Which foods have the biggest water scarcity footprint?
From your burger to your tomato, water powers every aspect of food production. What foods have the biggest water footprint, and is this a good way to measure the impact of our food?
Water scarcity refers to a low volume of available water in a region. When we think of what contributes to water scarcity, we might think about how much we drink, or how much water we use in the shower. But 70% of all freshwater withdrawn is used in agriculture.
The amount of water required to create and deliver a food product through its entire supply chain is termed its water footprint. Different foods have different water footprints, and they may be higher depending on location – for example, it will take more water to grow crops in very dry areas versus very wet areas.
A high water footprint isn’t always critical – in areas which aren’t as affected by water scarcity, high water footprints will have less of an impact on water resources, but as we face a global water crisis, the concept of a water footprint can be helpful in making informed choices about which foods we want to grow or buy based on their impact on water systems.
Meat and dairy have big footprints
Not only do farmers have to use water for their cattle to drink, and to clean out housing, but also to grow food for those cattle to eat. Feedcrops like grass and grain use around 98% of all fresh water used in animal farming. Beef, for example, requires around 2,741 litres of fresh water per kilogram of meat produced; for pork the number is around 1,800 litres.
When considering dairy products, we have to add in the water used in processing milk. Cheese production requires around 5,605 litres of water for every kilogram of cheese – that’s twice as much as beef meat.
Through the lifetime of animals, and the processes required to turn animal products into consumables, the water footprint builds and builds.
Nuts: among the world’s most water-intensive crops
It’s not just animal products which require a lot of water. Though it is perhaps less well-known, nuts are among the most water-intensive foods grown in the world. On average, 4,134 litres of fresh water are used per kilogram of nuts harvested.
Nut milks have become popular in recent years, but their production requires large volumes of water. Consider the almonds which go into almond milk: one study found that a single almond grown in California requires 12 litres of water, while groundwater levels in the central valley, home to most of California’s almond farms, have decreased massively over recent years.
Reducing the water footprint of rice
Half the world’s population depends on rice as a staple food, but rice is among the thirstiest staple crops. It requires around 2,248 litres of fresh water per kilogram produced. One reason is that rice plants are usually almost completely submerged in water while growing. But new innovations in rice growing suggest it can thrive without as much water, which would drastically reduce its water footprint.
Should we stop producing these foods?
Not all food water usage is equal. Meat, for example, uses a lot of water, but it also provides high nutritional value per gram for those who consume it. It takes around 500 litres of fresh water to provide 1000 kilocalories in the form of beef, while in the case of tomatoes, to deliver the same nutritional energy would require 3.5 times as much water.
Some crops provide a much higher nutritional return for their water use. Among them are some of the most widely-consumed foods in the world: to provide 1000 kilocalories, tofu requires just 55 litres of water; maize uses 48 litres, and barley just 3 litres.
The future
We will always need food, and food production will always need water. We can, though, think carefully about which crops and animal products are most efficient in terms of the energy produced for the water volumes used. We can also embrace new sustainable technologies and crops which reduce water use, to help reduce the impact of farming on wider water systems.
