Learning from Past Civilizations
By Lester R. Brown
To understand our current environmental dilemma, it helps to look at earlier civilizations that also got into environmental trouble. Our early twenty-first century civilization is not the first to face the prospect of environmentally induced economic decline. The question is how we will respond.
As Jared Diamond points out in his book Collapse, some of the early societies that were in environmental trouble were able to change their ways in time to avoid decline and collapse. Six centuries ago, for example, Icelanders realized that overgrazing on their grass-covered highlands was leading to extensive soil loss from the inherently thin soils of the region. Rather than lose the grasslands and face economic decline, farmers joined together to determine how many sheep the highlands could sustain and then allocated quotas among themselves, thus preserving their grasslands. Their wool production and woolen goods industry continue to thrive today.
Not all societies have fared as well as the Icelanders. The early Sumerian civilization of the fourth millennium BC had advanced far beyond any that had existed before. Its carefully engineered irrigation system gave rise to a highly productive agriculture, one that enabled farmers to produce a food surplus, supporting formation of the first cities and the first written language, cuneiform.
By any measure it was an extraordinary civilization, but there was an environmental flaw in the design of its irrigation system, one that would eventually undermine its food supply. The water that backed up behind dams built across the Euphrates was diverted onto the land through a network of gravity-fed canals. As with most irrigation systems, some irrigation water percolated downward. In this region, where underground drainage was weak, this slowly raised the water table. As the water climbed to within inches of the surface, it began to evaporate into the atmosphere, leaving behind salt. Over time, the accumulation of salt on the soil surface lowered the land’s productivity.
Shifting from wheat to barley, a more salt-tolerant plant, postponed Sumer’s decline, but it was treating the symptoms, not the cause, of their falling crop yields. As salt concentrations continued to build, the yields of barley eventually declined also. The resultant shrinkage of the food supply undermined this once-great civilization. As land productivity declined, so did the civilization.
