• Farming practices can?increase?the?efficiency of energy transfer?in order to increase the total amount of energy available for?human consumption
• This can be achieved by:
  • Reducing?the?energy lost?by crops to?other organisms?(e.g. pest species that feed on crops)
  • Reducing?the?energy lost?by livestock (e.g. cattle) through?respiration

   

Reducing energy loss to other organisms

• In the?food web?below, the weed, the harvest mouse and the caterpillar are all considered?pests?because they?reduce?the?energy?available?for the?growth?of the crop (corn)
  • This means they?reduce?the?net primary production?(NPP) of the corn
  • This, in turn,?reduces?the amount of?energy?available to?humans?(who consume the corn)

   

• Corn farmers can?simplify?the food web below by getting rid of the pest species
  • The?reduces?the?energy lost?by the corn to these organisms
  • This will cause the?NPP?of the corn to?increase

   

Energy that would otherwise contribute to the net primary production of crops can be lost to pest species either directly (i.e. to organisms that feed on the crop) or indirectly (i.e. to organisms that compete with the crop)

Removing pest species

• Farmers can?simplify?food webs using?pest control
• One method of pest control is to use?chemical pesticides
  • Insecticides?are chemicals that kill insect pests that eat and damage crops, reducing the NPP of the crops
  • Herbicides?are chemicals that kill weeds (unwanted plants) that?compete?with crops for sunlight and water, reducing the NPP of the crops

   

• Another method of pest control is to use?biological agents?to reduce the number of pests (this is known as?biological control). For caterpillar pests, for example:
  • Toads that consume caterpillars can be used
  • Parasitic wasps that lay their eggs inside caterpillars can be used (when the larvae hatch they consume and eventually kill the host caterpillar)
  • Pathogenic bacteria and viruses that kill caterpillars can be used

   

• Often, farmers will use?both?these methods (chemical?and?biological) together to reduce pest numbers more effectively

Reducing energy loss through respiration

• Farming practices can?increase?the?net production?of?livestock?(e.g. cattle)
• This can be achieved by carefully?controlling?the?conditions?that the livestock are raised in so that the energy lost through?respiration?is?minimised?and the energy available for?growth?is?maximised. For example:
  • Respiration rate is?increased?when animals?move, so keeping livestock in?pens?where their movement is?restricted?lowers energy loss through respiration
  • Respiration rate is?increased?when animals need to?generate body heat?to keep warm, so keeping livestock?indoors?and in?heated?pens also lowers energy loss through respiration

   

• These farming practices ensure that more chemical energy is stored as?biomass?in the livestock, increasing their?net production
  • This means more energy is available for human consumption
  • It also means that in a?given period?of time, a?greater?amount of food can be produced, sometimes even at a?lower cost
  • However, some people think it is?unethical?to keep livestock in?cramped,?unnatural?conditions where their movement is restricted and they may have a?lower quality of life