The species concept, biodiversity and the status of organisms.
So far we've illustrated the state of things by looking at extinctions in general, and then at
specific examples of extinctions. This was followed up by examining the status of
individual species.
In order to talk intelligently about "species" and wether or not they're endangered
requires us to review some concepts about species in general.
1) A very brief review of higher taxonomy
- everyone should know this -for a more detailed explanation see my notes for
Biology 303, on the web at (near the bottom of the page):
"http://osf1.gmu.edu/~alaemmer/bio303/lect-evol-tax.html"
- the following categories are used in order from broad to narrow to classify
organisms:
Kingdom/Phylum/Class/Order/Family/Genus/species
- these may be supplemented with:
Super (= above), Sub (=below), Infra (= below "sub")
and with:
Domain (above Kingdom) and Tribe (between Family and Genus)
- a difficulty is that very often when we look at the fossil record we use taxa
(groups) higher than species to talk about organisms (e.g., Stegosaurus is a Genus,
not a species).
- when trying to make comparisons between what is happening today with what
has happened in the past we are often trying to compare what happened at
different taxonomic levels (e.g., xx genera went extinct, or yy families went
extinct).
- many groups use this classification system help split out groups of particular
concern or as a means of sorting endangered animals (this is obvious - e.g.,
"mammals" or "birds").
2) The species concept
- it is very important to realize that the only "objective" category we have is that
for species. But even this is under assault.
- Classical definition of a species:
- two organisms are considered the same species if they can reproduce and
produce viable offspring (and cannot produce viable offspring with a
different species)..
- Problems with this definition:
- It makes very little sense with plants. One estimate indicates that 70% of
flowering plants originated as a result of hybridization. Yet we consider
all these different species.
- What about Wolf-Dog? Or Wolf-Coyote?
- A big controversy surrounds the "Red Wolf". It is listed as
Critically Endangered by the IUCN. Yet it may be the result of a
Coyote-Wolf hybrid. If so, does it deserve the "Critically
Endangered" status?
- Numerous alternative definitions have been proposed, based on
ecological, morphological, evolutionary or other characteristics. None
seem to have really caught on.
- It can be important, though. For example, depending on the
species used, there are anywhere from one to 30 species of Drimys
(a tree) in New Guinea.
- As Conservation Biologists, this is obviously important!
- But, even given it's drawbacks, there doesn't seem to be a widely used
alternative to the classical definition. So we'll sort of stick with it,
realizing that it does have shortcomings (since we're dealing primarily
with animals, it probably does okay).
- So given all this, the next question might be, how many species are there?
- As usual, this depends. Most conventional estimates show about 2
million species. Some sources estimate up to 111.7 million species!!
More realistic estimates for an upper end are just over 10 million.
- Why the disparity? Some groups of organisms, particularly
bacteria and nematodes remain grossly understudied (how many
people in this class want to study nematodes for a living?).
Incidentally, the IUCN doesn't seem to list a single nematode (or
bacteria). Until we get a better idea of what's going on, estimates
will fluctuate drastically.
- To date 1.7 million species have been described (this figure seems high).
Out of these over 1 million are arthropods (w/ 400,000+ beetles!).
- Summary:
- we don't even know for sure how many species there are. But it is clear
that diversity is greater than we generally realize. For many groups we
need more information.
3) The status of organisms.
- Let's use these concepts to delve into the various classifications used by
different conservation organizations.
- First, let's discuss some of the major organizations (this is only a partial list) out
there:
- IUCN. The "International Union Probably for the Conservation of Nature and
natural resources:
- arguably the most important of the bunch. The IUCN collects and
maintains information about species from around the world and lists them
in to one of several categories if it is judged (by scientists working in the
field) that there is some concern about the species. It attempts to be
apolitical (though by it's very nature it is conservation oriented).
- many governments pay close attention to the lists provided by the IUCN.
- Scheme use by the IUCN (graphic from their web site):
- categories are as follows (also from the IUCN web site, though abbreviated somewhat):
EXTINCT (EX) A taxon is Extinct when there is no reasonable
doubt that the last individual has died.
EXTINCT IN THE WILD (EW) A taxon is Extinct in the Wild
when it is known only to survive in cultivation, in captivity or as a
naturalized population (or populations) well outside the past range.
The following three categories are all considered
"THREATENED":
CRITICALLY ENDANGERED (CR) A taxon is Critically
Endangered when the best available evidence indicates that
it meets any of the criteria A to E for Critically Endangered
(see Section V), and it is therefore considered to be facing
an extremely high risk of extinction in the wild.
ENDANGERED (EN) similar to above, but is considered
to be facing a very high risk of extinction in the wild.
VULNERABLE (VU) similar to above, but is considered to
be facing a high risk of extinction in the wild.
NEAR THREATENED (NT) A taxon is Near Threatened when it
has been evaluated against the criteria but does not qualify for
Critically Endangered, Endangered or Vulnerable now, but is close
to qualifying for or is likely to qualify for a threatened category in
the near future.
LEAST CONCERN (LC) A taxon is Least Concern when it has
been evaluated against the criteria and does not qualify for
Critically Endangered, Endangered, Vulnerable or Near
Threatened. Widespread and abundant taxa are included in this
category.
DATA DEFICIENT (DD) A taxon is Data Deficient when there is
inadequate information to make a direct, or indirect, assessment of
its risk of extinction based on its distribution and/or population
status.
NOT EVALUATED (NE) A taxon is Not Evaluated when it is has
not yet been evaluated against the criteria.
- a comment about the criteria for listing in one of the threatened
categories:
- these vary depending on the category, but include five major
criteria:
- reduction in population size
- reduction in range
- small population of very few individuals and indications
of continued decline.
- very small (smaller than above) population size.
- results of analysis indicating that the species faces
extinction soon.
- if a species meets any of the 5 criteria it is listed. Depending on
the stringency of these criteria, it is listed in one of the three
threatened categories.
- for a more detailed breakdown, see the IUCN web page.
- CITES. "Convention on International Trade in Endangered Species of Wild
Fauna and Flora"
- Member states are expected to enact laws that govern the trade of
wildlife products as listed by CITES (or better, each nation has to enact
laws that are in compliance with CITES).
- CITES regulates the trade in wildlife based on three "appendices"
(quoting directly from the CITES web page):
- Appendix I includes species threatened with extinction. Trade in
specimens of these species is permitted only in exceptional
circumstances.
Examples include elephants, many whales, cheetahs.
- Appendix II includes species not necessarily threatened with
extinction, but in which trade must be controlled in order to avoid
utilization incompatible with their survival.
Examples include whales not listed under Appendix I, and
some populations of both elephant and cheetahs (organisms
may be listed in different Appendices depending on region).
- Appendix III contains species that are protected in at least one
country, which has asked other CITES Parties for assistance in
controlling the trade.
Examples include deer (same species as around here(!), but
in Guatamala) and various Gazelles (e.g. Gazella dorcas) in
Tunisia (presumably very rare there, though the species
overall is declining (listed as vulnerable by the IUCN)).
- Countries are expected to adhere to the listings in CITES
- Through a rather complicated process of scientific input and
voting by members (& regions) species are placed on various
Appendices. The details are available on the web site
(www.cites.org).
- On occasion, this can have a major impact on a species, for example
when all trade in elephants or elephant products was stopped.
- Web site claims that none of the species listed by CITES has gone extinct
since the inception by CITES.
- CITES now includes 164 parties (i.e. countries).
On the national level (U.S.):
Fish and Wildlife Organization - administers the endangered species act
and is charged with protecting national species. Their listings may or may
not be in accordance with CITES* or the IUCN. Incidentally, they have
27 different categories for listings (talk about bureaucracy!).
They also cooperate with international organizations (e.g. CITES).
* the U.S. is a member of CITES, so this presumably means that
we follow CITES rules and regulations, but may have more
stringent protections in some cases (several other countries may
also have more stringent protections than that provided by CITES).
Animals are listed as threatened or endangered after scientific review.
Since this includes several political personnel, the process can generate
controversy (it's only fair to say that CITES generates a fair amount of
controversy as well).