Further action needed to deal with invasive species threat

Today marks the start of Invasives Species Week, which aims to raise awareness of the huge problem of invasive non-native species like the American Signal crayfish and Floating Pennywort.

During Invasives Species Week a group of conservation organisations led by Wildlife & Countryside Link will be pressing the UK government to do more to work alongside other European Union member states to prevent the spread of invasive species across the continent.

Signal Crayfish (Pacifastacus leniusculus) defence posture in chalk stream, Hertfordshire, UK

American signal crayfish (Pacifastacus leniusculus)  in chalk stream, Hertfordshire, UK (c)National Trust Images/NaturePL/Andy Sands

According to Dr David Bullock, Head of Nature Conservation, invasive species are a growing problem for the National Trust.

“Dealing with invasive species at our places costs the National Trust thousands of pounds every year. As a conservation charity looking after 250,000 hectares of countryside and hundreds of ponds, lakes and rivers, we’re very aware of the impact of invasive species on native wildlife.

“We’ve joined the call for the UK government to do even more to work with other EU countries to tighten up existing regulations to prevent invasive species from areas such as the Ponto Caspian in eastern Europe reaching our shores.”

Under existing EU regulations 37 invasive species are banned from sale, breeding, transport, keeping or release. However, the list does not include species native to one Member State that could be invasive in another.

The existing regulations allow member states to create national and European regional lists of invasive species and help stop them spreading from other parts of the continent. For Invasives Week, we are calling on the UK government to create such a list and slow the influx of invasive species like the quagga mussel.

However, it’s the invasive non-native species that are already on our shores that are creating such problems for the National Trust.

Floating pennywort, a plant with small fleshy stems that grows rapidly in ponds and slow-flowing streams, has spread quickly across southern England since it was first spotted in the early 1990s. The pennywort forms a dense mat over the water, cutting out sunlight for plants below and impacting other aquatic life.

On one of the only chalk streams in London, Floating pennywort is rife. At the River Wandle, south London, National Trust volunteers from Morden Hall Park have been working alongside our partners in the Wandle Trust to pull pennywort from the river by hand. This can only control the problem; the Floating pennywort has proven impossible to eradicate.


Volunteers remove Floating pennywort from the River Wandle (c) National Trust

Elsewhere, control measures against predatory invasive species have found more success.

Lundy Island, in the Bristol Channel has long been a haven for seabirds. The jewel in its crown is the Manx shearwater.

Even just a decade ago, Lundy’s Manx shearwater were faring poorly. Just a few hundred pairs were left on the island and their eggs and chicks were being preyed on by rats. There was real danger that within a few years the shearwater would have disappeared from the island.

View south towards the Landing Bay in early morning light on Lundy Island, in the Bristol Channel, Devon

View south towards the Landing Bay in early morning light on Lundy.  (c) National Trust Images/Joe Cornish

In 2002, in a bid to restore Manx shearwater numbers, the National Trust embarked on an ambitious project with RSPB, English Nature (now Natural England) and Landmark Trust to eradicate rats from the island.

The speed of the recovery has been remarkable. There are now thousands of pairs of the seabirds breeding on the island.

Continuing to keep the Lundy free from rats is vital, warns David Bullock.

“Off the UK’s coasts there are thousands of islands on which seabirds breed. The spectacle of huge colonies of Manx shearwaters and other species is only possible because the islands are free from invasive non-native predators. It is vital that we ensure that rats do not get to seabird islands, and that if they do, we remove them.”

Elsewhere we’re experiencing mixed success in tackling invasive non-native species:

  • The American signal crayfish carries a plague that has wiped out the globally endangered native white clawed crayfish. The River Allen, which flows through the Kingston Lacy estate in south east Dorset, used to be a stronghold of the native white clawed crayfish with thousands recorded two years ago. After an extensive search last year only 5 native crayfish were found.
  • Signal crayfish have wreaked havoc in historic National Trust lakes and ponds, burrowing into lake sides and causing thousands of pounds worth of damage. At the Vyne, Hampshire, one ranger could At the Vyne one ranger could fit the length of his body into the hole in the bank that the Signal crayfish had created. Fitting wire netting to the lake banks at the Vyne to prevent the crayfish from burrowing into the lake sides has cost the National Trust around £40,000.
  • At Little Sea, a rare freshwater lagoon in Studland, near Bournemouth, carp that were illegally introduced around 10-15 years ago are threatening the lake’s future. Carp churn up the sediments as they feed on the lake bottom, making it harder for the specialist aquatic plants to grow and causing nutrient levels in the water to rise. Recent surveying in Studland for the Cyril Diver Project suggests that removing carp from the lake is allowing native plant species like Six-stamened waterwort to return. Studland is just one of a number of places along the south west coast where the National Trust is working on a bigger scale to manage landscapes for nature.
  • In Snowdonia, we have spent around £1.2m over 15 years clearing hundreds of hectares of rhododendron from Nantgwynant and Beddgelert, Snowdon’s wooded foothills. Rhododendron grows quickly and its thick canopy lets through little light, outcompeting many native plants. A single Rhododendron ponticum flower can produce more than 7,000 seeds.

There’s plenty that people can do to stop the spread of invasive non-native species. The “Check, Clean, Dry” campaign encourages people who use waterways – from anglers to recreational boat users – to clean their equipment properly. In doing so they could really help stop the spread of species like Floating pennywort.

During Invasives Species Week partner organisations will be running a series of events and workshops exploring how we can tackle the spreading problem. Find out more at www.nonnativespecies.org/invasivespeciesweek



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