The updated watchlist of invasive non-native species that could threaten Great Britain in the next 10 years was published during this year’s Invasive Species Week. The list includes species with potential to cause significant risks to biodiversity, ecosystems, human health, and the economy.
The latest version of the watchlist, which again includes known problem species such as the yellow-legged (Asian) hornet, raccoon and twoleaf watermilfoil, has been produced by experts led by the UK Centre for Ecology & Hydrology (UKCEH) and commissioned by Defra.
The experts identified 145 non-native animals and plants that have the potential to become invasive in the near future, impacting biodiversity and ecosystems and also, in some cases, human health and/or the economy. Some of these species, from a diverse range of taxonomic groups and habitats, have already been recorded in Britain but are not established, meaning they have not managed to sustain populations so far. Others have yet to arrive.
Non-native species arrive in Britain through global transport and trade, either intentionally or are hidden in plants, other imported goods or ship ballast water. Climate change is enabling many species from warmer climates to survive and spread in Europe.
Top 20 threats
From the 145 species of concern, the experts compiled a ‘top 20’ that pose the greatest risk in order to inform monitoring efforts, policies and communications to the public, businesses and local authorities. The new entries include:
- Pink salmon (Oncorhynchus gorbuscha) is already recorded in some rivers in Scotland and northern England but it is not known if these populations are self-sustaining. It outcompetes already vulnerable native salmonoids, such as Atlantic salmon.
- Pine wood nematode (Bursaphelenchus xylophilus), a threadworm that causes pine wilt disease, which has resulted in extensive deaths of trees in all regions where it already occurs. Also Pine sawyer beetle (Monochamus galloprovincialis), a carrier of the nematode.
- Spaghetti bryozoan (Amathia verticillata), a colonial filter-feeding invertebrate that forms large, bushy colonies, outcompeting native species and disrupting food chains by consuming large quantities of phytoplankton. It can grow on and smother seagrasses and foul boats and fishing equipment. When detached, it forms large drifting rafts that can clog intake pipes and aid dispersal of small motile non-natives that live on it.
- Purple Asian clam (Corbicula largillierti), a species that can reproduce rapidly, outcompetes native molluscs and clogs pipes, obstructing infrastructures such as drinking water facilities, resulting in expensive repairs. It is closely related to the Asian clam (Corbicula fluminalis), which is also in the top 20, and the Asiatic clam (Corbicula fluminea), which is already invasive in Britain.
- Veined rapa whelk (Rapana venosa) is a voracious predator that feeds on native oysters, scallops and mussels, outcompeting other predators and potentially resulting in economic impacts for fishing communities.
- Asian fan weed (Rugulopteryx okamurae) is an invasive seaweed that displaces native species. When detached it can be deposited as decomposing masses on shores, smothering small invertebrates and affecting tourism and, potentially, human health.
This is the third ‘horizon-scanning’ exercise to predict invasive non-native species that could be a threat to Britain, following lists in 2013 and 2019.
The above information is taken from the UKCEH website where full details can be found.