Invasive Non-Native Species: Should all Nature be Championed?

18 May 2022

Invasive Species Week 

The international community is facing twin emergencies: climate change and biodiversity loss. These entangled crises demand swift action from policymakers and Nicola Sturgeon’s recent commitment to showing leadership on both crises is very welcomed.

Tackling the nature crisis can feel even more complex than the climate crisis and yet it is paramount that biodiversity is interwoven into all decision-making processes. As we progress through the UN Decade of Ecosystem Restoration, Scotland must continue to take real, sustained and effective action to restore ecosystems. However, when it comes to Scotland’s nature restoration, considerable attention needs to be paid to the intricacies of specific ecosystems and the situated threats that they encounter.

Invasive Species Week 2022 (16-22 May) is an important opportunity to highlight the considerable damage and expense caused by invasive non-native species in Scotland and the UK. It may be surprising to some to learn that invasive non-native species have been identified as one of the five key drivers of global biodiversity loss, alongside changing use of sea and land, direct exploitation, climate change, and pollution (IPBES, 2019). Furthermore, a 2020 study published by Global Change Biology suggests that even moderate increases in invasive species expansion (between 20-30%) are expected to cause major impacts on biodiversity in most sociological contexts.

Discussions of invasive non-native species are set to be at the forefront of the UN’s upcoming COP15 – ‘the biodiversity COP’ – where the attending parties will be formalising The Post-2020 Global Biodiversity Framework. Similarly, it is paramount that tackling the spread of invasive non-native species is included in the new Scottish Biodiversity Strategy and delivery plan, to be delivered in October 2022.


What are invasive non-native species?

Just like humans, over time many species migrate into new hospitable habitats and gradually adjust to fit into their new ecosystem. However, there are certain species that have been translocated into non-native ecosystems, whether intentionally carried by humans or not, in which they have considerably adverse effects. These species are known in these ecosystems as ‘invasive non-native species’.

It is important to note that not all non-native species are invasive. When a species simply moves outside of their normal range and outside of the ecosystems that they have adapted with for millennia, they are just known as ‘non-native’ or ‘alien’ species. When these have been transported as a result of human activity, these are also occasionally termed ‘introduced’ species. As a result of centuries of accelerating trade and migration, there are many non-native species that are found within Scotland, and many of these pose no threat to their surrounding ecosystems. The issue is with those ‘invasive’, non-native species – those species that are outside their normal range and which negatively affect other native organisms and environments. Through their translocation, these species may have escaped the predators, parasites and herbivores that would have limited their spread within their own native ecosystems.


What impacts do invasive non-native species have?

Invasive non-native species can negatively impact native ecosystems through a variety of ways. They may predate or become parasitic upon native species, or they may simply outcompete native species for resources, reproduce more quickly and dominate native habitats.

To give an impression of the scale of the issue, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) published their Global Assessment Report on Biodiversity and Ecosystem Services 2019 which stated that nearly one fifth of the Earth’s surface is at risk of invasive non-native plant and animal species. Equally, cumulative records of non-native species expansion suggest that there has been a 40% global increase in non-native species proliferation since 1980, and the rate of introduction of invasive species is higher than ever. For islands like Great Britain, the effects of invasive non-native species are particularly serious as these ecosystems are likely to have developed with little alien interference and are more likely to be susceptible to extinction. 


Invasive species in Scotland

In Scotland, invasive non-native species are covered by Section 14 of the Wildlife and Countryside Act 1981, alongside the Wildlife and Natural Environment (Scotland) Act 2011. These Acts state that it is an offence to release or cause the release of any animal or plant to a place outside of its native range. The Scottish Government has also published a non-native species Code of Practice to ensure people act responsibly within the law so that non-native species do not cause increasing harm to Scotland’s envhironment. But what about those invasive species that are already present in Scotland?

There are almost 2,000 non-native species established in the UK and some 10-15% of these species are logged as invasive (Defra, 2012). Alongside degrading Scotland’s biodiversity, these invasive species especially impact agriculture, forestry and horticulture sectors, costing the Scottish Government £300 million a year.

Some examples of invasive non-native species that are established in Scotland include American Mink, Giant Hogweed, Grey Squirrels, Japanese Knotweed, Himalayan Balsam, American Skunk Cabbage, White Butterbur, and Rhododendron Ponticum. Each of these species detrimentally disrupt Scotland’s native ecosystems in different ways.

The American mink (Neogale vision), for example, spread throughout Scotland after they escaped from fur farms in the 20th century. As they spread, they predated on a variety of species, including water vole and ground-nesting bird populations, which were especially negatively affected. As the Scottish Invasive Species Initiative notes, American mink are believed to be responsible for the disappearance of moorhen from Lewis and Harris, and a 94% decline in water vole populations. To combat the spread of American mink in the Western Isles, NatureScot led a successful project to eradicate the species, costing over £4.5 million over 17-years.

Within the plant kingdom, Rhododendron ponticum is Scotland’s most threatening invasive non-native plant. Despite its attractive flowers, Rhododendron forms dense thickets which shade out native plants, its leaf litter is toxic to many plants, and it harbours the phytophthora – a disease that can kill a wide range of plants. In 2010, Forestry and Land Scotland began a ten-year, £15.5 million project to remove rhododendron from 50,000 hectares of land – a task that is continued by two of LINK’s members, John Muir Trust and National Trust for Scotland.


COP15 and the way forward for Scotland’s Biodiversity Strategy

As the world prepares for the UN’s upcoming biodiversity conference, COP15, it is clear that invasive species must be at the forefront of the Post-2020 Global Diversity Framework. Within the first draft of the UN’s Framework, the 21 targets for 2030 include a draft commitment for “a 50% greater reduction in the rate of introduction of invasive alien (non-native) species, and controls or eradication of such species to eliminate or reduce their impacts”. This is a promising direction considering the accelerating spread of non-native, invasive species and the catastrophic effects they have upon endemic ecosystems – a proliferation which continues to increase as a result of climate change, transport and socioeconomic change.

As the Scottish Government prepares its upcoming Scottish Biodiversity Strategy Post-2020, it is critical that the attention to invasive species with the UN’s Biodiversity Framework and the IPBES Global Assessment of Biodiversity is matched within the Scottish Biodiversity Strategy. As the Statement of Intent to the upcoming Scottish Biodiversity Strategy recognises, joint working arrangements with the UK Government on addressing non-native invasive species is a positive direction in centralising this factor in Scotland’s biodiversity loss going forward, but as with COP15, tangible targets are required to protect Scotland’s fragile ecosystems. 


Andy Marks, Nature Champion Coordinator, Scottish Environment LINK

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