Biological Diversity: Can We Live Without It?
supplied by National Audubon Society
"To keep every cog and wheel is the first precaution of
intelligent tinkering." - Aldo Leopold
e share the Earth with an incredible variety of living
organisms. Scientists estimate that 5 to 50 million species- animals, plants
and microorganisms exist on Earth. Of these, only 1.4 million have been
discovered and named.
This wealth of species and the variety of ecosystems
they make up provide the life-support system for our own species. Yet we
are in the midst of destroying large parts of that system.
A burgeoning human population expected to reach 10 billion
by 2050-is eliminating or altering natural habitats all over the globe,
with devastating consequences to species diversity. We risk losing one-quarter
of the world's species in the next 20 to 30 years. Many species not on the
verge of extinction are being diminished in numbers. As subspecies and diverse
forms are wiped out, species are also losing internal genetic variability,
which threatens their adaptability and ultimate survival.
Why preserve species diversity?
Some people argue that extinction is a natural process,
that species have always come and gone. But today species are vanishing
from the Earth at a rate of one a day, surpassing even the mass extinctions
6 million years ago when the dinosaurs perished. And there is a major difference:
today's extinctions are being caused by humans. Do we have the right to
destroy a quarter or more of the Earth's species and consequently shift
the course of evolution forever? And what price will we pay?
The cost of species loss
Our lives depend in myriad ways on the Earth's great
diversity of species, subspecies and ecosystems. Collapsing biological diversity
threatens our food supplies, medicinal advances, the development of new
industrial products and many other practical needs. Even greater is the
price of losing all the indirect values of rich, diverse ecosystems - including
water and soil protection, climate regulation, pest control, as well as
such intangibles as re-creational, scientific and spiritual values.
The world's more than five billion people are precariously
dependent on a handful of crop plants: fewer than 20 plant species produce
90 percent of the world's food. We have made great advances in breeding
crops for greater productivity and for resistance to diseases, pests and
drought. It couldn't have been done without the genetic traits of wild relatives
of crop plants. For example, after a fungus wiped out 15 percent of the
U.S. corn crop in 1970, biologists bred resistant hybrids from a species
of Mexican wild corn.
Without infusions of genetic material from fast-vanishing
wild crop species and strains, we won't be able to keep ahead of rapidly
evolving pests or adapt crops to changing environmental conditions, such
as the temperature and rainfall shifts likely to come with global climate
Half of all prescriptions written in the United States
contain a drug of natural origin. Some of the most promising treatments
for cancer come from vanishing species. Two examples are the Pacific yew
of the endangered ancient forests of the Pacific Northwest and a soft coral
(called Hana's deadman seaweed) found only in a few places on Hawaii's reefs.
Medical researchers have discovered that certain skin compounds in frogs
are potent antibiotics, but with amphibians declining planetwide, we may
lose a whole new generation of antibacterial products.
Wild plants and animals supply us with oils, gums, resins,
construction materials, and other raw materials. As our ever more sophisticated
technology allows us to develop new products, we are losing the raw materials
from which to make them.
Habitat loss and overfishing are imperiling numerous
fish species that are a crucial food source and the mainstay of many regional
economies. The U.S. National Marine Fisheries Service estimates that the
destruction of U.S. coastal estuaries cost the nation more than $200 million
a year in revenues lost from commercial and sport fisheries.
In the U.S. Northwest, commercial and sport fisheries
for salmon, steelhead and trout provide 60,000 jobs and contribute $1 billion
in personal income to the region. Each "run" or type of salmon
is adapted to its unique river habitat and holds the secrets to its remarkable
ability to journey thousands of miles upstream to spawn in the place where
it was born. Already, more than 100 native runs of salmon and steelhead
have been lost, and 200 more are at risk.
Water cycling and purification
Rich, diverse ecosystems, such as forests and wetlands,
protect watersheds, filter out pollutants, prevent erosion, and avert floods
by absorbing stormwater. For example, the U.S. Army Corps of Engineers estimated
that preserving a wetland near Boston, MA, saved $17 million a year in flood
Natural environmental controls
Diverse ecosystems provide homes for species that control
pests, pollinate crops, and disperse seeds. Widespread destruction and alteration
of habitat upsets the delicate natural balance of ecosystems and allows
some species to expand their populations to a point where they become nuisances.
Ecological warning signs
Like the canary in a coal mine, species can indicate
when the entire ecosystem is in trouble. In the Everglades, for example,
some of the last few Florida panthers are succumbing to mercury poisoning-sounding
a warning about toxics permeating the Everglades aquatic ecosystem. "We
probably would have known nothing about the dangers until people showed
up ill in the hospital," wrote a Florida newspaper.
For more information contact: Endangered Species Campaign,
National Audubon Society, 666 Pennsylvania Ave., SE, Washington, D.C. 20003.
What is biological diversity?
Biological diversity, or biodi-versity, is the variety
and variability of living organisms - all species of plants, animals and
microorganisms and the ecosystems they comprise. Biodiversity is generally
described in three ways:
- Diversity of species: the different types of living organisms.
- Diversity of ecosystems: the variety of ecosystems as well as the
variety of ecological processes and interrelationships within each type
- Diversity within species: the variety of genetic information held
in the genes of individuals of a species.