Ancient Black Pea Holds Promise for a Warming Himalaya

Ecologist Harman Jaggi first visited India’s cold desert Trans-Himalaya mountains to study snow leopards. But while climbing the steep, rocky slopes above the tree line, something else caught her attention: the black pea and barley powder that local hosts offered her to mix into tea. “It would sustain us for hours,” recalls Jaggi. Years later, she came back—to study the peas.

In the Spiti Valley, up above 13,000 feet, most families farm for a living, and transitioned a generation ago from subsistence farming to growing commercial crops like green peas. But for their own communities and monasteries, some still cultivate traditional foods with a 3,000-year local legacy, including barley (Hordeum vulgare) and a local variety of black pea that lacks a scientific name. Prized for centuries as a source of superior nutrition and sustained energy, these black peas are an integral part of traditional recipes like Tsampa, ground barley and black pea, stirred into soups or butter tea. Nearly a decade after first encountering the crop, Jaggi and fellow researchers have published a new study in Science Advancesexamining the genetic diversity, ecological traits, and dietary value of black peas for the first time.

“Black pea 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 Dr. Jaggi, the study’s lead author and a postdoctoral researcher working with Simon Levin and Jonathan Levine at Princeton University’s High Meadows Environmental Institute. “One of our findings was what the local farmers knew all along – that, when compared to introduced cash crops like green peas, the traditional black peas are more ecologically resilient and more nutritious.”

Scientists generally agree that peas, first grown around 10,000 years ago in the Fertile Crescent, can be classified into two species, one domesticated and one wild. But the new study, which provided the first whole genome sequencing data for Himalayan black peas, suggests that they form distinct genetic clusters from wild germplasm and domesticated varieties, “highlighting a complex cultural and environmental selection over thousands of years,” explained Jaggi.

The research team examined whether black peas were better adapted to the local climate, a question of outsize importance as the region receives significantly decreased snow, due to climate change. These rangelands and mountains, along with the Tibetan plateau, are known as the Third Pole, the world’s third-largest repository of freshwater and glacial ice after the Arctic and Antarctic. Farmers have traditionally irrigated crops through water channels called kuhls, built alongside mountains to divert snowmelt from glaciers to fields. But in recent decades there has been a significant decrease in snow cover—and thus in irrigation—leading to increasing crop failure.

Black peas prove resilient in this changing climate. Across sites at three elevations and with varied watering treatments, the traditional crop showed a higher probability of survival and more successful traits. The results corroborated anecdotes from farmers, who have consistently found that black peas outperform green peas, even as they require less water.

“Local farmers say black peas are easier to grow and less vulnerable to vagaries of climate change,” Jaggi explains. “However, hardly anyone outside this valley knew about them. With our collaborator Kulbhushansingh Suryawanshi from Nature Conservation Foundation, 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 black peas – called sanmoh nako or dhoopchum in Tibetan. Jaggi and colleagues collaborated with three villages to set up field study experiments on working farms. “Local farmers, who have generations of knowledge, gave crucial input and expertise on the experiment and co-authored the paper,” Jaggi said. They’ve perfected techniques for raising the crop in this unique climate. Growing practices that might work for green peas in, say, the floodplains of India, would not have worked for black peas in the cold, dry desert ecosystem of the Trans-Himalaya.

While only 10 percent of the families were still growing the traditional crop, many told Jaggi that they would like to plant more, if the crop had market demand beyond their valley. According to census data, many of these farmers earn just $2,300 USD per year.

The traditional crop is nutritionally superior, too. The researchers drew up a nutritional profile of black peas in collaboration with India’s Central Food Technological Research Institute. Compared to green peas, black peas are richer in protein – boasting 21 percent per 100 grams – and higher in fiber, magnesium, calcium, iron and Vitamin C.

Jaggi conducted this research with her PhD advisor Shripad Tuljapurkar, Dean and Virginia Morrison Professor of Population Studies at Stanford, and senior author of the study, whose work has long examined how human demography relates to environmental and climate-related challenges. “Harman conceived and carried out a wonderful combination of ecological and genetic studies,” said Tuljapurkar.

The study authors emphasize that black peas could be a valuable genetic reservoir, even potentially what’s known as a “crop wild relative,” that could enhance other crops, equipping them to withstand increasing heat and drought stress.

They also recommend the Trans-Himalayan farming systems for recognition within the Nationally or Globally Important Agricultural Heritage Systems (NIAHS or GIAHS). The landscape is home to incredible biodiversity, including snow leopards, wolves, red foxes, Asiatic Ibex, 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.

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.

“This work is path-breaking in many respects,” said Tuljapurkar. “I think our results are promising for the study population and also suggest many extensions to other populations that are balanced between traditional and modern lifestyles.”

Perhaps this nearly-forgotten pea from the past could help support these communities in the future.