Study indicates species
extinction is not a random event
new study indicates that thousands of bird and mammal species
worldwide are at greater risk for extinction than previously thought
because they possess certain identifiable risk factors. The findings
were reported in the April 14 issue of the journal Science.
findings suggest that extinction events result in a further loss
of biodiversity, possibly even the extinction or threatening of
thousands of additional species of animals, including large, charismatic
ones such as rhinos and chimpanzees," said John L. Gittleman,
associate professor of biology at U.Va., one of the study's authors.
have identified a number of characteristics that make certain
species prone to greater extinction risks, and we have determined
that extinctions do not occur randomly. Species that are biologically
prone to certain risk factors are far more likely to go extinct
than suggested by models of random extinction. The resulting potential
loss of biodiversity is enormous."
said the biological characteristics that place mammal species
at greater risk of extinction include eating high on the food
chain, low population density, long gestation length, and especially
small geographic range size.
believe that the threat of extinction for many species is real
and because of a cluster effect could result very quickly in further
loss of biodiversity and genetic history," Gittleman said.
that have many close relatives are the most likely to be saved
from extinction, Gittleman said, but species that are of a unique
lineage with few relatives, such as the giant panda, are at severe
risk. Once lost, there would be a significant loss of evolutionary
history as well.
pointed out that in addition to the particular biological characteristics
that make some species prone to extinction, there are several
environmental factors that also can accelerate risk.
species become endangered because of human activity such as habitat
destruction for agriculture or development purposes, and by exploitation
of species through fishing and hunting. Many species also become
threatened by the introduction of exotic species and disease.
The reality is, extinctions are not random events."
The other authors of the study are Andy Purvis and Paul-Michael
Agapow of the Department of Biology, Imperial College, U.K.; and
Georgina M. Mace, Institute of Zoology, the Zoological Society