Biological Diversity: Can We Live Without It?

"To keep every cog and wheel is the first precaution of
intelligent tinkering." - Aldo Leopold

supplied by National Audubon Society
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 change.


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.

Industrial materials

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 control.

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: