International Day for Biological Diversity

What do the Brown Hare, Red-legged Partridge and Horse Chestnut have in common? None of them are native to the UK. They were in fact introduced here by people several hundred years ago and have since gone on to naturalise – they have formed populations that can survive and reproduce in the wild without human help.

There are 2271 non-native species found in England ¹. Many of these were deliberately introduced for purposes such as agriculture and forestry and have contributed to our social and economic well-being. There are however, a number of invasive non-native species which are extremely damaging to our natural environment, and can create huge economic costs.

International Day for Biological Diversity 2009 aims to increase understanding and awareness of the issue of invasive non-native species. The South East region has the highest number of non-native animals, fungi and microbes of all the English regions ². Information about some of the invasive non-native species recorded in Sussex is provided below, along with ideas on what you can do to help and what to do if you find an invasive non-native species.

Photo: Hugh Clark/Sussex Wildlife Trust

So what’s the problem?

• Non-native species didn’t evolve here. This means they have none of the usual predators, parasites and pathogens that keep populations of our native species in check, which can give them a distinct advantage.
• Invasive non-native plants often form a dense monoculture, which removes habitats for other plants and animals, and can also reduce food supplies.
• Invasive non-native animals can severely impact our native species through competition or by feeding on them. Our native species can be vulnerable as they have not evolved strategies to outwit these new predators.
• Invasive non-native plants are often fast growing and adaptable so can take advantage of many situations. This could further increase with climate change.
• Non-native species sometimes reproduce with native species producing a hybrid. These hybrids are sometimes infertile, but those that are not can begin to alter the genetic pool, endangering native species.

Photo: Tony Buckwell/Sussex Wildlife Trust

Some Invasive Non-native Species in Sussex

American Mink Mustela vison are native to North America. They are now found throughout Britain as a result of releases and escapes from fur farms in recent decades. American Minks have had a significant impact upon many of our native species of waterfowl and the Water Vole, which has undergone a dramatic decline of around 90%. Sussex’s Water Voles have been reduced to only three core areas.

Floating Pennywort Hydrocotyle ranunculoides is native to North America. It has naturalised in Britain from discarded pond plants ³ – mainly found in the south east, it is spreading rapidly. Floating Pennywort quickly dominates water bodies where it blocks light and reduces temperature and oxygen levels, affecting many native pond species. In Sussex a large area of Pagham Rife is periodically dominated and choked by this species, and ongoing management is carried out.

Harlequin Ladybirds Harmonia axyridis are native to central and eastern Asia and were intentionally introduced in parts of Europe to control aphids. The ladybirds can fly across the English Channel and also arrive in imported goods. Since being found in England in 2004 they have steadily increased their range across much of Britain and a rise in numbers has been noted across Sussex. Harlequin Ladybirds are large and can out-compete native species for food even; consuming other ladybirds.

Rhododendron Rhododendron ponticum is a large shrub native to south west Europe. It was introduced to the UK in the 18th century and has spread to sensitive habitats such as heathland, where it is capable of restricting growth of other plants through secretions into the soil. West Sussex County Council has been removing Rhododendron from sites such as Buchan Country Park for the last 12 years.

Chinese Mitten Crabs Eriocheir sinensis are originally from Asia, but with the help of shipping are now found in Europe and have been in British waters since 1935. The crab spends much of its life in rivers and travels long distances from the sea. It is a voracious predator and could threaten native species of fish and the endangered White-clawed Crayfish. It can also cause significant damage to riverbanks through its burrowing activities. The crabs have been recorded at Shoreham and Dungeness.

Red Valerian Centranthus ruber is originally from the Mediterranean and has now begun to invade Sussex’s rare coastal vegetated shingle habitats from gardens. Red Valerian is fast growing and appears to be more tolerant of extreme weather, enabling it to out-compete native plants. Around Pagham Spit over 30 species of non-native garden species have been recorded.

Photo: Graeme Lyons/Sussex Wildlife Trust

What can be done?

• Know your non-natives! Factsheets are available from the Non-native Species Secretariat and the Environment Agency
• Report invasive non-native species. This can be done through Sussex Biodiversity Record Centre and plants such as Giant Hogweed and Japanese Knotweed on public land should be reported to your local council. Plantlife is conducting a survey on invasive pond plants and The Harlequin Ladybird Survey want to hear about your sightings.
• Help tackle non-natives as a volunteer. A list of local opportunities to volunteer in Sussex is available on the publications page.
• Many non-natives escape from gardens or ponds. To prevent this, use native species that are local to your area. Flora locale provide information on finding native plant species.
• Never release any plants or animals in to the wild – it is against the law ⁴. Your local council can advise you on how to dispose of garden waste correctly.
• Sussex Biodiversity Record Centre has compiled the Sussex Invasive Alien Species Report, listing 49 species that are considered to pose a threat in Sussex.
• In May 2008 Defra launched The Invasive Non-Native Species Framework Strategy for Great Britain . The strategy covers education, development of a web-based directory of invasive species, and provision of a framework for responding to detection of invasive species.

¹ Defra
² Natural England
³ GB Non-native Species Secretariat
⁴ Wildlife and Countryside Act 1981 (as amended)