Fast-growing rhododendron poses a huge threat to the future of our unique rainforest in Argyll. Drone technology is helping us to survey the spread of the invasive shrub more quickly and accurately than ever before, making it easier to create a robust plan to tackle it.  

Walk through remnant temperate rainforest in Argyll and you’ll encounter native trees such as oak, ash and birch dripping with lichens, mosses and liverworts. Ferns and fungi, alongside a mix of bryophytes, carpet the woodland floor. Butterflies, songbirds, red squirrels and pine martens are among the inhabitants of this increasingly rare native habitat. Half of what remains of Scotland’s rainforest can be found in Argyll and Bute, but it is under threat from Invasive Non-Native Species like Rhododendron ponticum, which spreads rapidly and creates dense colonies that drown out our native species.  

Community collaboration

That’s why we’re working with landowners in Knapdale, where rhododendron is particularly widespread, to survey the extent of the invasive shrub. Drone technology makes it possible for us to build a detailed picture of the distribution of rhododendron over a large area. 

Fig 1. The initial analysis of drone imagery identifies where rhododendron is growing across the site. The data could be used in future projects to look at other species, but for this project, we are quantifying rhododendron only.

Working with local landowners, the drone flights covered three key areas of Knapdale. Starting in April, before the trees came into leaf for the season, we surveyed over 900ha using drones for the first time.

“We’re really pleased with the results. The data is incredibly detailed and we’re able to make really accurate assessments of the coverage and distribution of rhododendron,” said ACT woodland coordinator Philippa McKee who is leading this project. “We’re now finalising our analysis by getting out there in person and assessing some targeted areas on the ground.”

On the ground

It’s important to also consider the logistics for future control and treatment, for example, where access could be tricky as the ground is very steep. Using a combination of drone and on-the-ground surveys is proving successful so far and will give us the information we need to plan our approach. 

“The management of such a large and unwieldy dataset has not been without its challenges,” said Philippa. “But we are pleased to be making progress and are confident that the data is giving us the level of detail that we need to map accurate quantities and costs"

Fig 2. Buffers are applied to the points as part of the analysis. In this image, you can see the surrounding predominant native species, a mixture of oak and birch as well as open areas of heather.

Landowners around Knapdale have been hugely supportive of the initiative and are also committed to tackling rhododendron for the benefit of our native habitats. We’re now sharing our findings with individual landowners and using the new data to work out and cost a plan for dealing with rhododendron in the area. Working out the best way to fund the clearance of rhododendron is the next crucial step in the process.

Looking ahead

“There is no doubt that the scale of this task is considerable,” commented Philippa. “It will require a long-term commitment to stand the best chance of succeeding in the landscape-scale sustainable clearance of rhododendron. And, ultimately, the restoration of native woodland in the heart of Scotland’s rainforest.”

There is no doubt that the scale of this task is considerable. It will require a long-term commitment to stand the best chance of succeeding in the landscape-scale sustainable clearance of rhododendron.

Project funders

• This project is supported by the Scottish Government’s Nature Restoration Fund, managed by NatureScot, and Scottish Forestry.

     

Alliance for Scotland's Rainforest

We work as part of the Alliance for Scotland's Rainforest, which is a voluntary partnership of more than 25 organisations, committed to collaborative action for the benefit of Scotland’s rainforest. The Alliance is supported by Plantlife Scotland and Woodland Trust Scotland.

Our vision is that Scotland’s rainforest will thrive once again.

Why we're tackling rhododendron in Argyll

Find out more about why we’re tackling rhododendron in our blog article, 5 reasons we’re tackling rhododendron.