APES 5.4 Impacts of Agricultural Practices

Enduring Understanding:

  • When humans use natural resources, they alter natural systems.

Learning Objective:

  • Describe agricultural practices that cause environmental damage.

Essential Knowledge:

  • Agricultural practices that can cause environmental damage include tilling, slash-and-burn farming, and the use of fertilizers.
  • Arable land is land that is capable of being cultivates
    • This land can be depleted of nutrients however and become unusable

Tilling

  • Tilling is breaking up and turning over soil to make it looser to prepare for planting seeds

    • This mixed non-crop plants into the soil as nutrients
    • Provides aeration

  • This bare soil is susceptible to soil erosion and increased evaporation

    • After soil erosion, run off is more common, causing downstream eutrophication
    • This increases the need for fertilizer

  • Turned soil impacts the soil structure and microecosystem

  • Turned soil is also not as capable of sequestering carbon, and so it releases CO2

  • Tilling with machines also releases emissions

    • Remember that fossil fuel use goes all the way back to extraction and all the negative consequences along the way

Slash-and-Burn

  • Typically occurs in Northwest Africa, Indonesia, Central America, and South America (especially Brazil)
  • Most common is developing countries
  • Typically tropical rainforests
    • Low-nutrient soil
  • Subsistence farmers
  • The ash from the burnt foliage is used as fertilizer, since the soil alone is not suitable for agriculture
    • This means that the area cannot just be clear cut
  • The soil is then rich but only for a few years before the nutrients are depleted
  • Because it is so unsustainable, the farmer will move to a new plot of land and repeat the process
  • Desertification can occur
    • After all the nutrients are used up, the trees cannot grow back
  • Soil erosion occurs, and all negative effects along with it
  • The albedo decreases, destabilizing the local climate
  • Evaporation increased, drying out the soil and salinization may occur
  • Water is unable to infiltrate into groundwater supply

Intensive Agriculture

  • Typically occurring alongside agribusiness, intensive agriculture uses lots of inputs for economic gain
  • Since intensive agriculture tends to see one crop grown on a large scale, biodiversity is lost
    • That makes the crop very susceptible to catastrophe

Fertilizer

Synthetic vs. Organic

  • Synthetic fertilizers are made through the Haber-Bosch Process
    • 3H2 + N2 → 2NH3
  • Synthetic fertilizers contain nitrogen, phosphorous, and potassium
    • When these run off into nearby bodies of water, eutrophication can occur
  • Synthetic fertilizers are easy to transport, release nutrients consistently over time, and can be customized for the plant
    • However, they are often overused, and so nothing to improve soil structure
  • Organic fertilizer is biomass, usually animal waste
  • Organic fertilizers have to be gathered by hand or machine, the nutrients are unknown and uncontrollable, and they are generally hard to use
    • Despite these weaknesses, they work with the soil and improve structure

Pesticide Overuse

  • Can kill nontarget species
  • Can cause a pesticide treadmill
  • Does, however, maximize crop yield
  • Pesticides running into waterways does not cause eutrophication, but it can kill nontarget species in the aquatic biomes