Reviving the River Calder: A Nature-Based Blueprint for Biodiversity and Climate Resilience
By Ewan Harris MRICS
Nestled in the uplands of the River Spey catchment, the River Calder has long been a vital artery for wildlife and local communities. But in recent years, concerns over its ecological health—particularly the dwindling numbers of juvenile salmon and trout—sparked a bold and transformative restoration initiative. Supported by the NatureScot Biodiversity Challenge Fund, SEPA, and the Woodland Trust, the River Calder Restoration Project set out to breathe new life into this upland tributary through a landscape-scale approach that blends science, sustainability, and collaboration.
Restoring the River’s Rhythm
The first phase of the project, completed in 2020 and 2021, focused on revitalizing the river channel itself. Historically, the Calder’s habitat had become too uniform, lacking the gravel beds, pools, and riffles essential for a thriving freshwater ecosystem. To address this, 29 Large Woody Structures (LWS) were installed along 1.6 km of the river. These structures, crafted from locally sourced trees with root balls intact, were embedded into the riverbed and banks to mimic natural deadwood. The result? A more dynamic channel that encourages sediment deposition, flow diversity, and habitat complexity—key ingredients for supporting fish at every stage of their life cycle.
Re-wooding the Riparian Zone
Equally transformative was the creation of up to 15 hectares of riparian woodland along 3.5 km of the river. Previously bare of trees, this stretch now hosts over 15,000 native trees, including birch, rowan, and other species suited to the upland environment. Protected by 5.5 km of deer fencing and innovative water gates designed to withstand the Calder’s spatey flows, these enclosures are already showing signs of success. Natural regeneration is thriving, with pioneer species taking root and older trees in the glen providing a seed source for future growth.
Benefits Beyond the Riverbanks
The ecological benefits of the project are wide-ranging and deeply interconnected:
- Habitat Diversity: The new woodland corridor enhances terrestrial habitat, supporting birds, mammals, and invertebrates. It also contributes to in-stream health by stabilizing banks and enriching the river with nutrients and deadwood.
- Improved Aquatic Habitat: The LWS have begun to reshape the river’s flow, creating cooler pools and gravel beds ideal for spawning. These features offer refuge during high temperatures and spates, boosting resilience for species like Atlantic salmon and trout.
- Climate Resilience: Shading from the new woodland helps regulate water temperature, a critical factor as summers grow hotter. Cooler water is essential for fish survival, and the trees also slow runoff, reducing flood risk downstream.
- Natural Flood Management: Woodland acts as a sponge, absorbing rainfall and smoothing out peak flows. This nature-based solution protects communities and farmland along the Spey from increasingly frequent flood events.
Three Years On: Signs of Success
By 2024, three years after project completion, the Calder is showing promising signs of recovery. Salmon have spawned in the newly formed gravels, and early electrofishing surveys by the Spey Fishery Board suggest improved juvenile fish numbers. The planted trees are thriving, and natural regeneration is robust, with healthy growth of birch and rowan in the protected enclosures.
Monitoring continues, tracking water temperature, fish populations, invertebrates, birdlife, and tree growth. While long-term data is still being gathered, the early indicators are encouraging. The River Calder Restoration Project stands as a powerful example of how integrated, nature-based solutions can restore ecosystems, support biodiversity, and build resilience against climate change.
Written By: Ewan Harris MRICS, Director, Head of Estate Management Scotland, Savills
Ewan will be speaking at our upcoming Scottish Conference: Source to Sea – Working Across Landscapes