If green sea turtles disappeared, the ripple effects would spread across oceans, beaches, and coastal economies. These turtles are one of the few large animals that graze on seagrass, and that single role connects them to carbon storage, commercial fisheries, shoreline stability, and dozens of species that depend on their bodies as habitat. No other marine animal fills the same ecological niche, so their loss would leave gaps that nothing else could easily close.
Seagrass Meadows Would Become Overgrown
Green sea turtles are the ocean’s lawnmowers. They crop seagrass blades regularly, which keeps meadows short, productive, and healthy, much the way periodic mowing keeps a lawn thick. Without turtles grazing, seagrass beds would grow tall and dense at first. That sounds like a good thing, but overgrown seagrass accumulates dead organic material, shades out new growth at the base, and becomes more vulnerable to disease. Historically, when other large seagrass grazers disappeared from marine ecosystems, the meadows they maintained eventually degraded.
Interestingly, research from marine protected areas in the tropics shows that the relationship between turtles and seagrass is a delicate balance. When turtle populations rebound too quickly in a confined area, they can actually overgraze, digging up roots and rhizomes and pushing meadows toward collapse. The healthy middle ground, where turtles trim leaves without destroying root systems, is what keeps seagrass thriving. Remove turtles entirely, and that balance vanishes in the other direction.
Carbon Storage Would Shift
Seagrass meadows are one of the planet’s most efficient carbon sinks, sometimes called “blue carbon” ecosystems. Turtle grazing does reduce the rate at which seagrass pulls carbon from the water. In a Caribbean study, grazed seagrass areas showed 79% lower net carbon uptake compared to ungrazed areas (about 25 versus 120 millimoles of carbon per square meter per day). So at first glance, losing turtles might seem beneficial for carbon storage, since ungrazed meadows absorb more carbon in the short term.
But this overlooks the bigger picture. Grazed meadows stay healthier and more resilient over time. Without grazing, seagrass beds can become choked with decaying material and eventually decline, taking their carbon stores with them. The same research found that grazing doesn’t cause existing carbon locked in seafloor sediments to be released. In other words, turtles reduce future carbon uptake slightly but protect the massive carbon reserves already banked in the sediment. Losing that long-term stability could ultimately hurt carbon storage more than the short-term boost from overgrowth would help.
Commercial Fisheries Would Lose Nursery Habitat
Seagrass meadows serve as nurseries and feeding grounds for commercially important species, including tiger prawns, conch, Atlantic cod, white spotted spinefoot, and Caribbean spiny lobster. Globally, seagrass provides nursery habitat for roughly 21.5% of the world’s top 25 most-landed fish species, including Alaska pollock, the single most harvested fish on Earth.
If green sea turtles vanished and seagrass health declined as a result, those nursery grounds would deteriorate. Juvenile fish and shellfish that shelter in seagrass during vulnerable life stages would have fewer places to hide from predators and feed. The connection isn’t instant or dramatic. It would play out over years and decades as degraded meadows supported fewer and fewer young animals, gradually reducing the populations that coastal fishing communities depend on.
Beaches and Dunes Would Lose a Fertilizer
Every nesting season, female green sea turtles haul themselves onto beaches and bury clutches of roughly 100 eggs in the sand. Not every egg hatches. The unhatched eggs, along with eggshell fragments and fluids from successful nests, decompose and release nitrogen and other nutrients into dune soils. Research along a 40-kilometer stretch of Florida coastline found that soil nitrogen levels were directly correlated with the density of turtle nests. On beaches with more nests, dune plants like sea oats showed higher nitrogen uptake from marine-derived sources.
This matters because dune vegetation is what holds beaches together. Healthier, more vigorous plants mean more extensive root systems, which stabilize sand against wind and storm erosion. Without the nutrient input from turtle nests, dune plants in heavily nested areas would grow less vigorously, potentially making those shorelines more vulnerable to erosion over time. On beaches where turtles nest at densities above 1,000 nests per kilometer, this fertilization effect is substantial.
Predators Would Lose a Seasonal Food Source
Tiger sharks are the most prominent predators of adult green sea turtles. At Raine Island in Australia, home to the world’s densest green turtle nesting colony, tiger sharks time their movements to coincide with nesting season, targeting turtles as a predictable, plentiful food source. Outside nesting season, these sharks shift to other prey, suggesting turtles are a seasonal staple rather than their only food. Still, losing that reliable annual feast would force tiger sharks to find alternatives, potentially increasing predation pressure on other marine animals like rays, smaller sharks, and seabirds.
Juvenile green turtles also feed a wider range of predators, from large fish to crocodiles and birds of prey. The loss of juveniles from the food web would be felt most in tropical and subtropical coastal waters where young turtles concentrate.
Tiny Species That Live on Turtle Shells
A green sea turtle’s shell is a mobile reef. Barnacles, algae, small crustaceans, and microscopic organisms called diatoms colonize the rough surface of the carapace. Researchers have identified at least 18 diatom species living on sea turtles, and some of these appear to be obligate epibionts, meaning they exist nowhere else. The diatom genera Poulinea and Chelonicola, for example, have been described only from sea turtle shells and have never been found on any other surface in the ocean.
If green sea turtles went extinct, these specialist organisms would likely go extinct with them. The broader community of hitchhikers, including small crabs and algae clumps, would lose one of their primary hosts. While some of these organisms also colonize other turtle species, losing the most abundant tropical sea turtle would dramatically shrink available habitat for the entire epibiont community.
Ecotourism Revenue Would Disappear
Green sea turtles are among the most recognizable marine animals, and snorkeling or diving with them drives tourism in tropical destinations worldwide. In the Maldives alone, sea turtle tourism generated at least $1.08 million in direct revenue in 2019. That figure represents just one small island nation. Across the Caribbean, Southeast Asia, Australia, Hawaii, and Central America, turtle-based ecotourism supports dive operators, guides, conservation programs, and coastal hotels. The loss of green sea turtles would erase a significant draw for visitors to these regions, hitting small coastal communities hardest.
The Current State of Green Sea Turtles
Green sea turtles are currently listed as Least Concern on the IUCN Red List as of 2025, an upgrade from their previous Endangered status that reflects decades of conservation work. Nesting populations have rebounded in many areas thanks to beach protections, fishing regulations, and marine protected areas. But this global classification masks regional variation. Some local populations remain critically low, and threats like habitat loss, plastic pollution, boat strikes, and climate change (which skews the sex ratio of hatchlings by warming nest temperatures) continue to put pressure on the species. The fact that their loss would cascade through so many systems is precisely why conservation efforts remain urgent even as overall numbers improve.