Mass Extinction
Mass extinctions are episodes when global biodiversity falls and it effects life forms for short periods of time (Chellam2001,
62). There have only been five mass extinctions since the dawn of time. The “Big Five” they are called, because they caused, in their times, most of the life on this planet to die out. When these species failed they are known to be called “background” extinctions on earth (Johnson2009,
28). Even though extinctions may happen, species normally bounce back to normal after a few decades. And on average species live, from start to finish, over 10 million years.
This is known as the background rate of extinction (Chan2010,49). Those extinctions are generally caused by disturbances in their geographic areas and these species tend to suffer horribly during these types of depressions. For example if a group of middle sized birds (such as geese) move to a hunting ground they could easily all be killed and put an end to their kind. Hunting is a serious leading cause in mass extinctions, in some cases more than others.
The very first mass extinction was the Ordovician period. This happened 443 million years ago. And a towering 85% of species were lost from the earth (Johnson2009,35). All types of species perished, including land and sea creatures. This event was caused by changing sea levels that manipulated oceanic circulation so drastically that most organisms could not adapt and that lead to death (Johnson2009,35).
The Denovian came second. Though not as drastic as the Ordovian it still made its way into mass extinctions. In this era, 376 million years ago, 75% of all species died off (Weise2011,10). This was most likely caused by global cooling, followed by global warming (of a sort) and an increase of carbon dioxide caused by plants dying that resulted in the death of carnivores, herbivores, and decomposers of that time. In addition to the destruction a meteor might have been added into the equation, having it strike the earth and giving an end to the Denovian period.
The Permian era was one of the deadliest mass extinctions. 250 million years ago, this happened, and 95% of marine life was killed and 70% of terrestrial life was wiped out (Johnson2009,30). This was caused by gas emerging from erupting volcanoes that caused acid rain and increased carbon dioxide levels (Johnson2009, 36) Because of this reefs were destroyed and half of the brachiopod family disappeared (Johnson2009,38). This put their Permian on the “Big Five” list of mass extinctions. It was also the main event that took place before Pangaea a great land mass was formed.
Occurring 200 million years ago the Triassic Mass Extinction occurred. A huge mass extinction it turned out to be, out of the millions of life on earth during the period about half of the marine life and 80% of all the land animals as well (Cook2010, 94). The cause of this extinction, like the others is not 100% proved but the information has been backed up properly. A possible explanation to it was that volcano’s eruption caused Pangaea to break apart. This lead to a rise in carbon dioxide and rising temperatures. Though it was dreadful, this Triassic extinction was very important to the human race ages later.
The most recent mass extinction happened 65 million years ago. Ages after the other four extinctions, the Crestacous-Paleogogena or known as K-PG extinction occurred (Johnson2009, 29). This was the era we lost the dinosaurs and in addition 76% of all species were lost. Though this made way for the “Age of Mammals” as it was referred to by Tom Holtz (Johnson2009, 40). The death of the dinosaurs was caused by something tremendous, an asteroid slammed into the Yucatan Peninsula that caused firestorms that “dusted” the earth and cooled it (Ingham2010, 78). No large animals survived and water levels grew increasingly. The Crestaccous was the last mass extinction, till now.
The sixth extinction is it upon us? The answer is now more than ever yes. Extinction rates of mammals has gone up, as a result of humans expanding their lands about 500 years ago, as before just a few species dies out every million years (Ingham2010,76). We do not know how many species there really are on earth but we do know many, and out of those 5,570 species at the least 80 mammals have gone extinct (Allvne2011, 22). And those extinctions are expanding, to marine and large land mammals as well. In this day and age there are now 18,351 species on the threatened species list and of those 1,940 are dangerously endangered (Weise2011, 5). These numbers have been growing and still grow, this tells us that we are heading into the sixth mass extinction.
Many animals and plants may even surprise, that they are on the “list”. For example some livestock and crops have gone extinct from our usage (Chellam2001, 70). This threatens species as well as humans, in addition fish and frogs, even wild tigers have been hitting the red list. These downfalls show us that our earth is headed down the same road as the former five extinctions. Many causes have occurred to turn us down the wrong path. Humans are the biggest instigators in this world. People push down species habitats and ways of life by overfishing oceans and rivers, hunting endangered animals and corrupting the nature around us. Like releasing fossil fuels and greenhouse gases and spreading germs (Ingham2010, 75)
.Humans will eventually (if not corrected) release enough CO2 to change ocean ph and oxygen will be scarce (Cook2010,97). And though human beings may be one of the most successful mammals, extinctions are 1000 times higher than before there were any humans. But, we may be a big cause, there are other factors massing with the natural balance of extinctions. Temperature changes has caused glaciers to melt and climates to disperse strangely and cause short food supplies and environments (Chan2010,56). But even if nature itself was to perfect, humans would have to still change their ways drastically in order to save the planet from a sixth extinction. America has lost 75% of large land animals and Australia more than 85% (Chan2010, 54).
In America alone we could lose 45,000 species plus those that aren’t recorded (Chellam2001, 69). We may even take out half of the world’s species in a few centuries. The mass extinction is starting now but the price to pay will not come till the next 3 to 22 centuries (Ingham2010, 77), if we don’t change our ways that number will grow closer and closer. Although right now things seem drastic we have not reached the other levels of the “Big Five” extinctions yet.
All sorts of species, land and water, are at risk of the sixth mass extinction. Not one scientist can figure what species will go first and which will survive. But the species are showing themselves. For example passenger pigeons in the United States died off, over 2,000 million species of pigeons were lost. This was the effect of hunting and destruction of their natural habitats (Chellam2001, 68). Though this happened in 1896 it is still relevant to our lives now, considering only one bird was left and died in captivity.
Another example, was the disturbance of island birds. When first visiting the Pacific Islands humans killed more than 2000 birds (Johnson2009, 45). And over the last 150 million years 1,500,000 birds have evolved but now only 9,000 survive (Chellam2001,65). But not only birds have disappeared large mammals are disappearing as well. The tigers in India, Aslatic Lions, and rhinos have been killed off. But there is still hope for these species yet, because 193 countries have agreed to protect 17% of ecosystems and 10% of marine areas, though it is a small contribution, with time the numbers will grow.
Now is the time to fix what has happened to our earths species. We3 need to start now if we are going to preserve our species. It may sound impossible but there is still time. This process is being called the NBSAP- National Biodiversity and Action Plan (Chellam2001, 73). We can’t give up on it. This does not mean giving up towns and cities but downsizing construction and pollution, although there is still much land to protect and preserve. We as human beings have to take full responsibility due to the fact that we have caused sufficient damage to the earth.
Through Pollution, habitat fragmentation, disease, global warming, hunting, and the introduction of invasive species ((Allvne2011,21). A way to correct these ways would be to protect environments by the use of bans of hunting and trapping in areas where endangered species live. And cutting off some wilderness from human interactions. It will take years to gain the biodiversity that was lost but if the sixth extinction does occur it will result in new levels of biodiversity and complexity of species afterwards (Johnson2009, 48). Though this will take place years/centuries after time matters to people. This could happen in the next 3 to 22 centuries. This may seem like a long time but for a mass extinction this is a short and dangerous period of time. We can only guess about how much damage will actually come to be.
In conclusion, the Sixth Mass extinction is upon us. Will it occur in the next few years, no, but our ways as people will speed up the process if not put to an end. Many species have already gone extinct in humans times and so many more are on that road. We can only hope this travesty will come to a halt but unfortunately if we do not change our ways it will still come with ferocity and disaster.
1) Allvne Richard, Science Correspondent, Has the Earth's Sixth Mass Extinction Already Started, 2011
2) Chan Ken, Are We really Living in the Age of Another Mass Extinction, 2010
3) Chellam Ravi, Follio, The Age of Extiction,2001
4) Cook John, Earths Five Mass Extinctions, 4/15/2010
5)Ingham Richard, Worlds Sixth Mass Extinction May be Underway, 3/4/2010
6) Johnson, Deciphering Mass Extinctions, 2009
7) Pappas Stephanie, Life Science, HUmans on Verge of Causing 6th Mass Extinction, /2/2011
8)Weise Elizabeth, USA Today, Study Offers Warning About Naxt Potential Mass Extinction, 3/2/2011