Agriculture and Environment: Cotton
Environmental Impacts of Production: Soil Erosion & Degradation
Even though the global area devoted to cotton cultivation has remained constant for the past 70 years, cotton production has "used up" many areas, leading to their abandonment, and expanded into new areas.
Main cause for shifting production areas
Soil depletion and degradation are the leading causes of the globally moving cotton production frontier. However, as with many crops, there are no global estimates of the extent of land degradation and abandonment that has resulted historically from cotton production.
Altering ecosystems & biodiversity
Cotton farmers in the last half-century sought not only to transform the ecological system, but to eliminate some forms of biodiversity, such as certain insects, altogether through the use of pesticides. The result of this strategy was high mortality of birds and downstream aquatic organisms.
Impacts on soil quality & fertility
In addition, it caused a severe reduction in soil quality and fertility through the impact of the constant and increasing use of pesticides on soil microorganisms (Banuri 1999). These organisms give soil its vibrancy.
They are essential to processing organic material and making it available, once again, to plants. Without such organisms, soil becomes little more than a growth medium to which producers must add all the necessary nutrients required by cotton.
Huge losses in productivity from salinisation
Salinisation from irrigated cotton production also causes the degradation and eventual abandonment of productive land. One estimate indicates that in 6 leading cotton-producing countries, between 12-36% of the currently irrigated area is already damaged through salinisation (Dinar 1998).
Investigations in Australia included that irrigated cotton production can lead to a chain of events that cause soil salinisation. Irrigation runoff into groundwater results in rising water tables and eventually the establishment of shallow water tables. The rising water table dissolves salts present in the soil and carries these to the surface.
In dry climates this leads to the salinisation of soils as water is pulled up through the soil to the surface where it evaporates, leaving behind salts (Zilberman 1998). As soil salinity increases, productivity decreases until crops can no longer be grown.
In regions where evaporation exceeds both rainfall and the fresh water provided through irrigation, salinisation is inevitable. Salt build-up happens most rapidly on soils that are poorly drained. Half of the irrigated land in Uzbekistan has lost productivity due to salinisation. Pakistan and Brazil report similar problems (Gillham 1995). Even if cotton production were to cease, it is unlikely that native local plant communities would be able to recolonise soils that have been contaminated with high levels of salt.