High, on the craggy side of a mountain, there is a ledge. You could barely lie down on it, but from it, the view is breath taking. Above this ledge the mountain rises, imposing, to its summit. Beneath, the ground drops away in a scree of angular rock to a tarn far below; on a good day, the blue of the sky shines back from the water’s surface – on a bad day, you can’t see the lake, never mind reflected colour. In the grip of winter, wind can scream along the rock faces, scouring off life; snow and ice find refuge for months in the desolate hollows and crevices. In summer, the North facing stone barely feels the sun. Throughout the year weather can be severe, frequently arctic and at no point is water plentiful, though this is not through lack of rain, rather a rapid run off from the rock.

And yet, on this ledge that I write of, little willow trees cling to life. Their strong roots anchor them tightly into the soil that has collected on the shelf of rock; here these little willows have grown for centuries, isolated and undisturbed. Undisturbed that is, except for the slow but steady stream of botanists who have scrambled up the mountain face to take a look at these tiny trees, mostly no higher than a climbing boot, the odd one at knee height. For these willows are downy willows, relics of the ice age, and the only known specimens in the whole of England.

Towards the end of the last ice age, as the glaciers carved their way through this landscape, they were surrounded by tundra. Devoid of tall trees, the subsoil of this habitat was permanently frozen. Alpine plants like the downy willow thrived, finding the perfect mix of open ground and cool climate. However, as the temperatures rose, glaciers melted away to be replaced by woodland; the tree line climbed higher and higher up the slopes. Alpine plants were forced up to the rocky summits, finding a home on cliffs and screes, the unstable slopes where trees could not survive. Later on, people arrived. They opened out the woodland, and perhaps the alpines could have expanded their range downwards again, had these people not brought grazing animals with them, suppressing and restricting the sensitive alpine plants still further. Meanwhile warm rains were acidifying the soil, and the removal of rare alpines by well-meaning Victorian plant collectors did not help matters. Unvisited by man and animal, it is likely these landscapes would now be abundant with biodiversity and flowers; instead they are impoverished, with the rich mountain flora largely confined to inaccessible crags, ledges and gullies.

And so it is with the downy willow. First discovered by James Backhouse 1872, these specimens have been carefully watched and recorded through the years. Many famous botanists have noted their presence, and they feature in all the important plant literature describing the area. But these tiny trees are trapped. In 2002, Derek Ratcliffe wrote in his book Lakeland, ‘A few [species] have critically small populations for reproduction, notably the downy willow whose few surviving bushes are all female.’ And even if there was a male plant enabling these individuals to produce seed, the chances of a seed successfully germinating in another ungrazeable position is highly unlikely. These plants have not spread for over a century and during this time, the odds have become increasingly stacked against them.

So back to my timeframe. When my first child Joe was born there were, at the most, ten healthy specimens living in relative good health on the mountain ledge, and a few less vigorous specimens in equally inaccessible places nearby; they had changed very little in all the time they were being recorded. These were the only plants in England, and a couple of well-placed rock falls could wipe out the whole population, bury them deep beneath a pile of rubble.

It was my husband Mark who had come across the story of these plants, at work. He had come home with the tale and, in my evolutionary biologist’s head, I wondered. Should someone intervene? Is this just evolution in action, are these relic plants destined to go extinct because the ice age is over? They are doing just fine in Europe as a whole, does it matter that England may soon be without them? Or is it more involved than that? Is it our doing, our animals contributing to this, tipping these plants into extinction here? Is it our responsibility to repair some of the changes we have wreaked upon the landscape? Do we need this biodiversity?

And as I touch the smooth bark of the tiny downy willow sapling I hold in my hand, I still debate with myself what the answer should be…