12 October 2014

It was previously outlined in Comment how hazelnuts probably came to Scotland after the last Ice Age by floating along on ocean currents, and getting washed up in sheltered west coast inlets, from which hazel would seed and then start to move inland.
The full account is located here: http://www.gocscotland.org.uk/general-landuse-environment/do-hazel-nuts-float
Japanese Knotweed around Loch FyneWebOn a recent trip to the west coast, I was looking at the Japanese knotweed around Loch Fyne. I always knew it was there, but never really gave any thought to how it got there, or how it was spreading about. There is certainly a lot of it, and it is invading a lot of coastal habitats, crossing the road in some places to get in to woods and farmland, and pushing up river corridors when the tide comes in.
A close inspection of the shoreline reveals how it is spreading. Most of the debris is old stems of Japanese knotweed. The plant dies back in the winter months, when the stems are fairly brittle. They are obviously shattered by the ocean waves, and the debris is taken out to sea, to be deposited somewhere else when the tide comes back in again.
Knotweed debrisWebA proportion of this debris will still be alive and capable of rooting. I am sure most of it ends up just a short distance from where it was produced, but no doubt some of it travels very long distances as well. It must do, because invasive species are present along huge tracts of west coast shorelines, and they cannot just have spread from lots of coastal houses and their gardens. No, the ocean waves are spreading Japanese knotweed around like they appear to have spread hazelnuts around in the past. Himalayam balsam is also very much in evidence, and no doubt the seeds of this plant can get transported around by the waves as well.
It follows then that dealing with this invasion is a massive undertaking. This is no doubt why most people seem to just ignore it. Ownership of the foreshore is often complex in such communities. Usually the Crown Commission is the actual owner, with local people having various rights as well.
Beds of Japanese knotweed among coastal woodlandWebBut who is responsible for dealing with invasive plants? I suspect no-one has thought much about it. Sometimes, you can see debris from Japanese knotweed washed up on large lochs as well, such as Loch Tay or Loch Ness. It is not just the sea that moves this plant around. It does of course move down rivers very readily as well.
Somewhere along the line, someone has got to take the issue seriously, but the cost will already now be very significant. Many things on the west coast are notoriously left until another day, but no benefit will be gained from putting this issue off for too long.
Argyll’s biodiversity and local economy gained very considerably in the past from having hazel nuts washed up, but no good is likely to come from these invasive species. They need to be stopped before they can move too far inland or become too well established along our western shorelines.

The writer's pictures show, from the top: Knotweed aroun Loch Fyne; Knotweed debris; and beds of Knotweed among coastal woodland habitat.

by Victor Clements
who works as a woodland advisor based in Aberfeldy

 

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