Overexploitation is the use in a non-sustainable way of a natural resources. (Images from www.pabineaufirstnation.ca, www.deltana.com, www.thomashawk.com)
There are many factor involved in overexploitation. Many blame the rich countries for over consuming but it is the poorer countries that are putting pressure on the natural world with a rapidly growing population. The estimations show that Africa will be at a population of 3 billion by the end of this century which is five times what it is now. This human pressure will displace the habitat of other species in the form of land for agriculture, urbanisation and infrastructure.. There is a lack of incentives for any country to clean up its act, if there were environmental taxes enforced worldwide then countries would by forced to take notice. It is suggested that economic growth causes environmental degradation but lowering the rich countries economic growth will in turn lower the poorer countries. As has already been mentioned the pressure put on the environment will carry on increasing as long as the human population carries on increasing, current estimates expect the human population to be around 12 billion by 2100 and all of these people will need a place to live, food to eat and clean water to drink.
The Aurochs is an example of overexploitation, showing that it is not a modern phenomenon. It was a member of the Bovidae family with a huge range from Britain all the way to Africa. By the 13th century it was only seen in Poland, Lithuania and Prussia and by 1564 it had been hunted down to 38 animals. At this point the rulers of the land imposed a ban on hunting the Aurochs that was punishable by death, they had noticed its rarity, but it only stopped the common folk from hunting it and by 1627 it was extinct. (Image from en.wikipedia.org/wiki/Aurochs)
The sea cow was a relation to the dugong or manatee. It was discovered by a group of sailors who had become shipwrecked off Kamchutka in November 1741. They survived on the Sea cow and reported that the sea cows were about 28 feet long and 7-8 tons and moved in the water in herds. When the shipwrecked men made their escape in the august of 1742 they told everyone back home about the riches to be had by hunting this sea cow and by 1768 the animal was extinct. (Image from explorenorth.com/library/yafeatures/bl_seacow)
The great Auk is another example of our ancestors being particularly ignorant. It was a flightless sea bird with a huge range in the North Atlantic. The bird had few natural predators and so was unafraid of humans and with it being flightless it was a hunters dream. The bird was used for food and feathers and when it became rare it was quite the thing to have one stuffed or keep its eggs. The last pair were killed by a particularly evil hunter who not only killed both the adults but also smashed the egg for good measure. (Image from en.wikipedia.org/wiki/Great_Auk)
The last example I have for you of humans ignorance is the demise of the passenger pigeon. This bird was seen in huge numbers in North America and was an easy target as they all roosted together. The hunters thought up many cruel ways to kill these birds ranging from feeding them grain soaked in alcohol to beating them down with long sticks. By 1900 all of the birds had gone. (Image from www.wbu.com/chipperwoods/photos/paspigeon)
The whole fur trade is an example of overexploitation. Animals are killed for their pelts for human vanity and no more. When one species with suitable fur becomes scarce then an alternative is looked for, this has lead the trade to go from squirrels to minks to sea otters and has left depleted animal numbers wherever it looks. (Images from www.peterpalms.com and http://www.vam.ac.uk/vastatic/microsites/1250_ossieclark/designs/clients/)
A good example of over exploitation is seen in the fishing industry. There are 21,000 fish species known to science and only 9,000 of these are utilised. Only 22 of these species are harvested in excess of 100,000 tonnes per year. Fish stocks are declining across the globe in salt and fresh water. In the great lakes in north America there has been an over all decline in fish numbers due to over fishing and 2 species have gone extinct in one of the lakes. (Image from akiskayehtcharters.com)
Here are some figures on the amount of fish taken from 3 rivers throughout the world. Fish seem to be considered an endless resource by some people. Now fishermen are fishing down the food chain because they have exhausted the supply of predatory fish they are now looking to the pelagic fish to keep their profits up. For an overview of over fishing look at http://archive.greenpeace.org/oceans/globaloverfishing/index.html (Images from www.worldisround.com, url.co.nz, www.public-health.iowa.edu)
As a case study I want to look at the exploitation of herptiles by humans. This exploitation has gone on for centuries. Pliny wrote a book entitled 'Natural History' and in it is an account of the many uses of crocodiles. The ancient civilisations in America used toad secretions as a hallucinogen during religious ceremonies. Some of the artefacts that come from the sites of these ancient people are toad shape or have pictures of toads on them. (Image from www.roman.org.uk)
Amphibians and reptiles have always been used by humans as food, they are a good source of protein. Now they are more regarded as a delicacy or oddity rather than the staple of a few. (Images from crawfishcoofcentralflanc.com, gardkartsen.com, planetbarbecue.co.uk)
. Certain frog species are particularly persecuted along with a few lizards, turtles, crocodiles and alligators.(Images from www.fscnet.tamu.edu/herps/herps, www.pdubois.free.fr, www.biofil.pl, www.animalpicturesarchive.com, www.cyclura.info, norman.walsh.name, www.botswana-tourism.gov.bw, www.spsclub.org)
I have taken some figure from the literature for you so that you can see the enormity of this trade.
The skins of these animals are also sought after, reptile skins are made into shoes, purses, belts etc and amphibian skins are also made into shoes purses and belts along with book bindings, glue and fishing lures. (Images from eastofedenleathers.com,designerleathercraft.co.uk, www.italiano.jp, www.toadtraders.com/gifts, www.shodor.org )
Here are some figures to show you how large this trade is on top of the food industry. Notice that most of these are different species so they are additional to the food figures. All of these numbers are taken from legal trade, with the addition of illegal trade no one knows what the real numbers are.
One of the most worthless use of a species is for cheap souvenirs. Unfortunately many of these animals end up as just that. Crocodiles have their feet and teeth taken, rattle snakes have their rattle taken and even frogs get stuffed and varnished to be used as ornaments. In the last 45 years it is estimated that 115,000 horned lizards were stuffed for souvenirs. (Images from www.toadtraders.com/gifts, www.geocites.com, www.vngold.com/hcm/ngocdang2)
Using various parts of amphibians and reptiles as medicine goes back years as Pliny tells us. Here are some uses of animals and what they are supposed to cure. Snake and tortoise broth fights disease, fat from monitor lizards fights bacterial infection, oil from monitor lizards is an aphrodisiac, the fat and oil from a crocodile will treat burns, ulcers and cancer in Madagascar and will cure asthma in the Dominican Republic and Haiti. Scientists have found a frog that produces an alkaloid that in humans is a pain killer more powerful than morphine.
The pet trade is another drain on the amphibians and reptiles of the world. I have put in some figures of what people declared they were taking out of the wild in Florida but it is an underestimate because not everything will have been declared. Sadly most of these animals will die in transit or in bad conditions once they have been bought. Very few make it to an owner who knows what to do with it.
On top of everything else scientists are not helping the matter. Animals are taken from the wild in huge numbers for dissections. The leopard frog in the USA was collected in its millions for teaching although hopefully this is changing as more and more animals are being bred in the lab. However there is still collecting and shipping going on the South Africa of Xenopus laevis. (Image from www.scs.unr.edu)
The reptiles and amphibians of the world cannot go on being utilised like this, the figures I have given you over the past few slides are enormous and most of these species have long lives, are slow to reach sexual maturity and have low reproductive rate. Add to this the problems with habitat destruction and invasive species and there is a very large problem. On top of all this is human persecution of amphibians and reptiles, the photograph here is taken from a 'rattlesnake roundup' in North America where thousands of Rattlesnakes are collected from the wild and there are events like timed snake skinning and here the two boys have paid $10 each to skin their own snake. (Image from www.fieldherpers.com/view)
The problem of overexploitation is not confined to the west, it is occurring in Africa as well. In west Africa there is a tradition of semi nomadic farming where the animals were taken to the north in the rainy season for good fodder and in the dry season permanent water was found. The stocking rate was close to the carrying capacity as it was set by the resources available. The system broke down after a 15 year period of drought where the government did nothing to help he farmers other than build wells and give money for animal health. This problem was exacerbated by the population growing at a rate of 2-2.5% per year. Trying to make enough food to feed everyone caused the system to become overexploited. Now farmers that were semi nomadic are becoming sedentary either with their remaining live stock or starting crop farming. The alternative that a lot of them have chosen is to move into towns and cities and look for work.