Mediterranean marine turtles are threatened with extinction as their situation continues to decline. Females used to nest on several Mediterranean shores. At a nesting beach in Syria which is used by the endangered green turtle, researchers in 1991 found that all the nests had been opened and the eggs removed by egg collectors. This beach is also foul-smelling and degraded by raw sewage effluent. Today, Greece, Turkey, and Cyprus retain the largest concentration of nesting females. The last remaining important nesting beaches are threatened by habitat degradation due to coastal development, tourism, sand removal, pollution and other human interferences. Added to this are deaths caused by incidental catches of turtles in fishing nets and on long lines baited for swordfish, and the deliberate harvesting of turtles. Other environmental hazards for turtles are toxic effluents, entanglement in discarded and broken fishing nets and ropes, feeding on discarded plastic (mistaking it for jellyfish), thus blocking their digestive systems, and contamination by tar and oil.