鈥淗umble鈥� and 鈥渓owly鈥� are the words traditionally paired with 鈥渨orm鈥�, and unless you have an interest in making compost, the earthworm may have entirely escaped your attention. Well, maybe it鈥檚 time to take notice. Thousands of scientists around the globe certainly are: they are using earthworms in anything from biomedical research to environmental monitoring. Earthworms are now regarded as 鈥渙ne of the world鈥檚 keystone organisms鈥�.
Who says so? The huge crowd of biologists who gathered in Cardiff last week for the International Symposium on Earthworm Ecology. They have every right to be proud about their worms. Charles Darwin himself said: 鈥淚t may be doubted whether there are many other animals which have played so important a part in the history of the world than the earthworm.鈥�
For earthworm scientists, history can be divided into two eras. In the dark ages before 1881, earthworms were regarded as some kind of vermin, quite possibly harmful and best poisoned. Light dawned with the publication of Darwin鈥檚 鈥淭he Formation of Vegetable Mould through the Action of Worms, with Observations on their Habits鈥�. From then on, the worm was recognised as the great creator of the planet鈥檚 soil.
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What would a world without worms be like? There would probably be a lot less plant life for a start. Normally, a couple of centimetres of soil can take up to 1000 years to form through weathering and decomposition, but earthworms speed this up to about 5 years by distributing nutrients and opening up channels through the soil.
What is special in worm research 120 years after Darwin? In a word: 鈥渆cotoxicology鈥�. Earthworms are proving vital barometers of soil quality and toxicity. They are affected by most pesticides and herbicides, and observing them is a good way to check out the health of soil ecosystems. The worms鈥� reproductive success, and the number and viability of their cocoons 鈥� special sacs that contain the eggs from which the next generation will hatch 鈥� are good measures of life underground. Tests now under development go a step further and look at the membranes of worm blood cells which are sensitive indicators of chemical stresses.
Earthworms can help repair damaged soil, too. A research group in Oxford has recently found that sprinkling earthworms over the surface of contaminated land is a great way of getting the chemicals used to treat the problem down into the subsoil.
There is much to investigate. Remember that there are more than 3000 species of earthworm including one, the giant Gippsland in Australia, that grows up to 4 metres long, and others that live comfortably in estuaries.