History of Irish Oaks - Prof. Mike Baillie
For many years now, Mike Baillie has been researching something called “dendrochronology”. This is a technique for dating past events (climatic changes) through the study of tree ring growth. The annual rings that a tree produces (those seen when a stem is cut) consist of larger cells earlier in the year and smaller cells towards the end of summer and autumn. There is no growth during winter. These rings can be counted to show the age of a tree – one ring representing one year of growth.
The patterns that are created by the rings as a tree gets older are unique. Rings are narrower during years when conditions are not so good for tree growth and wider when conditions are better. This combination of wide and narrow rings allows very accurate dating of which year a ring was produced. By collecting samples of wood from trees growing now and wood from trees cut down in the past (going back several thousand years!) has allowed Mike to overlap samples and create a pattern of rings in Irish oaks going back to 6,000BC (over 8,000 years).
What this study has allowed Mike to do is to suggest possible links between climatic ‘events’ in the past and periods of change and disruption for humans. For example, trees across the northern hemisphere showed considerably poorer growth around 540AD. This coincided with outbreaks of plague that killed hundreds of thousands of people and the death of ‘King Arthur’. Mike suggests that something like the impact of a comet and the debris thrown into the atmosphere may have caused a number of years of climate downturn leading to crop failure and disease.