![]() An indestructible renewable resourceīut just as experts have their reservations and misgivings about carbon footprint calculators, they also warn about water footprint calculators. And anyone curious enough to check their water footprint will find themselves assigned a figure of thousands of litres, almost just by existing. In the style of the carbon footprint calculators that have proliferated on the Internet, there are also similar calculators for estimating the water impact of our lives and activities. With such dizzying figures, and with the world’s population approaching eight billion and rising, it seems we are heading inexorably towards a water apocalypse in which we will soon have no water to produce food or consumer products, or even to drink. ![]() This is what is known as virtual water, as opposed to the real water we consume directly. But it’s not just about food production: making a cotton shirt uses almost 3,000 litres of water, or nearly 4,000 litres for jeans. The food we each consume every day requires an average of 3,000 litres of water, rising to 9,000 for US citizens. Credit: Sam SommerĪnd yet, if we look at the published data, anyone would think that we are in dire straits of running out of this essential resource: 1,500 litres of water are used to produce a kilo of grain, 10 times more if the kilo is meat, between 400 and 11,000 litres to obtain a litre of milk, and even a crop as basic to humanity as rice uses water at a rate of 3,400 litres per kilo (with estimates varying from just under 3,000 litres to 5,000 ). Almost 97% of water we have on Earth is salt water of the remaining fresh water, 68% is trapped in ice and glaciers. ![]() So if we are talking about a necessary transition to a more sustainable world, water is at the top of the list of essential resources that we must protect to ensure our survival and that of all life on Earth. ![]() But at least here on Earth, water is the first requirement for this to remain a living planet. Although science fiction and speculation have imagined other non-aqueous biochemicals in conditions very different from those on Earth, they have yet to be shown to be viable. When scientists study the habitability of other star systems, there is a sine qua non condition-not sufficient, but essential for the planet in question to be a candidate for the existence of life: can liquid water exist? We know that some forms of life do thrive without the need for oxygen or light, but not without water. ![]()
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