Nuts and seeds might be grouped together on MyPlate, but they are far from similar in their water use. Sprout co-editor Sam Jones explores the differences in water needs between these tiny snacks.
Water is essential for growing food. Most of the world’s farmland gets its water requirements from rainfall or recycled water, but a significant proportion of our food supply is irrigated with water from lakes, rivers, reservoirs, and groundwater. Globally, agriculture accounts for 85% of all water use. These water sources are being depleted at a faster rate than they can be naturally replenished, which means we could eventually run out of fresh water.
Tree nuts are one of the most water-intensive crops grown in the United States per unit of output. Almonds are scattered across headlines as bee-killers and water-guzzlers for their somewhat unique characteristics of production. However, almonds—and all nuts—are lumped together in dietary recommendations alongside another tiny crop: seeds. But while nuts and seeds are lumped into the same food category, they actually have very different impacts on water use.
According to one study, pumpkins, squash, and watermelons only use an average of 100 m3 of water per ton. But that’s for the entire edible plant, not just the seeds. On the flip side, tree nuts use thousands of m3/ton each growing season, just for the nuts. Cashews use nearly 1,400 m3 of water per ton while pistachios use roughly six times that amount. Almonds, walnuts, and hazelnuts fall in the middle, ranging from 1,400 m3/ton for unshelled hazelnuts to 6,800 m3/ton for shelled almonds.
Where the water use of nuts and seeds is comparable is with peanuts to sunflower seeds. Peanuts use an average of 380 m3 of water per ton compared to roughly 350 m3/ton used for sunflowers.
Most sunflower seeds, while comparatively low water users, are grown in North and South Dakota, which have experienced high water stress levels recently. However, most of the watermelon and pumpkin grown in the US come from states with relatively low water stress levels. Similarly, 99% of the US’s hazelnuts are grown in the lush Willamette Valley in Oregon while most of the US’s peanuts come from southern US states, namely Georgia, that do not appear to be water-stressed either.
However, the intense water use required of tree nuts is particularly environmentally degrading because of where most of them are grown. Here in the United States, California is the largest producer of food, and of nuts in particular, but has also been repeatedly stricken with droughts in recent years. A regular and dependable supply of water increases crop yields and food security, making repeated droughts in our nation’s “breadbasket” especially alarming. Water-stressed California produces 82% of the world’s almonds, 98% of the US’s pistachios, and 99% of the US’s walnuts — the three most water-intensive nuts on the market.
When needed in high quantities, like for growing tree nuts, water is sometimes diverted from natural ecosystems that house salmon populations, among many other species. These species have faced an increased incidence of disease and lower fertility rates as a result of low water levels in their rivers and streams.
Some tree nut growers are also taking water from their neighbors. When groundwater is diverted to irrigated tree-nut orchards throughout California, that water cannot be used for other nearby crops. While most farmers have a legal right to extract the water that abuts their land, groundwater is technically a shared resource. With wells on various farms all tapping into the same supply and little regulation on groundwater extraction limits in California, there are few incentives for water conservation.
Because some farmers don’t have access to the scarce water supply, they have to leave their land fallow (without anything planted) during the winter, which enables soil erosion from wind and water runoff. Soil naturally regenerates, but not as quickly as it is being washed or blown away in many parts of the country. Leaving fields bare and exposed to the elements is one of the leading causes of soil loss in the U.S. By degrading the soil we have today, we may not have enough soil to grow food for future generations.
Every time we buy food, we impact the environment in one way or another. Nuts and seeds are tiny yet mighty foods that provide only a small portion of the overall calories in the US food supply. But by equating them when we make dietary choices, we fail to separate their impacts on the environment. In terms of water use, these differences can have significant effects on the planet for current and future generations.
Sam Jones is the co-editor of the Friedman Sprout and is interested in the environmental impacts of our food choices. She currently works as the Nutrition Communications Intern at 88 Acres.