New handbook lists Europe's 11,000 alien species

10 December 2008

More alien species live in Great Britain than any other European country according to the 'Handbook on Alien Species in Europe' published recently that details 11,000 alien species found throughout the continent.

Harlequin ladybird

The newly-arrived Harlequin ladybird, Harmonia axyridis - the most invasive ladybird on Earth.

Of the 100 most problematic species found in Europe, 62 have already reached Britain.

Some alien species can become invasive and threaten native species and biodiversity. The North American grey squirrel, prolific Japanese knotweed and the Harlequin ladybird are perfect examples. But they're not just a menace to native species - some affect human health and the British economy.

An alien species is any animal, plant, fish, insect or crab-like creature that was introduced either deliberately or by accident. Because they often have no natural predators to control their spread, they can take over habitats, altering populations of native species.

These issues led the European Union to fund the most comprehensive inventory of invasive alien species ever undertaken for Europe - DAISIE or the Delivering Alien Invasive Species Inventories for Europe. The project has just published a handbook of its findings.

Dr David Roy from the Centre for Ecology & Hydrology who led the three year scheme says, "During this project, we identified around 11,000 alien species in Europe. Over 3000 of those are in Great Britain.

We have more complete records than many other European countries.

- Dr David Roy, Centre for Ecology & Hydrology

"The fact that we have so many alien species is most likely due to human intensity factors such as population density, levels of imports, the extent of transport networks and the fact that we're an island. With increasing trade, it's incredibly difficult to keep alien species out.

"But the large number of alien species here could be down to Great Britain's long tradition of monitoring. We have more complete records than many other European countries," adds Roy.

The story of how alien species have invaded every continent on Earth is not new, but the scale of the problem was completely unknown until now.

"The number of alien species in Europe and the rising trend for most groups of species had been hugely underestimated," says Roy.

Cost to the economy

Politicians have long been aware of the considerable impact of invasive species. Around 16 per cent of the invading species found in Britain have some environmental, economic or health impact according to the DAISIE database. When Climate Minister Joan Ruddock was Minister for Biodiversity, she highlighted that invasive species cost the British economy around £2 billion every year.

Not only are programmes to control invasive species expensive, they also take up a significant amount of time.

And then there's the risk to human health. Species like giant hogweed can cause blisters and burns if sap from the plant comes into contact with skin, while oak processionary moth caterpillars can cause severe skin irritation and allergic reactions.

At the moment, ecologists are having trouble controlling Britain's invasive species, partly because there are so many and responsibility for dealing with them is not down to a single organisation.

And now another alien invader, the rhododendron, is spreading two new plant diseases that could seriously affect native species and wipe out important heathland. This has led the National Trust to check the problem on its own land. Its lead adviser on these issues Iain Wright says the new diseases could be rampant in Great Britain within years.

But Roy says the information unearthed by the DAISIE project will be invaluable in helping conservation agencies like Natural England in their efforts to control alien species.

So that conservationists know how to handle each species, the DAISIE database lists the top 100 worst offenders, including details about where the species is found, how to control its spread and what expertise exists elsewhere in Europe.


Want to find out more? The DAISIE 'Handbook of Alien Species in Europe' is published by Springer. ISBN 978-1-4020-8279-5