At its height, Rome was a vast and powerful empire that dominated the world for six centuries with its technical and military might. To Romans, it must've seemed inconceivable that one day their civilisation could fall.
And yet, fall it did.
The causes of the collapse of a civilisation are complicated and we can never be certain what the prime factor was. Or, more likely, it was combination of things.
One thing we do know however, is that they depleted their soils.
Although we use the disparaging term "dirt", the equation is simple: without soil, there is no food.
And when food becomes scarce, people become desperate and society crumbles.
As the adage says, "there are seven meals between civilisation and chaos".
The Mediterranean environment is a delicate and complex patchwork of microclimates.
In the early days, Italy was densely forested, but by the end of the Roman Imperium, much of the region had been cleared. Timber was sold, and forest lands were converted into pasture.
While the soil in cleared lands was initially rich in nutrients and good for production, it became depleted over time.
Wind and water removed much of the soil, while overgrazing caused further deterioration.
While there's never a good time to damage soils, for the Romans it was disaster because they'd become entangled in foreign military escapades, and the empire was under stress from multiple sources.
To feed its growing population, they embarked on a form of globalisation, where they needed to exploit ever more land.
Produce was transported over a huge area via a system of roads and shipping lanes across the Mediterranean. One source was Egypt, the "breadbasket of the Empire", which faced its own environmental challenges.
To make it more complicated, the benign climate of earlier years was interrupted, perhaps due to air pollution from volcanic activity.
The climate descended into the "late antique little ice age" and, in AD 244 and 246, the Nile waters failed to rise.
The price of wheat rose, while the food crisis in Egypt was felt throughout the Empire. The Roman economy was battered as its coinage collapsed and inflation soared.
The difficulties faced by the Romans in feeding their population and their armies may have been enough to tip the empire into chaos.
By the sixth century the population of Rome had shrunk to less than 30,000 from its peak of more than a million, and much of the city fell into ruins.
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