Halloween has passed, with rain and wind and falling autumn leaves. And all over the forest: the very spooky ‘consumers of the death’, the creatures of the dark soils feasting on what has fallen: the saprotrophs and detritivores. What better time is there to put them in the spotlight, than All Hallow’s Eve.

A mushroom sprouting from a rotten log in a Danish forest. In autumn, the death burst of life

When visiting Aarhus in Denmark last week, I had a little walk through a seaside forest, where this spooky destruction was in full swing. The forest floor was covered with piles of dead leaves, logs, and branches, and the variety of organisms feasting on them was astonishing.

Autumn on the Danish seaside

Yet what we get to see on the outside – mostly cute little mushroom heads- isonly the tip of a dark and soily iceberg. The soil microbial community hosts countless organisms underneath the surface, many of them never see the light. There is the mycelia of the fungi, there is wiggly worms of all sorts and kinds, there is beetles, bacteria, springtails and such. When a leaf has fallen, it journey has only just begun…

With modern techniques and global collaborations, scientists are diving deeper into this dark and secret world than ever before. Yet every new discovery reveals how much there is still to learn. For example, a recent long-awaited paper in Science finally describes the global distribution of earthworm diversity (showing that their diversity is highest at higher lattitudes).

When a leaf falls, its journey has only just begun…

Earthworms, you might say, are they much of a secret? They live right under our very own eyes in the soil of our gardens! True, yet there is so little we knew about their global distributions, and which species of them are occurring where. An earthworm is not just an earthworm, mind you!

Yet there they are again: the fruits of increasing global collaboration! Now we do have a map of global earthworm diversity, as we do for nematodes (even tinier worms) and mycorrhizae (fungi living in roots of plants). But those are the easy ones to tackle, what about all this diversity that hardly anybody has ever even heard off?

The road is long, yet the blackbox that our soils are is slowly, day by day, loosing parts of its spooky unfamiliarity. In return, we get an even more spooky sense of wonder: what a mysterious bunch of creatures and ecologies we find belowground, and how intricately are their communities woven together!