20. Human influences on ecosystems

• How technology result in an increase in food production:

  • agricultural machinery: use on larger areas & improve efficiency
  • chemical fertilisers: increase production yield
  • herbicides: a type of pesticide that kills weed
  • selective breeding: improve production by crop plants & livestock (cattle, fish, chicken..)
• Negative impacts of large-scale monoculture:

  • if a natural disaster occurs, the whole crop could be wiped out
  • if pests & diseases attack crops, they could harm them really easily
  • reduces variety of species - decreases biodiversity
  • when insecticides are used repeatedly, pest could become resistance to them
• Negative impact of intensive livestock production:

  • waste can pollute land and waterways nearby
  • disease can spread easily among them
• Reasons for habitat destruction:

  • deforestation
  • logging
  • building houses
  • industrialisation
  • livestock production
  • marine pollution
  • extraction of materials
  • eutrophication

  --> alternating food chain have a negative effect on the habitat
• Effects of deforestation:

  • reduce biodiversity
  • destroys habitat -> extinction
  • loss of CO2 fixation = increase CO2 = global warming
  • soil erosion: less trees = less tree roots to retain soil = goes into rivers = dirty water = soil loses fertility
  • flooding: less trees for interception of precipitation & absorption of water, water accumulate in valleys after deforestation
• Pollution:

  • insecticides: may kill useful insects such as bees (pollinators)
  • herbicides: can be harmful to animals which eat the plants
  • untreated sewage: a food source for bacteria - depleting oxygen in the water
  • chemical waste: doesn't break down and can build up in food chains -> poisoning top carnivores
  • discarded rubbish: remains for long, animals eat them and can get into food chains
  • fertilisers: eutrophication from getting into rivers/lakes
• Eutrophication:

  • fertilisers are put into soil by farmers
  • fertilisers with nitrates/detergents with phosphate leach into river/lakes after rain
  • water plants grow more than usual
  • algae bloom and cover water surface
  • no photosynthesis - plant die - decomposers uses remaining O2
  • fish and other creature dies
• Non-biodegradable plastic:

  • fill up animal's stomach so they can't ingest food
  • get in ways of animal's habitat - can get stuck on them
  • can release toxins that affect marine organism/ land is no good for growing crops/ grazing animals
• Air pollution:

  • methane released from cow burps
  • CO2 from daily routines (vehicles, factories, burning fossil fuels)
  • creates a layer that traps in radiation from the ground -> global warming

  
• Acid rain:

  • sulfur and nitrogen in fossil fuels are converted to oxides during combustion --> dissolve in water = acid rain
  • leaching of minerals, inhibition of decomposition
  • water in lakes/ rivers collects excess minerals - death of fishes & invertebrates = food chain disrupted
  • leaching of ions in soil, destruction of photosynthetic tissue
  • clean up emission by catalytic converters - letting pollutants react with each other to give less harmful products
• Female contraceptives:

  • animals can digest the water leading them to avoid producing offsprings - bad for farmers if wanting high yields
  • can produce infertile offspring
• Sustainable resource - one which is produced as rapidly as it's removed from the environment so that it does not run out
• Sustainable development - development providing for the needs of an increasing human population without harming the environment
• Conserving non renewable energy source:

  • finite resources
  • takes time and money to find energy source that would replace them
• Conservation of forest:

  • replanting (afforestation) - replace back the same n. of trees that has been cut
  • education - raise awareness on importance of buying stuff from sustainable sources
  • protected areas - doesn't let deforestation happens there, ensure safe environment for plants to grow
  • quotas - limiting amount of trees being cut down
• Conservation of fish stock:

  • education - teaching people about their food choices
  • closed season - no fishing allowed while the fish breed
  • protected areas - no fishing allowed in an area where the fish reproduce
  • control net types and mesh sizes - letting small fishes go for them to grow and reproduce
  • quotas - limiting amount of fish can be taken
  • monitoring - can only catch fish of certain sizes
• Sustainable development includes:

  • management of conflicting demands
  • planning & co-operation at local, national and international levels

  Recycling:

  • paper: sent to special centres where it is pulped to make raw materials for industry
  • plastic: fossil fuels, bottles -> fleece clothing
  • glass: remelt to be used as new bottles
  • metal: mining takes energy, so recycling save money
• Sewage treatment (activated sludge):

  • screening: using coarse materials to remove debris from water
  • first settlement tank: allows suspended solid to precipitate to be treated separately from the water
  • second settlement tank: water now has minimal pathogens and release back into natural waterways
• Extinction causes:

  • invasive species
  • overhunting
  • habitat loss
  • pollution
  • climate change
  • overharvesting
• Risk of population size drop:

  • less variation
  • high chance of extinction
• Conservation methods:

  • monitoring and protecting
  • education
  • captive breeding: capturing animals and letting breed together for offsprings
  • seed banks: preserve biodiversity & genetic diversity for plant species
• Reasons for conservation:

  • reducing extinction
  • protecting vulnerable environments
  • maintaining ecosystem function: nutrients cycle, resource provision (e.g. food, fuels, genes..)
  • increase biodiversity