Wars, political struggles, and weak leadership are common explanations for the fall of ancient empires. However, new research suggests that environmental stress also played an important role in weakening the Tang dynasty before its eventual collapse.
Researchers looked at climate records from northern China and found that repeated droughts and floods from the ninth to early tenth centuries likely strained agriculture, military supplies, and population stability in the Tang dynasty’s last years. Their findings, published in Nature Communications Earth & Environment, suggest that environmental stress played a part in the dynasty’s collapse in 907 CE, but it was not the only reason for this downfall.
The Tang dynasty was established in 618 CE and is recognized as a period of cultural and administrative achievement in Chinese history. The dynasty’s stability depended on an effective bureaucracy, reliable food production, and secure northern borders. According to the researchers, this balance became more vulnerable as climate extremes became more frequent.
Climate Records From Trees
The research team studied long-term tree-ring records from the area around the Yellow River basin. Tree rings act as natural records of climate. Wider rings usually mean wetter years, while narrow rings point to drought. Using these records, the researchers were able to map changes in river runoff during the ninth century. That runoff influenced the amount of water available downstream for irrigation and transport.
“The runoff eventually reaches further downstream and influences the amount of water available, for example, for irrigating the fields,” said author Michael Kempf, who conducted the work while at the University of Basel and is now based at the University of Cambridge.
Instead of focusing on isolated disasters, the study identifies a pattern of increasing instability over time. More frequent droughts and floods led to unpredictable conditions for agriculture and food storage in northern China.
Agriculture Under Pressure
The analysis shows that climate extremes had a direct impact on crop yields and grain reserves. Both were essential for keeping the Tang dynasty stable.
“Hydroclimatic extremes have a very direct influence on crop failure and grain storage conditions,” Kempf said. Seed shortages and rising food demand placed increasing strain on supply systems, meaning that a single bad harvest could have consequences lasting several years.
Decisions about which crops to grow may have increased the dynasty’s vulnerability. During this time, farmers began planting more wheat and rice rather than millet. Although wheat and rice were important culturally, they both required more reliable water supplies. Millet, on the other hand, is much more drought-resistant.
“As long as there is enough water, this is not a problem, but during prolonged dry periods, shortages occur,” Kempf explained.
Methods to redistribute food were also hampered by floods and droughts, which disrupted transportation networks. As food shortages worsened, transporting supplies became increasingly difficult.
Migration and Military Strain
Food shortages likely affected more than just farming. The study connects malnutrition and resource scarcity to the weakening of the military along the Tang dynasty’s northern borders.
“Of course, people were weakened and therefore more vulnerable,” Kempf said. Under mounting pressure from external threats, soldiers and civilians alike migrated southward in search of more stable conditions.
The researchers suggest that this migration contributed to political instability. As people moved and border defenses weakened, the Tang government found it increasingly difficult to control its territory amid internal unrest.
Climate stress was not the only cause of the dynasty’s collapse, but it did make the existing economic, social, and political challenges more severe.
Caution and Context
“Our results are approximations,” Kempf noted. “The actual conditions at that time cannot be reconstructed with certainty. It’s a complex interplay of many different factors.”
Political conflict and social changes were also important factors in the decline of the Tang dynasty. The study does not argue these factors, but it now adds climate variability to this complex set of causes.
The researchers present the Tang dynasty’s collapse as an example of how societies can reach tipping points when environmental stress upsets established systems. Even small changes can have large effects when they occur in already vulnerable situations.
Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds a Master of Business Administration, a Bachelor of Science in Business Administration, and a Data Analytics certification. His work combines analytical training with a focus on emerging science, aerospace, and astronomical research.