Reforesting bare river banks helps to stabilise banks, improve water quality, and restore freshwater biodiversity.
Scotland’s rivers were once surrounded by a complex mosaic of woodland, scrub, and wetland. Over time, many of these ‘riverwoods’ have been lost to deforestation and cannot grow back due to overgrazing from deer and livestock.
Re-planting native trees (e.g. willow, alder, hazel, aspen) can restore these important habitats and create a new seed source for future woodlands to regenerate.
How does it work?
Planting just a narrow strip of native trees alongside a river can deliver huge benefits, so can be integrated with other land uses such as agriculture and forestry. It’s important to select species that are suitable for the local climate and geology. Young trees must be protected from grazing to ensure survival, via a number of methods:
- Fencing along both sides of the river to exclude grazers from the planting zone
- Reducing deer numbers to the point where they will not impact the trees
- Protecting individual trees with a stake and biodegradable tree guard
- Planting ‘seed islands’ in fenced copses to encourage natural regeneration
Before restoration
This river bank has no trees or tall vegetation due to deforestation and overgrazing.
- With no tree roots to bind the soil together, severe bank erosion discharges sediment into the water. This smothers the clean, oxygenated gravel which fish need to lay eggs and spawn successfully.
- Without shade, the water heats up in the sun. Warmer water holds less oxygen so supports less life, from invertebrates to trout. Salmon thrive in cold water and cannot survive in water warmer than 28C.
After restoration
With trees and vegetation, the river’s ecosystem is restored to health.
- Tree roots stabilise the banks, reducing erosion and maintaining clean spawning gravel for salmon and trout.
- Dappled shade reduces water temperature by 3-4C compared to direct sunlight, helping species like salmon to survive the impacts of climate change.
- Roots trailing in the water create space for juvenile fish, e.g. salmon parr, to shelter from predators and flood events.
- Trees intercept and absorb rainfall, helping to mitigate downstream flooding.
- Trees intercept and absorb rainfall, reducing the amount of water that reaches the river channel during heavy rainfall events. This can help to mitigate downstream flooding.
CASE STUDY: The Eddleston Water Project in the Scottish Borders has so far planted 330,000 trees, improving spawning for salmon and providing natural flood management across the 69km2 catchment. Peak flows in Peebles, downstream of the project, are 29% lower than before.