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| The peat deposits here are being eroded now, though they have accumulated over the last 10 000 years. The history
of vegetation of the area since the final retreat of the glaciers can be reconstructed from plant remains and pollen
grains found in the peat. Tree remains are mainly birch, showing Cwm Idwal was once wooded and conditions were
warmer than today. The pollen record demonstrates the whole sequence of changes from tundra vegetation (c10 000 years b.p), including arctic or alpine plants that are now confined to cliff ledges and at higher altitude and some plants that are no longer found in the Cwm. As the climate ameliorated, there was an influx of species of warmer conditions and woodland gradually developed, reaching its maximum development about 5000 years ago, when woodlands were found 2000 feet above sea level in Snowdonia (stumps embedded in peat). The trees later died on the upper slopes, probably due to climatic deterioration. More recent clearance of woodland by humans are shown by more herb species being found in the pollen analysis. |
