Defeating the invaders

P1060899P1060917Loch Lomond NNR

As it is Invasive Non-Native week it is worth reflecting on all of the hard work by staff and volunteers is trying to defeat the invaders at Loch Lomond NNR.

Tackling invasive non-natives across a large site is never easy and nearly always more complicated that it first seems. At Loch Lomond NNR,  we has been working away at the problem of invasive non-native plants (INNS) since 2004. At times it has seemed an endless and thankless tasks but after 15 years of evolving techniques and marshalling forces,  progress is being made.

The NNR is about as highly designated a site as you can get, with UK and European designations covering 430has of habitats and species such as woodland, swamp and mixed fen, open water, rare vascular plants, invertebrates, lamprey, Greenland white fronted geese and wading birds. In 2004 the rapidly increasing amount of Himalayan Balsam in one of the best fen areas of the site was starting to affect the conservation features of the site. NNR staff decided to start work on trying to remove this invader but what started off as a limited project quickly started to grow as more and more areas of balsam were found. Over time more problem species were added to the list as staff surveyed the fen and woodland so at times the job seemed insurmountable.

But staff and volunteers stuck to the job and gradually the first discovered areas were cleared. To give an idea of the sheer amount of work undertaken, in 2015 – 45 000 balsaam plants were pulled, 2016 – 66 000, 2017 – 30 000. But all the time areas were being cleared and new areas started. So in 2019 only about 400 plants were pulled. Finally there was an appreciable effect on all of the effort. Likewise is another part of woodland a large area of bamboo was tackled – about 500 metres square. But this year there is just a very small amount of regrowth to deal with.  But the project on Loch Lomond NNR is by no means finished but there are encouraging signs that some of the INNS are declining or disappeared. But we can’t relax yet because even if the site is cleared of INNS plants we will need to continue efforts monitoring the site to keep on top of seedlings coming back and plants that have even washed downstream from invaded parts of the catchment upstream.  It is going to be a long-term job but really encouraging to see that all the effort is worth it.


The last few Himalayan balsam plants left to pull

Here are some of the learning points from 15 years of tackling INNS at Loch Lomond NNR.

  • Carry out a full survey of the whole area to assess the size of the job. Don’t stop at land ownership boundaries: our team works in people’s gardens next to the reserve, further up water courses and within the catchment. .
  • Work in partnership to cover wider areas and increase resources. We work with the RSPB, The Loch Lomond and Trossachs National Park and the Lomond Fisheries.
  • We couldn’t get anywhere without the help of volunteers. We work with our own volunteer group and also with RSPB, National Park, Lomond Fisheries and corporate volunteers.
  • Cherish your volunteers as it is a tough job – bake them cakes, give them good outdoor gear, allow them time to enjoy the site and its wildlife on a work day.
  • We had to do a bit of a hard sell to encourage people to come and help us. For them it was a chance to work on a rarely visited, hidden corner of the National Park and maybe see special wildlife like ospreys, kingfishers, otters and barn owls.
  • Research the species you are tackling, to find out control techniques that are successful elsewhere, length and viability of seeds, depth of roots etc.
  • Have a plan for the season. Work out what needs to be controlled when and then try to line up teams of volunteers for those times.


    Woodland starting to recover after the removal of a huge patch of bamboo.


Himalayan balsam free natural wet woodland.

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