That’s mainly because they’re a voraciously thirsty crop. Unesco’s water “footprint” data says nuts need 139 litres per gram of protein, compared with milk at 31 litres, sheep protein at 63 litres and beef at 112 litres. (New Zealand beef takes 67 litres per gram.)
The protein-yield gap closes up a little when the water use of crops grown to feed livestock is factored in, but given their thirst and requirement for consistent high temperatures, tree nuts are not yet a magic bullet for global food production. As plant protein, they’re outgunned by the drinking habit of humble legumes – beans and peas – of 19 litres per protein gram.
Still, the world appetite for tree nuts is growing, alongside anxiety about how best to supply this densely nutritious food more sustainably. Figures reported to the United Nations show world consumption grows several percentage points every year, with more than 2.2 million tonnes now traded annually. It’s a lucrative crop but overwhelmingly feeds wealthy and moderately wealthy countries – often at the expense of the low-paid workers who tend and harvest them. Increasing efforts to improve labour conditions are likely to make them more expensive rather than more accessible as a staple food.
The dominant producers are the United States (almonds), China (walnuts), Turkey (hazelnuts) and India (cashews).
The UN has a global programme to foster more sustainable production, along with raising labour conditions among nut growers. This is yielding some sustainability improvements, such as in US pecan production, where new varieties are enabling production with 30% less water. Husks are being converted to cattle fodder and electricity, and agricultural waste water is being recycled back to the orchards as irrigation. There’s also increasing use of solar-powered processing.
But agri-business researcher Jacqueline Rowarth says it’s a long complex mission to grow nuts more sustainably. An emerging problem is the effect of monoculture, with evidence that California’s heavy almond production, which depends on honey bee pollination, has made the insect less able to survive. It is thought the state’s high rate of colony collapse is down to bees needing access to more than just almond blossoms to remain healthy.
Rowarth says despite abundant water, New Zealand is not likely to be a major nut producer any time soon, because its climate is not suitable, other than in small cottage-industry-sized pockets.
She says we might be able to expand further into legumes, depending on the success of a new large-scale cherry-planting programme in Central Otago, as both crops enjoy similar conditions. But for the foreseeable future, our successful crops of almonds, macadamias, walnuts and chestnuts (more of a fruit, with considerably less protein than a nut) will come in boutique- rather than commodity-sized batches.
This article was first published in the October 5, 2019 issue of the New Zealand Listener.