Isn't extinction a natural process? What makes us think we're so smart …

• Introduction
• Background extinction
• The causes of extinction
• Rates of extinction
• Population deletions
• Biological consequences of human-caused extinctions
• U. S. Endangered Species Act
• Allocation of benefits to endangered species
• Bibliography
• Figures
• Tables

Biology Articles » Conservation Biology » The Biology of Human-Caused Extinctions » Background extinction

Background extinction

- The Biology of Human-Caused Extinctions

Background extinction

It is the fate of most living things eventually to go extinct. The species diversity now is almost certainly greater than it ever has been in the past, but paleontologists tell us that more than 99% of the species that have ever lived are now extinct.

Some take comfort that we seem to have recovered from the great extinctions of the past

• Ordovician (440mya) - 50% of animal families

   

• Devonian (360mya) - 30% of animal families

   

• Permian (250mya) - 50% of animal families, including 95% of marine species

   

• Triassic (210mya) - 35% of animal families

   

• Cretaceous (65mya) - 60% of animal species

   

We're still here, and the world doesn't look so bad, but recovery from these extinctions took a very long time.

• Ordovician - 25 million years

   

• Devonian - 30 million years

   

• Permian/Triassic - 100 million years

   

• Cretaceous - 20 million years

   

So the optimist in me says that we are very unlikely to destroy life on this planet and that the diversity of life will recover once we are gone. The pessimist points out that the recovery of diversity will not happen on a time scale of any interest to human beings.