Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The Sixth Wave of Extinction

20.07.2004


History of life on the Earth witnessed five mass extinctions of species as a result of natural calamities. Currently, biologists are talking more and more often about the sixth wave of extinction provoked in many respects by human beings. This opinion is shared by a Russian sea fauna diversity specialist A.V. Adrianov (Institute of Maritime Biology, Far-East Branch, Russian Academy of Sciences). Research in this area has been supported by the Far-East Branch of the Russian Academy of Sciences, CRDF, Ministry of Education and Science of the Russian Federation, and the Foundation for Promotion of Russian Science and the Russian Foundation for Basic Research.



As of today, taxonomists have already described nearly 2 million species, although in fact their number varies, according to various estimates, from 5 to 100 million. But 90 to 99 percent of species ever existing on the planet have already become extinct. The overwhelming majority vanished as a result of the so-called normal or background extinction due to the limited period of biological species existence, which fluctuates from 1 million years with mammals through 11 million years with some marine invertebrates. Besides the background extinction, the fauna experienced five mass extinctions, as a result of which 50 to 95 percent of then existing species disappeared within a limited historical period. The first mass extinction occurred 440 million years ago, at the end of Ordovic, as a result of temperature fall and the ocean level lowering. The second wave took place during the late Devonian, again due to temperature fall and sea reliction. During the third wave of extinction, at the end of Permian, approximately 250 million years ago, 95 percent of marine species and nearly 70 percent of terrestrial ones disappeared. The catastrophe was probably caused by active reconstruction of the earth’s crust and change of climate during formation of the supercontinent Pangaea. The forth extinction happened in the late Trias, and the fifth one – the most renowned extiction – hit 65 million years ago. Researchers are inclined to believe that the Earth came into collision with a large bolide at that time. As a result, sea shoals suffered from tsunami and acid rains, the seabed was covered by enormous amount of organic matter, and only 12 percent of the then existing species survived on land.

At present, according to numerous specialists’ opinion, the sixth - pleistocene - wave of extinction is coming, which has been in many respects provoked by men. Given the current average extinction rate of 40 species a day, it would take only 16 thousand years for the extinction of 96 percent of the contemporary biota – exactly as much as died out during the period of disastrous Permian extinction. The major reason for the oncoming calamity is destruction of plants’ and animal’s ecotope. Scientists have estimated that the species life span for contemporary mammals and birds has decreased up to 10 thousand years, i.e. it became 100 to 1000 times shorter than that of fossil forms. If the habitat continues to be destroyed at the same pace, the life span of these species will soon make only 200-400 years. There are no such estimates for the invertebrates, but they are undoubtedly affected both by the global environment and climate change, and by disappearance of local biotopes.


Death reigns on land and at sea. Thus, about 1 percent of tropical rainforests disappears annually. Up to 70 plant and animal species become extinct every day, which makes about 3 species per hour. At present, one tenth of coral reefs – zones of the highest biological diversity at shallow water – perishes; about 30 more percent will be ruined in the next decades. Corals die out mainly due to global environment and climate change, reef fish catching, water contamination and warming, hurricanes, destruction of symbiotic organisms. Any events taking place in shallow water also affects sea depths. Perhaps only “autonomous” superorganisms of deep-water gas-hydrotherm have not been touched upon by anthropogenic impact and they will evidently be able to escape consequences of the planet’s global environment and climate changes even in case of nuclear holocaust.

Nevertheless, the sixth mass extinction is oncoming. That will be the first extinction which did not happed due to natural reasons but as a result of activity of one biological species, whose quantity increases annually by 100 million individuals.

Sergey Komarov | alfa
Further information:
http://www.informnauka.ru

More articles from Life Sciences:

nachricht Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory

nachricht How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>