Over the last two winters, I’ve spent a bit of time in the west Highlands helping my friend Louise with a reforestation project at Ben Damph, near Torridon. It’s beautiful there: the hills great curving shapes upholstered in tweed, carefully creased with the tracks of the deer and the sheep.

And it is because of those deer and those sheep that the landscape is as it is: treeless and sparse, the thin line of the horizon delineating heaven from earth and little else. A place where sunlight and shadow play out across a vast canvas. Trees can’t get started there. Or, if they do find a foothold, are shortly stripped of leaves and bark by hungry mouths.

So if you want them, you need to protect them: a deer fence—exclosure, not enclosure; or if you can’t spare the miles of wire and posts that requires, then plantation and protection on an individual basis. It’s physically demanding work, lugging lump hammers and stakes and all that protective tubing through peat bog. Long days on the hill in all weathers. The trees we’ve been planting—native species like rowan, aspen, downy birch, sessile oak—need to get in the ground during the coldest months, so that by the time of the growing season they’ve had time to settle in, to put down roots.

Working out there in the rain and the sleet and the hail—in these wide-open glens, gouged out in the Ice Age by glaciers—it’s hard not to think about the passage of time. What was the world like, when last these slopes were dense with woodland? What will the world be like when these seedlings are full grown?

This year, Louise was planting while heavily pregnant. Heavy lifting was out, but she still found plenty to do. While our partners busied themselves driving stakes into the rocky ground, we lagged behind and talked as we worked. I would step my spade into the earth and waggle it to create a narrow hole, then drizzle in a few grains of slow-release fertiliser. She would come behind me with a bag of tiny trees, selecting a good species for the site, then submerge its roots and bed it in gently with the edge of her boot.

In a few weeks—days, now—her life was to change utterly. That moment, the one we were standing in right then, was soon to be bundled with everything into a “before.” To her child, these trees will seem always to have been there. But to us they are a timer we have set ticking, a marker that will record the distance we have travelled from this moment of transition.

It felt a significant moment. But as with all moments it had to pass. In the north, winter days are short and twilight was already slinking in around us. Nothing for it but dig and plant, dig and plant, and do all we could do before dark.

On the way home, we revisited some of the trees we planted last year, righting bent tubes and replacing broken stakes, and found that most of them were thriving. A few brave rowans were stretching their limbs beyond the tops of their tubes. Already as tall as, or taller than, me.

This time last year, I could fit one in my pocket. It is as tangible a reminder as I could ask for: a lot can change in the space of a year. I hope that in 20 we meet there again, and eat our lunch in their shade.