Using drones to survey invasive species

78% of water bodies in the North West of England are failing to meet Good ecological status, one contributing factor to this is the prevalence of invasive non-native species (INNS) such as Giant Hogweed, Japanese Knotweed and Himalayan Balsam. These invasives out compete native species for food and resources and can be a danger to humans and other wildlife.

Here in the Irwell Catchment, we know that Giant Hogweed is a serious problem however, we know where the major problems are, but still keen to measure the full extent by tracking where the infestations start. It’s known that the lower reaches of the catchment are the worst effected, however it is often better to start clearance upstream instead, in order to prevent the spread of seeds in the future.

What are organisations doing about INNS in Greater Manchester?

In order to effectively manage INNS, as part of Natural Course, GMCA has procured a consultant to survey the presence of Giant Hogweed within the River Irwell Catchment. The Irwell Catchment Partnership created a working group who could strategically co-ordinate efforts to tackle the issue.

Staff and volunteers from member organisations including The River Stewardship Company will first carry out walking surveys on land adjacent to the river to understand where Giant Hogweed occurs.

This data will be used to acquire and assign the necessary resources to help tackle the invasive species.

Some areas along the river bank are also difficult to physically access due to cliffs, marsh, dense vegetation, and private land.

Because of this, Groundwork have employed a trainee drone pilot who is supporting the survey of invasive species along the Irwell Catchment as part of the Resilient River Valleys project.

The team are testing to see if footage recorded by the drone can be used to identify invasive species, rather than having to send a survey team on land, which is more labour intensive and presents the challenges listed above.

This drone survey includes several waterbodies in the River Irwell where ‘hotspots’ of Giant Hogweed indicates there is an issue further upstream.

As well as identifying Giant Hogweed, the team were also able to see vast patches of Japanese Knotweed, another invasive species dominating local riversides. From eye level the team couldn’t see over the top of the bushes and the pathway behind it was blocked by trees, but by using the drone they could see how widely it had spread in that area, while also seeing the Giant Hogweed among the infestation.

Chelsea Dudley, Groundwork’s Trainee Drone Pilot added:

“It’s great that my skills flying a drone can be applied to help the local environment. The footage we captured showed a spread much bigger than we imagined so it was good news that we found it when we did.”

Is there a future for drone surveying?

Paul Barrington, a Biodiversity Data Manager from Tameside Council joined the team on their trip, giving feedback about the experience:

“It was an eye opening introduction to drones on probably the worst site I’ve ever seen for invasives, Outwood Country Park. It’s truly terrible and that’s such a shame as it’s a large green area with river connectivity”

Paul commented on how useful it was to have photos taken in real time by the drone, when the invasive species is at its most prominent:

“We need the photography to be (a) recent and (b) taken around July. You don’t get that control from Google Earth, you just get what you are given which can often underrepresent the problem. If aerial photography is taken too early in the season it’s also hard to estimate how much there is.”

However, the team also found that one downfall of a drone is its inability to assess the ground conditions for the removal team.

“You can’t fly this through a densely wooded area, only over the top of them. Ground conditions in woods need to be assessed via a walkover visit.”


The Trainee Drone Pilot role is being funded through the Resilient River Valleys project.

Made possible thanks to funding from:

The Government’s Green Recovery Challenge Fund was developed by Defra and its Arm’s-Length Bodies.  The fund is being delivered by The National Lottery Heritage Fund in partnership with Natural England, the Environment Agency and Forestry Commission.


Want to learn more about invasive species and how to remove them? Check out our guides and projects below:

What is Himalayan Balsam?

How to get rid of Himalayan Balsam

Bee a Pollinator