http://www.raysweb.net/specialplaces/pages/wilson.html
Only
Humans Can Halt the Worst Wave of Extinction Since the Dinosaurs
Died
by E.O. Wilson
Edward O. Wilson, a
leading advocate of global conservation,
is Pellegrino University Professor at Harvard. His book The
Diversity of Life will soon be available in 14 languages
around the world.
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The Baiji is a graceful,
freshwater dolphin that once abounded
along a thousand miles of the Yangtze River. It may now be the
world's most endangered large animal. Caught in a vise of rising
pollution and indiscriminate fishing during the past century,
its population fell to only 400 by 1980, to 150 in 1993, and
is now below 100. Zoologists doubt the species will survive
in the wild for another decade. The baiji's closest rivals
for early extinction include the Sumatran rhinoceros (probably
fewer than 500 individuals survive) and the giant panda of China
(fewer than 1,000).
The media can be counted
on to take note when the last member
of each of these species dies, or, like the California condor,
is removed from the wild to be placed in a captive breeding
program. But for every animal celebrity that vanishes, biologists
can point to thousands of species of plants and smaller animals
either recently extinct or on the brink. The rarest bird in the
world is Spix's macaw, down to one or possibly two individuals
in the palm and river-edge forests of central Brazil. The rarest
plant is Cooke's koki'o of Hawaii, a small tree with profuse
orange-red flowers that once graced the dry volcanic slopes
of Molokai. Today it exists only as a few half plants--branches
implanted onto the stocks of other related species. Cooke's
koki'o may spend its last days in this biological limbo;
despite the best efforts of horticulturists to assist the
plant, no branches planted in soil have sprouted roots.
Around the world, biodiversity,
defined as the full variety
of life from genes to species to ecosystems, is in trouble.
Responding to the problem, conservation experts have in the
past two decades shifted their focus from individual species
to entire threatened habitats, whose destruction would cause
the extinction of many species. Such "hot spots" in
the U.S.,
for example, include the coastal sage of Southern California,
the sandy uplands of Florida, and the dammed and polluted
river systems of Alabama and other Southern states. Arguably
the countries with the most hot spots in the world are Ecuador,
Madagascar and the Philippines. Each has lost two-thirds or
more of its biologically rich rain forest, and the remainder
is under widespread assault. The logic of the experts is simple:
by concentrating conservation efforts on such areas, the
largest amount of biodiversity can be saved at the lowest
economic cost. And if the effort is part of the political
process during regional planning, the rescue of biodiversity
can gain the widest possible public support.
In hot spots around
the globe, mass extinctions of local
populations have been commonplace. Among them:
More than half the
266 species of exclusively freshwater fishes
in peninsular Malaysia.
Fifteen of the 18 unique
fishes of Lake Lanao in the Philippines,
and half the 14 birds of the Philippine Island of Cebu.
All of the 11 native
tree-snail species of Moorea in the
Society Islands. Those on nearby Tahiti, as well as in the
Hawaiian Islands, are rapidly disappearing.
More than 90 plant
species growing on a single mountain ridge
in Ecuador, through clear-cutting of forest between 1978 and 1986.
These well-documented
cases notwithstanding, it is notoriously
difficult to estimate the overall rate of extinction. Some groups,
like the larger birds and mammals, are more susceptible to
extinction than most. The same is true of fishes limited to
one or two freshwater streams. Most kinds of insects and small
organisms are so difficult to monitor as to make exact numbers
unattainable. Nevertheless, biologists using several indirect
methods of analysis generally agree that on the land at least
and on a worldwide basis, species are vanishing 100 times faster
than before the arrival of Homo sapiens.
Tropical rain forests
are the site of most of the known damage.
Although they cover only 6% of the land surface, they contain
more than half the species of plants and animals of the entire
world. The rate of clearing and burning of rain forests averaged
about 1% each year in the 1980s, an amount about equal to the
entire country of Ireland, and the pace of destruction may now
be increasing. That magnitude of habitat loss spells trouble
for the planet's reservoir of biodiversity. It means that each
year 0.25% or more of the forest species are being doomed to
immediate or early extinction. How much is that in absolute
numbers, as opposed to rate? If there are 10 million species
in the still mostly unexplored forests, which some scientists
think possible, the annual loss is in the tens of thousands.
Even if there are a "mere" 1 million species, the loss
is
still in the thousands.
These projections are
based on the known relationships between
the area of a given natural habitat and the number of species
able to live within it. The projections may be on the low side.
The outright elimination of habitat is the leading cause of
extinction. But the introduction of aggressive exotic species
and the diseases they carry follow close behind in destructiveness,
along with overhunting or overharvesting of plants and animals.
All these factors work
together in a complex manner. When asked
which ones caused the extinction of any particular species,
biologists are likely to give the Murder on the Orient Express
answer: they all did it. A common sequence in tropical countries
starts with the building of roads into wilderness, such as
those cut across Brazil's Amazonian state of Rondonia during
the 1970s and '80s. Land-seeking settlers pour in, clear the
rain forest on both sides of the road, pollute the streams,
introduce alien plants and animals and hunt wildlife for extra
food. Many native species become rare, and some disappear entirely.
The world's fauna and
flora are paying the price of humanity's
population growth. The levy may be acceptable to those who put
immediate human concerns above all else. But it should be borne
in mind that we are destroying part of the Creation, thereby
depriving all future generations of what we ourselves were
bequeathed. The ongoing loss in biodiversity is the greatest
since the end of the Mesozoic era 65 million years ago.
At that time, by current scientific consensus, the impact
of one or more giant meteorites darkened the atmosphere,
altered much of earth's climate and extinguished the dinosaurs.
Thus began the next stage of evolution, the Cenozoic era or
Age of Mammals. The extinction spasm we are now inflicting
can be moderated if we choose. If not, the next century will
see the closing of the Cenozoic era and the start of a
new one characterized by biological impoverishment.
It might appropriately be called the Eremozoic era,
the Age of Loneliness.
People commonly respond
to the evidence of species extinction
by entering three successive stages of denial. The first is,
simply, Why worry? Extinction is natural. Species have been
dying out through more than 3 billion years of history without
permanent harm to the biosphere. Evolution has always replaced
extinct species with new ones.
All these statements
are true, but with a terrible twist.
After the Mesozoic spasm, and after each of the four greatest
previous spasms spaced over 400 million years, evolution required
about 10 million years to restore the predisaster levels of
diversity. Faced with a waiting time that long, and aware that
we inflicted so much damage in a single lifetime, our descendants
are going to be--how best to say it?--peeved with us. Worse,
evolution cannot perform as in previous ages if natural
environments have been crowded out by artificial ones.
Entering the second
stage of denial, people ask, Why do we need
so many species anyway? Why care, especially since the vast
majority are bugs, weeds and fungi? It is easy to dismiss the
creepy crawlies of the world, forgetting that less than a
century ago, before the rise of the modern conservation movement,
native birds and mammals around the world were treated with the
same callous indifference. Now the value of the little things
in
the natural world has become compellingly clear. Recent
experimental studies on whole ecosystems support what ecologists
have long suspected: the more species living in an ecosystem,
the higher its productivity and the greater its ability to
withstand drought and other kinds of environmental stress.
Since we depend on functioning ecosystems to cleanse our water,
enrich our soil and create the very air we breathe, biodiversity
is clearly not something to discard carelessly.
In addition to creating
a habitable environment, wild species
are the source of products that help sustain our lives. Not the
least of these amenities are pharmaceuticals. More than 40% of
all prescriptions dispensed by pharmacies in the U.S. are substances
originally extracted from plants, animals, fungi and microorganisms.
Aspirin, for example, the most widely used medicine in the world,
was derived from salicylic acid, which in turn was discovered
in a species of meadowsweet.
Only a minute fraction
of the species or organisms--probably
less than 1%--have been examined for natural products that might
serve as medicines. There is a critical need to press the search
in the case of antibiotics and antimalarial agents. The substances
most commonly used today are growing less effective as the disease
organisms acquire genetic resistance to the drugs. The bacterium
staphylococcus, for example, has recently re-emerged as a potentially
lethal pathogen, and the microorganism that causes pneumonia is
growing steadily more dangerous. The age of antibiotics, it has
been said, is over. Not quite, but medical researchers are
nevertheless locked in an arms race with the rapidly evolving
pathogens that is certain to grow more serious. They are obliged
to turn to a broader array of wild species to discover the new
weapons of 21st century medicine.
Each species is a masterpiece
of evolution, offering a vast
source of useful scientific knowledge because it is so thoroughly
adapted to the environment in which it lives. Species alive today
are thousands to millions of years old. Their genes, having been
tested by adversity over so many generations, engineer a
staggeringly complex array of biochemical devices to aid the
survival and reproduction of the organisms carrying them.
Even when that much
is granted, the third stage of denial
usually emerges: Why rush to save all the species right now?
We have more important things to do. Why not keep live specimens
in zoos and botanical gardens--on ice, so to speak--and return
them to the wild later? The grim truth is that all the zoos
in the world today can sustain a maximum of only 2,000 species
of mammals, birds, reptiles and amphibians, out of about 24,000
known to exist. The world's botanical gardens would be even
more overwhelmed by the quarter-million plant species. These
refuges are invaluable in helping to save a few endangered
species. So is freezing embryos in liquid nitrogen. But such
measures cannot come close to solving the problem as a whole.
To add to the difficulty, no one has devised a plan to save
the legion of insects, fungi and other ecologically vital
small organisms. And once scientists are ready to return
species to independence, the ecosystems in which many lived
will no longer exist. Tigers and rhinos, to make the point
clear, cannot survive in paddies.
The conclusion of scientists
and conservationists is therefore
virtually unanimous: the only way to save wild species is to
maintain them in their original habitats. Considering how rapidly
such habitats are shrinking, even that straightforward solution
will be a daunting task. Many ecosystems have already been lost,
and others seem doomed.
In spite of all these
difficulties, there is reason for some
optimism. With appropriate measures and the will to use them,
the hemorrhaging can be slowed, perhaps eventually halted, and
most of the surviving species saved. Some of the most important
immediate steps that can be taken are outlined in the Convention
on Biological Diversity, signed by 156 nations and the European
Union at the 1992 Earth Summit in Rio de Janeiro (with its
Senate hesitating to ratify, the U.S. is one of the few nations
not yet a formal party to the agreement). The convention was
the turning point in the awareness of biodiversity as a world
issue. It served as a catalyst in accelerating conservation
efforts and has been especially important in awakening tropical
countries, where biodiversity is both the richest and most threatened.
One of the first moves
under way is the closer surveying of
biodiversity, country by country, to pinpoint the extinction
hot spots. Such information, when used to sequester parks and
reserves, can lead to the rescue of large numbers of endangered
ecosystems and species. A review of bird distribution by the
International Council for Bird Preservation, using the best
data available for any group of organisms, revealed that
20% of the world's species occur within 2% of the land area.
Protecting natural environments in these localities alone
would help greatly to slow the rate of bird extinction.
It would also shield larger numbers of other animals and
plants limited to the same habitat.
Saving the last remnants
of the natural environment requires
more than just scientific information. There are also formidable
economic and political problems to be overcome. Growing
populations need new land and increased food production.
The priorities of the desperately poor do not include saving
the fauna and flora of their country. Funds must be raised to
purchase much of the land from private owners, and then to pay
for the protection and management of the reserves. To gain
the support of local peoples, educational programs are needed
to convey the importance of wild lands to sustaining their
own environment in a healthy state. The poor need to be helped
to a better life on the land they already occupy.
Out of this welter
of conflicting interests has arisen a new
kind of environmentalism. It values the world's fauna and flora
not just aesthetically as the natural heritage of humanity
but also as a source of wealth and economic stability.
An infant biodiversity industry is now taking shape along
several fronts. More than 20 pharmaceutical companies have
contracted with private and national research organizations
to push "chemical prospecting" for new medicines in
rain
forests and other habitats.
Ecotourism, opening
the most spectacular wild lands to paying
visitors, has become a major source of income in many developing
countries. Reserves and the surrounding land are being reorganized
to create an outer buffer zone where local peoples are helped
to develop sustainable agriculture, enveloping an inviolate
core zone for the maximum protection of endangered species.
Some forest tracts previously scheduled for clear-cutting
are now selectively logged or cut along concentric swaths,
then allowed to regenerate. Because the practices yield higher
long-term profits, they are expected to be widely adopted.
The new approach to
biodiversity, uniting conservation
and economic development, is obviously far from perfect,
and it is not yet fully practiced in any country. But
it is a promising start. Some of the pilot projects have
succeeded dramatically. They offer a way out of what will
otherwise be a biologically impoverished future. With the
world population at 5.7 billion and sure to keep on growing
rapidly until well into the next century, humanity has
entered a dangerous environmental bottleneck. We hope
--surely we must believe--that our species will come out
the other side in better condition than when we entered.
We should make it a goal to take as much of the rest of
life with us as is humanly possible.
