When Rivers Run Free
With many of Scotland’s rivers straightened, dredged and de-wooded, ecologist Aidan MacCormick immerses himself in a dynamic free-flowing river system to better understand how natural processes drive abundance and diversity in nature.
I’m sitting by the water’s edge, watching a dragonfly slowly unfurl in the warm June sunshine. A few minutes later, it takes off on a very wobbly maiden flight. Then, almost immediately, a wagtail snatches it mid-air, rips off the barely dry wings, crunches it into a ball and feeds it to its chicks nestled in the roots of an alder tree. I’m left reeling. I’d become emotionally invested in this dragonfly after watching it emerge and take flight. It had spent three years living as a nymph, only for its adult life to be over in minutes.
Despite my lifelong obsession with nature and 25 years of ecological experience, I sometimes struggle to fully comprehend the complexities of natural processes such as predation. Like most people I know that frogs breed in small ponds, salmon spawn in gravelly pools and waterside meadows are rich in wildflowers. But understanding how these habitats form and evolve, and how they are shaped by the myriad species that interact with each other, is challenging. That’s why I’m sat by a section of the River Feshie in the Cairngorms – part of the Northwoods Rewilding Network – on a glorious summer’s morning – to immerse myself in a truly dynamic free-flowing river system and better understand how natural processes drive abundance and diversity in nature.
This section of the Feshie is part of SBP’s Northwoods Rewilding Network, where nature is given space and freedom to shape the landscape. Here, water levels constantly change in a dynamic cycle, routinely sucking in riverside trees, their root plates creating deep pools where young fish find sanctuary.
Dynamic habitats like this, where nature is left to flex its muscles unimpeded, are rare in Scotland. While we see coastal landscapes shift dramatically according to tides and storms, change inland is less obvious and often discouraged.
For most people, sanitised riverscapes have become the norm.
Over centuries, we’ve pacified Scotland’s rivers – brought them under our control – in pursuit of increased resource production and to minimise property damage. We’ve straightened and dredged river channels, tamed floodplains and felled native woodlands to ‘tidy’ riverbanks.
Today, for most people, these sanitised riverscapes have become the norm, leading to a society that is uncomfortable with natural processes that can lead to mess and disorder; preferring instead, a feeling of containment and control over nature. Such resistance to change is reflected in our approach to nature conservation. Indeed, the word ‘conserve’ implies preservation of the status quo, where nature's inherent dynamism is perceived as a threat.
Conventional conservation often involves activities such as containing the spread of scrub, managing the populations of predators and artificially controlling water levels. Such approaches are driven by the belief that success is measured by preserving static habitats or maintaining wildlife populations at a predetermined level.
There are countless ponds and backwaters, some tiny, others large enough to swim in.
I spend the day exploring a complex mosaic of habitats on the Feshie. At this time of year, each ribbon of water is perhaps only 10 metres wide, but viewed from above, in places its network of braided channels and islands spans more than 200 metres. There are countless ponds and backwaters, some tiny, others large enough to swim in. Each one supports a unique community of plants and animals—young fish, tadpoles, dragonfly larvae, aquatic snails, or caddisfly.
The river islands also vary greatly in age, size and character. Some are large, with mature Scots pine, willow, and alder trees full with singing warblers, and tracks of deer and fox crisscrossing the ground. Others are messy boulder fields littered with uprooted trees from winter floods. On a few islands, there are small, desert-like strips of sandy soil covered in a patchwork of colourful wildflowers, full of bees and butterflies. Here, among the purple thyme and yellow kidney vetch, I discover colonies of the UK’s smallest butterfly – the small blue. This incredibly rare butterfly is entirely dependent on kidney vetch, on which its caterpillars feed and hibernate.
The small blue thrives in this section of the River Feshie due to floods that deposit sand onto the banks and islands, creating the ideal habitat for kidney vetch. Over time, as these areas are colonised by other plants and trees, kidney vetch disappears and the small blue colonies die out. However, winter floods periodically reset this process, allowing the butterflies to relocate and flourish, as they have done for millennia.
It all looks gloriously chaotic!
The importance of allowing dynamic processes to shape our river systems is evident where the river has eroded steep banks after flash floods. A colony of sand martins has found the perfect home here, easily excavating nest burrows in the newly exposed soft sand, with the steep banks over deep water protecting them from foxes and badgers.
The Feshie’s influence extends far beyond its banks. Long ribbons of mature alder trees mark the path of old river channels. Winter storms have brought down swathes of woodland, which will be left to provide homes for redstarts and woodpeckers. Some alders and willows lie on the ground, some are suspended – snagged by other trees – while others have fallen into the river. It all looks gloriously chaotic!
Wildflower-filled meadows flourish in areas that were once sandy river beaches and gravelly pools. In shallow puddles, I find tadpoles where deeper pools once held big trout. Signs of badgers digging up pignuts in lush grassland indicate places that were once ideal for spawning salmon.
If we could rewind time over decades and centuries, we would see how this untamed Cairngorms river has crafted an incredibly rich landscape; one that constantly shifts between wet and dry, sand, stone and soil, mosses, scrub and woodland, and back again. Over and over.
Being in a living landscape like the River Feshie is profoundly enjoyable and rejuvenating.
After spending an entire day immersed in this mosaic of rich habitats, I’ve deepened my understanding of the vital role of natural river processes that are constantly playing out, even those often seen as destructive or negative. Earlier in the day, I witnessed the death of a dragonfly that fed a wagtail family. Similarly, the cycle of destruction and renewal by a flooding and channel-morphing River Feshie is the driver for the rich biodiversity I encountered.
Yet it’s not only the rare species or abundant wildlife that matters. Being in a living landscape like the River Feshie is profoundly enjoyable and rejuvenating. Scrambling through areas of storm-felled trees and peering into pools on my belly reignited a childlike curiosity and joy of nature – feelings that are increasingly rare in our domesticated landscapes, where awe and wonder often feel absent.
Embracing the unpredictable forces of dynamic rivers will no doubt be challenging for many people, but I believe we must. When rivers are free to flow naturally and interact with the broader landscape, nature thrives – and so do we.
#Northwoods
Aidan MacCormick is SBP’s in-house ecologist, working with our Northwoods partners to enable more rewilding actions on the ground.
