IB Geography A.3.2 Environmental Consequences of Agricultural Activities Notes

Pollution and Soil Degradation Affecting Water Systems

1. Agricultural activities can degrade water systems through pollution and soil degradation.
2. Two major processes, eutrophication and salinization, illustrate how these impacts unfold.

Eutrophication: A Chain Reaction of Nutrient Overload

1. Eutrophication is the process where water bodies become overly enriched with nutrients, leading to excessive algal growth and a decline in water quality.
2. Eutrophication is mostly caused by nutrient runoff
   1. Fertilizers rich in nitrogen and phosphorus are applied to crops to boost yields.
   2. Rainfall or irrigation washes these nutrients into nearby rivers, lakes, and streams.
3. The impacts of eutrophication include
   1. Algal Blooms
      – The excess nutrients act as a "superfood" for algae, causing rapid growth.
      – Thick mats of algae form on the water's surface, blocking sunlight.
   2. Oxygen Depletion
      – As algae die and decompose, bacteria break them down, consuming large amounts of oxygen in the process.
      – This creates "dead zones" where oxygen levels are too low to support most aquatic life.
   3. Loss of Biodiversity
      – Fish and other aquatic organisms suffocate or migrate, disrupting the ecosystem.
      – Species diversity declines, and the water body becomes less resilient to environmental changes.

Salinization: The Hidden Cost of Irrigation

1. Salinization is the accumulation of salts in soil, often caused by improper irrigation practices.
2. It happens because of
   1. Irrigation water contains dissolved salts, even if it appears fresh.
   2. When water evaporates, these salts are left behind in the soil.