The green sea turtle is one of the largest hard-shelled marine turtles and the only sea turtle whose adults feed almost entirely on plants. Found across tropical and subtropical seas worldwide, it grazes seagrass meadows and algae beds, helping shape these habitats. Decades of coordinated protection have reversed many of its historic declines, making it one of the most closely watched recovery stories in marine conservation [NOAA 2024].
Biology and Identification
Adult green sea turtles typically measure about 3 to 4 feet (roughly 1 to 1.2 meters) in shell length and weigh between 250 and 400 pounds (about 110 to 180 kilograms) [NOAA 2024]. The species takes its common name not from the color of its shell but from the greenish tint of the body fat, a result of its plant-based diet. While hatchlings and juveniles are omnivorous, adults are uniquely herbivorous among sea turtles, feeding mostly on seagrasses and algae [NOAA 2024]. Their grazing alters the structure of seagrass meadows and shapes the wider herbivore community, and in some shallow reef and seagrass habitats green turtles can become the dominant grazers [Cardona et al. 2020].
Green sea turtles are slow to mature, often requiring decades to reach breeding age, and individuals are estimated to live 70 years or more [NOAA 2024]. Females undertake long migrations between foraging grounds and the beaches where they hatched, returning to nest at intervals of several years [Seminoff 2023].
Habitat and Range
The species occurs in the Atlantic, Pacific, and Indian Oceans and in the Mediterranean Sea, generally in warm coastal waters where seagrass and algae are abundant [NOAA 2024]. In United States waters, green sea turtles are found along the Atlantic coast from Texas to Maine, in Puerto Rico and the U.S. Virgin Islands, and across the Pacific from southern California to Hawaii, American Samoa, Guam, and the Northern Mariana Islands [NOAA 2024]. Major nesting aggregations occur in the wider Caribbean, including the Costa Rican Caribbean coast, which hosts one of the largest green turtle rookeries in the region [NOAA 2024]. The turtles move seasonally between offshore developmental habitats, nearshore foraging meadows, and natal nesting beaches [Seminoff 2023].
Conservation Status
The green sea turtle is listed as Least Concern on the IUCN Red List, following a global reassessment adopted in 2025 that downlisted the species from its long-standing Endangered classification [IUCN 2025]. The previous global assessment had listed the species as Endangered under criteria A2bd, a status carried from 2004 through an amended 2023 assessment by the IUCN SSC Marine Turtle Specialist Group [Seminoff 2023]. The 2025 reassessment reflected an overall global increase of roughly 28% in green turtle abundance since the 1970s, driven by recoveries at major nesting sites [IUCN 2025]. These findings are consistent with peer-reviewed analyses showing that most regional management units for sea turtles, including green turtles, have shown increasing rather than decreasing nesting abundance in recent decades [Mazaris et al. 2017].
Recovery is well documented in the United States. On Florida's standardized index nesting beaches, annual green turtle nest counts have risen from fewer than 300 when systematic surveys began in 1989 to record highs exceeding 60,000 nests in peak years [FWC 2025]. Despite the improved global category, the population remains far below historical levels, and several regional subpopulations are still assessed at higher risk; in the North Indian Ocean green turtles remain Vulnerable overall, and in some areas such as the Maldives they remain Endangered [IUCN 2025]. Under the U.S. Endangered Species Act, the species is managed as eleven distinct population segments, three listed as endangered and eight as threatened, and it is listed on Appendix I of CITES, which prohibits international commercial trade [NOAA 2024].
Threats
Although the global trend is improving, green sea turtles continue to face serious, documented threats. Incidental capture (bycatch) in commercial fishing gear remains a leading source of mortality [NOAA 2024]. Direct harvest of turtles and their eggs persists in some regions despite legal protection [NOAA 2024]. Coastal development degrades and destroys nesting beaches and foraging habitat, while vessel strikes and the ingestion of or entanglement in marine debris add further pressure [NOAA 2024]. The disease fibropapillomatosis, which causes tumors that can impair feeding and movement, affects green turtles in several areas [NOAA 2024]. Because the species matures slowly, recovery from these pressures is gradual, and changing environmental conditions pose longer-term risks, including warming sand temperatures that skew hatchling sex ratios and the erosion of low-lying nesting beaches [IUCN 2025].
What Is Being Done
The green sea turtle's recovery has been credited to sustained, coordinated conservation across many nations. Long-term nesting-beach protection, restrictions on harvest, and international trade bans under CITES Appendix I have allowed populations to rebuild [IUCN 2025]. Peer-reviewed assessments have documented these gains and underscored the value of long-term monitoring in detecting recovery [Mazaris et al. 2017]. In the United States, NOAA Fisheries and the U.S. Fish and Wildlife Service share jurisdiction under the Endangered Species Act, implementing recovery measures, designating critical habitat, and requiring turtle excluder devices in certain trawl fisheries to reduce bycatch [NOAA 2024]. The IUCN SSC Marine Turtle Specialist Group compiles the global and regional assessments that guide these efforts and track population trends [Seminoff 2023]. State agencies contribute essential monitoring; Florida's standardized index nesting beach surveys, run by the Florida Fish and Wildlife Conservation Commission, provide one of the longest continuous records of green turtle nesting recovery [FWC 2025].
How You Can Help
Members of the public can support green sea turtle recovery in straightforward, non-coercive ways. Supporting established, science-based conservation organizations and agency monitoring programs helps sustain the long-term data and protection that underpin recovery [NOAA 2024]. Coastal residents and visitors can keep nesting beaches dark and undisturbed during nesting season, avoid disturbing turtles, and reduce single-use plastics that become harmful marine debris [NOAA 2024]. Reporting stranded, injured, or nesting turtles to the appropriate wildlife authority contributes valuable citizen-science data [FWC 2025]. Choosing seafood from fisheries that use bycatch-reduction measures, and supporting informed policy that maintains those protections, helps address the threats that still affect the species [NOAA 2024].
References
[IUCN 2025] IUCN SSC Marine Turtle Specialist Group. (2025). Chelonia mydas (Green Turtle), global reassessment to Least Concern. The IUCN Red List of Threatened Species. https://www.iucnredlist.org/species/4615/11037468
[Seminoff 2023] Seminoff, J.A. (2023). Chelonia mydas (amended version of the 2004 assessment). The IUCN Red List of Threatened Species 2023: e.T4615A247654386. https://doi.org/10.2305/IUCN.UK.2023-1.RLTS.T4615A247654386.en
[NOAA 2024] NOAA Fisheries. (2024). Green Turtle (Chelonia mydas): Species directory — biology, range, threats, and Endangered Species Act listing. National Oceanic and Atmospheric Administration. https://www.fisheries.noaa.gov/species/green-turtle
[FWC 2025] Florida Fish and Wildlife Conservation Commission. (2025). Index Nesting Beach Survey Totals (1989–present) and Sea Turtle Nesting Trends in Florida. https://myfwc.com/research/wildlife/sea-turtles/nesting/beach-survey-totals/
[Mazaris et al. 2017] Mazaris, A.D., Schofield, G., Gkazinou, C., Almpanidou, V., & Hays, G.C. (2017). Global sea turtle conservation successes. Science Advances, 3(9), e1600730. https://doi.org/10.1126/sciadv.1600730
[Cardona et al. 2020] Cardona, L., Campos, P., & Velásquez-Vacca, A. (2020). Contribution of green turtles Chelonia mydas to total herbivore biomass in shallow tropical reefs of oceanic islands. PLOS ONE, 15(2), e0228548. https://doi.org/10.1371/journal.pone.0228548