The Water We Eat: Combining Virtual Water and Water Footprints

Every form of life on the Earth depends on water, and it is in water that billions of years ago the first life forms appeared. Also today, the almost 9 million living species found on our planet base their existence on water, a resource which is, therefore, not only essential but also very precious. Despite it being a renewable resource, it still, however, remains limited and vulnerable. Even if our planet viewed from afar appears as a prevalently blue sphere, with 71 % of the surface covered by water, we know very well that not all this water is actually available to humans. First of all, 97 % of the water is salt water found in the seas and oceans and only 3 % is freshwater, of which, however, most (68.6 %) is locked up in ice and glaciers, 30.1 % in groundwater and 1.3 % in surface water. The liquid water on the land surface is mainly found in the large lake basins, such as the North American Great Lakes or Lake Baikal in Russia, which contain 20.1 %, equal to 0.26 % of total freshwater, and in the swamps which make up 2.53 % (0.03 % of total freshwater). The atmosphere contains 0.04 % of total freshwater in the form of water vapour and the land 0.05 %, while the river systems contain a relatively low portion (0.006 %) (Fig. 1). Moreover, the geographic distribution of water is not homogenous—Brazil has 15 % of the global reserves and 64.4 % of the total water found on the Earth is found in only 13 countries http://ga.water.usgs.gov/edu/earthwherewater.html Shiklomanov in Water in crisis: a guide to the world’s freshwater resources, Oxford University Press, Oxford, 1999). For this and for reasons of economic inequality, despite only 54 % of the world’s freshwater reserves presently used being accessible, a billion people do not have access to drinking water and 2 billion people do not have sufficient water for hygiene–sanitary services (Prüss-Üstün in Safe Water, Better Health, WHO, Geneva, 2008; IWMI in Water for Food Water for Life, Earthscan, USA, 2007).