A Talk by Tam Ward – 16th August 2006
Knowledge of woodlands from the past in Scotland is normally gleaned by the collection and study of charcoal and pollen from archaeological sites. We are able to tell what the landscape was like at any given period, and to show what types of woodland, if any, existed.
Wood is not a good survivor from ancient times in Scotland, principally because our acidic soils decay most organic matter quite quickly. However, if the wood has been semi burned and turned into charcoal, then that charcoal will not decay at all because it is pure carbon. Two very important aspects of charcoal exist for archaeologists; one is that the cell structure of the tree survives in the charcoal allowing identification of species to be made and two; we can date it quite accurately using the radio carbon method.
Most people will have heard about radio carbon dating but I suspect few will understand it. Here it is in simplest terms; all plants absorb radioactivity from outer space during the process of converting the sun’s energy into leaves. When animals or fish eat the plants, they ingest the radioactivity and if any strictly meat eating animals eat other animals, they then absorb the stuff, so all living things end up with this radioactivity in their make up. The radioactivity is an isotope called carbon 14 and it has the unique property of decaying at a fixed and measurable rate. Roughly after about 5000 years half of it has gone and it decays proportionally until it disappears completely after about 45,000 years. So you cannot date samples over 45,000 years by this method.
The process destroys the sample so we have to identify its species first. A Geiger counter linked to a computer works out the age. Radio carbon years are actually younger than real calendar years and this is all worked out by the computer. Carbon 14 dating has been tested against tree ring dating from the world’s oldest living trees, the bristlecone pines and America which are over 3000 years old, so we know that it works. If a sample is about 5000 years old we get to an accuracy of about 50 years, but the older the sample, the more accurate the date gets.
So now you see why charcoal is so important to us, we get to know the type of tree it was and, if there is £300 to spare, we get to know its age.
Pollen is much more difficult to find, but in the right conditions it survives very well. Like the cell structure in plants, pollen is distinctive for each species.
So if we find a lot of tree pollen then that means there was a forest and if we get grass or plant pollen then that might mean there were no trees, and so on.
We know about lots of events in tree history, for example there was a sudden decline in Elm around 5000 years ago, this used to be thought of as the first farmers clearing away woodlands for their fields and houses, but now it is more likely that there was a serious Dutch Elm disease outbreak, and of course we lost nearly all of our Elm trees in Britain recently due to that disease. (explain it)
So what do we know about our tree landscapes of the past? Trees only appeared in Scotland less than 12000 years ago when the last ice age melted away. 15000 years ago there would have been at least a half mile of ice above our heads here.
When the ice melted away, very quickly plants re-established themselves and soon what we call the pioneer trees arrived. These were birch, willow. Then we have oak, alder, elm and hazel appearing about 10,000 years ago. Things get a bit warmer and pine arrives to form the so called Caledonian forest. Many others species such as rowan, cherry, crab apple became well established.
All of this information is now in the archaeological and botanical record.
In pre-historic times we never find charcoal or pollen from trees such as beech, chestnut, sycamore, lime and many others. This is because they were not here at that time, they have since been brought in by people and of course in the last 200 years all sorts of foreign trees can be seen in parks and gardens now.
People and trees have been linked since the first people arrived in Scotland about 10,000 years ago, at that time all of Britain was covered in blanket forest; trees like birch grew high on the hills up to about 1500 feet above sea level. The west coast islands were covered and only in the most northerly island of Shetland were they absent. This tells us something else, and that is that the climate was much better then than it is today, slightly warmer and drier, and in fact we know that this optimum climate lasted until around 3000 years ago when it deteriorated to what we have today. People arrived for one reason only – food, and the forests were teeming with it. There were giant elk, wild cattle, deer, wild boar, so lots of lovely dinners for the people. The animals and the forest provided everything the people needed. Other animals included wolves, bear and beaver, now all sadly gone – some even extinct.
These first people are called hunter gathers and they never stayed long in one place, making camps using birch, hazel and willow to make their little huts. They lasted from about 10,000 to 6000 years ago and it seems likely that for 4000 years, they used and respected the woodlands, just as similar people in rain forests still do today, taking what they need and moving on to conserve their rich paradise. The hunter gatherers probably cleared patches of woodland so they could hunt animals better, but their impact would not be great.
This all changed around 6000 years ago when the first farmers made their appearance. Now large areas of woodland had to be cleared to make fields to grow crops such as wheat and barley. Trees were cut down to build houses for the first time and also to be used as fuel for permanent settlements. This was when the stone axe appears, because a tool was needed to chop down trees. This is called the New Stone Age and these people used only stone for cutting tools; of course tools were also made from bone, antler and wood. This is also when the first pottery was made and used.
This period lasted for 1500 years until about 4500 years ago, the first metal was invented. First copper, then copper and tin mixed to make the much harder bronze, and gold was also exploited at this time. By now, the tree species were still the same as before, but the pollen record shows that large areas had no major woodland; this was because farming was spreading over the landscape, with large grazing areas needed for domesticated cattle, goats and sheep, and more and more ground was being cultivated.
It would appear that up to about 3000 years ago, people lived in relative harmony with each other, there were no defended settlements. However, that was about to change quite suddenly because the climate altered from warmer and drier to what we live in today. Winters were longer, colder and wetter; all of the high ground where people lived and farmed was now useless for anything but grazing. People found they had to move down the valleys for new ground, but other people were already there, so the obvious happened, they fought for the land. This coincided with a new metal being invented – iron, by 2000 years ago we were in the Iron Age and now find people living in villages of timber houses surrounded by stockade fences and ditches, you can imagine all the timber these fences required. The new metal meant that swords, spears and arrow heads were much better at killing – not animals but people! We’ve been trying to kill each other off ever since! By this time huge areas of the landscape were treeless, and because of farming and grazing, natural regeneration of trees could not take place. The cold wet climate meant that peat began to grow faster on the hills and that meant that trees could not grow in it.
The Romans arrived in the first century AD and they built timber forts, trees were disappearing fast. Wood became the fuel for industrial processes like smelting copper, iron and lead, heating pottery and glass kilns, eventually coal was used for these activities – but not yet.
As the centuries rolled on people continued to cut down woodlands for houses, castles, churches, building larger and larger ships until by the 17th century in southern Scotland, you would be lucky to see a single tree anywhere. This sounds hard to believe but it is true, because we have many comments made by travellers who were amazed by the fact.
In the 18th century people started to plant trees for the first time, often this was on large estates for ornamental purposes and we can still see many of these trees today. Many new species were now brought to Scotland for the first time. This continued through the 19th century with shelter belts appearing along side fields and roads, these can also still be seen today. Then in the early 20th century large areas of Scotland were planted with conifers such as spruce, larch and Douglas fir, this was used as pit props in mines and telegraph and electricity poles, railway sleepers and for a boom in the building trades. Coal had replaced wood as the major fuel across the country for most domestic and industrial uses.
Finally, new quick growing species of Sitka spruce were introduced to be harvested in 40 years; massive areas were planted and still are for this timber which is used mostly for paper making and for chipboard. But now there is a serious glut of this timber and these forests are ruining the landscape as they increase acidity in the soils and in the rivers, killing off wildlife.
The other important thing trees allow archaeologists to do is to date buildings by counting the annual tree rings. In Scotland it is not much good because our wood didn’t survive, but in England and Ireland they can go back in real year time for hundreds of years.
So hopefully you found this of some interest and can now appreciate why archaeologists love trees.
Contribution to the Opening of Little Mitchellwood on 26 August 2006