Examination by the Forestry Commission in Freiburg West Germany of growth rings from the trunk of a Black Forest fir tree, showing evidence of acid rain damage. Each ring is an expression of one year's growth & reflects the growing conditions over the period. The fir tree examined here shows a collapse of ring growth over the last 20 years (outer rings immediately beneath the bark). The rings are smaller & closer together than previous years (inner rings), indicating a stunted growth history. This is linked to acid rain pollution, the lowering of pH levels in rainfall due to sulfur dioxide emissions into the atmosphere.
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