New findings show that the historical decay of a mighty empire was caused by climate change., says S.Ananthanarayanan.

The largest empire of the ancient world was the Neo-Assyrian – an Iron Age civilization that flourished for three centuries, 911 to 609 BCE. This was in Mesopotamia, the Tigris-Euphrates floodplain in Western Asia, where we now have most of Iraq, Kuwait and parts of Syria and Turkey. After its peak of success in 670 BCE, however, the empire rapidly declined, and in sixty years, ceased to exist as an independent state.

Scholars have attributed the disintegration to political reasons, ambitious expansion, uprisings and civil wars, and alliances formed by hostile Iranian, Persian and Babylonian power centres. Ashish Sinha, Gayatri Kathayat, Harvey Weiss, Hanying Li, Hai Cheng, Justin Reuter, Adam W. Schneider, Max Berkelhammer, Selim F. Adali, Lowell D. Stott, R. Lawrence Edwards from California State University, at Carson, Yale University, Universities of Minnesota, Colorado, Illinois, of Southern California, in the US, University of Ankara and Xi’an Jiaotong University, Xi’an, China, however report in the journal, Science Advances, that root cause of the decline may have been quite different.

They identify a two century-long period of ample rainfall, in comparison to the preceding 4,000 years, as the reason for the rapid rise of the empire from 911 BCE. And then, a century of mega-droughts, lasting decades at a time, that wrecked economic havoc and led to the sharp decline in the seventh century BCE.

The paper explains, in its supplement, that the neo-Assyrian state arose with the revival of what remained of the earlier, middle Assyrian Kingdom, which had gone into decline two centuries before. It is recorded that the earlier regime had collapsed as a result of severe regional drought, which had the twin effect of weakening the state and driving neighbouring tribes to carry out foraging raids. However, the Assyrians, who had scattered, regrouped in 934 BCE and regained their lost territory. The state soon began to flourish and over the next two centuries, “became the dominant power in West Asia and the Eastern Mediterranean.”

History records that fissures in the neo-Assyrian armour began to show in 705 BC, when the Assyrians suffered a military defeat against a less powerful opponent and the Assyrian king was killed. His successors still carried the standard forward and the early 7th Century BCE saw major civil engineering work, a 100 km network of canals and aqueducts, to sustain expanding borders. But foes proved intractable, there was discontent and rebellion and by the end of the century, the state fell before an alliance of what became the Neo-Babylonian Empire and a powerful state in the mountains of central western Iran.

While the role of the variability of rainfall and the proneness to drought in the region are recognised, the fall of the Neo-Assyrians has so far been considered to be predominantly the result of politics and war. The fact that there are scant records of climate during the time, while there are ample historical and archeological records, has turned the spotlight away from the role that climate may have played, the paper says.

As a departure, the present study takes a closer look at an accurate proxy for rainfall, which has been discovered in the heart of the region, to arrive at data, well resolved in time, of rainfall and moisture levels right through 4,000 years. “These data provide a climatic context for the rise, expansion, and ultimately the collapse of the Assyrian Empire during the mid-to-late seventh century BCE. Our data also permit us to place the recent multiyear droughts and a near-century- long drying trend over the eastern Mediterranean and Middle East region in the broader context of the region’s hydroclimate variability during the past four millennia,” the paper says.

The data was collected from Kuna Ba Cave (shown by the white star in the picture), in the foothills of Zagros Mountains, western Iraq. The Kuna Ba (or ‘hole in the wind’) caves are part of a system which includes caves where skeletons of Neanderthals were found. The Kuna Ba cave contains a large, cavernous interior full of hanging structures, like stalactites, or stalagmites, made of minerals deposited by dripping water from the roof.

“The vegetation above and surrounding the cave is sparse mostly consisting of grasses and shrubs. The soil cover is thin, less than 1m deep, and the total earth above the cave is less than 15 meters”. Rainwater is thus able to seep through and drips from the roof of the cave. Over years and centuries, the structure and content of the mineral deposits have formed a record, of the quantity of rain as well as the composition of the water that seeped down to the cave.

This record of wet and rainfall reveals that the first part of the three centuries when the Neo-Assyrians flourished was the best-watered period in all the 4,000 years for which the record exists. The rainfall, the record shows, in some periods, was 15% to 30% higher than what it has been in modern times. This extended period, about 200 years of plentiful water, clearly made for good crops, robust economy and supported military conquest.

And then, the record shows that towards the end of the three-century period, there was a series of extended droughts, and, despite the system of canals that was in existence, the mega-dry-spells spelt doom for the agriculture-based economy. The State policy being one of expansion and filling urban centres with population, often by force, the financial crunch gave teeth to the forces of opposition, leading to revolt, military losses and rapid disintegration of the empire. “These data provide a climatic context for the rise, expansion, and ultimately the collapse of the Assyrian Empire during the mid-to-late seventh century BCE,” the paper says.

In the current crisis of global warming, the effects of climate change would not stay local, as in the Assyrian empire, but would spread out in the economy of today’s connected world. The most affluent societies may be the badly affected and there may be reversal of the pecking order.

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