The earth’s oceans cover 71% of its surface area, contain 97% of its water and play a crucial role in maintaining its climate. They contain much of the planet’s biodiversity and supply over 15% of humanity’s dietary intake of animal protein. Yet 60% of the world’s major marine ecosystems that underpin livelihoods have been degraded or are being used unsustainably and, by the year 2100, more than half the world’s marine species may stand on the brink of extinction. To date, only 1% (by area) of the planet’s oceans and seas have been protected in reserves. Threats to the planet’s oceans include acidification due to increasing carbon dioxide emissions, coral reef bleaching, and pollution from sewage, agricultural runoff, oil spills, radioactive spills and plastic garbage.
The MarineBio website has extensive information on marine ecology, sustainable fisheries and much more.
The Worldwide Fund for Nature also has good information on oceans, with pages on the open ocean, the deep sea and threats.
Sustainable Development Goal 14 is dedicated to looking after life in the oceans. The site outlines the seven targets of the goal and progress to date, as well as current information about looking after our oceans and waterways.
The Intergovernmental Oceanographic Commission is the UNESCO portal to oceanographic issues, such as ocean monitoring, fisheries, ecosystems and marine environmental protection. The site contains a wealth of scientific data.
Excessive nutrients from sewage outfalls and agricultural runoff can create low-oxygen ‘dead zones’ in which most marine life cannot survive. There are now nearly 500 dead zones covering an area the size of the United Kingdom.
The US National Oceanic and Atmospheric Administration has information on ocean nutrient pollution, dead zones and many related topics.
The 2010 BP oil spill in the Gulf of Mexico discharged an estimated 780,000 cubic metres of crude oil, wreaking havoc on marine species and coastal communities. The oil may remain in the food chain for generations. The Smithsonian’s Ocean Portal and National Geographic’s ‘The Ocean’ site have detailed information on the BP oil spill.
Oceans are becoming increasingly polluted by plastic garbage, washed out from rivers or dumped or washed overboard from boats. Some of it ends up in the stomachs of marine animals and birds, causing their illness and eventual death. For example, nearly all the 1.5 million Laysan Albatrosses that inhabit Midway Atoll have plastic in their digestive system. Watch the video, “Midway” (above) and read further about the Great Pacific garbage patch.
The Fukushima nuclear disaster released between 15 and 30 petabequerels of Cesium-137, which has a half-life of 30 years, into the Pacific Ocean. The damaged plant is still releasing at least 400 tonnes of highly radioactive water each day. The crisis has been a major blow to the Japanese fishing industry, and could pose significant health risks to coastlines around the entire Pacific Rim.
This article provides information on the likely spread of radiation across the Pacific.
In addition to global warming, one of the consequences of burning fossil fuels is the increasing acidification of oceans caused by the absorption of carbon dioxide. Acidification can affect the ocean ecology in a number of ways, including making it more difficult for calcifying organisms such as coral and some plankton to form calcium carbonate. It therefore poses a threat to coral reefs and to food chains within and connected to the oceans. The risk of acidification would not be addressed by climate engineering technologies such as upper-atmosphere aerosols that reduced incident sunlight.
For more information, and to take action, see the Ocean Acidification website maintained by Ocean Ark Alliance.
Aquaculture provides half of all fish for human consumption, but requires the harvesting of wild fish to use as fishmeal. The collapse of the Atlantic northwest cod fishery in 1992, which put more than 35,000 people out of work, was a reminder that the planet’s oceans are not an inexhaustible resource. However, significant steps have been taken in recent years to maintain harvests within sustainable levels and the overall state of world marine fisheries has begun to stabilise.
The US Food and Agriculture Administration produces a 2-yearly report on the state of the world’s fisheries and aquaculture.
The Greenpeace website has information on overfishing.
The Earth’s coastal zones comprise only 10% of the ocean environment but are home to over 90% of all marine species. Coastal systems such as mangroves, salt marshes and seagrass meadows may store up to five times the carbon stored in tropical forests, and can absorb carbon up to 50 times as fast as tropical forest.
Coral reefs are home to 25% of all marine life on the planet, and have a diversity of life comparable to tropical rainforests (up to 2 million species). They are at risk from coral bleaching, acidification, overfishing, pollution and inappropriate tourism.
The International Human Dimensions Programme has good information about coastal zones.
For information about Australian reefs, go to the Great Barrier Reef Marine Park Authority site.