Irrigated agriculture is a pivotal practice in terms of the world’s ability to feed itself. Irrigation allows farmers to produce crops reliably in arid regions and elsewhere during extended dry periods. Even in areas with fairly regular rainfall, farmers use supplemental irrigation to maintain crops at peak condition and maximize their production.
Feeling the Pressure
In the US alone, more than half the value of crop sales comes from irrigated farms. In fact, one of the most productive agricultural regions in the world is in the Central Valley of California, an area in upheaval after years of extreme drought, only punctuated by an occasional year of flooding. A combination of intensive farming, cultivation of high value but also thirsty crops, and increasing demands on freshwater sources across the western states have squeezed natural water supplies to their limit. The mighty Colorado River, architect of the Grand Canyon, flows through seven western states in the US, supports the country’s two largest reservoirs, and powers the Hoover Dam. Today, the flow of that river has declined by nearly 20% over the last two decades.
Surface waters are not the only sources under pressure. The combination of growing, thirsty populations, high-tech industrial industry, and intensive, irrigated agriculture can draw enormous amounts of water from underground sources. California relies heavily on its aquifers and accounts for over 20% of the nation’s groundwater use, 80% of which goes to irrigation. In some locations, including California, exploitation of underground aquifers has been so devastating that the pockets themselves, where water collects, have begun to collapse in a phenomenon called subsidence. Geologists liken it to the collapse of an enormous water bottle.
As regional weather patterns change and the demand for freshwater increases, not only for irrigation, but for municipal, industrial, recreation, and environmental needs, the question of sustainability becomes ever more pressing. Yet policy makers often find themselves caught in an apparently unsolvable dilemma: How do you permanently curtail the use of water while still meeting the fundamental needs of a region? Irrigation is the largest consumer of water in large agricultural areas, but the food produced in those areas feeds the entire country, and in some cases, it feeds populations across the globe. Where is the balance?
The Game is Changing
The global demand for water has grown twice as fast as the human population in the last century. Water scarcity isn’t just a problem for a few regions or a few scattered countries -- it’s a problem on every continent where crops are grown and presents a major threat to food security everywhere. According to a study published earlier this year, the accelerating effects of weather pattern changes indicate that global agricultural water scarcity will worsen in up to 84% of croplands, with a loss of water supplies driving scarcity in about 60% of those croplands within the next 25 years.
Changes in precipitation patterns complicate scientists’ attempts to develop a viable action plan. The midwestern US and northwestern India are trending dryer, with more frequent and more intense dry periods, triggering the need for heavier and more frequent irrigation. In Northeast China and the semi-arid transitional region in Africa between the Sahara Desert and the savanna to its south, however, rainfall is expected to increase. In Africa, this may mean the emergence of a newly productive agricultural region and the need to establish infrastructure and develop farming practices that will bolster the local economy and preserve the region’s ecological health. In regions that are transitioning to arid savannah and desert, it may be time to develop a strategy that includes moving to crops that are better suited to the changes. This is a long-term process, and our thinking and actions need to be focused on the long term as well, although that’s an enormous challenge for our society.
Wait. There’s More (or Less?)
Sadly, when it comes to agriculture and food supply, it’s not just access to water or specific farming practices that are complicating the picture. Weather pattern changes are muddling entire ecosystems and that makes it impossible to get a complete picture. Not only are precipitation patterns changing, but unprecedented heat and cold waves are becoming, dare we say it: old news. Those obvious effects, though, trigger a whole series of downline changes. Dry seasons and drought are often accompanied now by extreme heat waves, which further dry out the soil, triggering wildfires that can encompass tens of thousands of acres overnight. Mild, dry winters promote increased survival rates of overwintering insects, which then move out into new territories, in search of food and water. Increased insect activity damages or destroys crops that are already stressed from heat and lack of rain, so farmers apply more pesticides, which are then washed into parched streams when the inevitable storms finally arrive. And on it goes.
In 2018, researchers at the University of California wrote that changes to the state’s climate were already so profound that the agriculture industry needed to immediately address accelerating trends like increased pest and disease pressure, crop yield declines, and increased water demands. The report even called out the question of whether some crops could even be sustained in the new reality. This is a sobering conclusion. California’s Central Valley produces ⅓ of the vegetables consumed in the US and ⅔ of the fruits and nuts. That’s an awful lot of eggs in a single basket, especially when that basket is teetering on the edge of a precipice.
