Earthworms under threat

Commentary by Jaboury Ghazoul, ETH Zurich

1st November 1837 was a disappointing day at the Geological Society of London. The men (and they were only men) of the Society were expecting great things from the young Charles Darwin, recently returned from his Beagle voyage. Yet on that day only William Buckland saw sufficient value in Darwin’s work to recommend it for publication – but then Buckland himself was an oddity, given his work on fossil feces and his proclivity for eating his way through the Animal Kingdom (moles and bluebottle flies, he reported, are particularly distasteful). Even so, Buckland was a leading geologist who did not mince his words, praising Darwin’s work as “a new and important theory to explain phenomena of universal occurrence on the surface of the Earth”, no less than “a new Geological Power”.

What did Darwin and Buckland recognize that others did not? In a word, worms. Earthworms in particular. In the years and decades that followed, Darwin watched worms drag leaves, sand, and stones into their burrows. He meticulously, and very precisely, calculated that there are 53,767 earthworms in each acre of English countryside. He noticed that as worms turn the soil over, objects on the surface begin to sink into it. By this process, Darwin argued, earthworms have preserved for us countless historical artifacts, all protected from the vagaries of wind and weather under a layer of soil. Moreover, he realized that the action of thousands of worms over thousands of years maintains a healthy and fertile soil.

Darwin, no doubt, would have been horrified by the way we have treated our soils in recent decades. Over the past 150 years, overuse and erosion has washed half of our planet’s topsoil downstream to smother coastal reefs and fisheries. We have denuded soils of their nutrients, and polluted them with heavy metals and salts. The pesticides we apply might temporarily increase yields, but they also disrupt soil biodiversity. Earthworms have declined. Soil fertility has been lost. Oh, and did I mention that we depend on healthy soils for 95% of the food we eat?

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