Eco-system
Community
Guild
Species
Organism
Gene
Bio-diversity is to be valued, if life is valued, for in biological diversity is the embodiment and the only guarantee of continued viability of life. Increased variation yields increased probability of survival, due to increased probability of successful adaptation to the environment.
Fraction of potential DNA sequences yielding successful adaptations to date:
10^8 species x 10^18 DNA variations per species (estimate)
----------------------------------------------------------
4^(10^9) <-- number of mathematically possible
combinations of DNA, given average DNA
strand length per organism of 10^9
nucleotide pairs.
Total 1,413,000 ---------------------------------------------------- Protozoa 30,800 Vascular (higher) plants 248,400 Algae 26,900 Fungi 69,000 Monera (bacteria & similar forms) 4,800 Viruses 1,000 Insects 751,000 Mammals 4,000 Birds 9,000 Reptiles 6,300 Amphibians 4,200 Fishes and lower chordates 18,800 Crustaceans, spiders, etc 123,400 Sponges 5,000 Corals, jellyfish, comb jellies, etc 9,000 Flatworms 12,200 Roundworms 12,000 Earthworms and relatives 12,000 Mollusks 50,000 Starfish and relatives 6,100
Greenland 56 Labrador 81 Newfoundland 118 New York State 195 Guatemala 469 Colombia 1,525
However, as shown in the following section, this growth has
been punctuated by 5 major dips (mass extinction events),
each lasting from 20 to 100 million years. Many more minor
dips and rises have characterized the evolution of bio-
diversity.
(Note: Need to add graphs here.)
Historical record of past mass extinction events
[16]
Notes:
Species: domestica
Genus: Felis
Family: Felidae (all kinds of cats: cheetah, panther, lion, tiger, lynx,...)
Order: Carnivora
Class: Mammalia
Phylum: Chordata
Kingdom: Animalia
Time (years Lost Lost Time for
before present) Families Species Recovery (years)
--------------------------------------------------------------------
Ordovician 440 million 12% 25 million
Devonian 365 million 12% 30 million
Permian 245 million 54% 77-96% 100 million
Triassic 210 million 12% 65 million
Cretaceous 66 million 12% 20 million
A chronospecies is a species, present for a period of time, which may adapt into one or more later chronospecies. A chronospecies therefore forms the basis of a clade.
Clade longevity, or the rate of clade extinction, is of more significance than chronospecies longevity (or extinction rate), for when a chronospecies disappears, it has sometimes been replaced by one or more evolved successor species.
Clade longevity:
Fish and invertebrate clades 1 - 10 million years Flowering plant clades 1 - 10 million years Mammal clades 0.5 - 5 million yearsThe survival and upward trend of life and bio-diversity as a whole depends on the splitting rate of evolving species exceeding the rate at which clades (whole subtrees) die out.
Chronospecies longevity seems to commonly come in at about 1 million years, according to the fossil record.
The general historical "background" chronospecies "extinction" rate, therefore, amounts to 1 species per 1 million species per year, or in absolute terms, multiplied by the current estimated total number of species, the background species extinction rate comes out to between 10 and 100 species per year (including all species such as insects, bacteria etc, not just charismatic mega-fauna.)
The current extinction rate, 1992
[16]
Specifically, in rainforests around the world, a conservative
estimate, based on rates of area reduction, yields a current
species extinction rate of 27,000 species per year, which is between
1,000 and 10,000 times the background rate.
Estimated bio-diversity loss over next 50 - 100 years
(from 1992)
[16]
Educated guess of Edward O. Wilson. Edward O. Wilson is
Frank B. Baird Jr. Professor of Science and Curator in
Entomology, Museum of Comparative Zoology, Harvard
University. Some of his books: On Human Nature (Pullitzer
Prize), Sociobiology, The Insect Societies, Biophilia, The
Ants (Pullitzer Prize), The Diversity of Life. His many
scientific awards include the U.S. National Medal of Science
and the Crafoord Prize of the Royal Swedish Academy of
Sciences.
If natural habitats continue to decline at present rates, estimated 25 % loss of present species.Human demographic success has brought the world to this crisis of bio-diversity. Human beings - mammals of the 50-kilogram weight class and members of a group, the primates, otherwise noted for scarcity - have become a hundred times more numerous than any other land animal of comparable size in the history of life. By every conceivable measure, humanity is ecologically abnormal. Our species appropriates between 20 and 40 percent of the solar energy captured in organic material by land plants. There is no way we can draw on the resources of the planet to such a degree without drastically reducing the state of most other species.If we respond with knowledge and technology already possessed, we may hold the loss to 10 % loss of species.
The difference amounts to millions of species.
Prior mass extinctions indicate that bio-diversity will likely recover to present levels (albeit with a different species mix.)
However, the prior extinction events suggest that bio-
diversity recovery will take on the order of 20 to 50
million years, or, put another way, about 10 to 25 times
longer than humanity has so far existed on Earth.
Characteristics of threatened populations
[16]
Below an effective population size of about 500 breeding individuals, the mutation rate is not high enough to compensate for loss of genes through genetic drift (chance fluctuation of gene percentages in the population.) The effect is a gradual loss of the ability of a species to adapt to changing environments.
Watched across long stretches of time, the species as meta- population can be thought of as a sea of lights winking on and off across a dark terrain. Each light is a living population. Its location represents a habitat capable of supporting the species. When the species is present in that location the light is on, and when it is absent the light is out. As we scan the terrain over many generations, lights go out as local extinction occurs, then come on again as colonists from lighted spots reinvade the same localities. The life and death of species can then be viewed in a way that invites analysis and measurement. If a species manages to turn on as many lights as go out from generation to generation, it can persist indefinitely. When the lights wink out faster than they are turned on, the species sinks to oblivion.
The meta-population concept of species existence is cause for both optimism and despair. Even when species are locally extirpated, they often come back quickly, provided the vacated habitats are left intact. But if the available habitats are reduced in sufficient number, the entire system can collapse. All the lights go out even if some intact habitats remain. A few jealously guarded reserves may not be enough. When the number of populations capable of populating empty sites becomes too small, they cannot achieve colonization elsewhere before they themselves go extinct. The system spirals downward out of control, and the entire sea of lights turns dark."
The sea otter is a keystone species. When it was almost hunted to extinction on the west coast of North America by the end of the 19th century, sea urchins, prey of the otters, consumed the formerly abundant kelp beds. Large stretches of the shallow ocean floor were reduced to a desert-like terrain, called sea-urchin barrens.
A conservation effort restored the otter populations. The
kelp forests grew back to their former luxuriance. A host of
lesser algal species moved in, along with crustaceans,
squid, fishes, and other organisms. Gray whales migrated
closer to shore to park their young in breaks along the kelp
edge while feeding on the dense concentrations of animal
plankton.
Estimated number of species in British Columbia in 1993
[13]
These figures include both forest and non-forest land.
However, since a comparatively large fraction of British
Columbia has been forested for 10,000 years or so, a
similarly large fraction of the species listed are forest-
dwelling species, although the exact breakdown is not given
here.
Numbers given are for native species, with species introduced recently by people listed in parentheses.
Vascular (higher) plants 2,022 (557) Lichens 1,000 Fungi 10,000 Mosses, Liverworts 1,000 Mammals 131 (12) Birds 440 (14) Amphibians 18 (2) Reptiles 15 (4) Insects 35,000 Sharks, Bony fish, Lampreys 452 (18)
Vascular plants 29 Freshwater fish 1 Amphibians 1 Reptiles 2 Birds 4 Mammals 7
Four species: The burrowing owl, white pelican, sea otter,
and Vancouver Island marmot.
Species and subspecies at risk in British Columbia, 1993
[13]
Definitions:
Red = Candidate for legal designation as endangered or threatened under the B.C. Wildlife Act
Blue = Sensitive or vulnerable species
The "% of existing" column gives the percentage of species and subspecies which are at risk, as a percentage of the total number of native species. This is a very slight overestimate, due to the small number of subspecies included in the "at risk" figures. To get an idea how many subspecies were included, consider that a separate figure was given in [13] that there are 702 species (of 732 species and subspecies) on the red list. The blue list was not broken into species and subspecies but a good guess is that the ratio is similar. If this is the case, then the total "at risk" percentage is closer to 37 %.
Red List Blue List | Total | % of existing
----------------------------------------------|----------|---------------
Vascular plants 638 217 | 855 | 42 %
Freshwater fish 28 7 | 35 | ?
Amphibians 4 2 | 6 | 33 %
Reptiles 4 5 | 9 | 60 %
Birds 33 55 | 88 | 20 %
Mammals 25 27 | 52 | 40 %
----------------------------------------------|----------|---------------
Total 732 313 | 1045 | 38 %
The single most important factor affecting wildlife in B.C. is habitat loss. [13]