biodiversity and humans

• Eutrophication— excessive nutrients from fertilisers are flushed from land into rivers/lakes by rainwater.
• Pollution causes aquatic plant growth of algae. Algae form bloom over water surface, preventing sunlight reaching other water plants and they die. Microbes increase as there is decomposition of dead plants, using and reducing oxygen levels during respiration. Low level oxygen causes aquatic insects and fish to suffocate.
• Fish farming:

  • Farm waste, chemicals, pathogens and parasites are released into the surrounding water

  • Carnivorous species of farmed fish need high amounts of protein in their diet so they are often fed on wild fish, reducing their population.

  • Fish escape and compete with indigenous wild species for resources, resulting in reduced biodiversity.
• Introduction of non indigenous species:

  • New species may outcompete/kill indigenous species and so reduced biodiversity and extinction.

  Eg. Cane toads (South-middle America) introduced to Australia to control pests that ate sugar cane — an important crop. Cane toads are poisonous, reducing predators and competes with native species for food.