How trees can record climate change |
| There are a number of ways to observe our changing climate, from keeping weather records over long periods, to geological analysis of rocks and soil sediments. But one of nature’s own ways is to record changes, such as moisture and temperature fluctuations, in the rings of trees. Counting and analysing these rings is a practice known as dendrochronology; this method for dating wood and determining climatic changes has been in use since the early part of the 20th century. |
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How dendrochronology works |
Every year trees form a ring of growth around their circumference. These rings are continually added each year, sometimes over hundreds or thousands of years. Tree growth is controlled by a number of complex factors which includes sunlight, wind, and soil conditions such as temperature and moisture - the more a tree’s growth is limited by environmental factors the more variation we see in the width of its rings.
It is not necessary to cut a tree down in order to see its ring growth as a boring tool is used which removes a long, slender core. For example, imagine a sample of wood from an ancient oak tree, perhaps a trunk which is several thousands of years old. The outer growth rings of the oak can be compared to the inner rings from living trees. In dendrochronology what we look for is an identical pattern of rings from both samples, once that has been established we can continue dating, and comparing climates, further into the past. |
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| Santorini & Irish bog oaks |
Through analysis of ancient Irish bog oaks archaeologists have discovered correlations between the volcanic eruption of Santorini in the Aegean Sea, and climate changes which affected the oaks – an event which took place more than 3,500 years ago, c.1628 BC. The trees showed significantly narrowed rings for several years after the eruption, indications that their growth was poor but that the climate was affected only temporarily. The story of Santorini is a fascinating one which has often been compared to the eruption of Vesuvius that led to the cataclysmic events at Pompeii in AD 79.
For more information about Santorini and the Irish bog oaks please visit the Thera Foundation Website. |
| Britain’s changing woodlands – spotting the changes |
 Woodland is an intrinsically important aspect of our landscapes, and our native trees have adapted to our local climates over a long period of time whilst current environmental changes seem to be taking place rather more quickly.
At the greatest risk from climate change are Britain’s native woods of oak, beech, ash and Scot’s pine. Sycamore and horse chestnut are responding fastest to the changes with hornbeam and the ever familiar hawthorn coming into leaf earlier than in previously recorded years.
 Monitoring the environment can be done in a number of ways and one currently popular method is phenology. Phenology is the study of recurring, natural phenomena and is carried out by observing the arrival and departure of species in our environment. A good example of a large scale phenological study is the BBC’s Springwatch campaign which involves the observation of various animal and plant species country wide.
Phenology can be an extremely effective way of gathering important environmental information, especially when thousands, or even millions of people, are involved in gathering that information.
It is, perhaps, through methods such as this that we will come to more fully understand the dynamics of the environment which supports us and the importance of our own place, and actions, within it.
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