Human activities

• Herbicides


  • kill weeds competing with crops
  • crops grow faster and larger
  • increases productivity
• Fungicides


  • kill fungal infections that damage crops
  • more energy is used for growth, rather than fighting infections
  • larger crops
  • increases productivity
• Insecticides


  • kill insect pests that eat and damage crops
  • less biomass is lost
  • crops grow larger
  • increases productivity
• Introducing natural predators


  • eats pest species
  • crops lose less energy and biomass
  • grow larger
  • increases productivity
• Fertilisers


  • chemicals providing minerals needed for growth
  • growth is not limited by this factor
  • lost minerals are replaced in soil
  • increases productivity
• Intensive livestock rearing

  • controlling conditions so more energy is used for growth
  • warm, indoor pens - restrict movement and less energy is needed to keep animals warm
  • high energy feed - increases energy input so more energy is available for growth
  • ethics - pain, distress of animals, not 'natural'