30 Sept 2022

The architecture of decay

Written by Roddy Hamilton, ranger from the North East region

A close-up photo of a section of brown bark, with yellow-ish swirls creating a pattern all over it.

Bark beetles excavate galleries in dead or dying wood beneath the bark.

New growth steals the headlines, but decay has an undeniable beauty of its own. Not only that, it performs a necessary ecological function.

Not for the first time, my way is blocked by a fallen tree. I can see that it has grazed past other trees on its way to the forest floor.

I pause. It is as if the bark has been stripped down one side and the cambium (the layer of plant tissue beneath the bark) now reveals a script of ornate, golden and curlicued characters. I run my fingers over the smooth patterns on the fallen spruce. The hieroglyphs or cryptograms on this bark will never be deciphered. Far from being some mystical message etched in gold, they are probably the work of a beetle larva.

But that is the thing. Decay and destruction are often hidden beneath the surface of what we look at. It takes luck or perseverance to find it, and when we do find it, it can be very beautiful.

A close-up photo of a section of birch bark, showing a pattern of swirls and bumps.

Lichens on birch, combining with contours of decaying wood, create their own composition.

Decay serves a purpose, because it begins to house new life. Its endless forms create endless innovations, and with that novelty comes even more strangeness and beauty. The clamour for space on dead birch by lichens and algae can, for instance, create its own wondrous composition. I can remember trees that have succumbed to disease and are hollowed out – there is one at Castle Fraser whose cavernous inside is a veritable cathedral of decay. The machinations of disease and bacteria lay down the foundations for other organisms to benefit. Diseased wood may become home to sawfly larvae, whose holes are widened out by woodpeckers. When the woodpeckers peck too many holes and the cavity gets too wide, tawny owls move in or perhaps a red squirrel. What was once decay becomes a habitat, a living place – architecture.

Nature’s recyclers are a classroom favourite, and it’s easy to see why. There are a plethora of amazing organisms that break down the earth’s waste material. Take millipedes for instance, artists of the tunnelling kind. And for colour, we have slime mould. One in particular – wolf’s blood – feeds on fungal spores and bacteria and produces in one of its life phases puffy pink balls, which aggregate on rotten wood. These bleed a substance like pale rose blush oil paint.

A piece of decaying wood lies on moss on a woodland floor. The stump has lots of small pink balls growing all over it.

An old branch has a yellow fungus, with white bits, growing on top. The fungus does look a bit like dog vomit.

A tree struck by lightning becomes if not architecture then sculpture. Its contorted figure, alone in the glade it has made with its demise, sometimes becomes habitat for many more things than when it was living. Its surfaces may become smoothed by sunshine or roughened by rain and ice – within its crevices, countless animals may live. It becomes adorned in the waste products of those animals too: bat guano in the fissures; birds that eat arils (the berry-like fruit of a yew) streak this burnished sculpture with purple droppings; and the poo of pine marten is blue from blaeberries or crimson red from rowan berries.

A tree has snapped a couple of metres up its tall trunk and has fallen to one side, leaving jagged torn splinters jutting up from the remaining stump. The tree has fallen at a 90-degree angle from the stump. Other tall trees stand in the glade.

Broken trees become sculptures in the glades of their own making.

And then there is the small-scale destruction which results in new life. At Castle Fraser I see the grazing trails of snails. Snails have a radula – almost like a tooth, made of the hardest biological material known – with which they scour the plant material they eat, like algae from a paving stone. I also see shattered snail shells discarded by thrushes near the log cabin. The shells have been crushed beneath feet and become like grains of a fresco to rival Renaissance artists, ready to break down into powder and release minerals again into the soil for hungry plants.

Elsewhere, a mushroom has been nibbled by a rabbit. The mushroom’s insides have been hollowed by the tunnels of fly larvae, sometimes leaving only a sentinel stalk. But where the gills are left is a habitat for others to use. Some mushrooms deliquesce. Inkcaps are renowned for melting into a substance which really was used as ink.

White, cone-headed fungi grow on a woodland floor. The mushrooms have a large cap, with a sticky ink-like residue around the gills at the bottom.

Lawyer’s wig is an inkcap mushroom. Inkcaps deliquesce and were once used as ink.

Of course, the agents of decay are persona non grata with the Collections Care teams at the National Trust for Scotland. Bird poo can corrode the most ornate metalwork with no regard to its importance to humans, and the common clothes moth can be the nemesis of a medieval tapestry. Cultural heritage professionals make reference to the ‘ten agents of deterioration’, some of which are human-induced but most of which hail from nature. Nature is a machine that takes then drives life and renewal.

The physical force of weather is an agent of decay in nature too, without doubt, and water also is a force for change. It’s not difficult to see how water changes an entire environment and of course it fosters decay, especially when allied to warm temperatures like we’ve been having. At Craigievar Castle there is an ongoing stand-off between the collections staff and furniture beetle (woodworm), which leaves its signature holes in wood of any age. The control of humidity is central to this fight. Conservation is often at odds with the agents of deterioration.

Detail of multiple flight holes and a small adult woodworm beetle beside holes on a carved wooden leg of a table.

Evidence of woodworm in a table leg

In autumn, the changing colours of the leaves can be viewed through Craigievar’s loophole windows – again, a process down to the agents of decay. Ethylene inside the tree controls the barrier between leaf and twig and starts a process of decay, basically strangling it. This causes the three differently hued chemicals inside the leaf to wane at different rates, producing those amazing colours. But think how many column inches the autumn colours get compared to the skeleton leaf, which rivals its former whole self in terms of intricacy and beauty.

At about the same time, the papery structures of wasp’s nests lie newly abandoned, a derelict marvel of engineering. This architecture becomes home to new life of spiders and their victims. Outside in the garden the seed heads of sweet cicely endure a long time and the skeletons of many ferns and docken plants can prevail into the snows of winter.

Once again, I examine the hieroglyphic-like patterns on the cambium of the fallen tree. For now, on this morning, it feels a little like a Howard Carter moment: like the opening of a pyramid door and an eye to the architecture of decay.