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In the high-elevation desert region of the Trans-Himalayas, most people farm for a living. In the 1980s, they largely transitioned from subsistence-based to market-oriented production of commercial crops, such as green peas (Pisum sativum L.), they could sell to other states in India.

For their own communities and monasteries, however, some farmers still cultivate foods with a 3,000-year legacy in the area, including barley (Hordeum vulgare) and a local variety of black peas that lacks a scientific name. Favored for nutrition and sustained energy, these black peas are an integral part of traditional recipes, such as soups and hot drinks.

In a new study in Science Advances, Stanford researchers examined the genetic diversity, ecological resilience, and dietary value of the black peas for the first time.

"Black peas and barley are intimately tied to the cultural, religious, and social life in the Trans-Himalayan region. That they are also climate resilient is what makes them so exciting," said the study's lead author, Harman Jaggi, Ph.D.

"One of our findings was what the local farmers knew all along—black peas are more ecologically resilient and have higher protein levels, as compared to the introduced cash crop green peas."

Scientists generally agree that peas, first grown around 10,000 years ago in the Fertile Crescent, have one domesticated and one wild species. But the new study, which provided the first whole genome sequencing data for the black peas, suggests that they form distinct genetic clusters, "highlighting a complex cultural and environmental selection over thousands of years," Jaggi said.

The research team examined whether, as compared to green peas, the black peas were better adapted to the local climate, especially as the region faces significantly decreased winter precipitation due to climate change.

Across sites at three different elevations and with varied watering treatments, black peas showed a higher probability of survival and more successful reproductive traits. This finding corroborated anecdotes from farmers, who said black peas are easier and less water-intensive to grow than green peas.

The researchers also drew up a nutritional profile of black peas in collaboration with the Central Food Technological Research Institute in India. Compared to green peas, black peas are richer in protein—boasting 21% protein per 100 grams—and high in minerals like magnesium, calcium, and iron. The peas are also a significant source of fiber and vitamins C, B1, and B3.

Promise of black peas

Jaggi first visited the sparsely populated Spiti Valley in Himachal Pradesh, India, in the Trans-Himalayas years ago to study snow leopards, a significant tourism draw for the area. While climbing the steep and rocky slopes above the tree line, she noted the lightweight black pea and barley powder that her local hosts ground and offered with tea.

"This would sustain us for hours," said Jaggi, who conducted research for the study with her advisor, Shripad Tuljapurkar, professor of biology in the Stanford School of Humanities and Sciences (H&S), and with support from the Sustainability Accelerator at the Stanford Doerr School of Sustainability.

"Anecdotally, local people would say black peas are very nutritional and less vulnerable to vagaries of climate change. But with our collaborator Kulbhushansingh Suryawanshi from the Nature Conservation Foundation, we noted that there was little science backing these claims. We were motivated to fill this gap by designing a study from a multipronged and multidisciplinary perspective."

Jaggi returned to the remote valley and interviewed over 300 residents about traditional agricultural practices, in particular, farming black peas—called sanmoh nako or dhoopchum in Tibetan.

While only 10% of the families she talked with were growing them, Jaggi learned that many more would like to if there were interested buyers and the science behind the crop's value. Many of these farmers earn as little as $2,300 per year, according to 2011 census data.

Following the 2022 interviews, Jaggi and her colleagues collaborated with three separate villages to set up field study experiments on working farms for the 2023 growing season.

"Local farmers, who have generations of knowledge, gave crucial input on the experiment and co-authored the paper," Jaggi said. "Growing practices that might work for green peas, say in the floodplains of India, would not have worked for black peas in the adverse climatic conditions and cold, dry desert ecosystem of the Trans-Himalayas."

Value and recognition

The study authors emphasize that black peas could be a valuable genetic reservoir as a potential wild relative that could enhance other crops, equipping them to withstand increasing heat and drought stress.

They also recommend the Trans-Himalayan agricultural systems for recognition within the Nationally or Globally Important Agricultural Heritage Systems (NIAHS or GIAHS). The landscape boasts exceptional cultural richness and biodiversity, including carnivores such as snow leopards, wolves, and red foxes; wild herbivores such as Asiatic ibex and blue sheep; and many species of flowering plants.

This United Nations declaration could help to safeguard the region's environment and farming practices and stimulate a market for black peas.

"This requires more research on understudied and lesser-known crops as well as integrating traditional agricultural practices," Jaggi said. "I want these findings to go back to the farmers so they can diversify their crops and not incur huge losses from continuing to grow more water-intensive green peas."

The authors hope future research will create a long-term field dataset on black peas and that their integration of traditional ecological knowledge will inspire future scientific studies. There are many benefits of that approach for local food security and global conservation efforts as climate change intensifies, they wrote in their study.

"This work is path-breaking in many respects," said Tuljapurkar, the Dean and Virginia Morrison Professor of Population Studies at H&S and the study's senior author.

"I think our results are promising for the study population and also suggest many generalizations and extensions to other populations that are balanced between traditional and modern lifestyles."