Our recent publication, 50 for the Future, lists 50 things that we believe should happen in Scotland over the next 50 years to benefit both people and wildlife. In this week's 50 for the Future article, Susan Davies, the Trust's Director of Conservation, explains the ecological and economic impacts of invasive species in Scotland.

Number 45: Strategically eradicate Rhododendron and other key invasive non-native species

The National Bee Unit confirmed in September 2016 that the first record of Asian hornet had been found in the UK in Gloucestershire. Soon after we had breathed a sigh of relief that a nest had quickly been found and destroyed, up popped another sighting, this time in the Mendip Hills in Somerset. This recent new arrival serves as a reminder of the ever-present threat that invasive non-native species present to our native wildlife – in this case principally to honey bees which are important pollinators for many of our wild flowers and crops.

'Non-native' species are those introduced either accidentally or deliberately by human actions into geographical areas that they wouldn't naturally occur in, nor get to under their own steam. Not all non-native species are pose a threat, but concerns really start to mount if their competitiveness, ability to spread geographically, ability to modify or destroy habitats, and/or risk of transferring disease have deleterious effects on our native wildlife. These harmful non-native species are classed as 'invasives'.

The Great Britain Invasive Non-Native Species Strategy, 2015 sets the policy context for the control of invasive non-native species (INNS). The UK Government estimates that there are around 2,000 non-native species in Britain and that of these between 15-20% are invasive. The impact on the economy is estimated to be a staggering £1.7billion. Ten to twelve new invasive species are thought to become established in Britain each year, illustrating that this is an ever-present threat and emphasises the importance of remaining vigilant (good surveillance) and acting quickly (rapid response).

In Scotland, the principal legislation governing the introduction of non-native species in Scotland is the Wildlife and Countryside Act, 1981 which contains provisions on release or planting of non-native species, keeping or sale of invasive species and species control agreements or orders. The more recent Wildlife and Natural Environment (Scotland) Act, 2011 introduced new measures to make it an offence to release or allow any non-native species to escape from captivity, to allow any plant (exceptions are specified) to grow outside its native range and introduced a ban on keeping certain types of non-native plants and animals. A Code of Practice on Non-Native Species, 2012 was also approved by the Scottish Parliament and clearly sets out the law, individual's responsibilities and provides best practice advice.

Tackling the problem of INNS requires collaboration across a wide range of stakeholders including national and local government, land managers and the general public. The Scottish Wildlife Trust plays its part as an influencer of policy and conservation action and as a land manager on 120 wildlife reserves across Scotland. The ideal scenario is to prevent INNS arriving in the first place and then, if they do break through the initial line of defence, to detect and eradicate them quickly before they become established. If, however, that second line of defence is broken, we have to focus on control and containing or mitigating their impacts and that takes us into long-term management of the effects of INNS at a national, regional and local scale.

One example of such long term investment by the Trust is through the Saving Scotland's Red Squirrels partnership which co-ordinates the actions required to control the impacts (competition and spread of squirrelpox disease) of grey squirrels on our native red squirrels. Over nearly eight years, the work undertaken through this partnership has enabled red squirrels to start to recover and thrive in the south of Scotland, Aberdeen City and Aberdeenshire. The action taken has also effectively protected the red squirrel strongholds north of the Highland boundary line from the incursion of grey squirrels. The Trust assessed as part of its Reserve Biodiversity, 2011 report the occurrence of invasive non-native species on our 120 Wildlife Reserves. The figure below shows the range of INNS which have been detected and have helped to focus on our management efforts.

In particular, action has been taken on Rhododendron ponticum, Himalayan balsam, Japanese knotweed and giant hogweed. We are often reliant on the dedicated commitment of many of the Trust's volunteers who donate many hours to helping us respond to this challenge and are grateful for their continuing support. We also can't tackle this without considering what other land owners and managers are doing. Our reserves are inextricably connected to others areas in river catchments and as such, it is important that landowners and stakeholders actively come together to tackle the problems at this landscape scale – starting at the headwaters and working systematically downstream. The Trust believes that landowners should receive support from the Scottish Government to tackle this issue more vigorously and to make the long-term investment required.

Invasive non-native species are of course not only confined to terrestrial and freshwater habitats. They occur in the marine environment too, where they can also cause environmental and economic impacts. Some of these marine INNS, including Japanese skeleton shrimp and the acorn barnacle, are now well established, whilst others such as wireweed have recently arrived. Others, such as the Chinese mitten crab, have arrived in English and Welsh waters but are yet to be detected in Scotland. Maritime shipping has been identified as a major pathway for moving species from their native areas to new areas through the discharge of ballast water. Because of this, the Trust continues to call for the full implementation of the International Convention for the Control and Management of Ship's Ballast Water and Sediments to prevent the further introduction of non-native marine species in Scottish waters.

Invasive non-native species pose a significant threat to our native flora and fauna, and whilst fully eradicating some of the now well-established species is no small task, it should certainly remain a priority over the next fifty years.

Let us know your thoughts by emailing thefuture@scottishwildlifetrust.org.uk or Tweet @ScotWildlife using #50fortheFuture.

Susan Davies is the Trust's Director of Conservation.