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It is possible that the next hundred years will become known as the “Century
of the Environment.” If in the fullness of time that prophecy comes true, the
beginning of this era might be marked by historians by environmental disasters,
such as the 11 million-gallon Exxon Valdez oil spill off the coast of Alaska, the 350
tons of depleted uranium weapons still lying on Persian Gulf War battlefields, and
the continued exploitation of precious ecosystems like the Brazilian Amazon, where
deforestation, mining and over-development continue to flourish.
I would like to summarize the whole picture by classifying global trends into
four categories:
1. Ozone depletion in the stratosphere, allowing increased penetration of
ultraviolet radiation to reach ground level.
2. Global warming due to the greenhouse effect, in which increased levels of
carbon dioxide, methane and a few other gases trap growing quantities of heat.
3. Toxic pollution, including acid rain.
4. Mass extinction of species by destruction of habitats, especially tropical rainforests.
The first three trends are dangerous to health and the economy—but they can
be reversed. It is a matter of converting to cleaner forms of energy, changing our
patterns of production and consumption, and above all, reversing population
growth with an aim toward reaching supportable levels country by country. However,
extinction cannot be reversed. No species can be called back. Extinction of species, or
the reduction of biodiversity, is the one process
that is being perpetrated not only on our children
and grandchildren but also on our descendants
10,000 years from now and beyond—as far into
the future as can be imagined.
With that somber but essential theme as
background, let me now review some of the key
facts about global biodiversity. The world is at
or close to its highest level of biodiversity in the
history of life, spanning 3.75 billion years. This
buildup has been associated with changes in the
ACIDIFICATION REDUCES THE DIVERSITY
OF AQUATIC LIFE, BECAUSE FEW SPECIES
CAN SURVIVE IN WATER WITH A LOW pH.
THE pH LEVEL CAN BE RESTORED
THROUGH LIMING; SOME OF THE PLANT
SPECIES LOST MAY RE-ESTABLISH FROM
SEED SOURCES IN NEARBY LAKES.
atmosphere, the most important of which were caused by organisms and their
innovations as they adapted to the changing atmosphere and other parts of the
B i o l o g i c a l
13 D i v e r s i t y