There has been life on earth for some three and a half billion years. During this time there has been continous changes in species composition. Species have become extinct due to changes in habitat and climate and better adapted species have evolved from previous forms. During the geological history earth has gone through periods when several species have become extinct during a relativly short time.But the wave of extinction that we currently experience and have experienced during the past century is new in character due to the rate of extinction.

The protection of threatened species plays an important part in working for biodiversity. About 10% of of Swedens species are threatened as their numbers/populations can not be secured in the long run.