How Giant Earthworms Have Transformed The Isle Of Rùm's Landscape

Arthur T Knackerbracket has processed the following story:

Renowned for a thriving and intricately studied population of around 900 red deer, the Isle of Rum [often written as Rum], part of Scotland's Inner Hebrides, is often considered an outdoor laboratory for scientific research. But the earthworms on Rum are equally remarkable. These invertebrates act as "ecosystem engineers", actively shaping the landscape, often after humans have left their mark on this remote island.

My investigations over 30 years have uncovered how people have influenced the current fragmented and uneven distribution, diversity and abundance of earthworms on this national nature reserve.

While taking my geography students on field trips to Rum in the mid-1990s, I realized there was scope for research on earthworm ecology. One of my Ph.D. students was studying soil development here and she quickly alerted me to differences in earthworm numbers found below different species of trees planted in the late 1950s. More worms lived below birch and oak trees than beneath pine trees or on unplanted moorland. This discovery spurred me into action.

Rum's human history goes back 9,000 years. Early humans came here to collect bloodstone, a flint-like mineral used to make arrowheads and other hunting or cutting tools. The island was deforested by early humans and the wet climate (with more than 2m of rain per year) led to the leaching of soil nutrients. The resulting poor-quality acidic soil supported moorland plants and low numbers of just three earthworm species.

If nothing else had happened to Rum soils, then this would be a very unexciting place to undertake research on earthworms.

But subsequent human inhabitants improved soils sufficiently to eke out a living as tenant farmers at a few locations around the coast. They used kelp seaweeds to fertilise the cultivated land and enrich soil quality. Then, some 200 years ago, these hardworking people were forcibly removed from their settlements on Rum (and much of Scotland) in the "Highland clearances".

At sites on Rum such as Harris, Dibidil and Kilmory, distinct ridges and furrows nicknamed "lazybeds" remain on the landscape. These indicate where the land was painstakingly dug by hand to grow potatoes and other crops. The furrows allowed drainage and the crops were grown on raised ridges. Two centuries since the last cultivation, these soils are still more fertile than surrounding areas, and they continue to support more earthworms.

At Papadil, another abandoned settlement, seldom visited these days, a brown forest soil has developed below stands of trees planted a century ago. Within these trees, colleagues and I found large earthworm burrows about 1cm in diameter. On an island with no badgers and no moles, a good supply of leaf litter for food and little disturbance from humans, we found the UK's largest Lumbricus terrestris ever reported in the wild.

At over 13g, some three times the normal weight for this species, these earthworms may have been up to ten years old. This really was an exciting find. We returned the worms to the soil-hopefully they have proliferated.

Read more of this story at SoylentNews.