Okay so no, INNS doesn’t actually stand for ‘it never never stops’. But for anyone reading this who has dealt with them before, you know exactly where I’m coming from. For those of you who don’t? Prepare to be enlightened…
INNS stands for Invasive Non-Native Species. This refers to any species – plant or animal – that is not native to the UK, but that is now found in the UK, and that has a significantly detrimental effect on native wildlife. It’s important to note that not all non-native species are invasive, while some native species can be invasive. Confused yet? It’s all about the adverse effects they cause our local wildlife, combined with their ability to readily spread across the Scottish landscape.
As it’s INNS week, that is what we shall focus on. And unfortunately we have several INNS present across Loch Leven NNR: Four major plant species (Himalayan balsam, Japanese knotweed, Giant hogweed and Skunk cabbage) and two mammals (grey squirrels and mink, both of which are native to North America).
How did they get here? Many plants – particularly very pretty or ‘ornamental’ ones – tend to have a story attached to them of some wealthy soul from yesteryear invading travelling the globe and deciding en route that “these plants are very pretty and so I will take them home with me and plant them in my mansion garden”. And the rest is, well, not history. Some animals have also historically been brought over and subsequently released. Sometimes by collectors and landowners who decided they wanted to jazz up the local ecosystem a bit.
Photo by Lorne Gill
What’s that? People doing things with neither thought nor care for the consequences? Shocking! And we have also seen much more recent examples of invasive species being allowed to run rampant. Which leads us nicely into the various INNS we have to manage here at Loch Leven NNR.
American Skunk Cabbage (Lysichiton americanus) is like something out of ‘The Day of the Triffids’. They are bog-loving beasts that can grow to massive sizes if left to their own devices. And since sales of this species were only banned in 2016, they basically were! It spreads in a twofold attack, by seeds and by rhizomes – a sneaky root system that can grow horizontally and put out roots and shoots of new plants. It is this root system that makes established plants so difficult to tackle, and why pesticides are often required. If you don’t remove the whole root system when digging the plants out they will simply grow back, so a highly targetted chemical dose into the centre of the plant’s stem is often necessary on older plants, while younger and smaller plants may still be possible to dig out.
The patch of skunk cabbage we control isn’t technically on the reserve, but the boggy waterway it has colonised leads directly to the loch. There’s no point dealing with INNS on a boundary-only basis, you’ll never win the ever-encroaching battle. Buffer zones and partnership working is the way to go, and due to the nature of Loch Leven’s waterways (providing an easy and extensive seed dispersal route), we have a dedicated catchment management group on the case.
Japanese Knotweed (Fallopia japonica) is another species that spreads by rhizomes and is so fast at taking over an area that contaminated soil has to be disposed of at registered sites. Apart from extensive digging and burning operations, which are costly and not always possible, pesticide is the best way to limit the spread of this plant and must be applied for several years at specific times – once at the beginning of the growing season, and a second time before natural dieback. We have a few small patches of this on the reserve that we cannot dig out and burn, but which must be prevented from spreading to nearby watercourses at all costs, and so pesticide is our only option.
Giant Hogweed (Heracleum mantegazzianum) is another species the reserve has thankfully not been overrun by, but which has set up shop along parts of the shoreline, likely spreading from the North Quiech. We control individual plants with pesticide – spraying newly emerging leaves – and (where possible) cutting the flowers off of stems before they seed. Giant hogweed is one we advise everyone to avoid as it has photoxic sap which can cause incredibly painful burns to the skin, as well as long term issues with exposure to sunlight. It’s probably one of the most dangerous plants you can come across – thank goodness for spray suits!
On the topic of pesticides, there are many valid criticisms to its use, and believe me I certainly would not be advocating for them if there was another equally effective way to manage INNS, especially on a nature reserve. They’re bad for the environment, they’re bad for wildlife, and they’re bad for us – in ways that only become increasingly evidenced as studies continue. I’m sure that in the not too distance future we’ll see widespread pushes for bans not only in gardens and urban areas, but within agriculture and for cases like ours too. We need to start thinking about how we will deal with INNS without the use of pesticides. But as it stands today, without them we’d be completely overrun and our natural biodiversity (which is already struggling) would take an even bigger hit.
Thankfully, our most prevailent INNS does not necessitate such chemical warfare.
But which species is this? Our nemesis, the final boss…is…
Himalayan balsam (Impatiens glandulifera) runs rampant across Loch Leven NNR. It’s already beginning to pop out in force and is perhaps the one we all dread the return of most. Taking up a significant portion of our summer management, from the moment it begins to grow until the point at which it begins to seed, every spare moment is dedicated towards ‘balsam bashing’. Staff, volunteers, contractors, any passers-by we can convince to join the cause all attempt to keep this plant from spreading as much as we possibly can.
We have a limited period of two to three months to tackle as many areas of the reserve, including the islands, as we can. Thankfully, it’s one of the easiest plants to control manually. Their shallow root systems do not spread via rhizomes, and their lack of ability to sting, burn or stab us means mean we can simply grab and pull handfuls upon handfuls (upon handfuls, upon handfuls…) of the stuff and leave it hanging above the ground on branches and logs to dry out and die.
We only have until it begins to set seed to do this, because balsam has a pretty unique way of spreading. The seed cases will reach a point where they are, quite literally, fit to burst. The cases explode! And this can disperse the seeds by several metres. They can also be forced to explode if disturbed as the plants, sensing danger, pop pre-emptively. This is why we have to stop, and why we try to discourage the public from popping them for entertainment too!
So why is it so prevelant? It’s shallow root system means it can grow pretty much anywhere. It’s also a very fast grower that can reach heights of up to 2.5 metres. This means that it overtakes and shades out plants that are growing in the same area before they’ve had a good enough chance to grow and establish. Over time, a lack of deeper root systems also leads to soil degradation and erosion (a particular problem along watercoursee). Bees do seem to love it, but it is important to remember that this is likely to the detriment of other native wildflowers, perpetuating a viscious cycle.
The pandemic didn’t help either, and we’re still seeing the fallout of just one year being missed. INNS need constant control and subsequent monitoring for years after their apparent eradication, as seeds can lay dormant in the soil. Lockdown meant we couldn’t keep anything in check for a whole summer, and it’s allowed the balsam in particular to bounce back with a vengence. We’ll be busy for many years to come, that’s for sure.
Thankfully, our invasive mammals don’t cause us nearly so much grief. American mink are good swimmers, and could decimate our breeding duck populations if they got their paws on some tasty eggs. We also have the occasional grey squirrel sighting in the local area, but our native red squirrels seem to be fairing well, and ongoing control of both INNS means that sightings are few and far between.
Across the UK, control of INNS is a costly (we’re talking hundreds of millions for total eradication!) and time consuming task that can at times feel endless. Certainly, by the end of last summer I was practically seeing balsam in my sleep! This year there will no doubt be more sweaty days spent inside chemical protection suits, and every spare moment will be devoted to pulling up plant after plant (after plant…). It’s a task that is definitely best undertaken in company, not least to ward of the balsam bonkers-ness, but because the more bodies we have on the ground the more of an impact we can make. This is why we are always so greatful for our volunteers who never fail to show up ready and willing to get stuck in – tackling the balsam at Loch Leven simply wouldn’t be possible without them.
So, if you see us out and about over the next few months kitted up in hazmat suits or ripping up plants with apparant abandon, worry not! There haven’t been any murders, and we aren’t some hooligans set on destroying this beautiful place. Rather, we’re a bunch of biodiversity protectors just trying our best to ensure that our wonderful reserve doesn’t completely succumb to encroaching invasives.
For more information on INNS management, check out organisations like the Scottish Invasive Species Initiative, Saving Scotland’s Red Squirrels and the Hebridean Mink Project. Remember to take care while gardening, and utilise organisations such as the RHS for their advice on how to best help protect our natural ecosystems.
Loch Leven National Nature Reserve 