The desirability of reducing our carbon footprints is generally recognised - if not necessarily acted upon - by governments, corporations and individual consumers. Yet the related and equally urgent need to address our water footprint is often overlooked.

Campaigns aimed at getting the public to save water are usually aimed at reducing domestic or industrial consumption of water. But only 10 per cent of our water consumption is related to industrial products, and only 5 per cent to domestic water consumption.

About 85 per cent of humanity's water footprint is in fact related to the consumption of agricultural products, particularly animal products, which generally use much more water per calorific value than crops. This means that if people are considering reducing their water footprint, they need to look at their diet rather than at their water use in the kitchen, bathroom or garden.

Feeding the animals

The biggest contribution to the total water footprint of all animal products comes from growing their feed, rather than the water volumes required for the animals to drink. Many grain crops are for animal consumption. In the US, for example, 68 per cent of the grains produced are used for animal feed. But this step is the furthest removed from the consumer, which explains why people generally have little notion that animal products require a lot of water.

Purely from a water-saving point of view, it is obviously more efficient to eat the crops directly than to have them processed into meat. Moreover, the water footprint of one beef product, for example, is not necessarily the same as another.

A water footprint generally breaks down into three components. The blue water footprint is the volume of fresh water that is extracted from surface and groundwater. The green water footprint is the volume of water extracted from rainwater stored in the soil. The grey water footprint is the volume of water that is required to dilute polluted water to such an extent that the quality of the ambient water remains above agreed water-quality standards.

Using water to make meat

The water footprint of beef from an industrial system may partly refer to irrigation water (blue water) to grow feed in an area remote from where the cow is raised. This can be an area where water is abundantly available, but it may be an area where water is scarce and where minimum environmental flow requirements are not met due to overexploitation. In contrast, the water footprint of beef from a grazing system will mostly refer to green water used in pastures. If the pastures used are either dry or wetlands that cannot be used for crop cultivation, the green water flow turned into meat could not have been used to produce food crops instead.

If, however, the pastures can be substituted by cropland, the green water allocated to meat production ceases to be available for crop production. So the social and ecological impacts of water use at a certain location depend on the scarcity and alternative uses of water at that location.

Protecting freshwater resources can no longer be regarded as an issue for individual countries or river basins. Let us take Europe as an example. The water footprint of Europe - the total volume of water used for producing all commodities consumed by European citizens - has been significantly externalised to other parts of the world. Europe is a large importer of crops such as sugar and cotton, two of the thirstiest crops. Europe also imports large volumes of animal feed, like soybean from Brazil. So European meat consumption relies heavily on water resources from outside Europe. How Europe is going to secure its future water supply may thus become a vital economic and political issue.

Global issues

Water problems are in fact an intrinsic part of a global economic structure in which water scarcity is not translated into costs to either producers or consumers. As a result there are many places where water resources are depleted or polluted, with producers and consumers along the supply chain benefiting at the cost of local communities and ecosystems. Animals are often fed with a variety of feed ingredients, and feed supply chains are difficult to trace. So unless we have milk, cheese, eggs or meat from an animal that was raised and grazed locally, it is hard to say how any individual product has affected the world's scarce freshwater resources. The increasing complexity of our food system in general and animal products in particular hides the existing links between the foods we buy and their resource implications.

It is only by understanding the relation between animal products and water resources that effective policy decisions can be made. Yet there is no national water plan in the world that even addresses the fact that meat and dairy products are among the most water-intensive consumer products, let alone that water policies somehow involve consumers or the food industry in this respect.

The latest 2009 World Water Assessment Programme report by the United Nations is nearly 350 pages long but mentions the word ‘meat' just 15 times. The analysis does not go deeper than stating that global meat demand will increase and thus water demand as well. The same bias can be seen in scientific literature, which generally addresses the issue of water-use efficiency within agriculture (more crop per drop), but hardly ever the issue of water-use efficiency in the food system as a whole (more kcal per drop).

What needs to be done

This situation has to change. Consumer and environmental organisations need to demand more transparency of animal products from business and governments, so that they are better informed about associated water resource uses and impacts. Governments can put regulations in place that urge businesses along the supply chain of animal products to cooperate in creating product transparency, and can tune their trade and development cooperation policies towards their wish to promote consumption of and trade in sustainable products. Businesses can cooperate in water labelling, certification and benchmarking schemes, and produce annual water accounts that include a report of the supply-chain water footprints and associated impacts of their products. Wise water governance must become a shared responsibility of consumers, governments and businesses.

Arjen Y. Hoekstra is professor in water resources management at the University of Twente, Enschede, the Netherlands

He will be speaking on water footprinting at Compassion in World Farming's Peter Roberts Memorial Lecture - ‘Beef, Bread and Water: Ethical food in a warm and thirsty world' - in London on September 20th.

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