How Many Species Can You Name?
Some people despair that most species will go extinct before they are discovered. However, such worries result from overestimates of how many species may exist, beliefs that the expertise to describe species is decreasing, and alarmist estimates of extinction rates. This is according to Griffith University researcher, Professor Nigel Stork. Professor Stork has taken part in an international study, the findings of which have been detailed in "Can we name Earth's species before they go extinct?" published in the journal Science.
In biology and ecology, extinction is the end of an organism or of a group of organisms (taxon), normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively.
Stork argues that the number of species on Earth today is 5 ± 3 million, of which 1.5 million are named. New databases show that there are more taxonomists describing species than ever before, and their number is increasing faster than the rate of species description. Conservation efforts and species survival in secondary habitats are at least delaying extinctions. Extinction rates are, however, poorly quantified, ranging from 0.01 to 1% (at most 5%) per decade.
"Surprisingly, few species have gone extinct, to our knowledge. Of course, there will have been some species which have disappeared without being recorded, but not many we think," Professor Stork said.
As long as species have been evolving, species have been going extinct. It is estimated that over 99.9% of all species that ever lived are extinct. The average life-span of most species is 10 million years, although this varies widely between taxa. There are a variety of causes that can contribute directly or indirectly to the extinction of a species or group of species.
Even so, Professor Stork says the scale of the global taxonomic challenge is not to be underestimated.
"The task of identifying and naming all existing species of animals is still daunting, as there is much work to be done."
Other good news for the preservation of species is that conservation efforts in the past few years have done a good job in protecting some key areas of rich biodiversity.
"Climate change will dramatically change species survival rates, particularly when you factor in other drivers such as overhunting and habitat loss," Professor Stork said. "At this stage we have no way of knowing by how much extinction rates may escalate."
Extinction as a result of climate change has been confirmed by fossil studies. Particularly, the extinction of amphibians during the Carboniferous Rainforest Collapse, 350 million years ago. A 2003 review across 14 biodiversity research centers predicted that, because of climate change, 15—37% of land species would be "committed to extinction" by 2050.
For further information see Extinction.
Dodo image via Wikipedia.