Posts Tagged 'Mass Extinction'

Sunday article by Mohan Pai

 
 
 Extinction is forever !

Over 99% of the species that ever lived are now extinct.

Mass extinction exhibits a cyclic nature. 5 major extinctions that occurred during the last 540 million years of earth history wiped out most living species.

 
Mass extinction is a sharp decrease in the number of species in a relatively short period of time. Mass extinctions affect most major taxonomic groups present at the time — birds, mammals, reptiles, amphibians, fish, invertebrates and other simpler life forms. They may be caused by one or both of:
*extinction of an unusually large number of species in a short period.
*a sharp drop in the rate of speciation.
 Over 99% of species that ever lived are now extinct, but extinction occurs at an uneven rate. Based on the fossil record, the background rate of extinctions on Earth is about two to five taxonomic families of marine invertebrates and vertebrates every million years. Marine fossils are mostly used to measure extinction rates because they are more plentiful and cover a longer time span than fossils of land organisms. Since life began on earth, several major mass extinctions have significantly exceeded the background extinction rate. The most recent, the Cretaceous–Tertiary extinction event, occurred 65 million years ago, and has attracted more attention than all others as it marks the extinction of nearly all dinosaur species, which were the dominant animal class of the period. In the past 540 million years there have been five major events when over 50% of animal species died. There probably were mass extinctions in the Archean and Proterozoic Eons, but before the Phanerozoic there were no animals with hard body parts to leave a significant fossil record.
 Estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from the threshold chosen for describing an extinction event as “major”, and the data chosen to measure past diversity.
 Extinction cycles
It has been suggested by several sources that biodiversity and/or extinction events may be influenced by cyclic processes. The best-known hypothesis of extinction events by a cyclic process is the 26M to 30M year cycle in extinctions proposed by Raup and Sepkoski (1986). More recently, Rohde and Muller (2005) have suggested that biodiversity fluctuates primarily on 62 ± 3 million year cycles.Much early work in this area also suffered from the poor accuracy of geological dating, where errors often exceed 10M years. However, improvements in radiometric dating have reduced the scale of uncertainty to at most 4M years – theoretically adequate for studying these processes.
The concept of periodicity has important implications for determining which factors cause extinction. Hypotheses invoking catastrophism have particularly been advanced utilizing this concept, which imply extra-terrestrial forces as extinction-causing agents. This is because only astronomical forces are known to operate on such a precise periotic time schedule. Contrary to catastrophism are hypotheses which focus on gradualism. These gradualistic hypotheses invoke various terrestrial extinction mechanisms including volcanism, glaciation, global climatic change, and changes in sea level. Most recently hypotheses centered on the new non-linear science of complexity have emerged. Under these hypotheses species-species interactions lead to occasional instability resulting in cascades which may ripple through entire ecosystems, with potentially devastating results.

Major extinction events
The classical “Big Five” mass extinctions: End Ordovician, Late Devonian, End Permian, End Triassic, and End Cretaceous. The Holocene extinction event is referred to as the Sixth Extinction.
 
Cretaceous-Tertiary. 65 million years ago, the dinosaurs were wiped out in a ma extinction that killed nearly a fifth of land vertebrate families, 16% of marine families and nearly half of all marine animals.
End of Triassic. About 200 million years ago, lava floods erupting from the central Atlantic are thought to have created lethal global warming, killing off more than a fifth of all marine families and half of marine genera.
Permian-Triassic. The worst mass extinction took place 250 million years ago, killing 95% of all species.
Late Devonian. About 360 million years ago, a fifth of marine families were wiped out, alongside more than half of all marine genera.
Ordovician-Silurian. About 440 million years ago, a quarter of all marine families were wiped out.

Most widely supported Causes
The most often cited as causes of mass extinctions are:
*Flood basalt events: 11 occurrences, all associated with significant extinctions.
*Sea-level falls: 12, of which 7 were associated with significant extinctions
*Asteroid impacts producing craters over 100km wide: one, associated with one mass extinction. *Asteroid impacts producing craters less than 100km wide: over 50, the great majority not associated with significant extinctions.
 
Evolutionary importance
Mass extinctions have sometimes accelerated the evolution of life on earth. When dominance of particular ecological niches passes from one group of organisms to another, it is rarely because the new dominant group is “superior” to the old and usually because an extinction event eliminates the old dominant group and makes way for the new one.For example mammaliformes (“almost mammals”) and then mammals existed throughout the reign of the dinosaurs, but could not compete for the large terrestrial vertebrate niches which dinosaurs monopolized. The end-Cretaceous mass extinction removed the non-avian dinosaurs and made it possible for mammals to expand into the large terrestrial vertebrate niches. Many groups which survive mass extinctions do not recover in numbers or diversity, and many of these go into long-term decline.
 
Sixth Mass Extinction is NOW !
There is little doubt left in the minds of professional biologists that Earth is currently faced with a mounting loss of species that threatens to rival the five great mass extinctions of the geological past.
The classical “Big Five” mass extinctions are End Ordovician, Late Devonian, End Permian, End Triassic, and End Cretaceous. The Holocene extinction event is referred to as the Sixth Extinction, that is the extinction event that is taking place NOW !
A study published in the international journal Conservation Biology reveals a sorry and worsening picture of habitat destruction and species loss. It also describes the deficiencies of and opportunities for governmental action to lessen this mounting regional and global problem. The review highlights destruction and degradation of ecosystems as the main threat.
A study published in the international journal Conservation Biology reveals a sorry and worsening picture of habitat destruction and species loss. It also describes the deficiencies of and opportunities for governmental action to lessen this mounting regional and global problem. The review highlights destruction and degradation of ecosystems as the main threat.

According to the IUCN Red List of Threatened Species, 2008
*Nearly 17,000 of the world’s 45,000 assessed species are threatened with extinction (38 percent). Of these, 3,246 are in the highest category of threat, Critically Endangered, 4,770 are Endangered and 8,912 are Vulnerable to extinction.
*Nearly 5,500 animal species are known to be threatened with extinction and at least 1,141 of the 5,487 known mammal species are threatened worldwide.
*In 2008, nearly 450 mammals were listed as Endangered, including the Tasmanian Devil (Sarcophilus harrisii), after the global population declined by more than 60 percent in the last 10 years.
*Scientists have catalogued relatively little about the rest of the world’s fauna: only 5 percent of fish, 6 percent of reptiles, and 7 percent of amphibians have been evaluated. Of those studied, at least 750 fish species, 290 reptiles, and 150 amphibians are at risk.
*The average extinction rate is now some 1,000 to 10,000 times faster than the rate that prevailed over the past 60 million years.

The Passenger Pigeon
In Michigan during a single hunt in 1878 an estimated 1,000 million birds were destroyed at nesting sites. On September 1, 1914 the last Passenger Pigeon named Martha died in captivity in the Cincinnati Zoo.
 Indian Vultures
In India, the White backed vulture population was estimated at 30 million birds in 1992. Today, it is a mere 11,000 birds and falling due to Diclofenac poisoning.

Extinction is irreversible.
This has been part of the evolutionary process which has produced more advanced forms of life – a process that has occurred over a vast span of time over millions of years. The greatest contribution of Charles Darwin, who propounded the Theory of Evolution, in his logical explanation for evolutionary changes and appearance of new form of life – natural selection – the success of those organisms that are capable of adapting to the environment, to survive and reproduce.

One of the world’s rarest birds and an almost extinct species, today lessthan 200 birds survive!

In India, the Cheetah, the lesser one-horned rhinoceros, the pink- headed duck and the mountain quail have become extinct in the last one century.

The Sangai, the brow-antlered deer is found only in Manipur and only 162 animals survive.
Many mammals and birds have become rare and endangered and many a natural range diminished in size with increasing deforestation, often confining the animals to small territories.
The Golden Toad of Monteverde, Costa Rica was among the first casualties of amphibian decline. Formerly abundant, it was last seen in 1989.

References: Wikipedia, J. C. Daniel (’Extinction is for ever’), IUCN Red List, park.org, Mohan Pai.

 
MY BLOG LIBRARY
For some of my articles visit:
http://biodiversity-mohanpai.blogspot.com/
For some key chapters from my book “The Western Ghats”, please log on to:http://westernghats-paimohan.blogspot.com/
For detailed blog (6 Chapters from my book) on Mahadayi/Mandovi River Valley, please log on to:http://mohan-pai.blogspot.com/
For the book ‘The Elderly’ please log on to:
http://oldagecare-paimohan.blogspot.com/
http://omashram.sulekha.com/blog/posts.htm
You can also access my blogs on Sulekha and WordPress:
http://mohanpai.sulekha.com
https://mohanpai.wordpress.com/
For my book “The Flight of Gods – Hindu Temples & Shrines of Goa” please log on to:
http://flightofgods.sulekha.com/blog/posts.htm
http://flightofgods.blogspot.com/

Biodiversity – Noah’s Ark

69. Biodiversity – Noah’s Ark – An article by Mohan – July 2009

 

Hello friends,

Good morning.

This Sunday’s article ‘Noah’s Ark’ was actually written for the World Environment Day (5.6.09) but for some reason could not be completed in time. Conservation of the biodiversity of our planet earth is now becoming a very serious and an urgent issue. We will have to build a
Noah’s Ark fast to save the species which are becoming extinct in
thousands and the loss of biodiversity puts the future of human kind
itself  in a jeopardy. Please read on.

Very best wishes,

Mohan Pai

 
 
 
Noah’s Ark
or Manu & the Fish

“With more and more species threatened with extinction by the flood that is today’s global economy, we may be the first generation in human history that literally has to act like Noah – to save the last pair of a wide range of species. Or as God commanded Noah in Genesis “ And every living thing of all flesh, you shall bring two of every sort into the ark, to keep them alive with you; they shall be male and female” – Thomas L. Friedman
 
 Native global flood stories are documented as history or legend in almost every region on earth. Old world missionaries reported their amazement at finding remote tribes already possessing legends with tremendous similarities to the Bible’s accounts of the worldwide flood. H.S. Bellamy in Moons, Myths and Men estimates that altogether there are over 500 Flood legends worldwide. Ancient civilizations such as (China, Babylonia, Wales, Russia, India, America, Hawaii, Scandinavia, Sumatra, Peru, and Polynesia) all have their own versions of a giant flood.
These flood tales are frequently linked by common elements that parallel the Biblical account including the warning of the coming flood, the construction of a boat in advance, the storage of animals, the inclusion of family, and the release of birds to determine if the water level had subsided. The overwhelming consistency among flood legends found in distant parts of the globe indicates they were derived from the same origin, but oral transcription has changed the details through time.
 
Perhaps the second most important historical account of a global flood can be found in a Babylonian flood story in the Epic of Gilgamesh. When the Biblical and Babylonian accounts are compared, a number of outstanding similarities are found that leave no doubt these stories are rooted in the same event or oral tradition.
Matsya Avatar

Manu – the Indian myth

The Matsya Avatara of Lord Vishnu is said to have appeared to King Manu (whose original name was Satyavrata), the then King of Dravida, while he washed his hands in a river. This river was supposed to have been flowing down the Malaya Mountains in his land of Dravida. According to the Matsya Purana, his ship is supposed to have been perched after the deluge on the top of this Malaya Mountains. (This land or kingdom of Dravida that was ruled over by Satyavrata or Manu might have been an original, greater Dravida, that might have stretched from Madagascar and East Africa in the west to Southernmost India and further to Southeast Asia and Australia in the east.) The little fish asked the king to save It, upon his doing so, kept growing bigger and bigger. It also informed the King of a huge flood which would occur soon. The King builds a huge boat, which houses his family, 9 types of seeds, and animals to repopulate the earth after the deluge occurs and the oceans and seas recede.This story is to an extent similar to other deluge stories, like those of Gilgamesh from ancient Sumerian Mythology, and the story of Noah’s ark from Judeo-Christianity.

With the human population expected to reach 9-10 billion by the end of the century and the planet in the middle of its sixth mass extinction this time due to human activity the next few years are critical in conserving Earth’s precious biodiversity. It is our generation and our civilization that is responsible for causing the flood of commercial development which is causing Global Warming and pollution that could wipe out much of the world’s biodiversity.

To quote E. O. Wilson “Except from giant meteorite strikes or other catastrophes every 100 million years or so, Earth has never experienced anything like the contemporary human juggernaut. With the global species extinction rate now exceeding the global species birthrate at least a hundredfold, and soon to increase ten times that much, and with the birthrate falling through the loss of sites where evolution can occur; the number of species is plummeting. The original level of biodiversity is not likely to be regained in any period of time that has meaning for the human mind.”
Since Man is causing this flood, it also now becomes his responsibility to build the Ark that is needed to preserve life on the earth.

Let us consider the following facts:

During the past 150 years, humans have directly impacted and altered close to 47% of the global land area.

Under one bleak scenario, biodiversity will be threatened on almost 72% of Earth’s land area by 2032.

48% of South East Asia, the Congo Basin, and parts of the Amazon will likely be converted to agricultural land, plantations and urban areas — compared with 22% today, suggesting wide depletions of biodiversity.

Starting some 45,000 years ago a high proportion of larger land animals became extinct in North America, Australia, the Caribbean, and elsewhere, coinciding with human arrival.

The current textbook definition of “biodiversity” is “variation of life at all levels of biological organization”.

Biodiversity can be defined as the totality of life on earth. It’s a vast field, encompassing all the world’s ecosystems, all the plant and animal species that populate those ecosystems, and all the genes that make up the hereditary material of each living species. To get some inkling of the vastness of the topic I am reproducing below E. O. Wilson’s speech given at the Explorer’s Club on March 18, 2006:

What is left to explore?

Why, the biosphere of course, that razor-thin membrane of life plastered to the surface of Earth so thin it can’t be seen edgewise from an orbiting space vehicle yet still the most complex entity by far we know in the universe. How well do we understand this part of the world? Proportionately not very much. We live on a little-known planet. Let me give you some examples. The best-studied animals are the birds, which have been carefully collected by naturalists and explorers for centuries. Nevertheless, an average of 3 new species are added each year to the 10,000 already described by scientists. Comparable to them are the flowering plants: about 280,000 species known out of 320,000 or more estimated to exist. From there it goes steeply downhill. You’d think that the amphibians—that is, frogs, salamanders, and caecilians—would be comparable to the birds, but in fact they are still poorly explored: from 1985 to 2001, 1,530 new species were added to the 5,300 already found, an increase of over one-fourth, and with more new species pouring in.

When we next move to the invertebrates, what I like to call the little things that run the world, we get a fuller glimpse of the depth of our ignorance. Consider nematode worms, the almost microscopic wriggling creatures that teem as free-living forms and parasites everywhere, on the land and in the sea. They are the most abundant animals on Earth. Four out of every five animals on Earth is a nematode worm. If you were to make all of the solid matter on the surface of Earth invisible except for the nematode worms, you still could see its outline in nematode worms. About 16,000 species are known to science; the number estimated actually to exist by specialists is over 1.5 million. Almost certainly the world’s ecosystems and our own lives depend on these little creatures, but we know absolutely nothing about the vast majority. To continue: about 900,000 kinds of insects are known to science (I’ve just finished describing 340 new species of ants myself, for example) but the true global number could easily exceed 5 million. How many kinds of plants, animals, and microorganisms make up the biosphere? Somewhere between 1.5 and 1.8 million species have been discovered and given a Latinized scientific name. How many species actually exist? It is an amazing fact that we do not know to the nearest order of magnitude how many exist. It could be as low as 10 million or as high as 100 million or more.

Those of us in biodiversity studies say that we have knowledge of only about 10 percent of the kinds of organisms on Earth. The nematodes and insects and invertebrates all shrink in diversity before the bacteria and archaea, the dark matter of planet Earth. Roughly 6,000 species of bacteria are known. That many can be found in the 10 billion bacterial cells in a single gram, a handful, of soil—virtually all still unknown to science. It’s been recently estimated that a ton of fertile soil supports 4 million species of bacteria. We believe each one is exquisitely adapted to a particular niche, as a result of long periods of evolution. We don’t know what those niches are. What we do know is that we depend on those organisms for our existence. A search is on right now at least for the bacteria that live in the human mouth. The number of species adapted to that environment so far is 700. These bacteria are friendly; they appear to function as symbionts that keep disease-causing bacteria from invading. For those species your mouth is a continent. They dwell on the mountain ridges of a tooth; they travel long distances into the deep valleys of your gums; they wash back and forth in the ocean tides of your saliva. I’m not suggesting that we give an Explorer’s Club flag to a dentist. But you get the point. Every part of the world, including Central Park where a new kind of centipede was recently found, has new kinds of life awaiting discovery.

But—if none of this impresses you, would you like an entire new living planet for your delectation? The closest we may ever come is the world of the SLIMES (that’s an acronym for Subterranean Lithoautotrophic Microbial Ecosystems), a vast array of bacteria and microscopic fungi teeming below Earth’s surface to depths of up to 2 miles or more, completely independent of life on the surface, living on energy from inorganic materials, possibly forming a greater mass than all of life on the surface. The SLIMES would likely go on existing if we were to burn everything on the surface to a crisp. In approaching biodiversity, we are all explorers, scientists and all others who care about the natural world, now put in perspective, like Cortez and his men on a peak in Darien, before the new ocean, staring, in Keat’s expression, in wild surmise at the unknown world stretching before us.

E. O. Wilson’s Explorers Club Speech 18th March, 2006

Coral Reef
 The highest percentage per unit of area of endangered species are in the tropical rainforests and coral reefs. These species are now disappearing at the rate somewhere a thousand times faster than they are born due to human activity. At this rate, in one human lifetime, half these species of the world which have developed over thousands or millions of years, could be eliminated. Conservation needs to be focussed on the hot spots of biodiversity and fresh water systems of the world. Fresh water systems deserve special attention because they are under heaviest assault from pollution and drainage.

Most of the species extinctions from 1000 AD to 2000 AD are due to human activities, in particular destruction of plant and animal habitats. Raised rates of extinction are being driven by human consumption of organic resources, especially related to tropical forest destruction. While most of the species that are becoming extinct are not food species, their biomass is converted into human food when their habitat is transformed into pasture, cropland, and orchards. It is estimated that more than a third of the Earth’s biomass is tied up in only the few species that represent humans, livestock and crops. Because an ecosystem decreases in stability as its species are made extinct, these studies warn that the global ecosystem is destined for collapse if it is further reduced in complexity. Factors contributing to loss of biodiversity are: overpopulation, deforestation, pollution (air pollution, water pollution, soil contamination) and global warming or climate change, driven by human activity. These factors, while all stemming from overpopulation, produce a cumulative impact upon biodiversity.

“The science of living beings in general, and especially of the human individual, has not made such a great progress. It still remains in the descriptive state. Man is an indivisible whole of extreme complexity. No simple representation of him can be obtained. There is no method of comprehending simultaneously in his entirety, his parts and his relations with the outer world.”
“We are beginning to realise the weakness of our civilisation. Many want to shake off the dogmas imposed upon them by modern society – those who are bold enough to understand the necessity, not only mental, political and social changes, but the overthrow of industrial civilisation and of the advent of another conception of human progress’’

– Man, the Unknown – Dr. Alexis Carrel.
References: ‘Hot, Flat, and Crowded’ by Thomas L. Friedman, E. O. Wilson’s work, ‘Man the Unknown’ by Dr. Alexis Carrel, Wikipedia.

MY BLOG LIBRARY

For some of my articles visit:

http://mohanpaiblogger.blogspot.com/
http://mohanpaisarticles.blogspot.com/
http://biodiversity-mohanpai.blogspot.com/

For some key chapters from my book “The Western Ghats”, please log on to:
http://westernghats-paimohan.blogspot.com/

For detailed blog (6 Chapters from my book) on Mahadayi/Mandovi River Valley, please log on to:http://mohan-pai.blogspot.com/

For the book ‘The Elderly’ please log on to:http://oldagecare-paimohan.blogspot.com/
http://omashram.sulekha.com/blog/posts.htm
You can also access my blogs on Sulekha and WordPress:
http://mohanpai.sulekha.com
https://mohanpai.wordpress.com/
For my book “The Flight of Gods – Hindu Temples & Shrines of Goa” please log on to:
http://flightofgods.sulekha.com/blog/posts.htm
http://flightofgods.blogspot.com/

 

 

 

 

 

 

 

 

 

 

 

 


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