Friday Five: Earthworms and the study of

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As it seems with most things, Darwin was the first to take the time to scientifically study earthworms. His final book, The Formation of Vegetable Mould, Through the Action of Worms With Observations on Their Habits, published in 1881 was a detailed study collating his experiment results from a 40 year period about the habits of the worms in his garden at Down House.

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Darwin concluded that over fifty thousand worms could inhabit an acre of soil. We now know that up to a million worms can inhabit an acre of soil in the right conditions and depositing their castings at the surface. A wonderful example are the earthworms of the Nile Valley capable of depositing a thousand tons per acre, which accounts for the amazing fertility of that region.

Earthworm castings: an excellent soil amendment.

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There are around 23 families, 739 genera, and over 4500 species of earthworms in the phylum Annelida. Depending on the species, each worm has one to five pairs of hearts. Worms breathe through their skin and while they have periods of inactivity, they don't appear to sleep!

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Earthworms are ecosystem engineers, changing the chemical and physical characteristics of the soil. As such they can be beneficial in increasing crop yields and providing the right nutrients to plants that protect them from pests and diseases. But, in the wrong situation, they can destroy. In the Banaue rice terraces in the Phillippines foreign worms have been accidentally introduced. When the terraces are drained at the end of the rice season, these worms fill the terraces with holes meaning that the terraces no long hold the flood water. If this cannot be prevented, then a whole way of life may be gone forever.

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Trials are taking place to find out if earthworms can be used to make vermicompost of human waste. Meaning that it would be not only safe, but also a rich compost that could be used in gardens and importantly over crop fields.

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Here's a documentary about worms. The first 20 minutes is about earthworms; talking briefly about Darwin as well as earthworm biology and ecology.


Resources:
Stewart, A. (2004) The Earth Moved, London, Francis Lincoln Ltd