The National Park has several botanical and mammalian invasive non-native species (INNS) which are having an adverse impact on our native biodiversity.
The species that are being targeted for control include:
The presence of invasive rhododendron is a major cause of designated native woodlands being classified as in unfavourable condition within the National Park – there are 35 designated sites (some of them overlapping, i.e. SSSIs and SACs) with designated features that are affected by invasive species. Ten of them have rhododendron present that affects the favourable status of the site.
Rhododendron, if left untreated, can inhibit the growth of all vegetation growing beneath its canopy, and eventually out-compete nearly all native tree and shrub regeneration. It casts dense shade and produces poor quality leaf litter, impacting on water quality and reducing invertebrate abundance. Re-colonisation with native species after removal of rhododendron is slow, resulting in a loss of native biodiversity and therefore the value of the woodland.
The NWSS in 2014, stated that the National Park had 5,787 ha of native woodland, with an estimated 7% (396 ha) being adversely affected by the presence of rhododendron. This may seem a small percentage, however, the task is a large and difficult one and key to controlling rhododendron is colony scale control which is co-ordinated, if required, over multiple land holdings.
Objectives by 2023
 Ben A’an and Brenachoile Woods, Boturich Woodlands, Craig Royston Woods, Cuilvona and Craigmore Woods, Fairy Knowe and Doon Hill, Glen Loin, Inchlonaig, Inchtavannach and Inchconnachan, Stronvar Marshes, and Trossachs Woods
The presence of invasive non-native species (INNS) within any habitat can reduce ecological connectivity due to the robust, structural growth of many INNS and the possibility of disturbance and spread.
The removal of INNS allows smaller native plants to recolonise including grasses, ferns and flowering plants. Re-colonisation of native species will result in an increase in native biodiversity and has the potential to encourage the expansion of vulnerable native species.
This working group aims to prevent, monitor and control the introduction, spread and extent of INNS that affect the riparian zones of the rivers and lochs in a sustainable manner on a catchment-wide scale. The focus will concentrate primarily on the control of invasive non-native plants: Giant hogweed, Japanese knotweed, Himalayan balsam and American skunk cabbage. Coordination will be included where overlap with the rhododendron working group occurs in the riparian zones.
It is recognised that complete eradication of INNS may not be attainable due to the high risk of re-infestations. The strategy is to manage INNS so that they do not severely affect the riparian corridor of the National Park’s water courses.
Objectives by 2023
Non-native animals are having a significant negative impact on our native ecosystems, being responsible for the decline of native species by direct predation, carrying diseases and viruses to which our native species have no resilience and out-competing our native species. In combination with direct control of the mammalian non-native species we want to undertake habitat restoration that will encourage the return of our native wildlife.
The work that is being carried out in the National Park complements the Scottish Invasive Species Initiative (SISI) which is led by Scottish Natural Heritage (SNH) and is funded by the Heritage Lottery Fund, SNH and by in-kind support from project partners and volunteers. This initiative is a four-year partnership project set up to tackle invasive non-native species alongside rivers and watercourses in northern Scotland.
The working group will concentrate primarily on the control of invasive non-native animal species – grey squirrel and North American mink, which will have beneficial results to the red squirrel and water vole populations, respectively.
Objectives by 2023