Worms! What are they for? When were they in the news? Why am I writing about them? Well, back in February, just as I was helping with a local farmland bird survey, another farmland wildlife survey hit the news. My survey involved a quiet stroll with a pair of binoculars and a pencil, but the more energetic farmer-surveyors of earthworms found themselves digging multiple pits across arable fields, counting shallow-burrowing, deep-burrowing and surface worms, and trying to gauge the health of their soil. This year’s survey is underway and the results of last year’s work were reported to the press. In spring 2018, 1318 hectares of fields, mainly wheat, and mainly in East Anglia, had 1260 soil pits dug and 12,010 earthworms counted. 77% of pits had at least one worm and 58% had all three types, but 21% of fields had no surface worms and 16% fields had no deep-burrowing ones.
Why are worms important, and should we be concerned that some fields didn’t have all three types? Earthworms have long been known to be necessary to maintain productive, humus-rich, well-aerated soil. They were extensively studied by Charles Darwin. He found them not only to be vitally important, but sociable and intelligent as well! Their habit of burrowing and drawing down leaves and other plant matter deep into the ground,mixes the soil, improving its structure,increases the availability of nutrients and creates good drainage. Worms facilitate the decomposition of organic matter by other organisms too.Fewer worms make for less fertile soil, and fewer worm-eating birds, such as song thrushes. The good news is that increased crop rotations and organic matter applications are thought to have the potential to reverse any decline.
Earthworms are found on every continent except Antarctica.Australia is home to an enormous species an inch wide and 13 feet long (and I thought they’d just been invented for the horror film Tremors!).Europe has 200 different species, Britain has 26. Darwin estimated that there are 53,000 earthworms per acre of land and it has been calculated that,every year, they shift 100 tons of soil per hectare.
The largest British earthworm, reaching 14 inches in length, is called Lumbricusterrestris. It is probably easiest to observe when it comes to the surface of your lawn at night. It feeds and mates above ground, but always has to keep a foothold in its burrow, in case it needs to beat a hasty retreat.It is much loved,(as a snack!),by blackbirds, not to mention badgers, moles, foxes and hedgehogs. Although earthworms are hermaphrodite, they choose to mate with another worm to fertilise their eggs.Each partner then deposits its eggs in the soil,inside a special egg capsule.
Woken your interest? Then watch out for World Worm Week.It happens in March, when earthworms are at their most active.