Monday, May 9, 2011

Holocene Extinction on the Horizon

Kaitlin Sodd
Professor Lutz2
English 151
May 4, 2011
Holocene Extinction on the Horizon
    Hundreds of years ago the Earth we know now looked remarkably different; huge fern-like plants covered the ground, large reptiles ruled the land, the only mammals to speak of were small rodents resembling todays mice and moles. But then something happened, a mass extinction caused by a meteoroid wiped out the vast majority of existing species. Those that survived evolved into the plants and animals we know today.

    Scientist agree the reign of the dinosaurs was ended by the world’s 5th mass extinction . The question now is, are we facing the worlds 6th mass extinction today? The first step to finding the answer is understanding what is meant by a mass extinction. According to Freeman’s Biological Sciences 4th edition, species go extinct all the time. It is common for species that prove not to be evolutionarily fit to eventually die off. In a short matter of time the extinct species will be replaced by a new species so that its environmental niche is filled. Without this cycle of extinction and speciation life on earth would be static and unchanging, which the fossil records have proved untrue (Freeman 316). It is crucial to understand what makes normal extinction different from a mass extinction; a mass extinction is due to some kind of catastrophe that wipes out at least three quarters of all living species at one time. It also has to occur in a geologically short time span, so we’re talking about hundreds to thousands of years. Another qualification is that, it has to cause devastation to a diverse group of species, all over the Earth, as oppose to a concentrated area of just a few phylum.

     Catastrophes that led to other mass extinctions have been due to external forces, such as meteorites or large volcanic activity. However the 6th mass extinction is a little different, the catastrophe in question is the human population. This extinction would be due to the direct result of human activity. Climate change, pollution, overfishing and exhaustive land use, just to name a few, are all leading up to what scientist are calling the Holocene extinction, due to the fact that we are currently in the Holocene era. The normal rate of extinction is one species every 4 years. However the current rate of extinction is somewhere between 30,000 and 100,000 species per year. The Holocene extinction is on its way to being the fastest extinction in the worlds history to date! Some scientist even estimate that over five million of the Earth’s species will be gone by the end of the century. The fact is we need to change.

    One huge source of extinction comes from the world’s marine habitats. We know so few of the species thought to reside in the ocean, and unfortunately human’s actions are causing them to die before even being discovered. There are many things leading to the death of so many marine species, according to the “loss of habitats, the spread of disease, pollution, and unsustainable fishing practices are directly related to the actions of humans.” In addition, the effects of green house gasses are causing the Earth to warm, having a devastating effect on one of the most biologically diverse ecosystems in the world. Coral reefs are like underwater tropical rain forest, they house such a diverse number of species, yet they are declining at a frightening rate.

    Despite popular belief, coral is actually an animal, not a plant. It consists of many very small animals that colonize and produce a hard, calcified shell that we know as the coral that washes ashore.  These animals are in a symbiotic relationship with a single celled algae known as zooxanthellae.  Neither can live without the other.  In fact, the algae are what give the coral their fantastic colors that make them so popular amongst tourist and divers. As the oceans warm, due to human caused global warming, the coral comes under a lot of stress. Coral is very accustomed to a certain temperature and even the difference of a degree or two can have a major impact. The coral will expel their algae in an effort to cool down. This causes coral reef bleaching, the coral is not dead yet but it is bone white and death is inevitable. Eventually, the coral dies because it cannot get enough energy without the help of its algae. In the same way, the Zooxanthellae die without their relationship with the coral.

    It has been estimated that one third of all reef building coral currently face extinction.  Unfortunately, that isn’t even the tip of the extinction iceberg. As a result of recent coral reef decline, it is estimated that over one-third of all coral reef fish are also in serious danger of becoming extinct. Other ocean ecosystems are facing a similar problem. Overfishing is a huge problem amongst other marine species not typically found in the reefs. According to PBS “Bluefin tuna populations in the Atlantic Ocean have declined over 70% in the last 30 years.” Despite this dramatic decline, the tuna are still being fished at an alarming rate. They have become a staple in many cultures diets and people are not willing to stop eating them until they are gone. Unless the current trend of fishing changes, it will not be long before this species is endangered and inevitably extinct.
     What people don’t realize is that the death of one species has a huge impact on the environment. Bluefin Tuna are not the only animals that are affected by overfishing. Humans aren't the Bluefin Tunas only predator. The death of tuna will mean the death of those predators main food source. With less food they will begin to die off. In addition, all those prey that the tuna normally feed on will become abundant. The tuna’s prey has prey of its own and with increased numbers means increased food intake. We need to realize that the death of one species impacts an entire ecosystem.

    Some better known animals on the endangered list are those that are hunted for sport. Animals like the giant panda, the African elephant, and the cheetah have become somewhat of the poster children for the endangered animal campaign.  Things like elephants’s tusks or cheetahs’s pelts were rare and valuable, and thus these animals were hunted to the brink of extinction. As people became more aware of these effects, laws were put in place to help these animals. Unfortunately,  even without the threat of hunting, most endangered animals still have a slim outlook for their future on planet Earth.

    The African Cheetah is a prime example of an endangered animal that has a bleak future. They were hunted almost to extinction, when people realized this, strict bans were put on the hunting of the animal.  As a result of such a dramatic decrease in population size, the species is experiencing a genetic bottle neck. This is when a population gets incredibly small and is then able to reproduce and grow. Due to such a few number of individuals in the parent generation there are very little genetic differences in the population as a whole. When they reproduce they have little variation from individual to individual; it is nearly equivalent to inbreeding(Charruau 722). According to ABC Science “humans rate at about 70% identical. But cheetahs rate at 97% identical”. As a result, the cheetah population as a whole is not very fit. It would only take one bad virus to wipe out the entire species, because they are all so genetically identical. It is sad to say that the conservation efforts probably will not help these cheetahs and many other endangered species in the end. The African Cheetahs are in a very bad situation, and it will not take much before they are gone forever.

    Fortunately, people are becoming more aware of the adverse effect we humans have on our planet; but some scientist doubt that we can turn things around. The Holocene extinction is already underway and there is no stopping it. However, we can prolong the tragic event in Earth’s history. It is estimated that the Holocene extinction will be complete anytime between 200 years and 2,000 years (Stuart 685). We may not have the ability to stop this extinction now, but who knows the kind of scientific breakthroughs we will make in 2,000 years time. It is my belief that the longer we postpone this wipe out the better our chances get at preventing it all together. There are things we can do as individuals, as well as humans as a species, that will help our dying environment.

    As individuals there are so many things we can do to make a difference. Everyone has heard about what they can do to help our planet a million times. To prevent sounding like a broken record, I’ll just link to some sites with excellent environmentally friendly tips and choices you can make in your everyday life.  However, many are not aware of the things that the human population as a whole can change. The human population has been growing exponentially and our environment is finally starting to feel the strain of this. If we continue to increase at the rate we have, we will only keep making things worse. We have destroyed too many habitats as it is. We can’t keep taking away other animals homes for ourselves. In addition, stricter regulations need to be put on animals such as the blue fin tuna. Although, there is a cap on how many pounds of tuna can be fished each year that number is exceeded by almost 50% annually, so enforcing, and obeying these laws is crucial to change our impact.

    We need to work now to make a change. Once a species goes extinct we will never get them back. With the current rate of extinction 100 times what is considered normal and 2.7 to 270 species going extinct a day we are facing a now or never situation. Humans need to work now to change what they have messed up. If we don’t the damage will be irreversible and we may end up like the dinosaurs.

Print sources
Charruau, P. ". Academic Journal Phylogeography, Genetic Structure and Population Divergence Time of              Cheetahs in Africa and Asia: Evidence for Long-term Geographic Isolates." Molecular Ecology              20.4 (2011): 706-24. Print.

Freeman, Scott. Biological Science. San Fransicso, CA: Benjamin Cummings, 2011. Print.

Stuart, A. J., P. A. Kosintsev, T. F. G. Higham, and A. M. Lister. "Pleistocene to Holocene Extinction              Dynamics in Giant Deer and Woolly Mammoth." Nature 431.7009 (2004): 684-89. Print.