Threats to biological diversity 2: Over exploitation Sam
Threats to biological diversity 2: Over exploitation Sam Hopkins Biodiversity and Conservation Biology Available at http://planet.uwc.ac.za/nisl/Eco_people/Presentations/ What is Overexploitation? Overexploitation is the use, by humans, of a natural resource to an extent that it is not sustainable What causes overexploitation? 1 A number of factors contribute to overexploitation Possibly the rich countries over consuming Lack of incentives to conserve such as
environmental taxes Economic growth causes environmental degradation however lowering economic growth in the rich countries will in turn lower it in the poor countries Increases in the human population number Examples of overexploitation: The Aurochs 2 Was a member of the Bovidae family Ranged from Britain to Africa By the 13th century it was only seen in Poland, Lithuania and Prussia
By 1564 only 38 animals remained Ban imposed over hunting Hunted to extinction by 1627 Examples of overexploitation: The Sea Cow 3 The ship the St Peter became shipwrecked off Kamchutka in November 1741 They managed to survive by hunting the Sea Cow The sea cow was estimated to be 28 feet long and
7-8 tons When the shipwrecked men got off the island in Aug 1742 they told everyone about the sea cow when they got back It had been hunted to extinction by 1768 Examples of overexploitation: The Great Auk 4 The Great Auk was a flightless sea bird It was found in Canada, Greenland, Iceland, Norway, Ireland and Great Britain As the animal had few natural predators it had no
fear of humans which made them easier to hunt Great Auk was hunted for food and feathers used for stuffing mattresses The last pair were killed while sitting on an egg and for good measure the egg was smashed Examples of overexploitation: The Passenger Pigeon 5 The passenger pigeon was a flocking bird found in North America Estimates suggest that there were at least 3 billion individuals The birds roosted together which made them an easy target
The hunter came up with several ingenious ways of killing the birds; suffocation by burning grass, fed alcohol soaked grain, beaten down with long sticks, netted and trapped using a decoy The last one was seen in 1900 in Ohio Examples of overexploitation: The fur trade The whole of the fur trade is an example of overexploitation In the past when one animal has become rare the trade has just looked for another source to keep people in fashion
At the height of the squirrel trade half a million skins were exported each year As land stocks of squirrels and minks became depleted the sea was looked to This lead to the demise of the sea otter and by 1911 there were only 1- 2000 left The fishing industry One of the most well known examples of over exploitation is by the fishing industry Commercial fishing fleets exceed the ecological limit This has been caused by greed, a lack of data on actual fish stocks and better fishing equipment6
Out of the known 21,000 fish species only 9,000 are actually used by humans7 22 species are harvested in excess of 100,000 tonnes per year7 In the great lakes in North America there has been a decline in fish numbers and the lake trout and Atlantic Salmon are extinct in Lake Ontario8 The fishing industry 8 The numbers of fish taken every year has declined recently but on average
500,000 tons of fish are taken from the Mekong river in S.E. Asia 210,000 tons of fish are taken from the Zaire river in Africa 210,000 tons of fish are taken from the Amazon river in S. America Now fishermen are fishing down the food chain, as they cannot get the top predatory fish anymore they go for pelagic fish The Amphibian and Reptile Industry 9 The exploitation of Reptiles and Amphibians can be traced back to the Romans In a book called Natural History Pliny wrote Romans carried stones from a crocodiles belly as charms against aching joints, bound crocodile teeth to their arms as an aphrodisiac, treated whooping cough in their children with doses of crocodile meet, and trustfully administered burned crocodile
skin mixed with vinegar as an aesthetic to patients about to undergo surgery. Woman used crocodile dung in a lint tampon as a contraceptive It wasnt just the Romans however, the Ancient people of America used toad secretions as a hallucinogen during religious ceremonies The Amphibian and Reptile Industry: Food 9 Amphibians and reptiles have long been used as a source of protein Now they are served as a delicacy or oddity for example, frogs legs au gratin, frogs legs teriyaki The Amphibian and Reptile Industry: Food 9 The commonly eaten frogs are Rana catesbeiana, Rana
esculenta, Rana tigrina and Pyxicephalus adspersus The commonly eaten reptiles are Green and Spiny Iguanas, Turtles, Crocodiles and Alligators The Amphibian and Reptile Industry: Food 9 Some facts and figures for you The USA imported 2.5 million kilograms of frogs legs from Japan and India in 1976 Between 1979 and 1987 45,000kgs of alligator were sold every year In the 1960s 150,000 Iguanas were eaten per year in Nicaragua alone 12 million fresh water turtles are sold to china
from S.E. Asia per year The Amphibian and Reptile Industry: Skins 9 Reptiles and Amphibians are also used for their skins Reptiles skins make Shoes Purses Belts Amphibian skins make
Shoes Purses Belts Book binding Glue Fishing lures The Amphibian and Reptile Industry: Skins 9
Some facts and figures for you In 1981 alone 304,189 pairs of shoes were made from Boa constrictors and 176,204 from Python reticularis Between 1980 and 1985 over 1 million Caiman crocodile skins were sold every year 12 million Tegu skins were imported between the years of 1980-1985 1-2 million Monitor skins are exported from Africa and Asia each year In 1986, 10.5 million reptile skins were sold legally in the USA The Amphibian and Reptile Industry: Cheap Souvenirs 9
One of the saddest trades is in cheap souvenirs Around the world amphibians and reptiles are killed to make Crocodile teeth necklaces Crocodile feet key rings Rattlesnake rattle key rings Rattlesnake head/fang mementoes Stuffed and varnished toads in
amusing positions! At least 115,000 horned lizards are thought to have been stuffed over the last 45 years The Amphibian and Reptile Industry: Medicine (Traditional and Modern) 9 The use of amphibians and reptiles for medicinal purposes has gone on for centuries as the excerpt from the book Natural History showed Iranians use a broth made from snakes and tortoises to fight disease Asians use fat from monitor lizards for bacterial infection People in Pakistan use oil from monitor lizards as an aphrodisiac
In Madagascar the fat and oil from a crocodile will treat burns, ulcers and cancer In the Dominican Republic and Haiti the fat from a crocodile cures asthma An alkaloid from the Epipedobates frog is a pain killer more powerful than morphine The Amphibian and Reptile Industry: Pet Trade 9 The exotic pet trade is growing rapidly In 1990 the Florida Game and Freshwater fish commission noted the number of legal removals from the wild in Florida alone
In total 119,831 animals removed 49,240 snakes 41,493 frogs 1,050 salamanders This is an under estimate as it only shows the traders that declared what they were taking Between 1992 and 1994 74,000 Gulf Coast box turtles were taken from the wild The Amphibian and Reptile Industry: Science, Research and Teaching 9
Amphibians and reptiles are taken from the wild as teaching aids in schools and universities Used in dissections in schools and universities In the 1970s it was estimated that 15 million leopard frogs were taken from the wild for dissection teaching Now people are more aware and more specimens are grown in captivity for use in research and teaching The Amphibian and Reptile Industry: The problems 9 As you can see from the enormous figures I have given you over the past few slides this industry is not sustainable
Many of these animals have very long lives and are slow to reach maturity and reproductive rates are low Over exploitation is not their only problem, add to the fact habitat degradation, invasive species, peoples persecution etc. and there will be a problem Overexploitation in Africa 10 This is not just a western problem, overexploitation is occurring in Africa too In the 1970s in West Africa a form of Semi nomadic farming was practised
This was suitable for the habitat Stocking rate was close to carrying capacity After 15 years of drought this system was not working anymore and instead of giving money to the farmers to carry on, the government gave money for well digging and animal health care The human population in the area has grown by 2-2.5% and to keep enough animals to feed everyone the system is being overexploited Farmers are turning to sedentary farming either settling with their few remaining livestock or growing crops or they move to an urban area References 1.
Fielder and Kaeiva (1998) Conservation Biology for the coming decade. Pp 396. 2. Wikipedia contributors, Aurochs [accessed 2006 July 10] Wikipedia, The free Encyclopaedia, 9th July 2006, 9:50 UTC, Available from: En.wikipedia.org/wiki/Aurochs 3. Lundberg, M. The Stellers sea cow [cited date 2006 Jul 15]. Available from:www.explorenorth.com/library/yafeatures/bl-seacow 4. Wikipedia contributors, Great Auk, [accessed 2006 July 10] Wikipedia, The free Encyclopedia, Available from:En.wikipedia.org/wiki/Great_Auk 5. Smithsonian institute [cited date 2006 Jul 15] Available from: www.si.edu/resource/faq/nmnh/passpig 6. US Environmental Protection Agency [cited date 2006 Jul 15]. Available from: www.epa.gov/bioiweb1/aquatic/overexpl.html
7. Fielder and Jain (1992) Conservation- the theory and practice of nature conservation, preservation and management. Pp 157 8. Cox, G.W. (1997) Conservation Biology concepts and applications. Pp 158. 9. Pough et al. (2001) Herpetology 2 nd Ed. Pp 500 10. Breman, H. (1992) Desertification control, the West African case; prevention is better than cure. Biotropica 24: 328-334
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