Dried tepary beans from 2014. Tepary means “it’s a bean” in the language of the Tohono O’odham people who live south of Tucson, Arizona, between the US and Mexico.

Beans are amazingly adaptable, having spread from their origin in northern Mexico to places around the world. Like many other crops, they depend on large amounts of water and moderate summer temperatures to grow. But with a warming world, they face weather extremes of high temperatures, both day and night, and increasing periods of drought across the planet. These conditions reduce bean production dramatically, posing a genuine threat to growers and consumers whose lives have already been upended by a warmer climate. The common bean is the most important protein source and dietary staple in low-income countries from the highlands of Central America to the vast expanses of sub-Saharan Africa.

Beans are threatened when overnight temperatures do not drop below 68°F (20°C). Daytime highs above 95°F (35°C) also affect plant development. Even using the best management practices—including irrigation and planting beans alongside corn plants to increase shaded, cooler areas for beans—doesn’t always compensate.

Fortunately, scientists are working on a globe-spanning project to make the common bean more resistant to heat. The secret lies in its wild ancestor, the tepary bean, which has been grown for at least 2,500 years in the hot, arid regions of the southwestern United States and northern Mexico. Due to its native habitat in the Sonoran Desert, domesticated tepary beans are considered to be the most drought-tolerant annual legume in the world. They are capable of producing a harvest of beans with a single rain in the harshest conditions.

Researchers are working to exploit the genes responsible for climate adaptivity in the tepary bean, known as Phaseolus acutifolius, and breed them into the common bean, or Phaseolus vulgaris, making cultures on petri dishes to enable pollination between two different varieties without using GMO processes.

In Nicaragua, black bean harvests were declining almost to the point of total collapse. The newly developed hybrid between tepary beans and black beans saved the day. Farmers in Nicaragua recently started cultivating one of these hybrid bean varieties and found it produced harvests twice as large as other beans that farmers were previously planting. Similar results were observed in Costa Rica.

We plant five varieties of tepary beans at Rio Del Rey, including one we developed over three years from tepary bean variants. Growing these specific varieties conserves water and produces more beans per acre than other heirloom beans. The future lies in this bean: It is heat- and drought-tolerant, grows on poor soils, and has a protein content near 24%! With continued research, the tepary bean will be a big part of the solution in our adaptation to climate change.

» riodelreyfarms.com

Make Tepary Beans with Pan-Fried Pacific Mackerel by chef Juan González of Mesa Agrícola.

Pacific mackerel is a sustainable and nutritious seafood choice—it’s also an underutilized common bycatch of commercial fishermen. Serve alongside summery tepary beans and enjoy this flavorful fish that is high in protein and omega-3s.

Adapting Beans originally published in the summer 2023 issue.

Cover image: Lauren di Matteo.
About the Contributor
Mike Reeske
Mike Reeske grows Rio Del Rey organic heirloom dry beans. For more information about heirloom beans and recipes, visit riodelreyfarms.com.