21.2) Habitat destruction
Removal of habitats:
- Farmland is not natural habitat but, at one times, hedgerow, hay meadows and stubble fields were important habitats for plants and animals.
- Intensive agriculture has destroyed many of these habitats; hedges have been grubbed out to make fields larger, a monoculture of solage grasses has replaced the mixed population of a hay meadow and planting of winter wheat has denied animals access to stubble fields in autumn.
- As a result, populations of butterflies, flowers and birds have cashed.
- The development of towns and cities (urbanisation) makes a great demand on land, destroying natural habitats.
- The crowding of growing populations into town leads to problems of waste disposal.
- The sewage and domestic waste from a town of several thousand people can cause disease and pollution in the absence of effective means of disposal, damaging surrounding habitats.
Extraction of natural resources:
- An increasing population and greater demands on modern technology means we need more raw materials for the manufacturing industry and greater energy supplies.
- Fossil fuels such as coal can be mined, but this can permanently damage habitats, partly due to the process of extraction, but also due to dumping of the rock extracted in spoil heaps.
- Oil spillages around oil wells are extremely toxic.
- Once the oil seeps into the soil and water systems, habitats are destroyed.
- Mining for raw materials such as gold, iron, aluminium and silicon leaves huge scars in the landscape and destroys large areas of natural habitat.
- Marine habitats around the world are becoming contaminated with human debris.
- This includes untreated sewage, agricultural fertilisers and pesticides.
- Oil spills still cause problems but is gradually reducing.
- Plastics are a huge problem: many are non-biodegradable so they persist in the environment.
- Others form micro-particles as they break down and these are mistaken by marine organisms for food and are indigestible. They stay in the stomach, causing sickness, or prevent the gills from working efficiently.
- Where fertilisers and sewage enter the marine environment, ‘dead zones’ develop where there is insufficient oxygen to sustain life.
- Any form of habitat destruction by humans, even where a single species is wiped out, can have an impact on food chains and food webs because other organisms will use that species as a food source, or their numbers will be controlled through its predation.
The removal of large numbers of trees results in habitat destruction on a massive scale.
- Reasons why: for timber, to make way for agriculture, roads and settlements and for firewood.
- 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 photosynthesis, increasing global warming. Climate change affects habitats.