Climate adaptation: match crops to climate

The megadrought in the West is a time of reckoning for farmers. In an August 5, 2022 Op Ed in the Arizona Republic, Joanna Allhands wrote

The West must rethink farming to save it. That means we’re going to have to rethink how we farm if we want to maintain even a scaled-back presence in the West. And, no, there will be no silver bullet for how we do that.

California is in a better position than western desert states, because some areas of the state have adequate rainfall.

Source: Western Regional Climate Center

For California, the problem is not so much growing water-intensive crops, but growing them in the driest areas in the state. The arid scrubland on the southern floor of the San Joaquin Valley gets about 7-8 inches of rain on average. The farmland in this region was traditionally used for grazing and low-water use crops such as winter wheat.

Following the completion of the Central Valley Project and the State Water Project, there was a huge expansion of agriculture. The land in the western San Joaquin Valley was relatively inexpensive, and huge tracts became available when the oil companies divested in the 1990s. The 2000s saw a continued boom in agricultural productivity, farmland value, and farm income. But the boom has been unsustainable.

The expansion of permanent crops has increased farm income, but has also been a major cause of groundwater depletion. According to tables from the Cal Poly Irrigation Training and Research Center, almonds in the western San Joaquin Valley need about 45 inches of water in a dry year, and with cover crops, they need about 55 inches. In this very dry region, all but 7 to 8 inches of this water must come from irrigation.Even in normal years, very few growers get that much surface water. Most get less than two acre feet per acre. So the growers put in wells and pump 1-2 acre feet of water a year, and twice that amount in droughts. Alfalfa, which is grown to feed dairy cows, is equally water intensive. The result has been an enormous drawdown in groundwater in the area, even before recent droughts.

Natalie Hansen recently wrote about West Goshen, California, “one of the key battlegrounds where residents say irrigation and overpumping have depleted drinkable water.” Hansen quotes Nataly Escobedo Garcia, policy coordinator at Leadership Counsel for Justice and Accountability:

Nobody is saying we need to get rid of all agriculture. We want to see it done in a way that does not come at the expense of their water.

As the table above shows, better crops for the arid San Joaquin Valley include grains and grain hay, as well as vegetables. A PPIC study by Caitlin Petersen et. al. found that winter wheat could be established with only 4 to 8 inches of supplemental irrigation. Petersen wrote of the benefits of winter grain crops:

Fallowed land must be tilled multiple times a year to tamp down noxious weeds, at a cost to both the landowner and air quality (tillage operations can be large sources of dust). Water-limited crops could generate some revenue while keeping agricultural land operational should water conditions become more favorable.

Growing winter cereals also helps with soil conservation. Leaving standing residue in the field after harvest can reduce dust emissions and conserve soil water during the hot, dry summer months. A winter crop also improves rainfall capture by aiding water infiltration. This directly benefits both the grower and the broader public.

Growing grain crops may also become increasingly important for US food security. In addition to geopolitical shocks, such as we have seen with the war in Ukraine, risk analysts are projecting increasing impacts of climate change on global wheat production.

A 2021 study by UK researchers Daniel Quiggin et. al. found that by 2050 “more than 35% of the global cropland used to grow [wheat and rice] could be subject to damaging hot spells.” A 2019 risk study by European researchers Miroslav Trnka et. al. found that, by the end of the century, global warming could cause simultaneous, major droughts in 60% of wheat-growing areas around the world.

In conclusion, changes to more sustainable crop patterns in California are essential not only for bringing surface and groundwater use into balance, but are important for future food security.

This blog post is updated from one originally published in April 2015.

Allhands, J. 2022. How many farms can Arizona and California lose before we feel it at the grocery store? Arizona Republic. August 5, 2022.

European Commission. 2022. Food Security crisis: 17 ways the EU is stepping up for people. June 16, 2022.

Hansen, N. 2022. A battle for safe drinking water grows heated amid drought in California’s Central Valley. Courthouse News. August 6, 2022.

Petersen, C. 2022a. Commentary: Can San Joaquin Valley Agriculture Survive with Less Irrigation? Here Are Ways To Do It. Fresno Bee. July 29, 2022.

Petersen, C. Pittelkow, C., Lundy, M. 2022b. Exploring the Potential for Water-Limited Agriculture in the San Joaquin Valley, Public Policy Institute of California, July 2022.

Quiggin, D., De Meyer, K., Hubble-Rose, L., Froggatt, A. 2021. Climate change risk assessment 2021: The risks are compounding, and without immediate action the impacts will be devastating. Chatham House. September 2021.

Trnka, M., Feng, S., Semenov, M., Olesen, J., Kersebaum, K.C., Rötter, R., Semerádová, D., Klem, K., Huang, W., Ruiz-Ramos, M., et. al. 2019. Mitigation efforts will not fully alleviate the increase in water scarcity occurrence probability in wheat-producing areas. Sci. Adv. 5(9). Sept 25, 2019.

Vrana, D., 1995. Chevron Agrees to Sell Land Holdings Worth $400 Million : Real estate: Sale of portion of oil company’s California properties would be one of the largest in recent history. LA Times, October 10, 1995.