There's more to the decline of the once mighty ancient Assyrian Empire than just civil wars and political unrest. Archaeological, historical, and paleoclimatic evidence suggests that climatic factors and population growth might also have come into play.

This is the opinion of Adam Schneider of the University of California-San Diego in the US, and Selim Adali of the Research Center for Anatolian Civilizations in Turkey, published in Springer's journal Climatic Change.

In the 9th century BC, the Assyrian Empire of northern Iraq relentlessly started to expand into most of the ancient Near East. It reached its height in the early 7th century BC, becoming the largest of its kind in the Near East up to that time.

The Assyrian Empire's subsequent quick decline by the end of the 7th century has puzzled scholars ever since. Most ascribe it to civil wars, political unrest, and the destruction of the Assyrian capital, Nineveh, by a coalition of Babylonian and Median forces in 612 BC. Nevertheless, it has remained a mystery why the Assyrian state, the military superpower of the age, succumbed so suddenly and so quickly.

Schneider and Adali argue that factors such as population growth and droughts also contributed to the Assyrian downfall. Recently published paleoclimate data show that conditions in the Near East became more arid during the latter half of the 7th century BC.

During this time, the region also experienced significant population growth when people from conquered lands were forcibly resettled there. The authors contend that this substantially reduced the state's ability to withstand a severe drought such as the one that hit the Near East in 657 BC.

They also note that within five years of this drought, the political and economic stability of the Assyrian state had eroded, resulting in a series of civil wars that fatally weakened it.

"What we are proposing is that these demographic and climatic factors played an indirect but significant role in the demise of the Assyrian Empire," says Schneider.

Schneider and Adali further draw parallels between the collapse of the Assyrian Empire and some of the potential economic and political consequences of climate change in the same area today.

They point out, for instance, that the onset of severe drought which, followed by violent unrest in Syria and Iraq during the late 7th century BC, bears a striking resemblance to the severe drought and subsequent contemporary political conflict in Syria and northern Iraq today.

On a more global scale, they conclude, modern societies can take note of what happened when short-term economic and political policies were prioritized rather than ones that support long-term economic security and risk mitigation.

"The Assyrians can be 'excused' to some extent for focusing on short-term economic or political goals which increased their risk of being negatively impacted by climate change, given their technological capacity and their level of scientific understanding about how the natural world worked," adds Selim Adali.

"We, however, have no such excuses, and we also possess the additional benefit of hindsight. This allows us to piece together from the past what can go wrong if we choose not to enact policies that promote longer-term sustainability."

Reference: Schneider, A.W. and Adali, S.F. (2014). "No harvest was reaped": demographic and climatic factors in the decline of the Neo-Assyrian Empire. Climatic Change. DOI 10.1007/s10584-014-1269-y