THE biodiversity crisis is highlighted in many ways, whether it's through a decline in our pollinator population, a plant species disappearing, or by the sudden population surge of a pest whose natural predators are either extinct or in very short supply.
We rarely think about what's happening underground, but a similar crisis is playing out in the earth beneath our feet.
Recent research has shown that populations of earthworms may have fallen by about a third in the past 25 years. Vital for the healthy soil that underpins all ecosystems, scientists believe the steep decline in the earthworm population should sit alongside concerns about "insectaggedon" and the global destruction of wildlife.
Described by Charles Darwin as the "the intestines of the soil", earthworms spend their days munching through half their body weight of dead organic matter, which is deposited out the other end as worm casts.
The gardener's attitude to earthworms can vary, depending on how they view worm casts. Traditional gardeners with a lawn fetish, who dedicate much of their time to creating a smooth, lush, bowling green-type sward, tend to regard worms as a bit of a nuisance. In this context, worm casts – the deposits left by worms on the lawn surface – are an annoyance and something to be deterred.
If, however, you're part of that increasing number of gardeners who aspire to be organic and work in tune with nature, then worms – and worm casts – are your friends and should be encouraged.
There are around 30 species of earthworm in Ireland and Britain, with each tending to prefer specific depths and soil types. Litter-dwelling earthworms are a few centimetres long, dark pink in colour and live near the surface. Top soil earthworms are a bit bigger and are yellow or light green in colour. They will move horizontally through the earth, creating burrows and helping improve soil structure and nutrient availability.
Living further down are the larger, deep-burrowing earthworms which are dark red in colour. The most common species in Irish soils are the common earthworm, Lumbricus terrestris, and the smaller, redder Lumbricus rubellus. While some introduced species are unwelcome, they all help create good soil structure and fertility.
However, if the recent population plunge continues unabated, our soil and the environment it supports will be in serious trouble.
"It would have widespread impacts on the species that feed on soil invertebrates, like birds, but also affect soil processing and nutrient cycling, the whole functioning of our ecosystems," said Prof James Pearce-Higgins, the director of science at the British Trust for Ornithology, which conducted the recent research.
The reasons for the decline of earthworms on farmland especially, is down to changing farming practices, including extensive drainage, pesticide use and inorganic fertiliser application. Repeated ploughing is also thought to be harmful.
Similar practices in your garden are likely to result in corresponding harm but by following these easy steps instead you can enhance your garden's earthworm population:
:: Regularly add homemade compost to your beds and borders
:: Let plants die down naturally in winter and don't be too eager to clear fallen dead leaves, unless diseased
:: Stop using pesticides, including metaldehyde-based slug pellets
::Reduce the amount of hard surfacing and lift unnecessary paving and plant the area up instead
:: Make mini log piles with twigs and woody prunings directly on the soil as they will eventually decompose into worm food.
