HUMAN INFLUENCE Flashcards
Sustainable resource
A resource that is produced as rapidly as it is removed from the environment so that it does not run out
Sustainable development
Development providing for the needs of an increasing human population without harming the environment
Food supply
Larger populations require more food, provided by improving methods of agriculture.
Modern technology has resulted in increased food production in a number of ways:
Agricultural machinery use of chemical fertilisers use of insecticides use of herbicides Selective breeding
Agricultural machinery enables
much larger areas of land to be cleared, and makes preparing soil, planting, maintaining and harvesting crops significantly more efficient. The process of farming in general has become more efficient.
The use of chemical fertilisers
The use of chemical fertilisers improves yield. These are mineral salts made on an industrial scale. Examples are ammonium sulfate (for nitrogen and sulfur), ammonium nitrate (for nitrogen) and compound NPK fertiliser for nitrogen, phosphorus and potassium. These are spread on the soil in carefully calculated amounts to provide the minerals that the plants need.
The use of insecticides improves
quality and yield. Crops are very susceptible to attack by insect pests. Insecticides combat these attacks, so the crops grow more successfully and show less damage.
The use of herbicides reduces
competition with weeds. Weeds are plants that compete with the crop plant for root space, soil minerals and sunlight. Herbicides are chemicals that kill the weeds growing amongst the crop plants.
Selective breeding
can be used to improve production by crop plants and livestock. An important part of any breeding programme is the selection of the desired varieties that have particular qualities, such as flavour and disease resistance in plants, and high milk or meat yield or resistance to disease in animals such as cattle, fish and poultry.
The negative impact to an ecosystem of monocultures
A monoculture is a crop grown on the same land, year after year. Every attempt is made to destroy organisms that feed on, compete with or infect the crop plant. This reduces the number of species in an area and has a negative impact on food chains.
The removal of hedges reduces
nesting sites for birds and habitats of other organisms. The use of pesticides on monocultures can reduce the number of important insect pollinators, which are required by wild flowers.
The negative impact to an ecosystem of intensive livestock production
Intensive livestock production is also known as ‘factory farming’. Chickens and calves are often reared in large sheds instead of in open fields. Their urine and faeces are washed out of the sheds with water, forming ‘slurry’. If this gets into streams and rivers, it supplies an excess of nitrates and phosphates, which can lead to water pollution. Over-grazing can result from too many animals being kept on a pasture. They eat the grass down almost to the roots, and their hooves trample the surface soil into a hard layer. As a result, the rainwater will not penetrate the soil, so it runs off the surface, carrying the soil with it. The soil becomes eroded.
There is not always enough food available
in a country to feed the people living there. A severe food shortage can lead to famine. Food may have to be brought in (imported). Fresh food can have a limited storage life, so it needs to be transported quickly or treated to prevent it going rotten. Methods to increase the life of food include transport in chilled containers and picking the produce before it is ripe. When it has reached its destination, it is exposed to chemicals such as plant auxins to bring on the ripening process.
The use of aeroplanes to transport food is
very expensive. The re-distribution of surplus food from first-world countries to a poorer one can have a detrimental effect on that country’s local economy by reducing the value of food grown by local farmers. Some food grown by countries with large debts may be exported as cash crops, even though local people desperately need the food.
problems that can result in famine include:
• climate change and natural disasters such as flooding or drought; • pollution; • a shortage of water through its use for other purposes, the diversion of rivers and building dams to provide hydroelectricity; • eating next year’s seeds through desperation for food; • poor soil and lack of inorganic ions or fertiliser; • desertification caused by soil erosion, as a result of deforestation; • poverty – the lack of money to buy seeds, fertiliser, pesticides or machinery; • war, which can make it too dangerous to farm or which removes labour; • urbanisation (building on farm land); • an increasing population; • pest damage or disease; • poor education of farmers and outmoded farm practices; • the destruction of forests, so there is nothing to hunt and no food to collect.
There are three key reasons for habitat destruction:
• an increased area of land is needed for food crop growth, livestock production and housing as the human population increases; • the extraction of more natural resources, as we need more raw materials for the manufacturing industry and greater energy supplies; • marine pollution – marine habitats are becoming contaminated with human debris, including untreated sewage, agricultural fertilisers, pesticides, non-biodegradable plastics and waste oil.
The effects of altering food webs and food chains on habitats
If human activity causes one population of organisms to die or disappear, a food web or food chain becomes unbalanced. For example, an increase in herbivores due to the over-hunting of a carnivore may result in the over-grazing of land. Once the plants have been removed, the soil is vulnerable to erosion because there are no roots to absorb water or to hold the soil together. The habitat would then be destroyed.
Undesirable effects of deforestation
The removal of large numbers of trees results in habitat destruction on a massive scale, which can have the follows results: • Animals living in the forest lose their homes and sources of food; species of plant become extinct as the land is used for other purposes such as agriculture, mining, housing and roads. • Soil erosion is more likely to happen, as there are no roots to hold the soil in place. The soil can end up in rivers and lakes, destroying habitats there. • Flooding becomes more frequent, as there is no soil to absorb and hold rainwater. Plant roots rot and animals drown, destroying food chains and webs. • Carbon dioxide builds up in the atmosphere, as there are fewer trees to photosynthesise, increasing global warming. Climate change affects habitats.
deforestation definition
Deforestation is the removal of large areas of forest to provide land for farming and roads, and to provide timber for building, furniture and fuel.
The undesirable effects of deforestation on the environment
• The reduction of habitats or food sources for animals, which can result in their extinction. Animal and plant diversity is reduced and food chains are disrupted. • The loss of plant species and their genes that may be important for medical use or genetic engineering in the future. • The loss of roots to hold soil together, which can result in soil erosion and leaching of minerals. Desertification can eventually occur. • The loss of roots and soil can lead to flooding and mudslides. Lakes can become silted up. • The leaching of nutrients into lakes and rivers, which can lead to eutrophication. • Less carbon dioxide is absorbed from the atmosphere, increasing the greenhouse effect. • Less oxygen is produced, so atmospheric oxygen levels can drop. • Less transpiration, which can lead to reduced rainfall.
Land pollution
Some insecticides are non-biodegradable and stay in the environment for a long time. For example, DDT has been used to kill mosquitoes to reduce the spread of malaria. However, because it does not break down, it enters water systems such as lakes, where it is absorbed into plankton. Bioaccumulation occurs: the top carnivores suffer from its toxicity. Some insecticides are non-specific: when applied to kill an insect pest, they also kill all the other insects that are exposed to it. This may include useful insects (e.g. bees, which are needed to pollinate crops). Food webs can be affected, threatening the extinction of top carnivores such as birds of prey.
Herbicides
are used to kill weeds in a crop field so that competition can be reduced and therefore crop yield can be increased. However, herbicides may also kill rare plant species near the field being sprayed.
Eutrophication
Sewage and fertilisers both contain high levels of nutrients such as nitrates and other ions. The nitrates act as fertilisers for producers, e.g. algae, which grow and die more rapidly. Decomposers such as bacteria feed on the dead organic matter and reproduce rapidly, using up dissolved oxygen in respiration. Animals in the water system die because of a lack of dissolved oxygen for aerobic respiration.
Recycling sewage
Sewage is mainly water, contaminated with organic material, solids, bacteria and minerals such as phosphates. In places where water is in short supply, the sewage is treated to provide water that is clean enough to drink. Any treated effluent that is returned to a water system such as a river will not cause problems such as eutrophication.
