How Long Have Humans Been Polluting the Environment?

As a result of the recent increase in headlines and column inches given over to manmade climate change and its effects on our planet, you’d be forgiven for thinking that human pollution was a modern-day phenomenon. However, a study conducted by researchers in the South China Sea suggests that our contamination of the planet stretches back as far as 4,000 years.

Global cooling fuels agriculture

Scientists have discovered that a cooling of planetary temperatures around 4,000 years ago caused major reverberations all over the Earth. Incapable of dealing with colder winters and poorer yields, civilisations such as the Indus in South Asia, the Akkadians in Mesopotamia and the Liangzhu people in eastern China saw their very way of life threatened.

A study published in The Holocene by Bangqi Hu from the Qingdao Institute of Marine Geology and Fangjian Xu at the China University of Petroleum has suggested that the island of Hainan off the southern coast of China might have suffered similar drops in temperature. As a result, the area experienced a reduced frequency of monsoons and coast upwelling, which in turn meant less productivity among marine-dwelling animals and fewer opportunities for the fishing industry.

To compensate, it has been suggested that Hainan inhabitants turned to agriculture. Of course, today we have ever-more sophisticated methods of growing crops (such as biodynamic farming), but back then farming methods were primitive and polluting. The use of metal implements and tools increased the amount of heavy metals in the soils, which then ran off into the seas surrounding the island.

Hu, Xu and their colleagues analysed sediment cores from just south of Hainan and found a sharp increase in lead and cadmium enrichment factors in the underwater samples. This increase occurred at roughly around the same time as the global cooling phenomenon, suggesting a link caused by the switch from fishing to farming.

Not everyone in agreement

While the study does point to the possibility of human pollution as far back as four millennia ago, the results are inconclusive according to other scientists in the field. A 2015 study conducted by Samuel Toucanne and the French Research Institute for Exploitation of the Sea found that an increase in lead, arsenic and copper can only be traced as far back as 1,800 years.

Toucanne insists that the upsurge in lead and cadmium levels found by Xu, Hu and others is only estimated to have taken place at the same time as the global cooling period, and that nothing can be taken for granted. Meanwhile, Louisiana State University scientist Peter Clift also believes that manmade pollution would only have taken a noticeable toll on the land at a later date.

“I find it difficult to believe that little Hainan island was much more developed 4000 years ago,” he told the New Scientist. Clift is more inclined to believe that heavy metals only really began to find their way into the environment as a result of human activity around 2,000 years ago.

Whatever the reality, it’s clear that manmade pollution is far from a recent development. With experts still unclear today as to the best way to clean up flooded lakes and reservoirs, it’s no surprise that such environmental concerns weren’t even on the radar of prehistoric farmers several millennia ago. But while the effects of global warming have been a long time in the making, they undoubtedly require clear and decisive action now.