Oceans – The Facts



The Ocean contains 90% of the planet’s biomass – ‘the weight of life’ – and more than 90% of all its water, which covers 70% of Earth’s surface. Yet most of us behave as if the Ocean didn’t matter. In its most recent State of the Marine Environment report the UN Environment Programme highlights nine main ‘areas of concern’ where human activity is harming the ocean.^1^ In most of these areas the scene is either ugly or getting uglier – though international agreements can make a difference. Other important areas – such as fish stocks and climate change – are not covered by this study.


PROBLEM: Highly toxic and stable organic chemicals entering the ocean. These accumulate in organisms and persist for years if not decades. They migrate to polar regions and can become magnified to 70,000 times background levels. The Arctic regions of Canada have the highest concentrations in fish.

CAUSE: Pesticides (such as DDT), industrial and associated by-products reaching the ocean as run-off from land or by dumping.

PROGNOSIS: Two decades of international controls have brought about some improvement. Atmospheric concentrations have decreased in remote regions of the northern hemisphere.

MARINE LITTER (worsened)

PROBLEM: Non-degradable substances enter the ocean and accumulate over time. Plastic litter kills more than a million seabirds and 100,000 marine mammals every year. The entire ocean surface is now contaminated with billions of small plastic particles. Millions of tons of military munitions have been dumped in the ocean.

CAUSE: Domestic and industrial waste, military activity, tourism, shipping.

PROGNOSIS: Bleak. No international agreements in place. Surveys indicate that the general public do not feel responsible.

SEDIMENTS (mixed results)

PROBLEM: Major increases or decreases in the flow of sediment from rivers disrupt natural ocean systems and smother coral reefs.

CAUSE: The construction of dams stops the flow; deforestation, industrial agriculture and mining increase it. In the Nile Delta, water input has decreased by 80% and deposition by 98% since the Aswan Dam was built in 1964, causing degradation of the surrounding land and the disappearance of sardines.


PROBLEM: By 2025 it is expected that 75% of the world’s population will live in coastal areas. In Southeast Asia 88% of coral reefs are threatened by human activity and mangroves are disappearing. In the Caribbean 2/3 of coral reefs are threatened by human activity.

CAUSE: Urbanization, land reclamation, destruction of wetlands and mangrove stands, coastal defences and industry.

PROGNOSIS: Bleak. No international agreements in place or in prospect.


PROBLEM: Thermal expansion of ocean, melting of polar and glacial ice, rising sea levels, changed chemical composition, destruction of habitats, bleaching of coral reefs. Some studies project sea levels will rise by 18-60 centimetres by the 2050s, radically changing coastlines and habitats.

CAUSE: The proportion of these changes that is clearly ‘anthropogenic’ (caused by humans) is still uncertain, but the more the evidence collected, the greater the human contribution it reveals.

PROGNOSIS: Despite international agreements and growing alarm, greenhouse gas emissions continue to rise.

HEAVY METALS (mixed results)

PROBLEM: Minute quantities of heavy metals (such as lead, mercury or cadmium) are necessary for life, but even slightly higher concentrations are dangerous. Their volatility means they can be carried long distances through the air. Levels of mercury in Arctic seals and beluga whales have increased by 2 to 4 times in the past 25 years in some areas.

CAUSE: Mining and burning fossil fuels. Heavy metals are also present in ‘electronic’ waste. In 2004 alone some 100 million personal computers were disposed of – more heavy metals will reach the ocean as a result.

PROGNOSIS: Some international controls. Atmospheric lead decreased with its removal from petrol. High levels of heavy metals in fish and wildlife persist.


PROBLEM: Although there are natural ‘background’ levels of radiation, small additions or concentrations can be extremely dangerous. The carcinogenic and other effects are well established.

CAUSE: Contamination from power stations, medicine, industry, research, space exploration, military operations. In the last century radioactive waste was dumped in over 80 oceanic locations. Oceans were contaminated by nuclear bomb tests. Long-lived, water-soluble fission products are still entering the ocean from reprocessing operations in Western Europe – France and Britain in particular.

PROGNOSIS: Almost under control. With some exceptions – eg France – there have been no atmospheric or submarine tests since 1964. Most contamination is now from natural sources. The problem of long-term nuclear waste disposal remains unresolved.

  1. Can be downloaded from [www.gpa.unep.org/bin/php/igr/igr2/supporting.php](http://www.gpa.unep.org/bin/php/igr/igr2/supporting.php)
  2. _State of the World’s Fisheries 2004_, FAO.
  3. _UN Atlas of the Oceans_, [www.oceansatlas.org](http://www.oceansatlas.org)
  4. MSNBC News Service, 23 October 2006.