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Invasive species: the silent threat to our ecosystems

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Image of a seedling growing through hard ground with the title, "Invasive Species Week, 15-21 May 2023"
This week, 15-21st May is Invasive Species Week, led by APHA’s GB Non-native Species Secretariat (NNSS).

Invasive non-native species (INNS) are one of the top five threats to global biodiversity, costing the economy nearly £1.9 billion a year, and can even harm our health. Once established, they can be extremely costly and difficult to control.

What are invasive non-native species?

Over 2,000 plants and animals have been introduced to Britain from all over the world by people. These are known as non-native species. Most are harmless but around 10-15% spread and become invasive non-native species, which impact the environment, economy or our health and way of life.

To reduce the future impact of INNS we need to prevent more species from being introduced and becoming established, which is part of the role of our Borders and Trade teams. As part of Invasive Species Week APHA Director of Science Transformation, Jenny Stewart and Lucy Cornwell from the GB Non-native Species Secretariat are sharing some of the ways that everyone can help.

Gardening to support wildlife and prevent the spread of invasive non-native plants

“To relax and keep fit I like to go walking in nature and work on my garden. Being in or near the natural world has been proven to reduce stress and improve wellbeing and makes me extremely proud of the work that we do at APHA to protect it.

Image of wildflowers growing in a raised plant bed.
Growing wildflowers in your garden will attract pollinators

It’s important to me that my garden is a home for wildlife and doesn’t harm the environment. Here are some of the things I do to help:

•  I fill two huge raised beds with wildflowers to support pollinators. I love hearing the garden buzz on a warm evening.
•  Many invasive non-native plants were originally introduced as ornamental garden plants. I avoid growing invasive species and try to use native plants where I can. This booklet has suggestions for plants to use in place of invasive species, including species to help wildlife.
•  I support UK suppliers and don’t bring back plants, seeds, flowers, or vegetables from my travels abroad as they could be carrying pests and diseases.
•  I leave dead plants standing over winter to provide shelter for birds, small mammals and insects.
•  In the spring I clear the garden and put my plant waste in the council garden waste bin so it doesn’t end up the wild.
•  I make sure any compost I buy is peat free. This year I’m thinking of starting my own compost heap to turn some of my garden waste into food for the garden. This list of non-native plants that can’t be composted at home highlights a small number of species that should continue to go in the green bin.

Find out more about invasive non-native plants and how you can prevent their spread through the Be Plant Wise campaign.”

Dr Jenny Stewart, Director of Science and Transformation, APHA

Recording ‘alert’ species


“In the UK we are lucky to have a wealth of information about our plants and animals that has been collected by enthusiastic recorders for over 200 years. This data helps to identify trends and track the distribution of different species, including non-native plants and animals.

One of the easiest ways to help prevent the spread of invasive non-native species is to look out for and record ‘alert’ species. These are species which are a threat to Great Britain (GB) but are not yet widely established. If we can intervene at an early stage and stop this from happening we can prevent future harmful impacts from taking place, protecting the environment and saving time and resources.

Currently there are 19 ‘alert’ species. Visit the NNSS website to view the full list, below are four examples:

Purple pitcher plant, Sarracenia purpurea

This carnivorous species likes high quality bog habitat and is usually found in protected sites including SSSIs, SACs, and NNRs. In this environment it can outcompete native plants, harm the invertebrate community, and disrupt nutrient cycling. Work in Ireland has shown that purple pitcher plant can reduce peat formation by restricting the growth of Sphagnum moss.Look out for:

• A cluster of modified tubular green, yellow or reddish leaves with purple veins and hooded open lids
• Downward pointing hairs on the inner surface of the leaf

Raccoon dog, Nyctereutes procyonoides

Image of a racoon-like animal in woodland
Image of a Raccoon dog, Nyctereutes procyonoides

Raccoon dogs are one of the top 100 most invasive species in Europe. They affect native wildlife and game through predation and competition and can carry several zoonotic diseases including rabies. Despite this, raccoon dogs have had some popularity as exotic pets, but due to their harmful impact there are now legal restrictions on keeping this species and other invasive animals and plants.

Look out for:

• Fox sized mammal with short legs and tail
• Blackish-grey fur, similar facial markings to a raccoon but lacking the long banded tail

Asian hornet, Vespa velutina

Image of a black and yellow insect
Asian hornet, Vespa velutina

Asian hornet is a highly effective predator of insects, including honey bees and other beneficial species. Since 2016 APHA’s National Bee Unit have responded to 23 confirmed sightings of Asian hornet, including 13 nests, all of which were destroyed with support from APHA’s National Wildlife Management Centre. View a previous APHA Science blog post: 22 confirmed Asian hornet sightings in Great Britain since 2016 … and counting.

Look out for:

• Legs that are yellow at the ends (dark in native hornet)
• Queen up to 3 cm long, worker up to 2.5 cm long (slightly smaller than the native hornet)
• Dark brown / black abdomen with a yellow / orange band on the fourth segment (native hornet has a more yellow / orange abdomen)
• Brown / black thorax (orange in native hornet)
• Never active at night (native hornet is)

Water primrose, Ludwigia grandiflora

Image of a floating plant with a yellow flower
Water primrose, I, KENPEI, CC BY-SA 3.0 via Wikimedia Commons

This aquatic plant rapidly grows clogging waterbodies, outcompeting native plants, and reducing oxygen and light in the water. If it were to establish widely in GB it would cost millions of pounds to manage each year. Anglers, paddlers, and boaters can help prevent its spread by remembering to Check, Clean, Dry boats, clothing and equipment after leaving the water.

Look out for:

• Creeping aquatic plant that can grow on the water’s surface, or out of it
• Leaves that can be long and slender (up to 9 cm long), or round / egg shaped
• Bright yellow primrose-like flowers up to 3 cm

Where to send records
All of these species can be recorded online through iRecord. Find other useful resources to help on the NNSS website, including:

• Full list of alert species
• Other recording websites and apps
Free ID sheets for invasive non-native species

Lucy Cornwell, GB Non-native Species Secretariat

Invasive Species Week

Advert for Invasive Species Week. Text reads, "15-21 May is Invasive Species Week. Invasive non-native plants and animals are one of the top drivers of biodiversity loss. Find out how you can help protect the environment:"

Find out more about Invasive Species Week and how you can help to prevent the spread of invasive non-native species:


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