5 questions to the scientist Markus Berger (PETA-Interview):



Mr. Berger, you deal intensively with the topic of “water footprints”. How many liters of water do you need to produce 1 liter of milk and why?


The water footprint for milk includes, on the one hand, the direct consumption of the cow and milk production - i.e. the water that the cow drinks, that is used for cleaning in the cowshed and that is consumed in the dairy. On the other hand, we also take into account the water that is used for the artificial irrigation of the forage plants. On average, we come to a water consumption of 15 liters of water per liter of milk. If the water that is polluted by milk production is also taken into account - especially by washing out fertilizers in agriculture - the result is a water footprint of 150 liters per liter of milk. If the rainwater is also counted that the forage plants of the cows (grass, maize etc.) evaporate, one would even arrive at a water footprint of 1,000 liters per liter of milk. However, we consider such a view to be dubious, since rainwater is also evaporated from natural ecosystems.




Not all water is the same - how should you weight water so that the calculation is really realistic? Because it makes a difference whether water is consumed in Northern Europe or z. B. in southern Spain or Africa.


That's right. A water footprint that only adds up the liters is incomplete, as volumes do not say anything about the resulting consequences. We therefore use local weighting factors that state how “bad” water consumption is in a particular region. In addition to local water scarcity, it also takes into account the prosperity of the population, for example. This is important because z. B. the water shortages in southern Spain and Somalia are comparable - unfortunately the resulting consequences for the people are not.




How important is it for the future that people develop an awareness of the “water footprint”?


I think it is important that consumers learn that even the production of simple foods, such as milk, can have relevant effects in different parts of the world. Perhaps that too can help reduce food waste and discarding. The impressive number of liters of the water footprint can certainly help to raise consumer awareness of the problem.




Of course, the production of vegan foods also uses water. What can consumers pay attention to in everyday life in order to manage or achieve the best possible water balance?


Vegan foods do not achieve the extremely high water footprints of meat (e.g. 15,000 liters per kilo of beef); however, their effects can be critical. 95% of the water consumption of beef results from the evaporation of rainwater during the cultivation of forage crops in predominantly water-rich countries. For the irrigation of tomatoes from Spain or nuts and pistachios from Iran, on the other hand, valuable groundwater is used in extremely water-scarce areas. (...) Conscious shopping of vegan products is required here in order to achieve a good water balance.


The recommendation „Seasonal & Regional“ applies. So if you make sure when buying your food that it is local food that is produced in the respective season, you can make an important contribution to climate and water protection.




Which message is particularly close to your heart on the topic of your doctoral thesis? What would you like to tell our readers?


A “message” might be applied a bit thick. With more than 1 billion people who do not have access to clean drinking water, I would like to point out the large amounts of water used to make our daily products. We are also working on evaluating the local consequences of water consumption more precisely. In this way, we want to give decision-makers in politics and industry the opportunity to analyze the effects of water consumption in global value chains. Hopefully this can help to identify critical water consumption in water-scarce areas of the world and to take targeted measures. Companies should perhaps pay less attention to saving the last liter of water in Germany, but rather support efficient technologies at suppliers in water-scarce countries. But it would also help if everyone pays attention to local and seasonal tomatoes, apples and other vegan products ...






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