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World's Biodiversity Becoming Extinct at Levels Rivalling Earth's Past "Mass Extinctions"
Volume 3 Number 3 - December 1999
Dr Peter Raven
Report of the paper "Plants in Peril: What Should We Do?" given by Dr Peter Raven, Director, Missouri Botanical Garden, St. Louis, U.S.A. and President of the XVI International Botanical Congress at the XVI International Botanical Congress in August, 1999 hosted by the Missouri Botanical Garden.
Over the past several centuries, the documented extinction rates of a wide range of well-known groups of organisms are several times higher than the background rate or rate at which species have been becoming extinct for the past 65 million years, since the major extinction event that closed the Cretaceous Period and the Mesozoic Era, which coincided with the loss of the last surviving dinosaurs. This was the fifth major extinction event in Earth history, a time when two-thirds of all terrestrial organisms that lived at that time disappeared and the character of life changed permanently. The current extinction rate is now approaching 1,000 times the background rate and may climb to 10,000 times the background rate during the next century, if present trends continue. According to the paper, species loss can be estimated even when the members of many groups of organisms are relatively poorly known because of the logarithmic relationship between species number and the area in which they live. On the average, a tenfold increase in area is correlated with a doubling in species number, and a tenfold decrease with a halving of the original number. Given the relationship between species number and area, one can determine the number of species that will survive in a given area. Fragments of a given habitat that have been reduced in size lose half of the species they are going to lose in about 50 years; three-quarters of them in a century.
The paper states that if current trends continue, and we retain just five percent of tropical forests in protected areas, which will be true within 50 years at present rates of destruction (and sooner if these rates are accelerated), then extinction rates will be three or four orders of magnitude higher than those prevailing between mass extinctions. At this rate, one-third to two-thirds of all species of plants, animals, and other organisms would be lost during the second half of the next century, a loss that would easily equal those of past extinctions.
The paper states that vast numbers of unknown plants, animals, and other organisms are currently being lost before they've been recognized. Only about 1.6 million organisms out of a conservative estimate of between seven and ten million have been recognized scientifically. A great majority of these are poorly known, often from a single specimen, a brief description, a locality, nothing more, according to the paper. Some 250,000 of 300,000 species of plants have been identified, leaving some 50,000 completely unknown.
The extreme depletion of genetic variation in individual plant species causes them to become more vulnerable to extinction, according to the paper. Genetically diverse traits in plants can often enable them to grow in harsher environments, for example, or survive the competition with weedy species. About 30 percent of the world's 300,000 plant species are in cultivation now, "which provides a good start for conservation," according to Raven.
The paper outlines a seven-point plan to slow the extinction rates of plants around the world. It suggests that a major United Nations-sponsored conference on this topic could move these steps into country-by-country actions.
"All plants are important in one way or another and this comprehensive plan seeks to save them all - a priceless gift to future generations," said Raven.
"Nations will only preserve biodiversity if they have their own institutions and their own scientists to make recommendations about what's best for them," said Raven.
The paper calls for the Convention on Biological Diversity (CBD) and the Global Environment Facility (GEF) to step up their efforts train scientists.
"Although this expenditure may seem high, we are living in an era when our great-grandchildren may live in a world in which more than half of the plant species that exist now will be known only as specimens," said Raven.
The paper was taken from the Biodiversity Action Network (BIONET) information services. For further information contact Stas Burgiel, Biodiversity Action Network (BIONET), E-mail: email@example.com, Internet: http://www.bionet-us.org