Agriculture and Environment: Cotton
Environmental Impacts of Production: Water Use
Cotton production requires 550 to 950 litres per square metre of area planted. Put another way, 7,000 to 29,000 litres of water are required for each kilogram of cotton produced (Soth 1999).
A consumate consumer of waterSome estimates indicate that it is the largest user of water among all agricultural commodities. Estimates indicate that cotton represents more than half of the irrigated agricultural land in the world. Cotton production and processing are also a major source of pollution of fresh water (Soth 1999).
Inefficient water management
In many cotton-producing areas, surface waters are diverted to irrigate cotton. Most cotton irrigation systems rely on traditional flooding techniques. Fresh water is taken from its source (e.g., river, lake, reservoir, or underground) and transported via a series of even smaller, open canals to the area to be irrigated.
Freshwater losses occur through evaporation, seepage, and inefficient water management. Globally, irrigation efficiency of all types is lower than 40% (Gleick 1993). This means that 60% of the water used in irrigation never makes it to the targeted plant.
Substantial damages in the Aral Sea basin
The continuous cultivation of cotton in the Aral Sea basin of Uzbekistan has caused a tremendous decrease in the surface area of the sea - it has shrunk by almost half. The reason is that two of the rivers that formerly fed the Aral Sea (the Amu Darya River and Syr Darya River) were diverted for cotton production.
Once the world's fourth largest lake, the Aral Sea formerly harboured many fish; today there are few. In addition, some 20 of its 24 native fish species are now extinct there, including the sturgeon that produced world-famous caviar.
In China's Yellow River Valley, where cotton is grown under both irrigated and rain-fed conditions, a shortage of irrigation water due to falling water tables has also been reported (Gillham 1995).
Wide ranging impacts
The main activities associated with cotton production that affect freshwater ecosystems and biodiversity include runoff from fields, drainage, pesticide application, water withdrawal for irrigation, extensive irrigation, dam construction, and land reclamation.
These activities result in a range of impacts from eutrophication and pollution to loss of soil and other biodiversity.
Groundwater depletion is another environmental problem associated with cotton cultivation. In many areas groundwater is pumped to irrigate cotton. In essence this water is mined from underground reserves.
In ossified aquifers, which are aquifers with solid caps that do not allow the water to be replenished from surface runoff, water is a non-renewable resource. Even in other types of aquifers, groundwater systems can take hundreds or even thousands of years to be refilled once they have been drained.
The total global freshwater demand for cotton production is between 50 and 210 cubic kilometres per year. This is between 1% and 6% of total global freshwater withdrawal (Soth 1999).