Some of America's favorite produce crops may need to get a move on by 2045

August 25, 2020

Record drought and heat have some farmers worried about where and when crops can be grown in the future, even in California where unprecedented microclimate diversity creates ideal growing conditions for many of the most popular items in America's grocery stores. A third of the vegetables and two-thirds of fruits and nuts consumed by Americans are now grown on more than 76,000 farms across the state, yet 20 years from now certain California regions may simply become too hot and dry for continued production.

New research from Lawrence Berkeley National Laboratory (Berkeley Lab) shows that by the years 2045-2049 future temperatures will have more of an effect on when cool-season crops, such as broccoli and lettuce, can be grown than on where, while for warm-season crops (cantaloupe, tomatoes, carrots) the impact will be greater for where they can be grown versus when. The scientists describe pairing computer modeling with information about historic and ideal growing temperatures for five important California crops in their paper, "Projected temperature increases may require shifts in the growing season of cool-season crops and the growing locations of warm-season crops," which appeared in the journal Science of the Total Environment earlier this month.

"To ensure food security for California and the rest of the country, it's important to predict how future warming will affect California agriculture," said the paper's lead author Alison Marklein. "We need reliable information about how future climate conditions will impact our crops in order for the agricultural system to develop an adequate response to ensure food security. For instance, one major challenge when considering relocating crops is that growers have specialized knowledge of their land and crops. If crops can no longer be grown in their current locations, then the farmer has to either move to a new area or grow a different crop, which presents a practical and economic burden on the farmer."

Now a scientist at UC Riverside, Marklein had previously led the project while completing a postdoctoral fellowship at Berkeley Lab and collaborating with Peter Nico, a study co-author and staff scientist in Berkeley Lab's Earth and Environmental Sciences Area. Scientists from the U.S. Department of Agriculture and UC Davis also contributed. Funded by the University of California's Global Food Initiative, the research represents a significant research focus for Berkeley Lab: sustainable agriculture. Another current Berkeley Lab study applies machine learning to developing microbial amendments that could replenish soils depleted of nutrients like carbon and phosphorus.

Growing accustomed to climate extremes

In carrying out the study, the researchers first selected five annual crops that are produced more in California than any other state - lettuce, broccoli, carrots, tomatoes, and cantaloupe. These nutrient-dense crops contributed 64% of the state's cash value of vegetable and melon crops in 2016 and are essential to food security, as evidenced by their place among the top vegetables and fruits donated to four studied California food banks.

The team then obtained 15 years of air temperature data beginning in 1990 from locations across the state, as well as information about crop temperature thresholds - or maximum and minimum air temperatures beyond which crop failure occurs - and growing locations for each of the five crops going back seven years. They also considered a crop's optimal growing-season length: for example, broccoli requires four consecutive months of minimum 39 degrees Fahrenheit and maximum 95 degrees.

Setting out to compare how each crop would do across California under different possible climate scenarios, one hot-dry and another cool-wet, the researchers looked at how higher temperatures may affect the crops in their historical growing locations. Next, they identified possibilities to expand any crop to a more ideal growing location based on that crop's temperature threshold, looking at all areas where that crop has not been grown, even where land had not previously been used for agriculture.

Finally, the team calculated how much of the land historically used for growing each of the five crops can be maintained under future warming scenarios (hot-dry, cool-wet); how much of the land used would be untenable due to temperature rise; and how much land not formerly used for agriculture could potentially support each of the five crops in comparison to historical agricultural land where these crops have not yet been grown.

Tomatoes could face some growing pains

"We found differences in how warmer temperatures will affect the cool-season crops versus the warm-season crops," Marklein said. "For cool-season crops like broccoli and lettuce, it may be possible to extend their growing seasons. But it may become too warm to grow warm-season tomatoes where they have been historically farmed in summer, and may require moving them to milder climates warm enough for growing tomatoes under the new climate scenarios."

The team found that both cool-season crops, broccoli and lettuce, are currently grown nearer to their lower temperature thresholds during fall and spring. The climate models predict an increase in winter temperatures above the minimum temperature threshold for both crops, suggesting that by mid-century these crops could also be grown into winter, even in areas where they have not historically been grown.

The warmer temperatures in fall and spring suggest that tomatoes might benefit from a shift in growing season. But that could prove harder than it appears.

"Looking at the hot-dry future climate scenario, although temperatures in fall and spring are likely to increase as will summer temperatures, a shift in growing season isn't a viable solution because the summer temperatures are likely to exceed the critical temperatures for tomatoes," Marklein said. "Tomatoes need four consecutive months for their growing season, so the gap in the middle filled by summer makes this unfeasible."

Opportunities could crop up all over

While it's true that some of the crops studied, tomatoes especially, will lose areas where they have been traditionally farmed due to future warming, there could be some ways to mitigate these potential challenges. For example, because their analysis focused on air temperature rather than crop temperature, in practice irrigation may be able to reduce some negative heat effects.

In total, Marklein said this study gives agricultural planners a lot to think about. "This is really a first step in planning for future climate scenarios. This work could be used to help prioritize resources like cropland and water to maximize agricultural productivity and food security," she said. "It's critical to plan ahead for future warming scenarios, particularly in areas like California that feed the nation."
-end-
Founded in 1931 on the belief that the biggest scientific challenges are best addressed by teams, Lawrence Berkeley National Laboratory and its scientists have been recognized with 13 Nobel Prizes. Today, Berkeley Lab researchers develop sustainable energy and environmental solutions, create useful new materials, advance the frontiers of computing, and probe the mysteries of life, matter, and the universe. Scientists from around the world rely on the Lab's facilities for their own discovery science. Berkeley Lab is a multiprogram national laboratory, managed by the University of California for the U.S. Department of Energy's Office of Science.

DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science.

By Christina Procopiou

DOE/Lawrence Berkeley National Laboratory

Related Agriculture Articles from Brightsurf:

Post-pandemic brave new world of agriculture
Recent events have shown how vulnerable the meat processing industry is to COVID-19.

Agriculture - a climate villain? Maybe not!
The UN's Intergovernmental Panel on Climate Change (IPCC) claims that agriculture is one of the main sources of greenhouse gases, and is thus by many observers considered as a climate villain.

Digital agriculture paves the road to agricultural sustainability
In a study published in Nature Sustainability, researchers outline how to develop a more sustainable land management system through data collection and stakeholder buy-in.

Comparisons of organic and conventional agriculture need to be better, say researchers
The environmental effects of agriculture and food are hotly debated.

EU agriculture not viable for the future
The current reform proposals of the EU Commission on the Common Agricultural Policy (CAP) are unlikely to improve environmental protection, say researchers led by the German Centre for Integrative Biodiversity Research (iDiv), the Helmholtz Centre for Environmental Research (UFZ) and the University of Göttingen in the journal Science.

Global agriculture: Impending threats to biodiversity
A new study compares the effects of expansion vs. intensification of cropland use on global agricultural markets and biodiversity, and finds that the expansion strategy poses a particularly serious threat to biodiversity in the tropics.

A new vision for genomics in animal agriculture
Iowa State University animal scientists helped to form a blueprint to guide the next decade of animal genomics research.

New pathways for sustainable agriculture
Diversity beats monotony: a colourful patchwork of small, differently used plots can bring advantages to agriculture and nature.

The future of agriculture is computerized
Researchers at the MIT Media Lab Open Agriculture Initiative have used computer algorithms to determine the optimal growing conditions to improve basil plants' taste by maximizing the concentration of flavorful molecules known as volatile compounds.

When yesterday's agriculture feeds today's water pollution
Water quality is threatened by a long history of fertilizer use on land, Canadian scientists find.

Read More: Agriculture News and Agriculture Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.