Earthed

I've been planting potatoes and, along with hard graft, pleased to find quantities of earth worms in the soil. 

Charles Darwin who spent 42 years studying them, considered them the most valuable creatures in the world in terms of their contribution to soil fertility. They create humus by pulling vegetable matter (leaves mainly) into the soil and they aerate the ground with their movements below the surface. All stones and boulders on the surface (including Stonehenge) gradually sink owing to the subterranean activity of worms.

I always  understood that North America lacked earthworms but recently I heard a radio programme that cast a less positive light on them. Although America had no native earthworms they arrived via settlers, both accidentally and deliberately (in an attempt to improve the soil)  and they have now become established in the cooler northern areas of the USA and Canada not to mention more widely across the arctic and sub-arctic. Unfortunately they have  proved highly damaging to the existing soil structure,  and its organisms, that has developed there over millennia without the subterranean activity of earthworms. The knock-on effect of invasive earthworm is proving catastrophic to a wide swathe of species  and will increasingly damage the natural environment across northern climes - including altering the planet's albedo effect by boosting plant growth in the arctic.

If you want to follow me down these wormholes see here, here and (for Darwin) here.