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How Humans Threaten Wildlife


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AQA Environmental Studies topic

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How Humans Threaten Wildlife

  1. 1. How Humans Threaten Wildlife Use the overview document to go through these slides and make notes. NB Any questions see the slide author by following the overview and student list on moodle L/O To understand the range of ways that humans threaten wildlife.
  2. 2. Deliberate Exploitation
  3. 3. Food <ul><li>Humans have relied on wildlife as a sources of food from the beginning, but without management of our resources, we are endangering the wild. </li></ul><ul><li>Although the wild can supply us with food and medicines, if we do not care to sustain it, we may lose some species forever. The need for food is high due to the increase in population and over the past few decades, over fishing and over hunting have endangered both fish and animals, including cod, swordfish, tuna, sharks, monkeys and gorillas. </li></ul>Bush meat <ul><li>In LEDCs such as Africa, hunting is a common way of making money, and endangered species such as apes and gorillas are prized highly. </li></ul><ul><li>Bush meat includes primates, ungulates (hoofed animals), rodents and birds </li></ul><ul><li>Bush meat hunters target the gorilla, chimpanzee, and bonobo, as well as other primate species, </li></ul><ul><li>Only 1% of the bush meat trade is in ape meat. However, the small population numbers and the pull of hunting them means the impact is considerable. Apes reproduce slower, at ¼ the rate of most other mammals. A study showed that Gabon suffered at least a 56% decline in its ape population over seventeen years. </li></ul>Over fishing <ul><li>Over fishing is an increasing problem, with a rapid boost in the last 50 years due to the advanced in technology, fishing is putting a strain on marine life. </li></ul><ul><li>New factory boats in the 50s and 60s meant an increase by 7% in the catches. However since then, a reduction of fish has meant little growth. </li></ul><ul><li>The nets used in fishing trap anything too big to pass through, consequently many species are killed for the catch of another: </li></ul><ul><li>“ For every one tonne of prawns caught, three tonnes of other fish are killed and thrown away. 20,000 porpoises die each year in the nets of salmon fishermen in the Atlantic and Pacific Oceans and tens of thousands of dolphins are killed each year by tuna fishermen” </li></ul><ul><li>Previously, fishing was a matter of luck on what was caught and how much was caught, however with new technologies fish can be detected and caught precisely. </li></ul><ul><li>At the same time, a reduction in fish can affect species further up the food chain, fish is a diet staple for many wild birds including puffin and with a decrease in fish stocks, the predator suffers as well with not enough food to go around. </li></ul><ul><li> </li></ul>
  4. 4. Deliberate Exploitation of Animals for FASHION <ul><li>-For the past 20 years, the Tibetan Antelope has been slaughtered to supply a high fashion trade in ‘Shahtoosh’ – fine, soft shawls </li></ul><ul><li>-The antelope are either shot in herds or caught in traps. Experts say some poachers have even found their calving grounds and kill females, as they are giving birth. </li></ul><ul><li>The shawls can cost as much as $15,000 each – are high fashion items. The wool is just one-fifth the width of human hair and the shawls are so finely woven that a full-size one can be drawn through a wedding ring. </li></ul><ul><li>WWF estimates that an average of 20,000 animals killed per year for their hide – 3 to 5 animals needed per shawl </li></ul><ul><li>The main demand for shahtoosh comes from Britain, France, the US, Singapore, Hong Kong and Japan. </li></ul><ul><li>In 1980s, thought to be over a million of the animals, now only 75,000 remain </li></ul>Links Case Study: Tibetan Antelope Throughout time, fur has been seen as a high status cloth. The trade in crocodile and snake skins for handbags is flourishing (about one million crocodile skins are sold each year) and the trade for high-quality leather (although not in the UK) is massive, with many countries breeding animals in order to kill for its fur. Opponents of the fur trade have engaged in direct action for many years, and have had a high level of publicity, meaning that it has become less fashionable since. Nevertheless, although the big cats such as leopard and jaguar are protected, there is still a demand for spotted cat skins for the fashion trade. In the USA for example thousands of wild lynx and bobcat are trapped for their fur each year.
  5. 5. The threat is to tropical animals and fish that are being taken out of their natural environment and habitat for pets and for the entertainment of humans. Many reptiles are trapped alive in their habitats and then sold on as pets. Larger lizards, snakes and crocodiles are valued for their beautiful skin. Also turtles and tortoises are hunted world wide for pets. Normally turtles can survive high losses of their eggs because they live long lives and can reproduce for many years but when too many turtles are removed the size of turtle populations can decline very quickly. Many countries have passed laws to protect the rare species and an international agreement called the convention in international trade in endangered species of Wild fauna and Flora (CITES) effective in 1975 has helped curtail international commerce in threatened reptile species. ( ) Parrots have always been popular because of their colours and behaviour and their ability to be trained to speak. Parrots mainly live in the tropical woods of south America, Australia, new Zealand and south-west Asia. But unfortunately this has lead to the decline of parrots in the wild, people take away the birds for make money. Rare parrot collectors are ready to pay huge amounts of money for rare and beautiful parrots, which unfortunately leads to a decline in their natural habitat. Parrots are also sold in black markets illegally where some of them die during their transportation and then the parrots that do eventually reach their own often suffer from inappropriate climatic conditions and lack of proper care. ( ) Plants are being taken out of the forest because of people collecting certain and rare plants to look pretty in their homes. Taking out plants from the forests is leading to less plants being in the forest. Also plants are being used for entertainment, people are realising they can make money out of growing certain plants illegally and then exporting them for use by humans for entertainment. Many plants and animals are being transported out of their natural habitats for use by humans as pets or for their own entertainment leading to a decline which could eventually lead to extinction among with other factors such as deforestation. Pets and Entertainment!
  6. 6. . Furniture and ornaments <ul><li>Demand for hardwoods and valuable materials such as mahogany, teak, ivory, coral and turtle shell for use as furniture and ornaments has led to large scale illegal deforestation, and illegal poaching/taking of valuable materials. </li></ul><ul><li>Example - Ivory </li></ul><ul><li>By the 1980’s, Kenya had lost nearly 85% of its elephant population due to high rates of poaching for ivory. A ban was put in place in 1989 and the number of elephants killed dropped, with the population numbers rising to around 450,000. </li></ul><ul><li>Despite this, an estimated 20,000 elephants are killed by poachers every year, just for their tusks which are sold onto the black market. </li></ul><ul><li>This year a one-off auction of stockpiled ivory was allowed, allowing South Africa, Namibia, Botswana and Zimbabwe to sell up to 100 tonnes of ivory; as the ivory was all supposed to have been collected from already dead elephants and from culling (mass killings to maintain balance of animals or prevent the spread of disease). However may people believe that this auction will just increase the popularity of ivory and start an increase in the illegal killing and trade of ivory. </li></ul><ul><li> </li></ul>
  7. 7.   For over 1000 years tiger bone has been used in traditional medicine in Asia. It is believed to have an anti-inflammatory effect; it is often used where people are suffering from arthritis. However, tigers now occupy 40 percent less habitat than they did 10 years ago and in the last 50 years alone, three sub-species of tigers have become extinct in Asia. This may be due to one of the many other threats that face tigers; on of the most dangerous threats is poaching to supply the illegal trade in tiger bones. Raising a farmed tiger to maturity is 250 times as expensive as poaching a wild tiger in India; therefore, tigers are poached from the wild to provide a cheaper alternative to legal sources. Traditional Medicine Traditional medicine is the health practices and beliefs that use plant, animal and mineral based medicines, amongst other treatments as a form of healthcare. Body parts from tigers, rhinoceroses, bears, seahorses and other endangered species have been used historically in these treatments and the practise carries on today. http://
  8. 8. Deliberate Exploitation of Other Products : deliberate use of animals and other wildlife in order to produce other products <ul><li>e.g. Whale Oils for Cosmetics </li></ul><ul><ul><li>Whaling dates back to 6,000 BC, and was used for meat and to produce candles for lighting, now whale oil is being exploited and used for unnecessary items such as cosmetics, pet food and paint </li></ul></ul><ul><ul><li>Whale oil was originally used for the cosmetics as it imparts a rich glossy sheen into the product </li></ul></ul><ul><li>Facts and Figures </li></ul><ul><ul><li>A large whale can produce as much as 3 tons of </li></ul></ul><ul><ul><li>whale oil </li></ul></ul><ul><ul><li>Over 1200 whales have been hunted each year since commercial whaling was banned in 1986 </li></ul></ul><ul><ul><li>Jojoba oil ahs now replaced most of the whale oils found in cosmetics as it is cheaper, legal and better for the wildlife </li></ul></ul>http:// /
  9. 9. Accidental Harm
  10. 10. Unintentional deaths caused by human activities Humans unintentionally cause the deaths of millions of animals every year though their everyday activities. Examples of these activities include fishing, farming and driving, as many animals are killed in collisions with vehicles. <ul><li>One example of an animal greatly affected by human activities is a bird. These include (these figures are for the US): </li></ul><ul><li>Collisions – building window strikes may account for 97-976 bird deaths each year. Collisions with communication towers and power lines also cause millions of deaths annually (as high as 174million). Furthermore, transport deaths are estimated at approximately 60million deaths per year with car collisions alone. </li></ul><ul><li>Poisoning – the spread of diseases such as avian cholera is increasing due to human activities such as the increase use of pesticides . The use of pesticides is estimated to kill at least 72million birds annually. Another source of poisoning is oil spills . One oil spill can cause the deaths of thousands of birds depending on its severity. </li></ul><ul><li>Attacks by introduced predators – humans introduce many new predators into ecosystems and one of these examples is cats . Cats especially, are a cause for millions of bird deaths each year. </li></ul><ul><li>Loss and degradation of habitat – this is the greatest cause of animal deaths each year, not simply the deaths of birds. However, the effects are especially devastating for migratory birds that require multiple areas for breeding and stop-over points. </li></ul><ul><li>By-catch – thousands for seabirds are estimated to die in US fisheries every year. Often the birds are attracted to the bait for the fish and become hooked on the line causing them to drown. This is often the cause of death for other species such as cetaceans (e.g. dolphins and whales). </li></ul>
  11. 11. <ul><li>A species is introduced, non-indigenous or alien in a certain geographical area, if that area is outside the species' native distributional range, and the species has arrived there by human activity. </li></ul><ul><li>Humans often introduce predator species which will reduce the population of a pest species in a certain area. However, introducing a predator species as biological pest control can be detrimental to species other than the pest, if the predator eats them once it has removed the pest species. Alternatively, in removing the pest, the introduced predator may be detrimental to other species as it takes their food supply away. The result is a reduction of biodiversity and so species which regulate environmental conditions or are good for other species are removed. Animals which are removed may also have been useful for humans, for example in providing future resources of life-saving medicines. </li></ul>Accidental harm from other activities Introduced species: Predators <ul><li>Case study </li></ul><ul><li>Cane Toads were introduced to Australia from Hawaii in June 1935 in an attempt to control the native Cane Beetle. </li></ul><ul><li>They bred immediately in captivity, and by August 1935 more than 3,000 young toads were released in areas around Cairns, Gordonvale and Innisfail in northern Queensland. </li></ul><ul><li>Since their release, toads have rapidly multiplied in population and now number over 200 million and have been known to spread diseases affecting local biodiversity. </li></ul><ul><li>The toads have steadily expanded their range through Queensland, reaching the border with New South Wales in 1978 and the Northern Territory in 1984. </li></ul><ul><li>It is estimated that Cane Toads migrate at an average of 40 kilometres per year. </li></ul><ul><li>Declines in populations of the Northern Quoll have been observed after toads have invaded an area. </li></ul><ul><li>There are a number of reports of declines in goanna and snake populations after the arrival of toads. </li></ul><ul><li>Therefore, the introduction of this species has resulted in an accidental decrease in biodiversity, as species other than the Cane Beetle have declined in number. </li></ul><ul><li> </li></ul>
  12. 12. Accidental harm from other activities - Introduced species - Competitors A species is defined as introduced (also known as non-indigenous, alien or exotic) in a certain geographical area, if that area is outside the species' native habitat, and the species has arrived there by human activity. The danger of some introduced species is that they may become competitors with indigenous organisms (plants or animals). This could lead to the native species becoming endangered or extinct if they cannot survive with the competitors, as the competitors may beat the indigenous organisms to food. The competitive exclusion principle, sometimes referred to as “Gause's Law”, states that two species that compete for the exact same resources cannot stably co-exist, and less there is an evolutionary shift of the inferior competitor towards a different ecological niche. CASE STUDY Red Squirrel: Sciurus vulgaris Distribution: Scotland, Wales, Ireland: a few habitats in England. Widespread in rest of Europe. Habitat: Coniferous forests of Scotland and Wales; mixed woodland in England and Ireland. Food: seeds of a wide variety of trees, buds, hoots, flowers, berries, nuts, bark and fungi. Numbers: The British Red Squirrel population is estimated at 30,000 in England, whereas the Grey Squirrel population is estimated at 2 million. In England, the Greys outnumber Reds 66:1. --- Introduced competitor: Grey Squirrel Until the 1940s the red squirrel was quite widespread. It has now disappeared from large areas of Britain and its place has been taken by the grey squirrel. The larger grey squirrel was introduced to this country in the mid-19th century. In reality, however, grey squirrels do not physically fight with red squirrels; so why is it that red squirrels disappear when grey squirrels move into their habitat? Research has shown that the answer may lie in the way each species uses the food available to them. It has already been mentioned that grey squirrels put on a lot more body fat than red squirrels which gives them a better chance of surviving. The larger, more robust grey wins in the competition for food and space and it is now widespread in England and Wales. It is more adaptable than the red squirrel and lives happily in hedgerow trees, parks and gardens as well as large woods and forests.
  13. 13. Disease Laura Gallop should have produced a slide for here!
  14. 14. Eradication of predators and competitors <ul><li>In areas where humans have expanded to predators are being eliminated through culling and lack of habitat. These could be for reasons such as: </li></ul><ul><ul><li>the human exploitation of their prey (chicken farming and pesky foxes) </li></ul></ul><ul><ul><li>The dangerous reputation of predators, hunting due to fear and dislike for animals such as wolves and caterpillars </li></ul></ul><ul><ul><li>Loss of habitat and prey leads to competing predators to die out </li></ul></ul><ul><li>With the loss of predators the food chain can get out of balance. Without the predators; the numbers in population of their prey, the secondary consumers, will rise. With larger numbers of smaller species other competing predators will flourish. </li></ul>Yellowstone National Park, Wyoming Gray wolves were completely eliminated from the Yellowstone region by the 1940s to help the livestock industry. A lot of people felt that eradicating wolves was for good reason because the culture of animosity that goes back thousands of years. Wolves were almost completely eradicated where they had roamed all of the U.S., except a few places in deserts, and the tip of Florida. They were eradicated from everywhere except the extreme northern portion of northern Minnesota. The population went from millions to 500. Doug Smith, a biologist specialising in wolves, has worked to reintroduce the wolves to the Yellowstone National Park. e.g. bears, wolves, foxes , agricultural pests, otters, birds of prey
  15. 15. Habitat change Inability to survive habitat alteration!
  16. 16. Habitat Change – Wetland Drainage – Isobel Scott What is wetland drainage and how does it affect the environment? Wetland drainage involves the human activity of removing water from wetlands. The reasons for this are that many of the wetlands are sources of freshwater, which is very valuable because it does not need large scale treatment to remove the salt. However it causes many problems because often the artificially altered habitats can no longer support the same wildlife. The wetland is abandoned once the water has been drained, leaving open space where there is low biodiversity and cannot be put to any other use, as it is unsuitable for building or agriculture. Case Study – Tollesbury Wick, Maldon, Essex Tollesbury Wick is abundant in its diverse range of wildlife. It is a freshwater grazing marsh, owned and protected by the Essex Wildlife Trust, covering around 600 acres of land. It is home to many species such as hunting hen harriers, short-eared owls, reed bunting, restharrow, golden plover and many more. It is protected by a sea wall supporting grassy slopes which contain many species of grass home to many invertebrates. The sea wall prevents the land from flooding which would destroy the many habitats within the area. Draining water from Tollesbury Wick would result in the loss of many rare species that live in the area. If the smaller species at the bottom of the food chain cannot adapt for survival in the new habitat, this will have consequences to the top of the food chain as a lack of food causes predators to move elsewhere. Because of this, the area is protected to ensure that the public remain aware of the importance of the area. The marina within the wetlands also produces funds, some of which go towards the maintenance of Tollesbury Wick. The bird shown in the image to the left is of the black-tailed godwit, a European bird that often migrates as far as Australia. It is a new red-list entrant, making it a severely endangered species. Its suitable nesting sites in Europe are declining, mainly as a result of wetland drainage and modern agriculture techniques. Numbers have fallen by 30% in 15 years. This is worrying because similar cases may appear as a result of wetland drainage, therefore causing a reduced biodiversity.
  17. 17. Selective Logging Selective logging is the removal of just a few trees from a forest so that there are not huge gaps in the forest canopy. As we all know, clear-cutting logging destroys animals and their habitats but there is a way to carry out logging in forests more sustainably and this is by selective logging. Although chopping down just a few trees sounds good, in fact it still has a large environmental impact as all the surrounding trees often get pulled down in the process. Selective logging has been found to reduce global biodiversity by destroying habitat for primary forest species. The impact of pulling just one tree down on the area. The area with no trees is vulnerable to erosion.
  18. 18. Changes to River Flow due to Canalisation River engineering is the process of planned human intervention in the course, characteristics or flow of a river with the intention of producing some defined benefit. Rivers whose depth changes due to cycles in the flow of a river (and so an adequate depth for navigation is unavailable) is a possible subject for canalisation. In some cases, the ordinary summer level has to be raised by increasing the flow with weirs at intervals across the channel, while a lock has to be provided alongside the weir, or in a side channel, to provide for the passage of vessels. A river is thereby converted into a succession of fairly level reaches like a canal (although it differs from a canal in the introduction of weirs for keeping up the water-level). Canalisation secures a definite depth for navigation. A canalised section of the Floyd River in Sioux City, Iowa Case Study: The Seine River – France The canalised Seine has secured a depth of 10 1/2 feet from its tidal limit until Paris, a distance of 135 miles, and a depth of 6 3/4 feet up to Montereau, 62 miles higher up. <ul><li>Advantages: </li></ul><ul><li>To make a stream more suitable for navigation or for navigation by larger vessels with deep draughts </li></ul><ul><li>To restrict water to a certain area of a stream lands so that the bulk of those lands can be made used for agricultural purposes </li></ul><ul><li>Flood control, to give a stream a sufficiently large and deep channel that flooding will be minimal. </li></ul><ul><li>Disadvantages: </li></ul><ul><li>Loss of wetlands - an excellent habitat for many forms of wildlife </li></ul><ul><li>Canalised streams are almost invariably straightened. This causes the streams to flow more rapidly, which can, in some instances, vastly increase soil erosion </li></ul><ul><li>It can also increase flooding downstream from the canalised area, as larger volumes of water travelling more rapidly than normal flow downstream so flood control in one area comes at the expense of another </li></ul><ul><li>Studies have shown that stream canalisation results in declines of river fish populations. </li></ul> Weir: a low dam built across a stream to raise its level or divert its flow
  19. 19. The inability to survive reservoir creation. Reservoir creation results in the decomposition of flooded organic matter and increased rates of mercury methylation. Methylmercury (MeHg), the most toxic form of mercury, accumulates through aquatic food webs. Also when rivers are dammed, habitat is not only drowned at the site, but hydrology and ecology of rivers and hardwood bottomlands downstream can suffer. Reservoirs may capture, in whole or part, floods that are critical to these ecosystems and to the coastal estuaries into which they empty. The Mattaponi River, considered by the Mattaponi Tribe in Virginia to be the place where life begins, will be impacted by a proposed reservoir and dam project that will pump water from the river and could damage its ecosystem. The Mattaponi River flows for 85 miles across the coastal plain of eastern Virginia, before joining the Pamunkey to form the York River. The Cohoke Creek lies between the two rivers and is the site of a dam and associated reservoir proposed by the city of Newport News, Virginia to support the region’s growing demand for water. They propose a pipeline that would take up to 75 million gallons of water a day from the river and store it in a 1500-acre reservoir, to be used by the city. The proposed King William Reservoir would fill over the Cohoke Creek and surrounding wetlands, and reach out to a point 2 1/2; miles west of the Mattaponi Reservation, which lies on the western bank of the Mattaponi River. Supersaturation occurs when air becomes trapped in water spilled over a dam as it hits the pool below, creating turbulence. Because air is comprised of 78% nitrogen, the level of nitrogen dissolved in the water can increase dramatically. The affected water does not lose the excess nitrogen quickly. For fish and other species, supersaturated water can enter tissues. If fish swim from an area supersaturated with nitrogen to a lower pressure area, a condition similar to &quot;the bends&quot; in scuba diving can occur. This effect causes injury and can even cause death to fish. Changing water levels and a lack of streamside vegetation can also lead to increased erosion. For example, the lack of vegetation along the shoreline means that a river or reservoir can start cutting deeply into its banks. This can result in further changes to a riparian zone and the species which it can support. Increases in erosion can also increase the amount of sedimentation behind a dam. When habitat is lost, animals are forced to move to higher ground or other areas where habitat conditions may be less suitable, predators are more abundant, or the territory is already occupied. As an example, ground birds like pheasant and grouse require cover and cannot successfully move to higher, more open, ground.
  20. 20. Habitat change : The inability to survive habitat alteration Flow regulation Flow regulation effects the movement and diversity of species living both in and around a running water source. Sources with a high water flow regulation are often subject to substantial erosion. <ul><li>Case Study: New South Wales, Australia – Lowland </li></ul><ul><li>Lowland consisting of 40 rivers were designated as regulated or unregulated, depending on how much their flows were affected by the operation of a dam upstream. Five replicate rivers of each type from the North Coast, South Coast, Darling and Murray regions had samples of fish communities taken in the summer and winter in two consecutive years. </li></ul><ul><li>The results of these samples show that regulated and unregulated rivers contained significantly different fish communities, although there were similar characteristic features in communities from each region. </li></ul><ul><li>In unregulated rivers, in all regions, the proportion of native species in the total catch was the greatest – Ranging from 27% in the Murray region to 100% in South Coast Rivers. </li></ul><ul><li>In regulated rivers, native species made up 20% of the catch in Murray compared with a maximum of 99% in the North Coast. </li></ul><ul><li>“ Carp, Cyprinus carpio , were the main alien species contributing to changes in the proportional abundance of native fish” </li></ul><ul><li>Native species most affected by river regulation were western carp gudgeons, Bony Herring and striped gudgeons. </li></ul><ul><li>There were fifteen native species in total that showed some effect on their population structures due to river regulation. </li></ul><ul><li>The responses of individual species varied. There were only three abundant alien species and seven native species that showed positive of mixed responses, as opposed to the 13 native species who presented only negative effects. </li></ul><ul><li>“ Flow regulation has reduced the resilience of New South Wales rivers and native fish communities to invasion by alien species” </li></ul><ul><li>“ New research has commenced to investigate whether recently introduced environmental flow rules are effective in reducing the effects of river flow alteration on fish communities in New South Wales rivers. </li></ul> New South Wales Rivers
  21. 21. Pollution Eleanor Agnew’s slide should go here!
  22. 22. Habitat Destruction
  23. 23. Deforestation Deforestation is the conversion of forested areas to non-forested land, for uses such as: pasture, urban use, logging purposes, and can result in arid land and wastelands. Deforestation results from removal of trees without sufficient reforestation, and results in declines in habitat and biodiversity, wood for fuel and industrial use, and quality of life. It causes the loss of many species of plants and animals as trees are cleared by loggers using trunks of trees and farmers needing more land. Most deforestation in the past 40,000 years has been anthropogenic: human induced With forest biotopes being irreplaceable source of new drugs (such as taxol), deforestation can destroy genetic variations (such as crop resistance) irretrievably. <ul><li>The deforestation of the Amazon </li></ul><ul><li>Amazon supports approximately 300 million hectares of tropical forest, the largest single area of tropical forest communities in the world </li></ul><ul><li>Source of 50 to 90% of all species on Earth </li></ul><ul><li>Some areas support over 300 tree species per hectare </li></ul><ul><li>Between 1 to 3 million hectares are being cleared annually in the Amazon Basin </li></ul><ul><li>Amazon may be losing as many as 11 to 16 species per day </li></ul><ul><li>Clearing has been encouraged by the Brazilian government to make money by producing more products </li></ul><ul><li>Deforestation jumped by 69% in 2008 compared to 2007's twelve months, according to official government data. </li></ul><ul><li>Deforestation could wipe out or severely damage nearly 60% of the Amazon rainforest by 2030, says a new report from WWF. </li></ul>
  24. 24. Habitat destruction Expansion of Farmland Case Study: New Zealand Habitat loss in New Zealand has been caused by whole ecosystems being converted into farmland, exotic forests and settlements. After humans arrived, large areas of New Zealand forest were destroyed by fire. Some fires occurred naturally (started by lightning strikes, for example), or were caused by humans hunting food or clearing land. After the the Treaty of Waitangi was signed in 1840, a flood of European settlers arrived. Half New Zealand’s remaining forest had been converted to farmland and towns by 1920, and many more plants and animals had been introduced, some of which displaced or preyed on native species. Most of New Zealand’s lowland forests, wetlands, dunes and estuaries have been converted into pasture or towns. Many lakes, rivers and streams have been modified by dams, drainage and irrigation schemes and by pollution from farms and urban areas. The increased area of farmland has increased the effect of pollution on lakes and rivers. Expanding farmland, most commonly in the countryside, means destroying the surrounding area leading to a loss of habitat and biodiversity. Farming and logging have severely disturbed at least 94% of temperate broadleaf forests; many old growth forest stands have lost more than 98% of their previous area because of human activities. An increase in the area of agriculture may often cause environmental problems because it changes natural environments and produces harmful by-products. Agriculture can also cause a decrease in biodiversity and the consolidation of diverse biomass into a few species. Intensive agriculture can create a surplus of nitrogen and phosphorus in rivers and lakes. Herbicides, fungicides, insecticides, and other biocides can hurt the environment. As well, natural ecosystems of all types are converted into arable land. Agriculture can also cause soil erosion, deforestation, and the depletion of minerals in the soil. When a habitat is destroyed, the plants, animals, and other organisms that occupied the habitat have a reduced carrying capacity so that populations decline and extinction becomes more likely.The single greatest threat to species worldwide is the loss of habitat. [
  25. 25. <ul><li>The movement of people from rural to urban areas, resulting in the growth of cities </li></ul><ul><li>Environmental Issues: </li></ul><ul><ul><li>Temperature – because of factors such as the high concentration of heat sources, cities can be warmer than the surrounding countryside, sometimes by 10 o C, which can change weather patterns </li></ul></ul><ul><ul><li>Air pollution – heavy traffic and energy production lead to a layer of smog over cities </li></ul></ul><ul><ul><li>Destruction of Habitat – when rural areas become cities, whatever was there previously is lost, and the destruction of habitats can have an affect on the whole ecosystem of that area </li></ul></ul><ul><li>Los Angeles: </li></ul><ul><ul><li>Urban area is 1600 sq miles, almost three times the area of London </li></ul></ul><ul><ul><li>Population in some areas has grown by 1million in 20 years </li></ul></ul><ul><ul><li>10% of the US’s agricultural income comes from LA, and significant amounts of this land has been built over </li></ul></ul><ul><ul><li>Increase in Landslides and Mudflows </li></ul></ul><ul><ul><li>The second most polluted city in the world </li></ul></ul><ul><ul><li>River in Colorado has been emptied providing water for all the </li></ul></ul><ul><ul><li>people living in LA, causing drought </li></ul></ul><ul><li> </li></ul>
  26. 26. Remaining Slides not submitted! <ul><li>Mineral Extraction (Anushka Sathiyakeerthy) </li></ul><ul><li>Flooding by reservoirs (Anastasia Callaghan) </li></ul><ul><li>Mono-cropping (Amy Chen) </li></ul>