Threats to biodiversity

• direct exploitation :

  • food :sharks , turtles , cod , tuna and many herbivores .
  • fashion : fur coats , leather bags (crocodile) , feathers.
  • pets and entertainment : parrots , lizard , zoos , marine life centres .
  • furniture and ornaments : jewellery made with sharks teeth , furniture made with oak and mahogany , coral and sea shells sold as tourist souvenirs .
  • traditional medicine : tigers ( claws as a sedative , tail for ski disease etc ) rhino's ( horn is used to cure ' any medical problems ).
  • other products : oil extracted from whale blubber
• Eradication of predators and competitors :

  Many species have been killed because they threaten humans or interfere with human activities

  • Animals which threaten humans : sharks , crocodiles and poisonous snakes
  • Pathogen vectors : malaria mosquitos
  • Redators of livestock : wolves , lions
  • agricultural pests : insects , fungi.
  • wild herbivores that eat crops
  • forestry pests : wood-boring beetles , deer , squirrels
• Changes in abiotic factors


  • Human activities may alter a habitat so that it becomes unsuitable for species that are not adapted to the new conditions
• Water availability

  • Over-exploitation of groundwater can cause surface wetland habitats to dry out, making it impossible for wetland species to survive
• Dissolved oxygen


  • A drop in dissolved oxygen levels can reduce the survival of aerobic organisms such as fish and insect larvae
• Temperature


  • Temperature changes can cause changes in the distribution of species as they colonise areas which become suitable, or die out in areas where they can no longer survive
• Water turbidity

  • Prevents plants from photosynthesising
• Physical damage :a wide range of human activities can cause physical damage such as discarding litter or old fishing gear
• Changes in biotic factors :

  The survival of a species may be affected by changes in the presence and abundance of of the other species in the habitat
• pollinators :

  if insects were to die out then the plants would not be able to reproduce Ince they rely on pollen being transported between their flowers by insects .

  The use of pesticides and loss of wild flowering plants has reduced populations of many insect species .  
• seed dispersal species :

  Many large herbivore species such as rhino , elephant and hippo are vital in seed and fruit dispersal but since they are endangered here is a threat on future plant survival .
• food chain impacts :

  over-exploitation of certain foods for humans has lead to the decline and in some cases extinction of some species .

  Over exploitation of one species may also cause the increase of another species .
• introduced species :

  if a species is introduced it may have adaptations that give it a greater chance of of survival than indigenous species which may then decline or die out .

  populations in isolated areas , such as islands, have been very seriously affected by the introduction of species that aren't indigenous .
• introduced competitors :

  The grey squirrel was introduced to the UK from north America . in many areas , it has out-competed the indigenous red squirrel as it is better adapted to exploit the available food . it can digest acorns from oak trees which the red squirrel cannot .
• Introduced predators ;

  The introduction of predators has reduced the population of many wildlife species , especially in areas where the indigenous species are not adapted to survive in the presence of predators . For example : the range of the European water vole in UK rivers has been reduced by the American mink that escaped from fur farms .
• Introduced pathogens :

  Humans may introduce pathogens , causing a decline in wildlife populations . The pathogens are often carried by other introduced species .

  When the grey squirrel was introduced to North America it brought the squirrel pox virus which killed the red squirrel but no the grey squirrel .
• species that hybridise :

  if an introduced species is very closely related to an indigenous species then cross-breeding may produce fertile hybrids . the natural gene-pool will be changed by the introduction of genes it would not normally carry .
• loss of species that control abiotic factors :

  some species change habitats and and produce abiotic features that other species rely on for survival . for example : African forest elephants create clearing and water poles that many rely on for survival .
• habitat destruction :

  Human activities may have impacts that cause complete habitat destruction .

  • deforestation
  • ploughing of grassland
  • reservoir creation
  • mineral extraction
  • urban expansion