Pluvials, Droughts, Energetics and the Mongol Empire

Orkhon Valley, Mongolia. Photo by N. Pederson. Please contact for permission to use.

Orkhon Valley, Mongolia. Photo by N. Pederson. Please contact for permission to use.

Sponsored by the National Science Foundation and led by Dr. Amy Hessl of West Virginia University and assisted by many collaborators, this project investigates the long-term dynamics between climate and humans in Mongolia and Central Asia.


Project Summary

The study of energetics has long been applied to biological and ecological systems but has only recently become a theme in understanding modern coupled natural and human systems (CNH). This is surprising since energy is critical for human and natural systems to overcome the entropy of thermodynamics. As energy sources become increasingly taxed, models of how past societies adapted to changing energy sources is critical. Similarly, as societies become rapidly urbanized, freshwater will be threatened by numerous human activities. Water allows biological systems to capture solar energy and human systems to capture, transform, and allocate this energy for developing sophisticated social and political systems far from thermodynamic equilibrium. Because water and energy are tightly linked in both human and natural systems, studying their synergies and interactions make it possible to integrate knowledge across disciplines and human history, yielding important lessons for modern societies.

Many studies of past CNH have focused on “collapse” – the disintegration of society following environmental stress, especially drought. We focus on the role of energy and water in the trajectory of an empire, including its rise, development, and demise. The success of the Mongol Empire, the largest contiguous land empire the world has ever known, is a historical enigma. At its peak in the late 13th century, the empire controlled or influenced areas from the Hungarian grasslands to southern Asia and Persia. Powered by domesticated herbivores, the Mongol Empire grew at the expense of sedentary agriculturalists in Eastern Europe, Persia, and China. What environmental factors contributed to the rise of the Mongols? What factors influenced the disintegration of the empire by 1300 CE? Until now, little high resolution environmental data have been available to address these questions.

Using the framework of ecological economics, we combine archaeological and historical data on human consumption with tree-ring records of past climate, modeled estimates of net primary productivity and livestock abundance, and lake sediment records of water resources to illuminate the role of energy and water in the evolution of the Mongol Empire. We focus on the Orkhon Valley, the seat of the Mongol Empire, where recent paleoenvironmental and archeological discoveries allow high resolution reconstructions of past human and environmental conditions for the first time.

We hypothesize that the arc of the Mongol Empire was influenced by the energy available to nomadic pastoralists for building a mobile military and governmental force sufficient to conquer and govern a significant portion of Asia and Eastern Europe. We also investigate whether the contraction of the empire was related to declines in moisture availability, grassland productivity, and water quality associated with rapid urbanization and climate change in the Orkhon Valley.

Blog: Here is a blog from the beginnings of the project.


Dangal, S., H. Tian, C. Lu, S. Pan, N. Pederson, and A. Hessl. Accepted. Synergistic effects of climate change and grazing on net primary production in the grasslands of Mongolia. Ecosphere.

Pederson, N., A.E. Hessl, [Joint First Authors] – B. Nachin, K.J. Anchukaitis, and N. Di Cosmo. 2014. Pluvials, droughts, the Mongol Empire, and modern Mongolia. Proceedings of the National Academy of Sciences 111: 4375-4379.  – PDF