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.
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.
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.
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.
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.