BBC Sounds Music Radio Podcasts Hello and thanks for downloading the More or Less Podcast. With a programme that looks at the numbers in the news, in life and in beef. I'm Charlotte McDonald. If you spend much time on social media, and we don't necessarily recommend it, then you've probably come across a strange fascination with water consumption. Mainly, this is people telling you that using AI is terrible for the planet because of how much water it uses. We've already made a couple of programmes about the numbers in those arguments and long story short, they probably aren't saying what you think they're saying. But on the platforms like X, Blue Sky and TikTok, an opportunity to keep an argument going is rarely missed. And one of the numbers that's been enlisted in that glorious cause concerns the water that's used for a seemingly unrelated pastime. Eating beef. Here's an example from Twitter, or X. A kilogram of beef requires over 15,000 litres of water to produce. A vegan who uses chat GPT every day is living a more sustainable lifestyle than someone who regularly eats beef while boycotting AI. Ignoring the AI part, is that true? Does it actually take 15,000 litres of water to produce a kilogram of beef? When the number comes in, people see that's easy to just take numbers and talk about. Beef is so bad and others are so good. But the whole idea of the water footprint is we show the numbers, but behind the numbers there is the story. This is Mesvin Mekinen, an assistant professor at the University of Alabama, and he definitely knows what this 15,000 number means. It features in scientific papers from the early 2010s that he co-wrote with Aayun Hoekstra, a Dutch professor who pioneered the idea of the water footprint. The initial motivation was to create awareness, similar to the carbon footprint and the land footprint, to create awareness that our water impact is not located only where we live, but it's far away places also. The issue is that the water footprint is being used to say that the amount of water beef uses is bad. And the story explaining what's wrong with that goes back to before the water footprint was developed. So I'm Professor Mark Mulligan and I'm Professor of Physical and Environmental Geography at King's College London. So my late colleague at King's College London, Tony Allen, came up with the concept of virtual water in the early 90s. Quick botany lesson. As they grow, plants absorb water from the soil through their roots. This is sucked up through the plant to the leaves where it evaporates. It's a process called transpiration. So Tony's concept for virtual water is that when a crop grows or when an animal like a cow eats a crop that's growing, they consume, if you like, all of the water that that crop had to evaporate over its lifetime in order to produce the biomass that is the crop. This might sound a bit technical, but for the work Tony Allen was doing, the importance of the water required to grow plants was pretty obvious. He developed the concept for drylands in the Middle East. In that context, when you're growing a crop, you're usually growing it with irrigation water from groundwater and rivers. In very dry places, water is a precious resource. The water you use for irrigation is water you can't use for something else, like drinking or sanitation. This water has a clear environmental cost. The idea of virtual water was taken on by Ardion Hookstra and expanded. He developed a method for figuring out how much water a food crop or animal used wherever it was in the world. But to point out the obvious, not all parts of the world are arid drylands where there's little to no rain. So for example, if we have a cropland that is growing coffee, let's say in Brazil, well that probably replaced forests that was there before in that kind of humid, wet environment. And indeed the forest would have consumed through evaporation more water than the coffee crop does. So in that case, the water footprint of the coffee crop is actually negative. Because the forest is gone, you actually have more water than you would have had if the forest was there. In this case, if you think a higher water footprint is a bad thing, then you'd be saying that chopping down rainforest for coffee plantations is good. What's more, the water we're talking about falls as rain. And to put it mildly, rain is not in short supply in a rainforest. When the concept of water footprint was first developed, it was recognised that not all water is the same. This is Tim Hess, a professor of water and food systems at Cranfield University in the UK. And a differentiation was made between green water that has come from rainfall, differentiated from blue water, that's water in our water resources, whether it's rivers, lakes, whether it's water that is underground in our aquifers. Green water is rain. Blue water is pumped out of rivers and lakes. There's a third category, grey water, which is the water that's needed to dilute any pollution like fertilizer runoff. Right, back to the beef. If we look at beef production and this 15,000 figure. The majority of the water is associated with producing feed. It takes a lot of feed to keep those animals alive for two years before they go into the food system. In the UK, cows mostly stand around in fields eating grass. That grass gets its water from rainfall. So they are just using the rain at the point where the rain falls and they're only using green water. But in other countries, we have systems where animals are fed on crops which have been irrigated. So in that case, we're taking the blue water to grow the crops like maize, silage, and then feeding those to animals. The different methods of farming make a massive difference to the amount of blue water you have to pump out of rivers, lakes and aquifers to produce the cow food. So in the UK, we have an average for animal production of about 67 litres per kilogram of beef of blue water consumption. But there are some figures that from the US, from Texas, Oklahoma, and Kansas, ranging from 900 through to almost 8,000. That figure we're looking at, that 15,000 litres of water are needed for each kilogram of beef includes all types of farming and all the types of water. It's a weighted average of the water use across all the different beef production systems the researchers analysed. And 94% of that figure, more than 14,000 litres of water, is green water. It's rain falling on grassland or other crops. This says Tim, makes it pretty useless if you're using the number to think about how good or bad eating beef is for the environment. As with coffee in the rainforest, it's unclear whether it's a good or bad thing. So if we want to make choices about sustainable diets, we want to make choices about is this product having more impact on the water environment than that product, then we shouldn't be including the green water. That's very misleading. At the same time, the 15,000 litre claim also averages out the blue water part, which as Tim said earlier can range from less than 100 litres to many thousands. The average is about 500 litres, but that hides the bit that potentially matters most in terms of the impact on water supplies. All of which means you can't use the global water footprint to say that beef is bad. And when mess Finn sees his numbers used like that, it makes him uncomfortable. There is a disappointment of the misuse of numbers. That's clear. The disappointment also goes back to myself where did I do my job very well and explain the numbers and the story behind it. That's it for this week. Thanks to mess Finn Meakinan, Mark Mulligan and Tim Hess. If you've seen another you think we should take a look at, email us on more or less at bbc.co.uk. Until next time, goodbye.
