What is Biodiversity?
The worst thing that can happen during the 1980s is not energy
depletion, economic collapse, limited nuclear war, or conquest by
a totalitarian government. As terrible as these catastrophes would
be for us, they can be repaired within a few generations. The one
process ongoing in the 1980s that will take millions of years to correct
is the loss of genetic and species diversity by the destruction of
natural habitats. This is the folly that our descendents are least
likely to forgive us.
--E.O. Wilson, 1985
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 Review the number of known species on the planet. |
What is biological diversity? In its narrowest sense this term refers
to the number of species on the planet, and it also is used more broadly
as an umbrella term. Biological diversity refers to the variety and variability
among living organisms and the ecological complexes in which they occur.
Diversity can be defined as the number of different items and their relative
frequency. For biological diversity, these items are organized at many
levels, ranging from complete ecosystems to the chemical structures that
are the molecular basis of heredity. Thus, the term encompasses different
ecosystems, species, genes, and their relative abundance (Office of Technology
Assessment, 1987). Or to paraphrase: biodiversity is the number and variety
of species, ecological systems, and the genetic variability they contain.
our estimates of the number of unknown species greatly exceed our count
of the number of known species. Most experts estimate the world's species
diversity at 10 to 30 million, but that is very approximate. Fewer than
2 million species are "known to science"--meaning that they
have been classified by a specialist. Most published accounts put the
number of known species at 1.4 million, but it may be approaching 1.8
million at this writing, due to the progress of science. The estimates
of 10 to 30 million species are based on expert opinion of how many species
are yet to be formally identified. One study of insects in the forest
canopy found five out of six to be new species. Even vertebrates are not
completely known--it is estimated that nearly half of the freshwater fishes
of South America are undescribed. New finds are made continuously in the
tropics, and exploration of deep-sea hydrothermal vents recently led to
the discovery not just of new species, but of new life forms at the family
level (20 families or sub-families). When you consider that virtually
every species has its own parasite, and how many groups such as nematodes
and bacteria have yet to be well-studied, it is apparent that the estimates
of 10 to 30 million are not out of line.
The global distribution of biodiversity--its geography--is interesting
in its own right, and relevant to conservation. Biological diversity is
greatest near the equator, and declines toward higher latitudes. Tropical
rain forests are especially known for their exceptional diversity. Some
locations, known as "hotspots," harbor an unusually rich local
diversity, perhaps because conditions there favored evolutionary diversification.
The global distribution of biodiversity--its geography--is interesting
in its own right, and relevant to conservation. Biological diversity is
greatest near the equator, and declines toward higher latitudes. Tropical
rain forests are especially known for their exceptional diversity. Some
locations, known as "hotspots," harbor an unusually rich local
diversity, perhaps because conditions there favored evolutionary diversification.
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