Ask A Scientist© Biology Archive

Author:      marge
Text:        About how many endangered species are there?

Response #:  1 of 1
Author:      Jim Murray
Text:        "Endangered" species are often defined legally, so if a species 
is on the verge of extinction; it may not be considered endangered unless 
someone complains about this.  As our rain forests are destroyed at 100's of 
acres per minute, many species are going extinct, perhaps even before they 
have even been discovered by humans.  I will try to see if i can find out how 
many are now considered endangered.  I just finished reading Last Chance to 
See by Douglas Adams.  He described his experience with seeing endangered 
species, before they went extinct.  I recommend it.  There are about 1.4 
million described species of living things.  About 1 million described animal 
species.  But it has been estimated that there are 10-100 million left to be 
discovered.  Extinction rates for the last few million years has been about 1 
species lost per century.  But since human populations have exploded, 
extinction rates have been accelerating.  Most extinctions within human 
history have occurred in the last 300 years (the "industrial revolution").  
Most of the extinctions in the last 300 years have occurred in the last 50.  
And most of the extinctions of the last 50 years have occurred in the last 10. 


Now extinction rates are around 1000's of species per year (that is a 100,000 
times increase over the last 5000 years!).  We are in the midst of a mass 
extinction, the likes of which has not been seen in 100's of millions of 
years!  Much of these are thought to be due to human influence.  Currently, 
there are about 5200 threatened animal species, and about 17,300 threatened 
plant species.  The saddest part perhaps being that we will never know how 
many species humans caused to go extinct, and will certainly cause the 
extinction of thousands of species, without ever having seen the organisms, 
and without ever firing a gunshot.  Habitat destruction is one of the most 
effective ways of reducing the number of species in an area.  If you want to 
see how to kill lots of fascinating species, go to one of the tropical 
islands, like Hawaii.  According to a pamphlet called Endangered Species from 
the U. S. Department of the Interior, more than 600 spp. of life were either 
endangered or threatened in the U. S. as of 1991.  Another 500 spp. were 
listed from outside the U. S.  About 50 to 100 spp. are added each year and 
there are thousands of species that are thought to be in danger but there is 
not enough data to prove it.