This article was originally published in Eos.

Along with Egypt and Babylonia, the Hittite Empire was one of the major powers of the eastern Mediterranean and Near East during the late Bronze Age. For more than 500 years, the empire’s military might and sociopolitical complexity allowed the Hittites to control the strategic region straddling eastern Anatolia and the northern Levant.

But by about 1200 B.C., the empire had collapsed. Researchers have cited armed conflict, disease, and political crises as contributing to its decline. Evidence hidden in ancient juniper trees points to what may have triggered that domino effect of calamities: a prolonged drought.

The Missing Piece of the Puzzle

In 2020, a group of scientists led by Cornell University archaeologist Sturt Manning began analyzing samples from juniper trunks used to construct the outer wall of a tomb in what is now Türkiye. The burial chamber, built in 740 B.C. in the Phrygian capital of Gordion (near modern-day Ankara), is the oldest standing wooden building in the world. The tomb is covered by an artificial mound about 53 meters (170 feet) high and 300 meters (1,000 feet) in diameter.

Junipers are characterized by their longevity, with some trees living for up to a thousand years. Manning and his colleagues analyzed more than 1,500 rings from the tomb’s 18 oldest trunks, dating from between 1775 and 750 B.C.

For junipers in semiarid circumstances such as those around Gordion, a thicker ring indicates wetter conditions during growth; a tree grows thinner rings when water is scarcer. The ratio of carbon’s stable isotopes (13C and 12C) within a tree ring is also related to moisture during growth. When a tree is under stress due to heat or lack of water, the pores in its leaves get smaller to conserve moisture, and the lighter isotope (13C) is preferentially taken in and incorporated into the outer ring. In the analysis, more 13C in a ring is a sign of drier conditions, Manning explains.

The juniper analysis, published in Nature, revealed a general shift to drier conditions from the late 13th into the 12th century B.C. The most dramatic period was a severe drought between 1198 and 1196 B.C.

The multiyear drought would have been fatal for crops, likely contributing to famine, poverty, and social unrest. University of Edinburgh archaeologist Ulf-Dietrich Schoop, who was not involved in the study, said that extreme centralization of resources and infrastructure, as well as widespread deforestation associated with agriculture and animal husbandry, may have increased the Hittites’ vulnerability even before the drought. Hittite leaders “took risks and were part of a domino effect,” he says. “Once [the empire] started to fall, it took everything with it.”

Hittites had strategies for resilience and adaptation to environmental dryness. But they were not prepared for a prolonged scenario, Manning explains. “Two or three [separate] years of extremely dry weather were a bit of a crisis, but two or three together became a real capital C crisis.”

For John Marston, an environmental archaeologist at Boston University who wasn’t part of the study, the work of Manning and his colleagues identified the moment when drought became a broad societal issue as opposed to simply an aspect of living in a relatively dry environment.

The Hittite drought scenario was a real stressor because it was a once-in-a-century event with which the state was unable to cope, Marston says. “And if the state can’t provide that backup, then why should the society trust them?”