Thus, not surprisingly, we have only a very rudimentary concept of how many species are endangered, threatened, or vulnerable, as defined below see Endangerment – Definition and Tables 2
Trang 1Endangered Marine Invertebrates
James T Carlton, Williams College and Mystic Seaport, Mystic, CT, USA
Published by Elsevier Inc
Glossary
Ecotone The transitional region between two habitats or
environments
Keystone A species with a critical regulatory role (often
disproportionate to its abundance) in a community
Planktotrophic Feeding on plankton by invertebrate
larvae to survive and grow
Stenotopic Occupying a highly specialized habitat or tolerating a narrow range of environmental conditions Supralittoral The portion of beaches, rocky shores, and other marine habitats that typically lies above the high tide
We do not know how many ocean species have gone extinct in
historical time Thus, not surprisingly, we have only a very
rudimentary concept of how many species are endangered,
threatened, or vulnerable, as defined below (see Endangerment –
Definition and Tables 2, 3, 4, and 5) This said, thousands
of marine invertebrates alone may be at risk of extinction
due to a plethora of human-induced pressures, including
physical habitat destruction, water quality, and climate
change
Endangerment – Definition
One set of internationally recognized definitions (IUCN,
2011) treats endangered and vulnerable taxa under the broad
category of threatened species Critically Endangered species face
an ‘‘extremely high risk of extinction in the wild‘‘ Endangered
species are at a ‘‘very high risk of extinction in the wild‘‘.
Vulnerable species are ‘‘considered to be facing a high risk of
extinction in the wild‘‘ (IUCN, 2011) To attempt to apply
quantitative boundaries to these otherwise seemingly hazy
categories, a series of criteria have been erected based on the
observed or projected changes in population size, the
geo-graphic range of a species, estimated population sizes, and an
overall assessment of the probability of extinction (Table 1)
Data required to populate these fields include temporal
data (e.g., rate of population decline and population
fluctu-ations), spatial data (extent of occurrence and number
of populations), and population data (size and number of
adults)
In the USA, the federal Endangered Species Act (ESA)
defines endangered as a species ‘‘in danger of extinction
throughout all or a significant portion of its range’’ and
threatened as ‘‘likely to become an endangered species within
the foreseeable future throughout all or a significant portion
of its range’’ (Environmental Protection Agency, 1973)
Although International Union for Conservation of Nature
(IUCN) (and other) definitions focus on global extinction,
there are other scales of endangerment as well These include:
• Local endangerment, when a species faces extinction
within a region, as in within a bay or estuary, or from a
habitat
• Regional endangerment, when a species faces extinction in
a broad region, such as a biogeographical province
• Functional endangerment, when a species that was per-forming a keystone or engineering role (as a competitor, predator, parasite, pathogen, or disturbing agent) in a community becomes so rare that it no longer operates to influence the system structure
• Commercial endangerment, when a species which is the focus of a fishery becomes so rare that it is no longer economically feasible to hunt it
It may be noted that certain species that are trade protected under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES, 2011) may, by virtue
of the convention name, be categorized as endangered species Species that are the ‘‘most endangered’’ are listed in CITES Appendix I (‘‘all species threatened with extinction, which are
or may be affected by trade’’); species that ‘‘are not necessarily now threatened with extinction, but may become so unless the trade in specimens of such species is subject to strict regulation
to avoid utilization incompatible with their survival’’ are treated in CITES Appendix II Marine invertebrates are treated
only under Appendix II and include the mussel Lithophaga lithophaga, giant clams in the family Tridacnidae, the queen conch Strombus gigas, black corals (Antipatharia), the blue coral Heliopora coerulea (Helioporacea), stony corals
(Scleractinia), organ-pipe corals (Tubiporidae), fire corals (Milleporidae), and lace corals (Stylasteridae) Although these taxa may thus be referred to as endangered under CITES, many (such as numerous stony coral species) might not be so listed under IUCN or ESA definitions
Causes of Endangerment and Examples of Endangered Species
Numerous studies in the 1990s and 2000s (e.g.,Pew Oceans Commission, 2003;U.S Commission on Ocean Policy, 2004) defined five general drivers of human-mediated pressures
on marine biodiversity: fisheries activities (both overextraction and the mechanical means by which the target species are collected), habitat destruction, changes in water quality, introduction of nonnative species, and climate change
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