The superheroes in our soil

Matt Phelps | Lead Ecologist

Our soils are in speedy decline. Some even say we only have “sixty harvests left”. That was a claim made by a UN official in 2015 and which inspired the title and message of a book by the author and compassionate farming advocate Philip Lymbery.

In our drive to produce higher yields from our agricultural land, we in the developed world have been destroying the living fabric of the soil that we need to grow our food. Artificial fertilisers and pesticides are contributing to the crisis in our soils. Ploughing also destroys the soil and all the creatures that live in it.  And no, contrary to myth, worms cannot survive when cut in two. As this subterranean life is devastated, and its live-giving processes are halted, intensively-farmed land is becoming more eroded, hostile and ultimately lifeless.

Throughout history, civilisations have valued earthworms as champions of healthy soils.  Aristotle described them as “the intestines of the earth” in the fourth century BC; and Cleopatra, in the first century BC, realising how vital they were to the ecology of the Nile delta, declared them sacred and that any harm done to them would be punishable by death.

Charles Darwin doubted “whether there are many other animals that have played so important a part in the history of the world, as have these lowly organized creatures.”

All hail the humble earthworm, a familiar creature to almost everyone. For lots of us, discovering an earthworm in the mud of our own garden may have been our very first encounter with the wonders and quirks of the natural world. As a child, I can remember being amazed at how simply digging a hole or lifting a rock or log in the garden would reveal a hidden world of strange-looking minibeasts, all scurrying and squirming to get away from the light.

And there are lots of them. Six thousand earthworm species have been described globally, although the true figure could be more like 30,000. In the UK, we have a more modest 31 species. They are, broadly speaking, the most abundant creature by volume in soil around the world.

There are basically three types of earthworms: deep-burrowing (anecic), shallow-burrowing (endogeic) and surface-dwelling (epigeic). The most common species in Britain, and the one you’re most likely to encounter in your garden, is the ‘lob worm’. Lob worms spend most of their time below ground, sometimes burrowing as deep as six feet, but return to the surface to find food, which they then draw down underground. This is why they’re such crucial ecosystem engineers. The tunnels they dig help aerate soil, reduce soil erosion, stimulate plant growth and bring revitalised earth to the surface through their casts – the tiny pyramids of excrement that look like piped chestnut puree on the top of the soil. 

Not only that, but recent studies show that the digestive systems of worms can eradicate bacteria like E.coli and salmonella, essentially cleaning the soil for the benefit of other creatures – so they can be used in the treatment of sewage. The bacteria in their guts can even breakdown and neutralise harmful synthetic chemicals such as PCBs, organochlorides and DDT, so worms are now used in clean-up operations on abandoned opencast mines and old industrial sites.

Two decades ago, when Knepp stopped intensive agriculture, our exhausted earth was little more than “dirt”, as leading microbiologist Elaine Ingham describes degraded soil. Nowadays, when our Tamworth pigs overturn swards of turf in their rootling for bugs, they reveal a writhing hub of earthworms. A healthy square foot of soil can contain around 25 individual worms, equating to a million per acre. So, in the 3,500 acres of Knepp Wildland, there could be 3.5 billion earthworms beneath the surface.

At Knepp, two studies have revealed a dramatic increase in earthworm abundance in the two decades since the rewilding project began. They reveal that Knepp now has an amazing 20 varieties of earthworm – around two thirds of all UK species.

The earthworm offers us a way forward, showing us that a nature-led approach to landscape management helps not only the wildlife we can see, but the wealth of life beneath our feet.

As the rewilding movement gathers pace, let’s hope that earthworms, too, will be fully recognised for their role as ecosystem engineers, our faithful, forgiving allies, on hand to clean up our mess and save the earth. In 2009, The Earthworm Society of Britain was set up to promote a better understanding and appreciation of the species, and to encourage more people to record them.  The Guardian runs a yearly Invertebrate of the Year competition, and last year’s winner was the common earthworm, the Lumbricus terrestris. This year’s poll has only just closed. When I posted a video on Instagram about earthworms for Worm Moon on 14 March this year it attracted a huge amount of engagement, likes and comments.  

I hope we’re at the dawn of a new era for earthworms, where, like Cleopatra, we recognise them as vital to our survival, perhaps even sacred.

Come and see Knepp for yourself. Find out What’s On, including our Ecology of the Rewilded Garden workshop, Rewilded Garden Tour and Rewilding Smaller Scale workshops.

Image: Richard Sandys-Renton