The only non-human predator large enough to endanger an adult green sea turtle is the shark. However, hatchlings are vulnerable to crabs, seagulls, sharks, fish and mammals. Despite being endangered, green sea turtles are also vulnerable to humans who kill them for their meat, shells and eggs.
Green sea turtles are most vulnerable when they have just hatched. As hatchlings, they work together to dig to the surface of the beach and head to the ocean, using the reflection of moon's light on the surface of the water to guide themselves. However, artificial lights can cause them to become disoriented and head in the wrong direction, contributing to hatchling deaths and exposing them to more predators. Out of a hundred hatchlings, only one or two survive their first year, on average.
Green sea turtles are also vulnerable to pollution, human development and diseases that greatly decrease their population. Some become tangled in commercial fishing nets and drown, while others may eat litter or marine debris and die that way. Each year, turtles are also injured in boat propeller accidents. Coastal development eliminates familiar nesting grounds, leaving female green turtles without a safe place to lay their eggs. Green sea turtles are also vulnerable to fibropapilloma, a disease of unknown origin that causes tumors to grow on their soft tissues.