International Day for Biological Diversity - 22 May 2012

Marine Biodiversity was the theme for International Day for Biological Diversity (IDB) in 2012. Designation of IDB 2012 on the theme of marine ecosystems provides Parties to the Convention on Biological Diversity (CBD) and everyone interested in marine life, the opportunity to raise awareness of the issue and increase practical action.

How Much Life Is in the Sea?

From 2000 to 2010, an unprecedented worldwide collaboration by scientists around the world set out to try and determine how much life is in the sea.

Dubbed the ‘Census of Marine Life’, the effort involved 2,700 scientists from over 80 nations, who participated in 540 expeditions around the world. They studied surface seawater and probed the deepest, darkest depths of the ocean, sailed tropical seas and explored ice-strewn oceans in the Arctic and Antarctic.

By the time the Census ended, it had added 1,200 species to the known roster of life in the sea; scientists are still working their way through another 5,000 specimens to determine whether they are also newly-discovered species. The estimate of the number of known marine species - the species that have been identified and the ones that have been documented but await classification - has increased as a direct result of the Census efforts, and is now around 250,000. (This total does not include some microbial life forms such as marine viruses.) In its final report, the Census team suggested it could be at least a million. Some think the figure could be twice as high.

Marine and Coastal Biodiversity

Along the Coast

The Continental Shelf

The Open Ocean

The Deep

Great Migrations

The Human Impact

Causes of Decline

A Warmer Ocean

A More Acidic Ocean

The Problem of Over-Fishing

Why We Should Care

Blue Carbon

The Value of Marine Reserves

CBD and the Jakarta Mandate

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A Warmer Ocean

The burning of fossil fuels such as coal, oil and gas is warming Earth’s atmosphere – and also its ocean: Average sea surface temperature has increased by 0.4 degrees Celsius since the 1950s.

Because warm water is lighter than cold water, the warmer sea surface is less able to sink and mix with the colder waters beneath it, limiting the flow of oxygen and nutrients from surface to deep water and vice-versa, and creating expanses of ‘ocean desert’. As temperatures change, some species will adjust their range – generally away from the tropics and toward higher latitudes – while the range of other species will expand and still others will contract.

Additionally, as water warms, it expands, and such thermal expansion of the ocean is the primary reason why, since 1880, sea level has risen by an average of 22 centimeters; increased warming, combined with groundwater extraction, the melting of glaciers and some melting of the massive sheet of ice covering Greenland, is likely to cause sea levels to rise by a meter, or possibly even significantly more, by 2100.

Some areas and environments will be affected more than others. In the Arctic Ocean, for example, sea ice extent is declining by an average of 12 percent per decade, profoundly altering Arctic marine ecosystems and threatening the survival of species such as ringed seals, walruses, and polar bears. Coral reefs are particularly susceptible, as they have a very narrow temperature band in which they can thrive; once the temperature exceeds the upper limit of that band, the corals become stressed, and when they do so they expel the symbiotic zooxanthellae that give them most of their color, a frequently-fatal phenomenon known as ‘coral bleaching.’ A widespread bleaching event took place in 2010, with bleaching observed in every ocean and major sea in which coral occurs, from the Persian Gulf to southeast Asia, the Central Pacific to the Caribbean. In the Caribbean, more than 80 percent of corals surveyed by researchers had bleached and in many places 40 percent or more had died.

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