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No respite on land or at sea
There is a near total egg removal in several countries, e.g. Thailand and Malaysia (although egg production in Sarawak dropped from 2,200,000 eggs in the mid-1930s to 175,000 in 1995) and disease and fisheries threatens populations elsewhere. As a result, populations are declining worldwide (including in Australia), with numbers in Indonesia decreasing by tenfold since the 1940s, and by more than half in French Polynesia.
It is uncertain whether the current increase in the nesting female numbers in Tortuguero, Costa Rica, will be hampered by the ongoing catch of thousands of green turtles for their meat in Nicaragua.Habitat loss and degradation
Uncontrolled development has led directly to the destruction of critically important marine turtle nesting beaches. Lights from roads and buildings attract hatchlings and disorient them away from the sea. Instead of finding the ocean, the hatchlings fall prey to predators or die the following day from the heat of the sun. Furthermore, vehicle traffic on beaches compacts the sand and makes it impossible for female turtles to dig nests.
Sea walls and jetties change long-shore drift patterns and can cause erosion or destruction of entire beach sections. Beach restoration projects aimed at protecting seaside buildings, through dredging and sand filling continue to destroy important nearshore feeding grounds and alter nesting beaches.
Additionally, important marine turtle feeding habitats such as coral reefs and seagrass beds are continuously being damaged or entirely destroyed as a result of sedimentation, nutrient run-off from the land, insensitive tourist development, destructive fishing techniques and climate change.
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Direct take
Researchers estimate that each year poachers take 30,000 green turtles in Baja California and that more than 50,000 marine turtles are killed in Southeast Asia (particularly in Bali, Indonesia) and the South Pacific.
In many countries, juvenile marine turtles are caught, stuffed and sold as curios to tourists. Marine turtle eggs are considered an aphrodisiac in some countries and eaten raw or sold as snacks in bars and restaurants.
International trade in products such as green turtle calipee has exacerbated the directed take of marine turtles.
Bali, Indonesia is one of the world's largest markets for marine turtles. Although Moslems in Southeast Asia do not traditionally consume the meat from marine turtles, green turtle meat and products are often used in Hindu rituals and for communal meals in Bali. Green turtle consumption in Bali peaked in the late 1970's when more than 30,000 green turtles were landed each year. In 2002, landings are estimated at 684 green turtles per month.
As a result of fishery and egg collection, Indonesian green turtle populations have declined severely over the past decades.
During colonial times, European countries were the major importers of marine turtle products, but now local consumption and trade within Asia probably accounts for the majority of the trade.
All marine turtle species are currently listed on Appendix I of CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) which prohibits any commercial trade by 166 signatory countries. Even so, trade between non-signatory countries and illegal trade persist.
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Disease
On some of the Hawaiian Islands, almost 70% of stranded green turtles are affected by fibropapillomas, a tumorous disease that can kill marine turtles. While the cause of the tumours has not yet been discovered, a herpes-like virus that causes similar tumours has been identified in the wild.
It has been suggested that the increased occurrence of fibropapillomas may be the result of run-off from land or marine pollution that may weaken the turtles immune system, rendering them more susceptible to infection by the wild herpes-like virus.
Indirect take
Each year, thousands of green turtles are trapped in shrimping operations. Marine turtles are reptiles and have lungs so when they cannot reach the surface to breathe, they drown.
Gill nets and long-line fisheries are now principal causes of marine turtle mortality. Worldwide, hundreds of thousands of marine turtles are caught annually in trawls, on long-line hooks and in fishing nets. Coastal small-scale gill net fisheries in particular are widespread, unmonitored, unquantified, and pose a potentially extremely serious threat.
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Natural predators
Marine turtles can lay more than 150 eggs per clutch and nest several times in a season to make up for the high mortality that prevent most marine turtles from reaching maturity. The subtle balance between marine turtles and their predators can be tipped against turtle survival when new predators are introduced or if natural predators suddenly increase in number as a result of human interference. On nesting beaches in the Guianas, dog predation now represent a major threat to marine turtle eggs and hatchlings.