Conserving global marine biological diversity

Protecting marine ecosystems of significant biodiversity and productivity

Conserving the number, variety and variability of marine living organisms. Biodiversity is often addressed at three levels: ecosystems, species and genes.


Marine and coastal systems form the largest set of biomes on the planet, covering some 71% of the earth's surface. In addition, nearshore waters support the world's most naturally productive ecosystems: estuaries and lagoons, brackish and saltwater wetlands, mud flats and other intertidal areas, coral reefs, and seagrass beds. The biological diversity of the oceans rivals that of tropical forests and indeed exceeds all other areas in diversity of genera, classes, and phyla. There are a total of 32 known phyla in the seas and of these, 15 are exclusively marine. (Only one phylum is not found in the oceans.) The diversity of life forms is unmatched. Marine biological diversity is notable at the mega scale as well. Ecological communities in the coastal and marine realms are generally more complex and cover far wider geographical scales in terrestrial biomes, with the presence of marine filter-feeders adding an extra trophic layer to the food web. Lastly, diversity of size is significantly greater in the seas, with organisms ranging in size from picoplankton to the great whales.

Biodiversity is being lost in all the world's seas, at catastrophic rates in some.

Biodiversity conservation has historically focused on the terrestrial environment, and while there are common principles for the conservation of terrestrial and marine biodiversity, there are also several characteristics of the marine and coastal environment that present decision-makers and resource managers with a unique set of problems. Marine resources fall under national ownership, but not in oceanic waters outside of this area; the fact that species straddle or migrate across political boundaries; the "invisibility" of marine, coastal and other aquatic environments, which makes research and monitoring particularly difficult; and the environmental continuity of the oceans, meaning that local impacts may have global effects. Adding complexity to this situation is the fact that aquatic organisms - primarily fish - are the only major human food resource harvested directly from wild populations.

This strategy features in the framework of Agenda 21 as formulated at UNCED (Rio de Janeiro, 1992), now coordinated by the United Nations Commission on Sustainable Development and implemented through national and local authorities. Agenda 21 recommends that states should identify marine ecosystems exhibiting high levels of biodiversity and productivity and other critical habitat areas and should provide necessary limitations on use in these areas, through, inter alia, designation of protected areas. Priority should be accorded, as appropriate, to: coral reef ecosystems; estuaries; temperate and tropical wetlands, including mangroves; seagrass beds; other spawning and nursery areas.

The Convention on Biological Diversity (1992) requires that contracting parties shall implement the Convention with respect to the marine environment consistently with the rights and obligations of states under the law of the sea.


The marine and coastal ecosystems of our watery planet are the richest biological areas on earth, far outweighing the forests at higher levels of taxonomic organization.

Type Classification:
D: Detailed strategies
Related UN Sustainable Development Goals:
GOAL 8: Decent Work and Economic GrowthGOAL 14: Life Below WaterGOAL 15: Life on LandGOAL 16: Peace and Justice Strong Institutions