Threats to biodiversity

• Direct threats to biodiversity:

  • food
  • fashion
  • entertainment
  • furniture and ornaments
  • traditional medicines
• Indirect threats to biodiversity:

  • eradication of predators and competition
  • changes to abiotic factors
  • changes to biotic factors
  • introduced species
  • habitat destruction
• Food:

  Historic - Dodo and passenger pigeon

  Modern - North Atlantic Cod from fishing and sharks for shark fin soup
• Fashion:

  Animal skins used for clothing.

  overexploited examples:

  • fur coats - mink, fur seals , snow leopard
  • leather bags and shoes - crocodiles and alligators
  • feathers - kingfishers, parrots, ostriches
• Entertainment:

  • pets - exotic = parrots, lizards, snakes, tropical fish
  • air plants
  • zoos
  • aquaria - marine fish
  • marine life centres - dolphins and orcas
• Furniture and ornaments:

  • mahogany - tropical rainforest timber
  • Ivory from elephants - piano keys
  • shark teeth, turtle shells and mollusc shells - jewellery
• Traditional medicines:

  • tigers - claws for sedative, tail for skin diseases
  • Rhinoceros - horn used to cure many medical problems
  • Seahorses - infertility, baldness, asthma, arthritis,
• Eradication of predators and competitors:

  • animals that threaten humans: sharks, poisonous snakes and crocodiles
  • Pathogen vectors: mosquitoes with malaria, badgers with bovine TB
  • predators of livestock: wolves, lions, birds of prey, foxes
  • Agricultural pests: insects (locusts), birds
  • wild herbivores that eat crops: deer, rabbits - overpopulated
  • forestry pests: deer, squirrels, beavers
• Changes in abiotic factors:

  • human activities may alter a habitat and change its conditions so it becomes unsuitable or some species - outside their range of tolerance

  Ex.

  • Water availability
  • Dissolved oxygen
  • Temperature
  • pH
  • Water turbidity
  • Physical damage
• Changes in abiotic factors:

  Water availability

  Changes due to:

  • extraction from aquifers
  • drainage
  • flooding for reservoirs
  • GCC = precipitation change
• Changes in abiotic factors:

  Dissolved oxygen

  • sewage water goes through aerobic decomposition which leads to deoxygenation
  • waste water from power stations = increased water temperature so decreased oxygen
• Changes in abiotic factors:

  temperature

  • Global climate change - species distribution changes, some increase some decease
  • reptile sex ratio e.g. turtle eggs
• Changes in abiotic factors:

  pH

  • mine drainage water
  • pollutant gases from combustion and smelting - acid rain
  • increase in acidic water: denatures enzymes; fish gills are burnt so they suffocate; shells break down, making creatures more vulnerable to predators.
• Changes in abiotic factors:

  Water turbidity

  • ploughing, mining and dredging increase turbidity
  • this affects photosynthesis and filter feeding
• Changes in abiotic factors:

  Physical damage

  • plastic pollution - doesn't degrade/breakdown, microplastic pollute the air and food, building up in food chains
• Changes to biotic factors:

  • an organisms survival is interdependent with other species: interspecies relationships
  • Food webs
  • pollination
  • seed dispersal
  • habitat provision
• Introduced species:

  interacts with local sp.

  • grey squirrel outcompetes Red squirrel for food. They have the same niche = introduced competitors
  • Cane toads feed on the insects eating sugar cane. They were used as a pest control species but in the Caribbean and Australia they have no competition or predators
  • Beavers are farmed for fur. They escape and create dams = flooding upstream and downstream drying up.
  • Domesticated cats breed with wild cats = hybrids that are infertile. Scottish Wild Cats are endangered due to this.
  • Dutch Elm disease - introduced pathogens through the timber industry
• Habitat destruction:

  • deforestation
  • Agriculture
  • mining
  • aquifers/reservoirs
  • dredging
  • building infrastructure and urbanisation
  • Habitat fragmentation - breaking up a habitat into chunks with roads, water pipes, farms etc
  • increased mortality when moving between fragments - more exposed to predators
  • decreased resource availability e.g. food, breeding sites, shelter
  • decreased gene pool size - population is decreased so there is a decrease in genetic variation which increases inbreeding. There is a decreased resistance to disease and sudden environmental change