Marine Species

The Ocean Health Index evaluates the condition or population status of ‘marine species’ to calculate scores for several goals. Data are only available for a small fraction of the species that live in the ocean for the following reasons.

Oceans cover 70% of the Earth’s surface and include more than 98% of the biosphere, or space where life exists. They are home to numerous life forms, including plants, vertebrate and invertebrate animals, and microorganisms, but the actual number of species they contain remains unknown. Of approximately 1,868,000 species known globally, about 15% are marine (Carpenter et al. 2011).

Scientists with the Census of Marine Life project reported that approximately 230,000 marine species have been identified to date, and at least three new marine species remain to be found for every one already known. Researchers have discovered an average of 1,650 new marine species each year between 2002 and 2006 (COML 2010).

Mora et al. (2011), predicted that ten times as many species remain to be found. They estimated the number of species on land and in the ocean based upon analysis of the taxonomy (classification) of the ~1.2 million species that have been scientifically described globally. Their analysis predicts that ~8.7 million species exist globally (~2.2 million are marine), and indicates that 86% of the species on land and 91% of species in the ocean remain to be discovered and described. They calculated that describing them all would require 1,200 years, 303,000 taxonomists and approximately US $364 billion (Mora et al. 2011).

Marine species face increasing risks of extinction caused by changing climate, ocean acidification, overexploitation, habitat loss due to development, pollution, and invasions by alien species. Approximately 15% of the species evaluated to date by the International Union for the Conservation of Nature and Natural Resources (IUCN) or Global Marine Species Assessment (GMSA) have an elevated risk of extinction and are classified as Critically Endangered, Endangered or Vulnerable to extinction.

Risks for Extinction are particularly high in some groups.

For example:

•      One-quarter of the world’s primary habitat producing species, such as reef-building 
        corals, mangroves and seagrasses, are at elevated risk of extinction.

•      More than one-quarter of seabirds are threatened.

•      17% of sharks and 12% of grouper species are listed as critically endangered, 
        endangered or vulnerable to extinction.

(Carpenter et al. 2011; Polidoro et al. 2009).

Which Goals Does This Affect?

How Was It Measured?

Risk of Extinction assessment, which began in 1973, is coordinated by the International Union for the Conservation of Nature and Natural Resources (IUCN) and Global Marine Species Assessment (GMSA). Assessments are carried out by Specialist Groups, and the resulting information is assembled by IUCN as the Red List.

There are many taxonomic groups of organisms, each consisting of many species. Assembling the necessary data requires time, and information remains incomplete even for groups that have been assessed.  For example, even though all known species of sharks and rays have been assessed, 47% are ‘data deficient’, the IUCN term indicating that there is not enough information available to determine risk category or population trend.

As of 2007, only ~1,500 of the 41,500 plants and animals assessed under the IUCN Red List Criteria were marine species. To address this gap, IUCN, Conservation International and Old Dominion University initiated the Global Marine Species Assessment (GMSA) in 2006, with the goal of completing IUCN Red List assessments for 20,000 marine species by 2012. Working with IUCN Specialist Groups, GMSA has completed assessments of all of the world’s known species of sharks and rays, groupers, and reef-building corals (Polidoro et al. 2008). 

The Ocean Health Index used information for the 2,377 marine species included in the IUCN Red List. The main taxonomic groups included were: habitat forming corals, mangroves, seagrasses, sea snakes, marine mammals, seabirds, marine turtles, angelfish, butterfly fish, groupers, wrasses, parrotfish, hagfish, and tuna and billfishes.

Larger samples will be available in the future, but it will require decades to prepare complete assessments for every relevant group, and additional time will be necessary to assemble information on newly discovered species. Owing to the large gaps in knowledge concerning most of the ocean’s species, measures used in the Ocean Health Index and other assessments will need to rely on incomplete samples for some time to come.   

What Are The Impacts?

The oceans comprise many diverse and complex ecosystems. In general, ecosystems with more biological diversity tend to have greater resilience (i.e. the ability of the system to withstand pressures).

Some ecosystems depend upon certain key species for optimal function and productivity. For example, Sea Otters play a key role in helping kelp forests flourish by preying on sea urchins that have the potential to denude significant areas of forest if left unchecked.
Over a billion people rely on fish and seafood as a daily source of protein. Two-thirds of that protein comes from ocean and inland fisheries and approximately one-third comes from aquaculture. Fish consumption is especially high in coastal regions and in small island states (WHO 2012).

Directly and indirectly, the depletion of marine species affects the livelihoods and income of hundreds of millions of people worldwide, including about 200 million people dependent on fisheries (Kwang-Tsao 2009). Worldwide, 45 million people fish for a living and are threatened by overfishing (UNDP 2011). Population depletion of marine species also can affect important economic sectors such as tourism and recreation.

Get More Information

Census of Marine Life (COML)
COML evaluates the status of marine species in order to inform appropriate conservation actions for numerous sectors, including scientists and policy makers, educators and the public, and the census community.

Global Marine Species Assessment (GMSA)
The GMSA project evaluates the global status for all marine vertebrate species, plants, and select invertebrates in order to determine the risk of extinction according to the IUCN Red List Categories and Criteria.


PHOTO(S): © Keith A. Ellenbogen
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