Human impacts on the environment

• conservation

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

  Species at risk of extinction because there are few breeding pairs left
• Extinction

  The total loss of a species
• Reasons for extinction

  • Natural selection
  • Habitat destruction
  • pollution
  • Hunting and collecting
  • Competition from domestic animals
• Conservation methods

  • Reserves and sites of special scientific interest are protected by law
  • Trade in endangered species and products, like ivory, are restricted or banned. This is an international agreement.
  • Captive breeding programs
  • Sperm and seed banks preserve gene pools for the future.
  • reintroduction programs enhance the number of endangered species
• Biological monitoring involves techniques such as random sampling and transects
• Monitoring enables prediction of possible effects of human activities to inform planning of conservation methods.
• Political decision making should be based on sound scientific principles to make informed choices
• Why conserve gene pools?

  • 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
  • Its 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
• Conflict

  There is conflict between the need for conservation of species and demand for increased food production
• Agricultural exploitation

  Describes the need to increase efficiency and intensity of food production to meet increasing demands by a rapidly increasing human population
• Agricultural exploitation can involve:

  • removal of hedgerows - destroys habitat
  • monocultures - reducing available niches
  • Use of insecticides, herbicides and fertilisers - causing eutrophication and the death of beneficial niches and habitats
  • Ecosystem destruction to provide additional agricultural land
• Deforestation

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

  • Soil erosion - soil is no longer protected from rain by the canopy; as roots decompose, they no longer hold the soil together so it is eroded by wind and rain.
  • Flooding - Evaporation from soil removes less water than transpiration, water logging encourages denitrification and soil loses nitrates.
  • Habitat loss reduces biodiversity
  • Less photosynthesis means that less CO2 is removed from the atmosphere. CO2 is a greenhouse gas, increased CO2 leads to global warming and climate change
• Solutions of deforestation:

  • Selective felling
  • Replanting the correct mix of species, the correct distance apart, and allowing them to regenerate
  • Protecting areas
• Overfishing - Fish are caught at a higher rate than they reproduce and grow. This occurs to the point where increased fishing efforts lead to declining catches.
• Consequences of overfishing:

  • Fish populations may be reduced in size to the extent that they lose genetic diversity.
  • Size of fish is reduced as they don't have time to grow.
  • Fish population has fewer individuals and cannot replace harvested fish.
• Solutions to overfishing:

  • Quotas are a maximum mass of fish that can be harvested; heavy fines are imposed for exceeding the government set quotas.
  • Restricted fishing seasons, to allow fish to reproduce.
  • Exclusion zones preventing fishing in certain areas.
  • Increase mesh sizes to allow smaller fish to escape and grow to breeding size.
  • Limiting the size of fishing fleets so that not as many fish can be caught.
• Fish farming - Where fish are intensively reared in ponds or tanks or nets. Sea fish are usually reared in large netted areas of the sea. This is a solution to overfishing.
• Pros of fish farming:

  • Less fish need to be harvested from the wild, allowing fish stocks to replenish.
  • Fish have been selected for high growth rates and therefore large size and increased yield.
• Cons of fish farming:

  • Excess fish food, egesta and excreta fall out of nets and cause eutrophication in marine habitats.
  • Parasites and disease spread quickly in the overcrowded area.
  • If farmed fish escape they could outcompete the wild fish or interbreed with them, passing on the alleles for fast growth, pushing wild fish to extinction - some farmed fish have been engineered to be triploid to avoid this issue.
  • The feed is often made from harvested wild fish.