Spey invasives

Last summer Toby and Callum, our summer students, got to know the lower river whilst completing a survey of invasive species. The survey targetted five species which were known to be present although their extent and abundance had never before been recorded. The aims were to:

  • Establish the distribution and extent of selected INNS
  • Identify the upper limit of distribution
  • Record evidence of management activties relating to INNS
  • Discuss control and management strategies for INNS
  • Report and disseminate the findings to stakeholders

This blog post helps fulfill the last and most important aim.

As expected we found lots of Giant hogweed (GHW) and Japanese knotweed (JK), less Himalayan balsam (HB), and a surprising amount of White Butterbur (WB). Ranunculus was recorded but it is difficult to combine surveying terrestrial and aquatic plants at the same time and the record of Ranunculus is likely to be an underestimate.

GHW originates in the Spey in the upper Mulben Burn where it grows in profusion in places. From the confluence of the Mulben Burn it rapidly increases in abundance along the banks for the Spey. Very few plants were recorded on the Spey upstream of the Mulben Burn confluence.

Dense stand of Giant hogweed

 

Knotweed colonising river gravel

Japanese knotweed colonising river gravel

Himalayan balsam is an annual plant and the exploding seed pods are becoming an increasingly common sight and sound on the banks for the Spey. Present as far upstream as Wester Elchies HB is now well established in the lower river where it thrives in the rich alluvial soil as well as on river bank shingle.

Himalayan balsam

Himalayan balsam on the spread

 

Stunted HB

Stunted but flowering HB on river bank shingle

The extent of White butterbur on the banks of the River Fiddich was a surprise. This rhubarb like plant is a non-native and along the Fiddich it has become totally dominant in places to the point where no other vegetation grows including sapling trees. This will have serious consequences for the ecology of the river in the long term.

White butterbur carpet

White butterbur carpet

Ranunculus is perhaps the most controversial invasive affecting the Spey. Research has found impacts on juvenile salmon and freshwater pearl mussels and it can have a direct impact on salmon angling when it grows in profusion.

Ranunculus growing in the Spey downstream of the Lour Burn

Early season growth of Ranunculus in the Spey downstream of the Lour Burn

It was an interesting survey and hopefully the report which can be viewed here will raise awareness of the growing invasives problem on the Spey. Someone asked me the other day what was the problem with invasives. He was aware of the threat to humans posed by the sap from Giant hogweed but the more insidious loss of native plant communities from the banks of the Spey is a harder issue to sell. The loss of ground cover vegetation along the riverbank in the winter and the consequent erosion is another easily grasped matter. But until you have seen the dominance of river banks by invasives and the total loss of the native flora the extent of the looming problem can be missed by many. The rich and diverse range of native grasses and herbs that grow so profusely on the banks of the Spey in the spring and summer are just one of the many features that make the Spey such a desirable river to fish. Action is needed now to maintain that high quality environment.

 

 

There are 5 comments for this article
  1. Andy Holtby at 3:18 pm

    There has been some interesting trials with grazing of young GHW plants as a form of control method. Difficult i know when pockets are either very small, difficult areas to get to/fence off, next to a river etc, but interesting all the same.

  2. Charlie Herd at 11:14 am

    Interesting and sadly not surprising. What do the Board intend to do to get rid of these problems?

    • Bryan Herbert at 1:12 am

      Charlie

      There are plans to tackle the problem not just on the Spey but on several other river catchments. But firstly as has been done on the Spey you have to ascertain the extent of the problem and identify the upper extremities of where the problem starts. Then you have to start the treatment up river and work down this will take a long time a lot of money and effort . I believe the seeds of giant hogweed can lie dormant for several years before germinating not sure about the other non-native invasive plants but I am sure someone in the know will be able to tell us. I am afraid there is no quick fix and could take in the region of 10 years to do but hopefully the board will get there in the end and no other budding gardener take home seeds other countries in the world and introduce another problem to deal with as that is where it all started.

      Bryan Herbert

      • Brian Shaw Author at 9:10 am

        Hi Charlie/Bryan,

        The Board/Foundation have taken the first steps towards tackling this problem. The Foundation is a partner in an EU Life+ bid which will provide significant resources to start tackling the problem. Some of the beats towards the upstream limit do a good job in controlling the hogweed but we will try and make a start this year in promoting best practice for control measures; we don’t want to be making things worse in the meantime.

        You are right Bryan, this will be a long term project but the Tweed showed what can be done with hogweed if there is the will.

        Best regards

        Brian

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