PATAGONIA, Ariz.

THERE was a frost expected here two weeks ago, but Gary Paul Nabhan, a conservation biologist and inveterate seed-saver, was out in his hardscrabble garden anyway, planting his favorite food, hot chilies.

Chiltepin, chile de árbol (the one that scrambles up trees), Tabasco, serrano, pasilla, Chimayó. These are only a few of the pungent peppers that Mr. Nabhan and two other chili lovers — Kurt Michael Friese, a chef from Iowa City, and Kraig Kraft, an agro-ecologist studying the origin of hot peppers — collected on a journey that began two years ago, in northern Mexico, and took them across the hot spots of this country.

In a van dubbed the Spice Ship, these three gastronauts set out to talk to farmers dealing with the effects of climate change on their crops, especially chilies, both wild and domesticated. Their collective tale, “Chasing Chiles: Hot Spots Along the Pepper Trail,” spiced up with recipes vetted by Mr. Friese, was published last month by Chelsea Green.

And now Mr. Nabhan was putting in his favorite chilies, all started from seed, beneath heirloom fruit trees like a two-year-old San Michel quince from the San Rafael Valley, a few hills over, and a Texas Mission almond, which has been grown for centuries from here to Southern California. He shares this hilly five-acre spread, ringed by the Patagonia Mountains, with his wife, Laurie Monti, a nurse practitioner turned anthropologist, whose desert herbs surround their adobe house.