51

At Stirling University, Helen leads the way along a breeze-block corridor to her lab. Helen's time span is not in the future but in the past. She opens an industrial-size fridge to takes out a metre-long core of peat, a thousand-year record of vegetation in Pollan Buidhe. Possibly it was the very core I watched her draw from the ground. The column of peat is notched at two-centimetre intervals where small samples have been extracted for analysis.

She talks about ‘pollen rain’, the shower of pollen grains that drenches the soil every year with monsoon regularity. Within this core of peat is the evidence of a thousand pollen storms. Through the microscope the separate pollen grains swim into view, each species having a distinctive shape. To my eyes, pine pollen has Mickey Mouse ears.

Her project is long term but already one tentative conclusion suggests that, 250 years ago, pine trees in the area of Glen Affric between the head of Loch Beinn a'Mheadhoin and the lower reaches of Loch Affric (including Pollan Buidhe) were sparse, with many fewer trees than grow there now. Most of the ground seems to have been open heath. This is a big surprise. The orthodox view has been that the pine forest has flourished abundantly from time immemorial. The Old Caledonian Forest may have been patchier than we thought.