Under climate change, Scotland is facing the very real possibility of a local extinction of Atlantic salmon.
Catches in the Scottish Highlands reached an all time low in 2022, representing just 75% of the five-year average. During the mid-1980s, there were between eight and ten million salmon swimming around Scotland’s Atlantic coast; that number has now dropped to two to three million.
During the extreme summer of 2018 – the warmest on record for Scotland – 70% of Scotland’s rivers experienced temperatures above the critical threshold for thermal stress in juvenile Atlantic salmon. And temperatures are going to rise: The UK Met Office predicts that summers like that of 2018 could occur every other year by 2050.
Temperature modelling undertaken as part of the Scottish River Temperature Monitoring Network (SRTMN) has identified that waters across Scotland, particularly in the uplands, are now at high risk.
Our riverbanks have been stripped of trees.
Part of the problem is that there are very few trees on Scotland’s riverbanks to shade the water. In fact, Scotland has lost 97% of its native woodland. Many river catchments that would have once been covered with rich woodlands of pine, willow, downy birch and alder have been stripped, leaving the riverbanks bare and exposed.
Without the cooling shade that trees provide on riverbanks, these hugely important river catchments are experiencing thermal stress. Today, that is already reducing the survival rates of commercially and culturally important species such as the Atlantic salmon, brown trout, and critically endangered freshwater pearl mussels.
Further, according to the Native Woodland Survey of Scotland, more than 60% of our remaining native woodland habitat is significantly impacted by herbivores, preventing natural regeneration.
Restoring riverbanks can protect salmon, store carbon, boost biodiversity, and benefit local communities.
A logical starting point is the restoration of woodland on riverbanks – an intervention that has been proven to keep water courses cool during hot summers, boost freshwater biodiversity and benefit salmon survival. Restoring riparian woodlands will provide critical nursery grounds for young salmon; the tree cover will shade the water, cooling the temperature to improve salmon survival rates; while the revegetation of the riverbanks will help to restore natural hydrological flows, providing sorely needed habitat and resources for invertebrates, birds and mammals. Carbon will be drawn in from the atmosphere as the trees grow. Additionally, restoring riparian woodland will help to naturalise the flow of water out from rivers and the drainage back into them, mitigating flood risk.
Why the Kyle catchment?
Today, there are 86 full time job roles on the Kyle river catchment related to salmon. If salmon disappear as our climate warms, the loss of these jobs would double the unemployment rate across the Kyle catchment.
Native woodland remains on under 20% of the Kyle of Sutherland area, with most headwater rivers featuring less than 5% native riverbank woodland cover.
Native woodland cover on the Kyle rivers (KSFT analysis):
The Cassley – 6%
The Shin – 4%
The Evelix – 19%
The Carron – 8%
The Oykel – 5%
Alladale Wilderness Reserve – where one million native trees have been replanted along the two glens, which flow from the Carron river – sits in the center of the Kyle catchment. It is a glistening example of what can be achieved with ambitious plans to improve the condition of habitats and restore healthy, functioning nature.