The Plantations

The First World War used up Britain's timber. Pit props, trench revetment, sleepers and packing cases had come largely from imports, the submarine campaign cut those off, and the country cut down a great deal of what it had.

The Forestry Commission was created in 1919 to make sure that did not happen again, with a straightforward remit: establish a strategic reserve of timber as fast as possible.

Upland Wales was cheap, marginal and available. Powys got a great deal of planting.

Why Sitka

Sitka spruce comes from the Pacific north-west of America — wet, cool, acidic, exposed. Which describes upland Powys accurately enough that the tree grows here faster than almost anywhere in its native range.

It tolerates poor peaty soil, it withstands wind, and it produces usable timber in forty to fifty years rather than the century a hardwood needs. From a 1920s strategic standpoint it was the obvious answer, and from a commercial standpoint it still largely is.

The blocks went in fast, at high density, in straight-edged compartments laid out for machinery rather than for the shape of the hill. Hafren above Llanidloes, the Radnor forest plantings, Crychan and Halfway in the south-west, and dozens of smaller blocks.

What was there before

Sheepwalk, mostly, and the farms that ran it.

The Commission bought land from estates breaking up after 1918 and from farms that were failing anyway, and in some districts the planting accelerated depopulation that was already under way. A hill farm sold for forestry took its household with it.

That is a more complicated story than either side of the argument usually allows. The plantations did not empty the uplands on their own; they arrived in country that was emptying, and they made the emptying permanent by changing what the land could be used for.

The archaeology underneath

Here is the part that surprises people.

Ploughing destroys earthworks. Forestry ploughing at planting does damage, sometimes severe, but once the trees are in, the ground beneath them is not touched again for half a century. Nothing is ploughed, drained, improved, reseeded or built on.

So the Powys forest blocks contain hut circles, field systems, deserted farmsteads, boundary banks and cairns preserved in a state that would be unthinkable on working farmland. They were invisible for decades under the canopy.

Lidar changed that. Airborne laser survey records ground level beneath vegetation, and hillshaded lidar imagery of the Welsh plantations has revealed a great deal that nobody knew was there. Welsh Government publishes the coverage free through DataMapWales.

Clearfell is now the dangerous moment. When a block is felled the archaeology is exposed and vulnerable to heavy machinery, and the surveying has to happen before the harvesters arrive.

The criticisms

Acidification. Conifer plantations on already acid ground increase acidity in the streams draining them, and the effect on fish populations in mid Wales was serious enough by the 1980s to prompt liming programmes.

Biodiversity. A dense even-aged spruce block supports very little. Recent management has moved towards varied species, open ground, riparian buffers and continuous cover, but a great deal of the estate is still first- or second-rotation monoculture.

Appearance. The straight edges are the complaint people make first, and they are being softened at each restocking.

Peat. Planting on deep peat releases carbon rather than storing it. Some blocks on deep peat are now being removed rather than replanted, which is a substantial reversal of the original logic.

Now

The public forest estate in Wales is managed by Natural Resources Wales, formed in 2013. Policy is towards mixed species, longer rotations, public access and carbon, rather than a strategic timber reserve, which nobody has needed in that form since about 1950.

What to look for

Straight-edged blocks on the 1:25,000 map, and the older field walls running underneath and beyond them.

Ruined farmsteads at the edge of plantations, often just outside the fence where they were left when the land was sold.

Ancient woodland indicator plants — bluebell, dog's mercury, wood anemone — surviving in the strips along streams that were never planted, which tell you where genuinely old woodland used to be.

And the felled compartments, which for a few years show you exactly what the ground looked like before 1920.