A decade ago, Mexico's national water agency hosted a climate and water conference in Mexico City. The director general of the agency opened the conference with words I'll never forget: "Climate change is the shark in our future, and water is its teeth."
At the time, I was leading the global water program of The Nature Conservancy and was well aware of the role that climate warming was playing in reducing river flows and impacting the habitats of freshwater species around the globe. In recent decades, those of us living in water-scarce regions have become much more attuned to the impacts of declining water supplies on the water needed to sustain our cities and farms.
The climate shark has been taking some vicious bites out of farmer livelihoods and food security as farms have repeatedly been cut off from irrigation supplies. In a new paper just published in Nature Water, we describe many of these water shortage events globally. We then take a close look at how six farming regions in the western US have changed in recent decades and assess how they can better adapt to lessened water supplies as the climate continues to warm.
We found some very surprising - and hopeful - trends in recent decades. Water consumption decreased in four of our study regions even while farmer revenues increased. In the Rio Grande of Colorado and New Mexico, water consumption went down by 45% during 2000-2019 while farm revenue grew by 24%. In the Lower Colorado River in California and Arizona, farmers consumed 18% less water but earned 34% more. Much of the increased revenue resulted from a doubling of the prices paid for alfalfa, a crop in great demand in the expanding dairy industry in the region.
But there are also some dark undercurrents in the trends we observed. Water shortages and other factors caused a lot of farmland to go out of production in our six study areas; the total irrigated area decreased from -3% in the Lower Colorado River to -44% in the Rio Grande. While the irrigated area of profitable crops such as alfalfa or nut crops (e.g., almonds and walnuts) increased, there simply was not enough water to irrigate other important food crops; durum wheat production along the Lower Colorado River dropped by 70%, for example. Some of the other crops most exposed to severe water shortage risks include tomatoes, apples, rice, grapes, and oats.
Increasing the production of water-intensive crops such as alfalfa or almonds in water-stressed farming regions may be lucrative but it is obviously a risky business venture. Within the western US, a third of alfalfa production and two-thirds of almond production is taking place in areas of high to severe water scarcity. Those findings caused us to ask: "What would an optimal mix of crops look like in this increasingly water-scarce region?"
Our results were very encouraging, and we hope they shed light on possible ways forward. We found that substantial reductions in water consumption - a critically important adaptation as water becomes more scarce - were possible, ranging from 28-57% less water required. Importantly, we constrained our analysis to be as practical and realistic as possible. For instance, we didn't allow farm profits to decrease as we changed crop mixes, and we didn't introduce any crops that weren't already being grown in each of our six study areas (although many alternative crops would make our projections even more exciting).
It is also important to note that water reductions of this magnitude are possible only when changes in crop mixes are combined with transforming some portion of existing farmland into other purposes, such as solar or wind production or habitat restoration, as is happening in the Central Valley of California. In many water-scarce farming regions, the size of the existing agricultural footprint - whether measured as irrigated area or water demands - is simply too large to sustain under climate changes that are reducing water availability. We argue that it is far better to thoughtfully plan these necessary farm transitions rather than to allow water shortages to increasingly wreak havoc on farm families and food security. Federal crop insurance payouts - which have increased six-fold in recent decades - have been an important pain reliever for many farmers but their increasing burden on taxpayers is not sustainable over the long term.
We readily acknowledge that transforming farm landscapes will require overcoming many obstacles, such as ensuring that markets, supply chains, and the farm labor force can facilitate these transitions. We are also concerned that the consequences for certain businesses such as seed or equipment providers could be severe and disruptive to local economies if not managed carefully. The options suggested by our optimizations are not prescriptive but instead are intended to reveal possible adaptive futures. Financial incentives and carefully planned transitions will be essential. But making cropland less vulnerable to water scarcity is a sensible national investment in a time of great water urgency.