California provides the majority of specialty crops – including fruits, vegetables, and tree nuts – for the United States and projected climate change is likely to threaten agriculture in this region. We addressed the impact of changing local temperatures on the viability of five major specialty crops in California: broccoli, carrot, cantaloupe, lettuce, and tomato. We compared where each crop has been grown in California between 2007 and 2015 (NASS Cropland Data Layer) with published temperature optimums and seasonality of each crop in different regions of California (UCANR Crop Reports). Next, we used thermal envelope modeling to estimate the effects of predicted climate change on the distribution of crops based on cool-wet scenarios (CNRM-CM5) and hot-dry scenarios (HadGEM2-ES365) for mid- and end-century with RCP 4.5 and RCP 8.5 (Multivariate Adaptive Constructed Analogs), which we compared with current temperature ranges (PRISM). We defined a range of projections based on the most and least optimistic scenarios for each crop and calculated the total change in temperature envelope and the percent of current range that remains unchanged.
Results/Conclusions
Our results predict that the temperature envelopes of these five crops will likely increase, with the geographic shift being quite significant for some crops. Tomatoes are most sensitive to temperature change, as the models predict that the current temperature range will be reduced by 11.5% (+/-5.1%), but predict that the total temperature envelope will increase by 17.5% (+/- 7%). Cantaloupes are the least sensitive, as the models predict that cantaloupe’s current temperature range will not significantly change (1.0%+/-5.3%), but the models predict the total temperature envelope to increase by 50.5% (+/-27.1%). The current growing areas for broccoli, carrot, and lettuce are projected to decrease slightly by 4.3% (+/-3.0%), 6.2% (+/-2.1%), and 2.6% (+/-1.9%), respectively, with total area increases of 6.3% (+/-3.5%), 10.6% (+/-3.3%) and 0.1% (+/-2.3%), respectively. While we predict the spatial extent of optimal temperature ranges for many of the crops to expand, the agronomic viability of the expanded range depends on many other factors, including water availability and soil quality. Our results indicate that specialty crops are sensitive to changing temperatures, and highlight the importance of new research into developing heat-tolerant varieties and management techniques and understanding the effects of climate change on crop yield and nutrition.