A Rewilding Diary by Emily Warner

Over the past months we’ve featured an occasional series by the writer and scientist Emily Warner, reflecting on her experiences in the Scottish highlands, conducting conducting ecological research in a rewilding project. In this final piece she contemplates the sum of her  life in Glen Affric, the scientific and personal.

Over the last two years, I have been carrying out scientific research in regenerating native forest in the Scottish Highlands. This has been an experience that has mixed the spiritual and personal with the objective and universal. The scientific questions that I am pursuing are extremely relevant to the exploding interest in tree planting in the UK, and I hope will play a small role in sculpting the policy decisions surrounding this. My research also attempts to increase our ecological understanding of an ecosystem set within a web of complex cultural and social interactions in Scotland. But equally, gathering data in such a place, living in sublime balance, has been a privilege and a delight, a rare chance to step out of normal life and retune to the frequency of nature.

In the summers of 2018 and 2019 I spent time in Glen Affric and Glen Moriston, transplanted from periods of planning, data analysis and writing to the intensity of data collection. These fragments of time mirror the glimpses of enlightenment that my results give to our understanding of native forest expansion. Using methodical comparison, between the reforested areas, unforested prior state and mature Caledonian Pineforest, it is possible to see patterns emerging. As I begin the process of transforming my results into scientific papers, I return again and again in my mind to the rhythm of my summers and the time that I spent in the relative wild.

As a scientist I am called upon to present my research in the most objective light. But the experience of conducting research is so much more than that. It provides the chance to live with simplicity in proximity to nature, disconnected from the rest of the world and yet wholly aligned with the ecosystem that surrounds you. The methodical precision of data collection draws your entire focus to specific parts of the landscape. Entwining mindfulness with the discipline of science, to reach a state of complete immersion. Sitting in total concentration for 15 minutes at a time, listening and watching for each bird that visits a plot. Crouching over a quadrat, meticulously identifying each plant species that is present. Searching the understorey, recording every tree seedling. Repeating these ritualistic processes again and again, in different sites and habitats. Comparing mature forest to young forest, the young forest to the unforested landscape. The days of work build into weeks, and those into months, until finally you are rewarded with an accumulated set of data containing thousands of observations. Somehow the process and the purpose inform each other, the tranquil calm of repeated actions perfectly complimented by the overall aims of the research. The physical days of fieldwork transition to the analysis of data and identification of patterns and trends, which will eventually be woven into the narrative of a scientific paper.  From there, that information enters the world, where each tiny fragment has the potential to shift norms and shape perceptions, altering our idea of how we should interact with the landscape in the future.

The backdrop to the repetition of everyday tasks was the ephemeral and shifting mood of the landscape, played out in an endless sequence of unique combinations of light and weather. For stretches of time days were demarcated only by their marginally differing depths of mist and weights of drizzle. Interspersed with evenings of golden sunlight, imparting a stillness over everything, or mornings where gathered mist would rise with the first rays of the sun to reveal the frosted tops of the mountains. There were days when rain poured down and the mountainside streams roared across the paths. Days where sites were inaccessible, out of reach beyond a deepened river. On some days we staggered across the landscape, plunging a leg hip deep into a bog, lurching over tussocks or crashing to our knees in a rocky streambed. On others we covered ground in bounds, springing off thick beds of heather and moss, propelling ourselves uphill from tree trunk to tree trunk, forging through streams, the ice cold water a welcome relief to bare feet on a hot day. On all days, we never felt anything less than insignificant on the scale of the landscape, our data collection trivial, the results received with indifference by a glen that has harboured nature and humanity for thousands of years.

I have sought science as a method to achieve a more objective understanding of the potential benefits of reforestation, or rewilding if you prefer, compared to the unforested state that dominates in the Scottish Highlands. Three years into my PhD, my expectations of the outcomes or answers to these questions have shifted. Science rarely provides complete and conclusive answers to questions. You pitch a question, seek to answer it, often refining and shifting your focus in the process, and frequently find that your results illuminate further recesses of the unknown. To say that my research has highlighted how much we don’t know would be going too far, but as much as it provides new information, it emphasises important things that we don’t know much about. Failure to acknowledge and explore these uncertainties will make predictions of the consequences of large-scale native reforestation in similar scenarios uncertain. The two main spheres that my work has addressed are the influence of native reforestation on biodiversity and on ecosystem functioning.

Firstly, given that the original motivation for planting areas of native forest in this part of the Scottish Highlands was to extend an existing ancient remnant of Caledonian Pineforest, how do the organisms living there respond to restoration? The Caledonian Pineforest is thought to cover just 1% of its former extent, but in Glen Affric a large remnant remains. This habitat supports a specific community, including rare lichens, invertebrates, birds and mammals. My work shows that in the reforested areas plant, bird and carabid beetle communities begin to transition towards those found in the mature forest habitat, moving away from the unforested community. This emphasises that reforestation drives the formation of a forest community. However, the particularly rare and characteristic species that specialise on the mature forest do not yet seem to appear in the reforested areas. This forest represents future potential, and intuitively we would expect the more specialist species to take longer to recolonise. So, the adage that the best time to plant a tree was 20 years ago holds. We create forests now, to become the forests of the future.

The second key finding relates to carbon storage, adding further evidence to our emerging understanding of the carbon balance with upland reforestation. My research shows that the soil carbon in the reforested sites is much lower than in the unforested and mature forest areas. This suggests that the process of tree planting may have led to a release of carbon from the soil, of a magnitude far greater than the carbon captured during tree growth, even after thirty years. During the short time that I have been working on my PhD, the interest in reforestation as a solution to climate change seems to have gathered pace exponentially. This ambition reflects the ability of trees to remove carbon from the atmosphere and store it in their biomass (trunk, branches, roots, leaves). Helping to erase some of the huge debt of carbon dioxide that has accumulated in the atmosphere. But this is not the whole picture, trees are not planted on a blank canvas or inert substrate, they are being introduced into existing ecosystems, with geological, ecological and human histories. In the Scottish Highlands a huge store of soil carbon, our most important terrestrial carbon stock, lies below the surface. Even outside the particularly carbon rich areas of peat bog, there can be high levels of carbon in the very organic soils. It is thought that tree planting alters the soil environment, aerating it and stimulating the microbial and fungal communities, which start to break down the carbon in the soil. In locations with carbon rich soils, tree planting could alter a delicate balance, stimulating the release of carbon that has been locked up for centuries. As the trees grow relatively slowly, they will take decades to centuries to compensate for this loss. At the sites I have studied, even in the oldest areas of reforestation, the accumulated tree biomass is still much smaller than the amount of carbon that appears to have been lost from the soil.

This presents a conundrum: unintuitively and inadvertently tree planting in some locations could release carbon. Simultaneously as I have reached these results, experimental work and modelling similarly show soil carbon loss after reforestation in equivalent areas of high soil carbon. The interpretation is however complex. We tend to think of carbon targets on decadal timescales, with relation to our ambitions for net zero, and reforestation with these methods and in these contexts does not seem to be a potential contributor. However, on much longer timescales these forests might begin to tip the balance, reaccumulating the carbon that they have lost.

Additionally, one of the key themes of the reforestation debate in the Scottish Highlands is the influence of grazing. Reduced pressure from deer would see the spontaneous heterogeneous establishment of native woodland, mixed with less forested habitat across a wide area. My feeling is that, under natural regeneration, the trees would establish more effectively in the lower carbon soils, whilst the wetter and more carbon rich areas might remain treeless. The risk of releasing large amounts of carbon from the soil seems likely to be reduced, soil disturbance will be avoided and the clumsy human judgement of where trees are appropriate is removed. Reduced grazing would also benefit the existing forest, stimulating regeneration to maintain the carbon stored in this habitat, and areas of peat bog, which have also been degraded by overgrazing. So other carbon-rich habitats would benefit from lower deer grazing. This is an area that still needs unpicking, we have very little information on large scale natural regeneration and lack monitoring data over the longer term. In a country where high grazing pressure in the uplands prevents natural regeneration and maintains the treeless state this is hardly surprising.

With both the carbon and biodiversity questions we need to think beyond the small scale and consider a wider landscape. Diversity begets diversity, and different habitats, both forested and unforested existing alongside each other would likely lead to the overall richest habitats for wildlife and potentially help to optimise carbon sequestration. Additionally, we should not be making judgements on one metric alone, the high value of these future forests for biodiversity might outweigh the carbon sequestration priority. What is crucial is that we are accurate in our understanding of what the reforestation brings and don’t assume that every forest expansion project equates with carbon storage.

My time conducting fieldwork has also had many human influences. The players in the social and cultural stories that are the context within which the landscape is set, but also personal relationships and bonds forged with like-minded people. On many days Glen Affric seemed to bustle with walkers, both groups and individuals, following the Affric-Kintail way or circumnavigating Loch Affric. Often, we had stepped sideways from the well-trodden path, and unobserved from the valley-side could chart the progress of other visitors to the glen. Occasionally we would cross paths, quadrats and bamboo canes drawing curious questions. My work in Glen Affric has also been a tale of collaboration: friends, field-assistants and family giving themselves wholly to my fieldwork for chunks of time; input from staff and volunteers at Trees for Life; the pick-me-up of a hot shower and fresh scones with Hanne at the youth hostel. The reforestation in the glen is also the result of much larger collaboration, driven forward by Trees for Life, Forestry and Land Scotland, and the National Trust over the last 30 years, the work of dedicated staff and countless volunteers who have felt compelled to do something to restore a dying ecosystem.

Even a year on from my last visit to Glen Affric I still catch a scent of heather and air and rock when I open my rucksack, an intangible essence of what it was to work in such an environment. It carries me straight to the view down the narrowing valley of the River Affric, Loch Affric at my back, and mist drifting across the gullies and slopes of the unfolding mountains. It reminds me of so many moments during fieldwork. An eagle gliding to meet us as we stepped out from the canopy of ancient pines on the shore of Loch Affric, the early morning sunshine burnishing the feathers on its back as it gyred upwards over the water. The gradual progression of the season marked in the unfurling and then fading of rowan flowers, followed by the appearance of bright red berries. The lifting of hours of drizzle to reveal brightness across the base of a deep mass of clouds.

My research has given me a chance to learn more about a landscape that I love, and to address questions that may help to drive decisions about its future. But it has been so much more than that. I have had a chance to be within something, observing and documenting, happy to better understand even a fraction of the perhaps unknowable whole. Human nature craves certainty, we seek simple messages and answers to our problems. The natural world is the opposite of that, it is inherently diverse, complex and contradictory. We can record emergent patterns, create experiments to answer specific questions and model expected future trajectories. But ultimately, in the real-world, things won’t always happen as we expect, our understanding is crude. We yearn for simplicity, but nature is complex, and if we want to construct any kind of narrative for our future, we must begin by embracing that.

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Emily Warner is a PhD student based at the Departments of Plant Sciences and Zoology at the University of Oxford. Her research aims to understand the benefits of replanting native forest, with a particular focus on the uplands of the United Kingdom.

Photography by the author.