human impact

• Deforestation


  The removal of trees to use as timber or fuel or to repurpose the land use for agriculture or building
• Overfishing


  Fish are caught at a higher rate than they reproduce and grow, to the point where increased fishing efforts lead to declining catches
• Fish farming


  Fish are intensively reared in ponds/tanks or nets; sea-fish are usually reared in large netted areas of the sea
• Fish farming is one solution to overfishing
• Extinction


  The total loss of a species
• Endangered species


  At risk of becoming extinct because there are few breeding pairs left
• Conservation


  The planned management of ecosystems to enhance biodiversity and protect gene pools
• Agricultural exploitation


  The need to increase efficiency and intensity of food production to meet increasing demands by a rapidly increasing human population
• Reasons for extinction


  • Natural selection
  • Habitat destruction, e.g. by deforestation
  • Pollution, e.g. PCBs used as antifouling agents, can cause female dog whelks to grow false penises and thus become infertile
  • Hunting and collecting, e.g. rhino horn and pangolin scales
  • Competition from domestic animals
• Conservation methods


  • Require careful monitoring
  • Involve field techniques such as random sampling and transects
  • Enable prediction of possible effects of human activities to inform planning
  • Allow alternative methods to be considered and implemented if necessary to reduce harmful effects
• Political decision making should be based on sound scientific principles to make informed choices
• Conservation methods


  • Nature reserves and SSSIs (sites of special scientific interest) are protected by law
  • Trade in endangered species and products derived from them, like skins and ivory, are restricted or banned. This is an international agreement
  • Captive breeding programmes in zoos and botanic gardens enhance species numbers
  • Sperm and seed banks preserve gene pools for the future
  • Reintroduction programmes, e.g. the beaver and red kite, enhance the numbers of endangered species
• There is conflict between the need for conservation of species


  And the demand for increased food production
• Agricultural exploitation can involve


  • Removal of hedgerows – destroying habitats
  • Monocultures – reducing available niches
  • The use of insecticides, herbicides and fertilisers – causing eutrophication and the death of beneficial insects, niches and habitats
  • Ecosystem destruction to provide additional agricultural land
• Plants may provide new medicines for the future
• Many crop plants have wild relatives that may have useful genes that could be bred back into crops to increase productivity
• It is unethical to drive species to extinction and reduce biodiversity as the long-term impacts are not yet fully realised
• Reduced gene pools make species more vulnerable to extinction as there is less variation