By Jack McClintock
Information Access Company
October 1, 2000
We may be losing 30,000 species a year. Some scenarios predict
50 percent of living species could be lost in 50 years.
The mountain gorilla of central Africa, largest and rarest of the
apes and one of our closest relatives, is down to several hundred
individuals. If it ever goes extinct--and it easily could in the
next 20 years--there will be headlines around the world and cries
of anguish about what could have been done. We're good at noting
the disappearance of distinctive creatures, if we know about it,
because we've had to do that so many times before. They become what
Harvard biologist E. O. Wilson calls animal celebrities.
Because handsome animals like the mountain gorilla attract attention
and protection, they stand a better chance of surviving than their
more obscure, and much more numerous, brethren. But fame didn't
save the dusky seaside sparrow--one of the most recent well-documented
extinctions of a vertebrate in the United States--and it may not
save the giant panda, the Sumatran rhinoceros, the Chinese river
dolphin, or the leatherback turtle.
In the past 20 years, thanks to the twin revolutions in computing
and genetics, we know more than ever before about the marvelous
genetic diversity and surprising kinship of species on Earth. But
just as biologists are beginning to reckon the importance of biodiversity
to the planet's history and health, the species themselves are vanishing.
In the United States alone, we've recently documented the loss of
the Santa Barbara song sparrow, the blue pike of the Great Lakes,
and Sampson's pearly mussel, a freshwater bivalve mollusk native
to the Wabash River in Illinois and Indiana. Other plants and animals
have probably slipped away, unnoticed.
Elsewhere, the tally mounts too. We've lost the strange gastric
brooding frog of Australia, which incubated its young in its stomach
and gave birth through its mouth. During the brooding period, the
mother's stomach stopped producing acids. If scientists had learned
how that acid production was shut off, it might have helped them
develop a new ulcer treatment for humans. We've also probably lost
the brilliant golden toad, with its great dark liquid eyes, once
a tourist attraction in the forests of Costa Rica. The list of extinctions
is frighteningly varied: more than a dozen species of the colorful
Oahu tree snail; long-legged bush wrens of New Zealand; about 180
different species of the once numerous cichlids of Lake Victoria,
Africa; the flowering Hibiscus liliflorus of Rodrigues Island in
the Indian Ocean. All have died off in the past two decades. Thousands
more species are just hanging on.
"We're on the verge of the seventh great extinction,"
says Wilson. While cosmic accident or climate change used to be
the cause of such biological cataclysms, humans alone are responsible
for nearly every loss of species in the past few thousand years.
Since the advent of Homo sapiens, Wilson says, extinctions have
occurred 100 to 100,000 times faster than before, principally because
we have degraded and destroyed forests, spread agriculture, introduced
animals into new environments, and polluted the air, water, and
soil. There are at least 10 million species on Earth, and experts
estimate we're killing 30,000 of them each year, a pace that appears
to be increasing. Some scenarios predict that nearly 50 percent
of all living species could be lost in the next 50 years. Think
of an Earth without elephants, orangutans, giant pandas, rhinoceroses,
dolphins, macaws, frogs, frankincense. That's the kind of world
we may be entering, an everlasting bear market in species a period
Wilson dubs the Age of Loneliness.
Habitat loss is the single biggest problem. In Hawaii, two thirds
of the original forest cover has been destroyed, half of the islands'
140 native bird species are extinct, and 30 more are endangered.
Birds of wider range are dying too. The Spix's macaw, native to
Brazil, is down to a single individual in the wild, and the ivory-billed
woodpecker, which once ranged over the southeastern United States,
is probably gone altogether. Twelve percent of all surviving bird
species worldwide are endangered, reports a BirdLife International
study. Roughly a quarter of the world's plant species will be threatened
over the next few decades, says Peter Wyse Jackson, of Botanic Gardens
Our primate cousins are particularly vulnerable because they depend
on shrinking tropical forests and endangered ecosystems for foraging.
Although most have made it through the last 100 years, an estimated
20 percent--some 120 types of prosimians, monkeys, and apes--will
be at severe risk of extinction within the next two decades. Among
them are some whose faces are as appealing as their names, including
the Tonkin snub-nosed monkey, the golden lion tamarin, and Miss
Waldron's red colobus monkey.
Extinction is not always a remote event. The African violet continues
to thrive in parlors around the world, yet it has all but vanished
from its native Kenya and Tanzania. Urban expansion recently wiped
out a wetland fern that lived just outside Cape Town, South Africa.
"Extinctions are occurring right under our noses," says
David Given, chairman of the World Conservation Union's Plant Conservation
Exactly what we're losing isn't known, because about 90 percent
of the disappeared are unnamed, unknown invertebrates-mostly insects--that
thrive in tropical rain forests. And insects make the world as we
know it work. They play a crucial role in pollination, they devour
detritus, and they contain pests. "If we lost half of all insects,"
says Norman Myers, British ecologist and author of The Sinking Ark,
"our agricultural system would be in deep trouble in just one
Indeed, our own survival depends on the survival of other species.
Studies show that the more biologically diverse a region is, the
more species it contains and the more resilient it is to environmental
perturbations. And ecologists already know that the loss of a species
can have a devastating ripple effect. David Hawksworth, former director
of the International Mycological Institute, estimates that every
time one plant goes extinct, at least 15 other organisms also vanish.
To understand how ecological systems stay healthy, biologists study
so-called keystone species, whose behavior helps shape the distinctive
features of an ecosystem. The elephant, for example, digs water
holes, clears paths in the forest, replenishes soil, and spreads
seed through its dung (some seeds will not germinate unless they
have passed through an elephant's digestive system). Sea otters
control the population of sea urchins that feed on kelp, thus protecting
kelp forests, which in turn shelter a variety of marine life and
protect coastlines from wave erosion. Unfortunately, we may not
learn that a species is a keystone until it's gone and takes others
In many cases, endangered creatures hang on at low numbers until
a small event, like an untimely drought, tips the balance toward
death. But strong efforts, such as the campaign to protect the American
alligator, save endangered species too, depending on the species.
The alligator breeds early and often and produces dozens of eggs,
so when hunting was banned, the gator rebounded. The Florida panther
and the West Indian manatee share some of the alligator's habitat,
but they need much more territory and breed far more slowly. Both
species could disappear well before 2020.
Some organisms are beyond saving because they can no longer reproduce
in the wild. The cafe marron, native to Rodrigues, a tiny island
off Mauritius, is a wild relative of the coffee plant that might
contribute genes that would allow coffee-growing in a wider range
of soils and elevations, except there's only one plant left. A cutting
flown to the Royal Botanic Gardens at Kew in London lived, but it
can't set seed because of a faulty stigma. Eventually, it will die
"If someone burned down the Louvre, you can be sure people
would be outraged," says Russell Mittermeier, president of
Conservation International. "We're burning down nature's Louvre,
and no one pays attention. Even if we keep a species alive in the
zoo, it doesn't mean we can keep the thing alive. You need several
hundred animals to keep a healthy gene pool."
And you need natural habitat. Even the most thoughtful and well-funded
zoo programs handle only about 2,000 of the 24,000 species of mammals,
birds, reptiles, and amphibians known to exist, Wilson says. So
for an endangered species the zoo may be more of a hospice than
a rehabilitation center.
Because rescuing all threatened species is impossible, Norman Myers's
proposed solution is triage. Collaborating with 100 other conservation
scientists, he has tallied 25 biodiversity hot spots, covering less
than 2 percent of Earth's land area but containing 44 percent of
vascular plant species and nearly 40 percent of four important vertebrate
groups. The areas include the Mediterranean region, New Zealand,
the southern tip of South Africa, much of Brazil, and the Pacific
Coast of the United States from southern Oregon down to Mexico's
Baja California. Myers says that if we spend our limited conservation
funds there, we'll protect the most species per dollar. He and his
colleagues estimate the cost would be $500 million a year for ten
To stamp in our minds the impending losses, E.O. Wilson created
the Hundred Heartbeat Club, a list of animal species that have fewer
than 100 individuals. The mountain gorilla, a shy vegetarian with
no natural enemies but humans, could soon be added to the roster.
Its best chance of survival is as a tourist attraction. Other members
of the club include Spix's macaw, the Hawaiian crow, the Chinese
river dolphin, and the Philippine eagle. But even species with several
hundred members face an uncertain future. Members of some highly
vulnerable groups appear on the following pages.
- Reporting by Melissa Mertl