Livestock depletes and pollutes global water sources – Happy #WorldWaterDay

Water is essential for the continuation of life as we know it, yet over the years it has become dangerously depleted and polluted. This post briefly highlights the impact commercial livestock farming has on the world’s water sources.

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While it is said that the average person uses between 30 and 300 litres of water a day 1, it takes up to 3000 litres of water to produce the food  in their daily diet, particularly meat and dairy.

Commercial livestock farming uses over 8% of global water, of which almost 90% is used to produce animal feed 1. Sadly, the vast majority of this animal feed is produced in areas that are already facing considerable water scarcity. Approximately 38% of the world’s population live in water stressed areas and it is predicted that by 2025 this will rise to 64% 1. By 2023, roughly 33% or 1.8 billion people will be living in water-scarce areas such as South Africa, India, China and Pakistan 1. Predictions such as these will have disastrous consequences on the food system, as it was already estimated that close to 350 million tonnes of food was lost to water depletion in 2012 4.

The concept of “virtual water” refers to the total volume of water needed to produce a  commodity or provide a  service 2. Animal products have a higher virtual water content than plant products, as the living animal needs drinking water, service water, and as mentioned before, the water needed to produce animal feed 2. Based on this concept, it is estimated that 200 litres of water is used to produce just 200ml of milk; 135 litres of water is used to produce one 40g egg; and 2400 litres of water is used to produce one hamburger patty weighing 150g 2.

The use of virtual water is not always monitored in terms of where the commodity is produced but rather where it is consumed. For example, the 90% of virtual water used for producing animal-based commodities in Japan actually comes from imported animal feed  2.|Thus it is  actually countries outside of Japan that shoulder the majority of water depletion necessary to meet the Japanese demand for animal products.

Apart from depleting water sources, livestock is also heavily involved in polluting them. Animal manure used as fertiliser is very nitrogen-rich and the excess remaining after plant uptake can saturate soils and contaminate surface and groundwater sources via leaching and soil runoff 5. Nitrogen then accumulates in water bodies such as lakes, rivers and oceans, and encourages the growth of oxygen-consuming algae. This leaves less oxygen available for aquatic life, a process known as eutrophication 5. It is estimated that livestock adds 32% of the nitrogen load and 33% of the phosphorus load into fresh water sources 1.

Algae overgrowth due to Eutrophication

Algae overgrowth due to Eutrophication

A significant amount of pollution occurs by way of antibiotics, pesticides and heavy metals 5, 6. The amount of antibiotics used in the livestock industry worldwide has also not been quantified due to the heavy reliance on estimated international data 6. Antibiotic use in livestock has been banned in the EU; however, approximately 11,200 metric tons are used each year by livestock producers in the US to promote animal growth 6. This may be contributing to the growing number of antibiotic-resistant bacteria circulating within the human population, for example Aeromonas spp, which was identified in human drinking water in the US from as early as the 1980s 6. Antibiotics can even be absorbed by certain crops, as once observed in carrots, corn and lettuce 7.

The sobering conclusion of the state of the world’s water is that the impact will only felt as the situation gets worse;  making it more difficult to implement improvement strategies, especially in poverty-stricken areas 7. Scientists at the Stockholm International Water Institute (SIWI) predicted that by 2050 there will be not be enough water to maintain the intense animal farming needed to feed an expected population of 9 billion 8. To avoid this, intervention is needed to reduce animal-based calorie intake from current levels of 20% to just 5%, as well as to improve water usage within the sector 8.

 

References

  1. Steinfeld H, Gerber P, Wassenaar T et al. (2006) Livestock’s Long Shadow: Environmental issues and options. FAO/LEAD, Rome, Italy.
  2. Chapagain AK & Hoekstra AY (2004) Water Footprints of Nations – volume 1: Main Report; Value of Water Research Report Series No. 16. UNESCO-IHE; http://www.waterfootprint.org
  3. Turner K, Georgiou S, Clark R, Brouwer R, Burke J. 2004. Economic Valuation of Water Resources in Agriculture, from the Sectoral to a Functional Perspective of Natural Resource management; FAO paper reports No. 27. Food and Agriculture Organization of the United Nations
  4. FAOSTAT (2013) Statistics Division of the Food and Agriculture Organisation of the United Nations. Available: http://faostat.fao.org/site/291/default.aspx
  5. Martinez J, Dabert P, Barrington S, et al. (2009) Livestock Waste Treatment Systems for Environmental Quality, Food Safety, and Sustainability. Bioresource Technology; 100; 5527–5536
  6. Kümmerer, K (2009a) Antibiotics in the Aquatic Environment – A Review – Part I. Chemosphere; 75; 417–434
  7. Kümmerer, K (2009b) Antibiotics in the Aquatic Environment – A Review – Part II. Chemosphere; 75; 435–441
  8. Jägerskog A., Jønch Clausen T (2012) Feeding a Thirsty World – Challenges and Opportunities for a Water and Food Secure Future. Report (eds.) Nr. 31. SIWI, Stockholm.