Commonwealth Scientific and Industrial Research Organisation (CSIRO) scientists interviewed 451 fishers across seven countries about how much gear they lose, then scaled the results to global fishing effort.
Each year an estimated 739,583 km of longline mainline, 2,963 km² of gillnets, 75,049 km² of purse-seine nets, 218 km² of trawl nets, more than 25 million pots and traps and about 14 billion hooks are lost to the ocean. The lost longline alone would circle the Earth 18 times.
Ghost gear matters because it keeps fishing after it is lost, entangling turtles, seabirds, seals and whales, and because nets make up nearly half the mass of the Great Pacific Garbage Patch.
The older figure of '640,000 tonnes of ghost gear per year' comes from a 2009 Food and Agriculture Organization of the United Nations (FAO) and UN Environment Programme (UNEP) back-of-envelope estimate that was never measured. Use these gear-type estimates instead.