity of existing threats and is therefore a cause for major concern. Green turtles are also highly vulnerable to anthropogenic impacts during all life-stages, and three of the biggest threats result from harvest for commercial and subsistence use (e.g., egg harvest, the harvest of females on nesting beaches, and directed hunting of green turtles in foraging areas). Diseases, particularly fibropapillomatosis, threaten a large number of existing subpopulations. Fisheries bycatch in artisanal and industrial fishing gear is also a major impact. These fisheries practices include drift-netting, long-lining, set-netting, pound netting, and trawl fisheries, and their adverse impacts on sea turtles have been documented in marine environments throughout the world. In addition, increasing incidence of exposure to heavy metals and other contaminants in the marine environment is of concern in some areas. Additional factors affecting green turtles include boat traffic and its modification of green turtle behavior in coastal areas, boat strikes as a major mortality source in some areas, the ingestion of and entanglement in marine debris that can reduce food intake and digestive capacity, and the interaction with oil spills.
ENDANGERED FLORIDA BREEDING POPULATION
The green turtle nesting population of Florida appears to be increasing based on 18 years (1989-2006) of index nesting data from throughout the state. Although in the last four years there are three ‘low’ years, this may be due to lesser reproductive effort as a result of environmental variability at foraging grounds rather than a decrease in the number of nesting females. The increase in nesting in Florida is likely a result of several factors, including: (1) a Florida statute enacted in the early 1970s that prohibited the killing of green turtles in Florida; (2) the species listing under the ESA in 1973, affording complete protection to eggs, juveniles, and adults in all U.S. waters; (3) the passage of Florida’s constitutional net ban amendment in 1994 and its subsequent enactment, making it illegal to use any gillnets or other entangling nets in state waters; (4) the likelihood that the majority of Florida adult green turtles reside within Florida waters where they are fully protected; (5) the protections afforded Florida green turtles while they inhabit the waters of other nations that have enacted strong sea turtle conservation measures (e.g., Bermuda); and (6) the listing of the species on Appendix I of CITES, which stopped international trade and reduced incentives for illegal trade from the U.S.
While nesting has increased, impacts to nesting beaches and the marine environment have also increased. Among the most significant threats to nesting habitat in Florida are structural impacts (e.g., construction of buildings, beach armoring, and beach renourishment) and beachfront lighting. These activities result in direct habitat destruction and degradation decreasing the extent and suitability of nesting sites on Florida beaches (e.g., increased erosion, altered thermal profiles). The high incidence of fibropapillomatosis disease among some foraging populations is a serious concern. Within U.S. waters, fisheries bycatch of Florida green turtles remains a threat. Human threats (e.g., directed killing, fisheries bycatch) outside of Florida may have profound impacts on the Florida breeding population because of the dispersal of Florida green turtles to juvenile foraging areas throughout the Wider Caribbean and Gulf of Mexico. Vessel strikes are a growing concern and, as human populations increase in coastal areas, vessel strikes are likely to increase.
ENDANGERED PACIFIC MEXICO BREEDING POPULATION
There is one primary nesting concentration in Pacific Mexico (Colola, Michoacan) and three lesser nesting sites (Maruata, Michoacan; Clarion Island, Revillagigedos Archipelago; and Socorro Island, Revillagigedos Archipelago). Based on nesting beach monitoring efforts, a mean of roughly 6,050 nests are deposited each year in Pacific Mexico. The only long-term trend data available are for Colola, the largest nesting concentration in Pacific Mexico, where nesting beach monitoring has been ongoing every year since the 1981-1982 nesting season. Based on the 25-year trend line, it is clear that green turtle nesting has increased since the population’s low point in the mid 1980s to mid 1990s. This observed increase may have resulted from the onset of nesting beach protection in 1979 – as is suggested by the similarity in timing between the onset of beach conservation and the age-to-maturity for green turtles in Pacific Mexico. The initial upward turn in annual nesting was seen in 1996, about 17 years after the initiation of a nesting beach protection program, and growth data from the Gulf of California suggest that green turtles mature at about 15-25 years. Although not a clear cause of the increasing nesting trend, the consistency in timing is nonetheless compelling. The 1990 presidential decree protecting all sea turtles of Mexico certainly helped the situation, but this occurred much later than the start of nesting beach conservation. It is more likely that this national legislation has had its greatest positive impact at the foraging areas, where green turtle hunting was once rampant.
Impacts to green turtle habitat are diverse and widespread in Pacific Mexico. Several of the lesser green turtle nesting beaches in Mexico suffer from coastal development, a problem that is especially acute at Maruata, a tourist site with tourist activity and heavy foot traffic during the nesting season. Artificial lighting is also a problem in many of these areas. Other significant impacts on nesting beach habitat include disturbances from feral and domestic animals. Coastal development also constitutes a major threat to marine habitats in several areas, perhaps none more so than in northwest Mexico where the development of a large marina network is planned for at least five major foraging areas. Green turtles are also highly vulnerable to anthropogenic impacts during all life-stages, and three of the biggest threats result from harvest for commercial and subsistence use (e.g., egg harvest, the harvest of females on nesting beaches, and directed hunting of green turtles in foraging areas). Because of the dispersal of green turtles nesting in Pacific Mexico to areas throughout the Eastern Pacific Ocean, human threats (e.g., global warming, fisheries bycatch, contamination) outside of Mexico may have profound impacts on the local breeding population.
From the 1998 recovery plan
Under the U.S. Endangered Species Act (ESA) of 1973, as amended, the breeding populations of Chelonia mydas from the Pacific coast of Mexico are listed as Endangered. Similarly, all populations of Chelonia mydas are classified as Endangered in the International Union for Conservation of Nature and Natural Resources’ (IUCN) Red Data Book, where taxa so classified are considered to be “in danger of extinction and whose survival is unlikely if the causal factors continue operating” (Groombridge 1982). Populations of Chelonia mydas are included in Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), a designation which bans trade in specimens or products except by special permit. Such permits must show that the trade is not detrimental to the survival of the species and is not for primarily commercial purposes (Lyster 1985).
Excessive exploitation of the East Pacific green turtle throughout its range has caused a dramatic decline in numbers over the 1900s. In Michoacán, Mexico where about one third of all East Pacific green turtles nest, the population has exhibited a clear decline in numbers over the last 40 years. Similarly, East Pacific green turtles were abundant and widespread in northern 8 Mexico feeding grounds (Gulf of California) and along the Pacific coast of Baja California as late as the 1960s. Today, East Pacific green turtles are rare in the Gulf of California and most appear to be juveniles (see Historical and Cultural Background).
In Mexico, a presidential decree (May 1990) banned the harvest of all sea turtles and their eggs, as well as trade in sea turtle products. This has drastically diminished (but not eliminated) clandestine harvest and trade in sea turtle products. Field enforcement, however, remains extremely difficult. Effective 30 September 1991, Mexico became the 111th Party to CITES. Mexico ratified CITES with no reservations.
Section 7 consultations
Section 7 of the Endangered Species Act directs federal agencies to use their authority to help conserve listed species. One way they do this is by consulting with the Fish and Wildlife Service and/or the National Marine Fisheries Service if any action they authorize, fund, or carry out might affect listed species. The graphs below show the consultations – formal and informal – for green sea turtles from January 2008 through February 2016.
Section 10 agreements
Section 10 of the Endangered Species Act creates a mechanism for non-federal parties to take threatened and endangered species if it is done in the context of a plan for conserving the species overall. The following Habitat Conservation Plans (HCPs) or Safe Harbor Agreements (SHAs) have been put in place for green sea turtles:
- Waddell, Raymond
- Volusia County
- Volusia Beaches
- Suggs, Raymond & Dale(Hancock, John) ABM
- Stallworth Preserve – amendment #1
- Stallworth Preserve
- Sizemore, Daniel (ABM)
- Sage Development Amendment #1
- Roberds, George
- Indian River County Sea Turtle
A future version of this page may include a microapp that displays tables and figures, such as shown in Defenders’ section 10 working papers here and here, for each species. If shapefiles of section 10 agreements are made available (or if Defenders digitizes them), those could easily be displayed here.