Enhancing the Malzie Burn (Bladnoch catchment)

The Malzie Burn is a tributary of the River Bladnoch and is considered particularly important as it hosts a rich and diverse fish population, including Atlantic salmon, Brown trout and Brook lamprey. The burn is covered by the River Bladnoch Special Area of Conservation (SAC) designation for Atlantic salmon. The watercourse is particularly sensitive as it contains a population of the highly endangered Freshwater pearl mussel (FWPM).

Due to the overall importance of the Malzie Burn, GFT have been undertaking a restoration programme to enhance habitats and reduce environmental stresses (particularly from climate change and increasing water temperatures). Salmonids and FWPMs lifecycles are inextricably linked. At the glochidial life stage of pearl mussels, they latch onto the gills of salmonid species and stay there until they are ready to drop off and grow further in suitable gravels. Therefore, healthy salmonid populations are needed to maintain FWPM populations.

A key priority identified to protect and improve the burn habitat was to establish a native riparian broadleaves woodland to provide shade to help keep the water at a stable and cool temperature during the increasingly hot summer months. This is very important for both salmonids and pearls mussels as they are intolerant of high water temperatures.

As the trees mature they will also drop woody debris into the burn, an important habitat for fish and aquatic invertebrates. Instream woody debris also plays an important role in allowing watercourses to function more naturally which further helps to improve climate resilience.

It was encouraging to find that there was strong landowner support for the project proposal. All of the main landowners along the burn agreed to allow some degree of riparian tree planting. The landowners included Forest and Land Scotland, private forest interests and farmers. In total the project so far has worked with six separate land holdings over a total burn length of 7,500 km. Working over so many different land holdings meant the restoration is being taken at a level of scale which will deliver significant ecological benefits.

Since the project started in 2019 over 1,900 native deciduous trees have been planted and protected from grazers. A range of techniques were used depending on what was agreed with each owner including:

• Erection of 1,400 m of new bankside stock proof fencing and then planting within the fenced area
• Dense riparian conifers were removed from both banks over a length of 700 m and replaced with native hardwoods
• Within areas of commercial forestry plantation, clumps of hard woods were planted over a length of approximately 2,000 m.
• Along a length of 2,100 m of the lower burn flowing through rough pasture, 1m x 1m wooden enclosures were constructed to protect individual planted trees.

These planted trees and their protection are being routinely checked and maintained. Any dead trees are replaced, repairs completed to fencing, wooden enclosures strengthened, etc. GFT aim to remove plastic tree guards as soon as the trees are large enough to allow them to grow as naturally as possible. We aim to reuse these guards where possible at other sites.

A section of the upper burn had been historically dredged and strengthened as part of agricultural improvements. This type of works severely degrades instream habitats and very little biota can be found here. The lack of substrates is particularly damaging to fish and FWPMs. Salmonids need gravels to lay their eggs in and pearl mussels need well oxygenated gravels to live in as part of their complicated lifecycle. To improve 600 m of this dredged habitat, we introduced by hand large numbers of cobbles and boulders. This introduced material provides important cover for juvenile fish, diversifies water flows and encourages the natural deposition and buildup of smaller gravels and pebbles around the added boulders. Monitoring has shown that these introduced material has improved habitats and now supports more fish than previously.

This project is on-going. As well as maintaining the works completed to date we plan to expand the planting into new areas.

This project has been financed so far by NatureScot (via the Biodiversity Challenge Fund), South of Scotland Tree Planting Grant and GFT.