This week has been devoted to the subject of INNS or Invasive Non Native Species.
Firstly a few definitions.
The Great Britain Non-Natives Species Secretariat (or GBNNSS) defines Invasive Non-Native Species as “Species that have serious negative impacts on our native British species, our health or our economy”.
Invasive or not
Not all non-native species are invasive; some are extremely useful e.g. Potatoes, Rhubarb and Chickens; some are decorative e.g. Monkey Puzzle trees and garden roses, but don’t dominate ecosytems.
Himalayan Balsam, Japanese Knotweed, Giant Hogweed and our old friend American Skunk Cabbage are large leafy plants which block out he light killing off the native sedges and flowers, creating patches of bare soil beneath. This then leads to a secondary effect of increased sedimentation, when the bare patches of soil erode into the burns and river.
This makes life more difficult for the native aquatic plants and invertebrates. Which has a knock on effect on wildfowl which feed on the aquatic plants and invertebrates.
Some native species can be very invasive; Bracken and Gorse, especially in “semi-natural” systems; Meadows, Heathland, Upland pasture. This is a result of land management changes. If not managed these species can dominate and massively reduce bio-diversity. However in the right quantities in the right place it’s a valuable addition.
INNS are a global problem, and some of our native species can be a problem outside the UK Gorse is a priority INNS in New Zealand, where it’s a horrendous problem. Purple Loosestrife; a much loved wetland plant, native to the UK; is reeking havoc in North American marshes The invasive non-native species have evolved to coexist with other species which keep them under control in their native habitat. Last weeks blog post on American Skunk Cabbage is a case in point.
Skunk Cabbage native to North West America is one of the first plants to appear in spring, following the harsh North American winter. The roots are dug up and eaten by Black and Grizzly Bears; mostly to have a bit of a clear out after their long winter snooze. In the absence of Bears on the NNR (which would cause a whole load of other problems), the Skunk Cabbage is free to populate all suitable areas of habitat.
Loch Lomond NNR has the most extensive list of invasive species of all the Stirling NNRs; as it’s at the bottom of the Endrick and Blane catchments. The catchment brings down seeds, plants and roots from a 264 km² area; and when the Endrick Water meets Loch Lomond, the flow slows significantly to less than 1m/s. ideal for depositing the afore mentioned seeds, plants etc on the reserve.
The Nature Reserve has within its boundaries, some 22 designated features (a technical term for habitats, species and assemblages of species of conservation interest, which have legal protection).
Most of these are, or can be, affected by INNS; along with the many non-designated species and habitats.
The most vulnerable are the plants; although ground nesting birds are directly affected by American Mink. The most obvious effect on plants, is being out competed. This is of key importance; as Loch Lomond NNR has 9 protected plants. From the grandiose Scottish Dock, to the tiny Narrow Leaved Water-starwort.
Over the last couple of decades; we’ve been working on reducing; and in some cases eradicating INNS from the NNR; or at least the ones we can.
There are some which we really have no idea how to cope with. These are the fully aquatic species Canadian Pondweed and Nuttalls Pondweed. These species grow beneath the surface of the water in depths of up to 3 metres, which make it impractical. In addition even if there was a way of eradicating these two; all it would take is a Duck or Goose to fly in with a fragment of the plant on their feet and we’d be back to square one. The best we can expect is to minimise the impact; by maintaining the best water quality possible, to prevent these plants from “blooming” and dominating the water bodies.
As there are a huge selection of INNS on the reserve, we have to prioritise by working out the risk of the INNS to the ecosystem and the effort required to reduce the impact.
This requires a cunning plan
It’s not all bad news though We have eradicated Giant Hogweed, Japanese Knotweed and New Zealand Pigmy Weed completely (as far as we know; we are still monitoring; never does to be complacent) and we are nearly there with Rhododendron Ponticum and Bamboo. Himalayan Balsam has been reduced from 100,000’s (possibly millions we’ve lost count when it was at its worst) to a few 1,000.
This wouldn’t have been possible without a consistent effort from our team of volunteers.
Placement students and staff. Despite reserve management boundary changes, fluctuating staff levels, and a global pandemic lock down We are now at the stage of spending more time looking for INNS than dealing with them. At the beginning of the INNS program, we spent about 140 staff and volunteer days per year managing INNS we now average about 45 volunteer and staff days per year on Loch Lomond dealing with invasive species. The National Park, Loch Lomond Fisheries Trust and the RSPB are also turning back the tide, both within the reserve and in the wider area.
Loch Lomond NNR is a bio-diversity hotspot and without the INNS program, it’s doubtful if it would have remained so
A big thanks to all the volunteers past and present; who’ve put in a mighty effort over the last 15 years to maintain this extraordinary habitat.