In this topic of IBDP Biology, we will learn about Measuring Biodiversity (Part 2).

• Forests are the natural climax communities.
• They have high diversity, with complex food webs.
  • High temperatures
  • Frequent rain
  • No frosts or drought
  • Great ecosystem diversity
  • Great species diversity
  • Very high SDI
• Tropical rain forests have been estimated to contain 50% of the world’s standing timber.
• Cover less than 10% of the Earth’s surface.
• Contain half of the Earth’s species.
• When it comes to IBDP Biology,  growth in the human population is increasing demand for land for farming.
• Humans have been clearing areas of forest for thousands of years.
• Large areas of Europe, Asia and North America.
• Recent and present deforestation affects manly tropical rain forests.

• Deforestation causes local extinction of species of trees.
• Removes the bases of many food webs.
• Removes the habitats of many other species
• Causes local extinction of other populations, or reduction in their size.
• Reduces the number of species present and numbers of individuals present.
• Reduces biodiversity.
• Leads to a lower biomass and productivity per hectare.
• Reducing the diversity produces a less stable and more extreme environment, where abiotic factors also become more extreme.

• Monoculture - large uninterrupted fields of one crop.

• It increases the productivity of farmland:
  • Only the best variety of crop is grown.
  • This allows more than one crop per year.
• When it comes to IBDP Biology,  sowing and harvesting of the crop is simplified.
  • Reduces labour costs.

• Monoculture reduces biodiversity:
  • It reduces genetic diversity:
    • Limited range of alleles.
    • This renders all crops in a region susceptible changing environmental factors.
  • It reduces ecosystem diversity:
    • Very few habitats exist.
  • It reduces species diversity:
    • Carrying capacity dominated by one species.
    • Food webs are very simple, being dominated by the crop.
    • Few species have the adaptations to survive.
    • This allows a pest species to get out of control
• Fertilisers are required to maintain soil fertility:
  • This can pollute surrounding groundwater due to leaching.
  • This reduces species diversity in rivers and lakes.
• Pesticides are required to keep crops healthy:
  • Wild plants decline due to lack of pollinating insects.

• Humans need to make balanced judgments between 2 needs:
  • The demands for increased food production.
  • The need to conserve the environment.
• The environment is a resource for all.
• When it comes to IBDP Biology,  the effects of human impact tend to be long term and far reaching.
• For example soil erosion will reduce the amount of land available for farming.
• It takes many years for soil to be replenished.
• Sustainable farming takes into account all of the possible remedies mentioned above.
• It tries to ensure, that, wherever possible, a wide range of habitats are preserved:
  • Manage fast growing tree plantations
  • Crop rotation
  • Replant hedgerows.
  • Use less inorganic fertilisers.
  • Use biological control instead of chemical pesticides.

That's the end of this topic.

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