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Human Impact on the Environment 1. Monoculture/Intensive Farming • Humans have managed to: • remove the threat of predation • develop vast areas of land for producing food • improve public health • As a result, the human population continues to increase • We try to cope with this by: • growing vast monocultures • employing intensive farming techniques • developing Genetically Modified Crops • A monoculture is the intensive farming of plants, where only one variety of crop is grown • Natural ecosystems are cleared to accommodate monoculture crops • The types of plants grown as a monoculture are: – – – – Wheat Maize Rice Potatoes • Farmers use intensive farming techniques to increase food yield from the same acreage of land • Usually intensive farmers will: – Grow large monocultures – Rely heavily on the use of chemicals – rear animals indoors, often in confined spaces (battery farming), leaving more energy for growth than it being lost as heat/movement Advantages Disadvantages Crop grown is suitable to climatic conditions Crops are genetically identical, so disease can spread easily More machinery can be used, so labour costs are reduced Reduces habitats available to wild animals, reducing biodiversity More than one harvest per year can occur Heavy use of chemical fertilisers 2. GM Crops • Genetically modified crops have had a useful gene from another organism inserted into their cells • Examples of plants engineered in this way are: • Maize - resistant to insect pests • Potatoes - resistant to fungal blight • Golden Rice – contains high dose of vitamin A Pros Cons GM crops allow farmers to No guarantee that crops will decrease their use of remain resistant to disease chemicals without decreasing their yield GM crops reduce the quantity of crop lost Some people believe these crops carry a risk to human health 3. Fertilisers & Pesticides • A fertiliser is a chemical that is used by farmers to improve plant growth • It is added to the soil to increase the minerals in the soil • Nitrogen, Magnesium, Phosphorus & Potassium are commonly found in fertilisers Nutrient Function of Nutrient in Plant Nitrate To make nucleic acids and amino acids Magnesium Required for the formation of chlorophyll Phosphorus For the production of ATP and nucleic acids Potassium For the formation of fruits/flowers • Leaching is when fertilisers are washed from the soil into freshwater (after heavy rainfall) • This makes the river ‘over-rich’ in minerals • Algae grow rapidly • The algae then die in huge numbers & bacteria in the water increases • Dead plants under the water (unable to obtain light to carry out photosynthesis) provide more food for the bacteria • Bacteria multiply and use up even more oxygen • Leaching causes an overall decrease in biodiversity of the ecosystem due to a lack of oxygen 4. Pesticides • A pesticide is a chemical used to kill organisms that are in competition with the crop plant • Pesticides are specific – – – – Herbicides are used to kill other plants Fungicides are used to kill fungus Insecticides are used to kill insects Bactericides are used to kill bacteria • Some pesticides sprayed onto crops accumulate (build up) in the bodies of organisms over time • This is called bioaccumulation • The level of pesticide found in the bodies of organisms increase as the position in the food chain increases 4. Pesticides • A pesticide known to cause bioaccumulation is DDT • It was used widely in the 1950s and 1960s • DDT was sprayed onto plants and entered the food chain when the contaminated plants were eaten by other organisms • It is now banned due to its harmful effects on biodiversity – E.g. it caused the thinning of egg shells meaning that chicks hatched before they were strong enough to survive – It has even been found in water ecosystems – It has been found in the tissues of penguins in the antartic! 5. Pollution • Pollution is the addition of substances to the environment that cause harm to organisms • An indicator species help indicate levels of pollution either by their presence or absence • Some examples of indicator species are: lichens, mayfly, stonefly or sludgeworms • There are many different types of Lichen (hairy, shrubby, leafy and crusty) • In areas of LOW pollution, mainly hairy lichen would be found • In areas of HIGH pollution, mainly crusty lichen would be found Sulphur dioxide and lichen biodiversity Sulphur dioxide concentration hairy shrubby leafy crusty Freshwater invertebrates Relative number of bacteria and concentration of oxygen Untreated organic waste added bacteria oxygen biodiversity Distance downstream 6. Biological Control • Biological control is the deliberate use of natural predators to control pests in farming • Ladybirds have been used to clear greenfly, as an example of biological control Carry out the research task for one of the examples Advantages of BC Disadvantages of BC Reduces effects of harmful Only effective in small chemical pesticides that may growing areas kill other organisms Bioaccumulation does not occur In some cases the natural predator has become the pest!