A new horizon-scanning assessment conducted by experts at the UK Centre for Ecology & Hydrology (UKCEH) has shed light on emerging invasive alien species that could severely impact biodiversity, ecosystems, human health, and economic sectors in Great Britain within the next decade. This comprehensive analysis identifies 145 non-native species with invasive potential, highlighting a critical environmental threat intensified by the expanding effects of climate change and global trade. The findings underscore the urgency of proactive monitoring to prevent irreversible ecological and economic damage.
Invasive species are organisms introduced—whether intentionally or accidentally—beyond their natural range, where they can establish and proliferate, outcompeting native flora and fauna. This latest watchlist, commissioned by the UK Department for Environment, Food and Rural Affairs (Defra), integrates expert consensus from over 40 specialists, utilizing a systematic review methodology to rigorously evaluate species based on their likelihood to establish populations and the magnitude of their potential impacts. The evolution of this three-phase exercise, with prior iterations in 2013 and 2019, reflects the dynamic nature of bioinvasion risks and the accelerating tempo of introductions driven by globalization.
Notable in the current watchlist are aquatic and terrestrial invertebrates such as the spaghetti bryozoan (Amathia verticillata), pine wood nematode (Bursaphelenchus xylophilus), and the purple Asian clam (Corbicula largillierti). The spaghetti bryozoan, a colonial filter feeder, forms dense, bushy colonies that aggressively outcompete native species by monopolizing phytoplankton resources, thereby disrupting fundamental food webs. Beyond ecological implications, detached mats of this bryozoan constitute a biofouling hazard, clogging industrial intake pipes and facilitating dispersal of associated motile non-native taxa, compounding their invasion potential.
Freshwater ecosystems face mounting pressure from invaders such as the pink salmon (Oncorhynchus gorbuscha), whose presence has been recorded in multiple British rivers. As an anadromous fish species native to the Pacific basin, pink salmon compete with indigenous salmonoids for critical feeding and spawning habitats, threatening vulnerable populations such as the Atlantic salmon. Their carcasses also contribute to nutrient loading within freshwater systems, risking eutrophication and further destabilizing aquatic communities.
Forest health is imperiled by agents like the pine wood nematode and its insect vector, the pine sawyer beetle (Monochamus galloprovincialis). The nematode incites pine wilt disease by attacking vascular tissues, leading to extensive tree mortality wherever it becomes established. The pine sawyer beetle functions as an efficient dispersal mechanism, enhancing the invasive nematode’s spread. Both taxa have yet to establish in Britain but have been detected via interceptions, making early detection an imperative biosecurity objective.
Marine environments are similarly threatened by multiple species, including the veined rapa whelk (Rapana venosa) and Asian fan weed (Rugulopteryx okamurae). The veined rapa whelk is a predatory gastropod that preys on economically and ecologically valuable shellfish such as oysters, scallops, and mussels. Its voracious feeding habits can precipitate the decline of native mollusk populations, disrupting trophic dynamics and critical ecosystem services like water filtration. The invasive seaweed, Asian fan weed, displaces native marine flora and, through stranded decomposing biomass along shorelines, degrades habitats and affects human recreational activities and health through possible toxic impacts.
The UK’s growing susceptibility to new invasive species arrivals is facilitated by international trade, shipping ballast water discharge, and the illicit transport of plants and animals. Climate change exacerbates this vulnerability by creating favorable conditions for species adapted to warmer climes to survive and expand northwards. This combination of anthropogenic vectors and environmental change underscores the complexity of predicting invasion trajectories and the necessity of integrated surveillance strategies.
Prevention, highlighted by Professor Helen Roy of UKCEH, remains the most effective and economically viable approach to curbing the deleterious effects of invasive species. Once established, eradication is notoriously challenging and costly; therefore, horizon-scanning plays a vital role in identifying emerging threats before they materialize fully. Coupled with public participation in monitoring and reporting, these proactive measures enable timely interventions and inform policy development tailored to minimize ecological disruption.
Historical perspective illustrates the effectiveness of early detection systems, exemplified by the yellow-legged (Asian) hornet (Vespa velutina) case. Predicted in the 2013 watchlist, this aggressive pollinator predator has been closely monitored since its first British sighting in 2016. Coordinated responses by the Animal and Plant Health Agency’s National Bee Unit, including nest removal and public engagement, have so far successfully prevented establishment, mitigating substantial risks to native pollinator populations essential for ecosystem functioning and agriculture.
The updated list also reaffirms concerns over terrestrial beetle pests such as the emerald ash borer (Agrilus planipennis) and Asian longhorn beetle (Anoplophora glabripennis), which threaten Britain’s forestry through larval tunneling and feeding damage. These activities reduce tree viability, increase susceptibility to disease and mechanical failure, and ultimately endanger woodland biodiversity and economic outputs from timber industries. Although not established, their detection in imports underscores the pressing need for stringent phytosanitary measures.
The presence of raccoons (Procyon lotor) among the high-risk species highlights zoonotic disease risks alongside ecological impacts. Introduced originally as exotic pets, escaped or released raccoons have established localized populations since the 1970s. Their omnivorous and adaptable feeding behavior makes them formidable competitors and predators, threatening vulnerable bird populations and native carnivores. Moreover, raccoons are reservoirs for rabies and other parasites with significant human health implications.
Among the botanical risks, invasive plants such as wireplant (Muehlenbeckia complexa) and twoleaf watermilfoil (Myriophyllum heterophyllum) pose serious threats to native flora and aquatic ecosystems. Their rapid growth rates and dense stands outcompete native vegetation, while dieback and decomposition events deplete oxygen from water bodies, inducing hypoxic conditions detrimental to fish and invertebrate fauna. Management of these species is complicated by their adaptability and climate resilience.
This latest horizon-scanning report, funded by Defra and meticulously compiled by UKCEH, provides an indispensable tool for environmental managers, policymakers, and stakeholders aiming to mitigate the multifaceted threats posed by invasive alien species. It emphasizes the integration of ecological risk assessment with practical prevention, early detection, and rapid response frameworks, aided by community involvement to safeguard Britain’s natural heritage, agricultural productivity, and public health in an increasingly interconnected and warming world.
Subject of Research: Invasive alien species threatening biodiversity, ecosystems, human health, and economies in Great Britain.
Article Title: Horizon-scanning for invasive alien species with the potential to threaten biodiversity and ecosystems, human health and economies in Britain
News Publication Date: 12-May-2025
Web References:
https://www.nonnativespecies.org/non-native-species/risk-analysis/horizonscanning
Image Credits:
Smithsonian Environmental Research Center, CC0
Keywords:
Invasive species, invasive animals, invasive plants, climate change, biodiversity, marine biodiversity, species diversity, animals, plants
