B18 - Biodiversity and ecosystems

• Biodiversity is the variety of all the different species of organisms on Earth, or within an ecosystem
• High biodiversity


  • Helps ensure the stability of ecosystems by reducing the dependence of one species on another for food, shelter, and the maintenance of the physical environment
• Humans reduce the amount of land available for other animals and plants by building, quarrying, farming, and dumping waste
• The future of the human species on Earth relies on us maintaining a good level of biodiversity. Many human activities are reducing biodiversity and only recently have measures been taken to address the problem
• Rapid growth in the human population and an increase in the standard of living mean that increasingly more resources are used and more waste is produced
• If waste is not handled properly, it may pollute the land, the water, or the air. Increased pollution kills plants and animals and reduces biodiversity in affected habitats
• Sewage


  Bodily waste and waste water from homes
• If human waste is not treated properly

  The soil becomes polluted with unpleasant chemicals and gut parasites
• Household waste and hazardous (dangerous) industrial waste

  • Household waste goes into landfill sites
  • Toxic chemicals can spread from the waste into the soil
• After the Chernobyl nuclear accident in 1986, the soil was contaminated thousands of miles away from the original accident
• Farmers use chemicals to protect their crops


  The chemicals get into the soil and can be washed out into streams and rivers
• Bioaccumulation


  Toxins build up in organisms along the food chain
• Farmers add fertilisers to the soil


  The minerals in these fertilisers, particularly the nitrates, are easily washed from the soil into local streams, ponds, and rivers
• Nitrates and other mineral ions stimulate the growth of algae and water plants


  This leads to a fall in the levels of dissolved oxygen in the water, causing aerobic organisms to die
• Toxic chemicals such as pesticides and herbicides or poisonous chemicals from landfill sites can also be washed into waterways
• Pollution levels in water can be measured in many different ways, including using bioindicators - species such as salmon and bloodworms that can only be found in very clean or very polluted water
• In the UK, a chemical called DDT was used up until the 1980s to kill insects
• Large birds of prey and herons began to die and their bodies were found to have very high levels of DDT in them
• Explain how this might have happened

  Suggest why it took a long time for any link to be made
• Pollution can occur in water from sewage, fertilisers, or toxic chemicals
• Pollution kills plants and animals, which can reduce biodiversity
• A major source of air pollution is burning fossil fuels
• The formation of acid rain

  1. Carbon dioxide is released into the atmosphere

  2. Fossil fuels often contain sulfur impurities, which react with oxygen when they burn to form sulfur dioxide gas

  3. Acidic sulfur dioxide and nitrogen oxides also dissolve in rainwater and react with oxygen in the air to form dilute sulfuric acid and nitric acid
• Acid rain


  • It can kill the leaves, buds, flowers, and fruit of trees
  • As it soaks into the soil, it can also destroy the roots
  • Whole ecosystems can be destroyed
  • As acid rain falls into lakes, rivers, and streams, the water in them becomes slightly acidic
  • If the concentration of acid gets too high, plants and animals can no longer survive
• The worst effects of acid rain are often not felt by the country that produced the pollution
• The UK and other countries have worked hard to stop their vehicles, factories, and power stations producing acidic gases
• Smoke pollution causes an increase in the number of tiny solid particles, called particulates, in the air
• Smoke pollution reflects sunlight so less light hits the surface of the Earth, causing a dimming effect that could lead to a cooling of the temperatures at the surface of the Earth
• Smoke pollution also affects human health directly as the particles are breathed in and can damage the lungs and the cardiovascular system
• Smog forms a haze of small particles and acidic gases that can be seen in the air over major cities around the world
• How acid rain is produced

  1. Acidic gases are dissolved in the rain and the snow

  2. Plants, animals, lakes and rivers are damaged by acid rain
• Deforestation is taking place at a tremendous rate
• When the forests are cleared, they are often replaced by a monoculture (single species) such as oil palms, which greatly reduces biodiversity
• Deforestation


  The loss or destruction of forests
• Peat bogs are another resource that is being widely destroyed
• Peat bogs and peatlands

  • They act as a massive carbon store
  • They are unique ecosystems, home to a wide range of plants, animals, and microorganisms that have evolved to grow and survive in the acidic conditions
• When peat is burnt or used in gardens, carbon dioxide is released into the atmosphere and the carbon store is lost
• The destruction of peat bogs also means the destruction of the organisms that depend on them, and more loss of biodiversity
• Large-scale deforestation in tropical areas has occurred to provide land for cattle and for rice fields and to grow crops for biofuels
• The destruction of peat bogs and other areas of peat to produce garden compost reduces the area of this habitat and thus the biodiversity associated with it