“Oceans in Peril: Protecting Marine Biodiversity“, published by the Worldwatch Institute in mid-September, outlines the factors causing damage to the ocean, namely fishing, pollution and climate change, and suggests a set of solutions.As much as 50% of the world’s fish stocks are fully exploited and 17% are over-exploited, putting marine biodiversity at severe risk.
The report cites overfishing, use of bottom trawling and other destructive fishing techniques, unsustainable aquaculture, and illegal, unregulated, and unreported (IUU) fishing as one of the major reasons for the depletion of fish stocks. Bottom trawling has been likened to forest clearcutting. As fishers drag heavy nets and other gear across the sea floor, this causes massive collateral damage to corals and other features that offer protection and habitat for many creatures. Bycatch is a growing problem, killing or injuring hundreds of thousands of seabirds, turtles, marine mammals, and other marine species annually. In some cases, industrial fishers discard nearly half their dead or dying catch back into the sea. IUU fishing accounts for up to 20% of the global catch and is worth $ 4-9 billion a year. As industrial countries see their own fish stocks fall and impose stricter controls, fishers often move to developing-country waters where effective control is absent, jeopardising the livelihoods of fishing communities.
Human-induced climate change, predicted to increase sea-surface temperature, raise sea levels, and reduce sea-ice cover, is also harming the world’s oceans. In one sector of the Southern Ocean, krill densities fell by an estimated 80% between 1976 and 2003, correlating with losses in the extent and duration of sea ice the previous winter and leaving penguins, albatrosses, seals, and whales especially vulnerable. In parts of the Arctic, the impacts of climate change on sea ice and snowfall may be affecting the breeding success of ivory gulls, ringed seals, and polar bears.
The third cause is pollution from chemical, radioactive, and nutrient sources; oil spills; and marine debris which all contaminate the marine environment, killing organisms, and undermining ecosystem integrity. Of particular concern is the effect on marine wildlife of persistent organic pollutants, especially those chemicals not yet regulated under the 2001 Stockholm Convention. Marine debris, including plastics and derelict fishing gear, is responsible for causing death and injury to many marine species, among them seabirds, turtles, and marine mammals. Large oxygen-depleted “dead zones,” made worse by excessive nitrogen runoff from fertilisers, sewage discharges, and other sources, are further signs that the oceans are under severe stress.