The farming town of Broo on Scotland’s Shetland Islands was no stranger to extreme weather. Located on an archipelago just south of the Arctic Circle, its inhabitants had braved lashing winds and bitter cold winters. But it was something else that did Broo in: sand. Beginning around 1665, a series of sandstorms like nothing seen before buffeted the island, burying homes, destroying fertile soil, and eventually forcing the townspeople to flee. Now, scientists think they know what caused the freak weather event—and why it left neighboring towns relatively unscathed.
People have built small farms on the nearly treeless Shetland Islands for thousands of years. They’re accustomed to windswept sand, which blows in from the islands’ long, beachy coasts. Usually, it’s a minor annoyance, but as a global cooling period known as the “little ice age” took hold in the 16th and 17th centuries, the sandstorms were unusually fierce.
Why Broo in particular suffered so much from the sands while neighboring farms survived was long a mystery. A team led by historian and archaeologist Gerald Bigelow of Bates College in Lewiston, Maine, excavated the site, and used a technique called optically stimulated luminescence that measures electrons to tell when a sediment was last exposed to light. With this method, Bigelow and colleagues from the Scottish Universities Environmental Research Centre in Glasgow identified a series of major sand incursions that likely occurred in the mid-1500s and late 1600s. These layers indicate that the sandstorms were much worse than typical, blanketing the ground in sand and piling it nearly 2 meters deep along walls and other structures.
Weather records from the time match these sandstorms with unusually windy conditions caused by the little ice age. Bigelow and colleagues ran a computer model of the island’s topography through a wind simulation program and found that near Broo, wind speeds drop off dramatically. “Sand falls out where the wind slows down,” explains the study’s corresponding author, Matthew Bampton, a geographer at the University of Southern Maine in Portland.
Broo’s farmers had fended off occasional incursions for hundreds of years, but the little ice age’s fierce winds and the township’s unfortunate location ultimately doomed it, the authors reported last week in the Journal of Archaeological Science. By the mid-1700s, the farmers had abandoned the village. Today, it remains an empty, uninhabited stretch of sandy fields surrounded by surviving farm towns.
But that’s probably not the whole story, Bigelow notes. It’s also possible that sheep grazing near the shoreline and the likely introduction of grass-eating rabbits around this time might have destabilized nearby sand dunes, which relied on the grasses to anchor them.
Neighboring towns like Hillwell and Quendale weren’t similarly abandoned, Bigelow says, which suggests that the effects of climate change can vary widely even among places just a few kilometers away from one another—something modern climate modelers should consider, he says.
“The use of the wind simulation is clever,” says Suzanne Pilaar Birch, a paleoecologist and archaeologist at the University of Georgia in Athens who wasn’t involved with the study. “This is a good case study in that it starts big, bringing together our general understanding of the conditions during the little ice age, then looks at regional comparisons, then zeroes in on the local historical records and archaeology … together, they provide a convincing argument.”