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It may seem from the above article that invasive species are just a terrestrial problem. This is far from true. At the moment, UK seas are experiencing an explosion of non-native species, some of which are invasive and destructive to native wildlife.

Many creatures came across to the UK with the introduction of the Pacific oyster around our shores as a food source in the 1970s. Animals now common because of this include the slipper limpet, strewn over our beaches and in some places carpeting the sea floor to the exclusion of most other life, and wireweed, a brown seaweed that now can be so dense in rockpools and on the seashore that it prevents any animals and plants living underneath it from getting any light.

It's not only the Pacific oyster, though, that is the villain of the piece.

Another major cause of animals and plants spreading around the world is them surviving long journeys on boat hulls, in ships' ballast water and in the water in ships' chests. Recent research shows that yachts and marinas in south east England contain, on average, nearly 11 non-native species - from seaweeds through to seasquirts and crabs that look like they are wearing mittens. Imagine every piece of grassland around you being so overtaken by so many species that aren't native to the UK.

The other day I was walking along a beach actually looking for non-natives as part of surveying our north Kent coasts for invasive species and I picked up an oyster shell.

It was a Pacific oyster - a non-native - that had a slipper limpet - a non-native - attached to it. The slipper limpet was sporting a frond of wireweed - another non-native - that had attached to the shell, and to top the whole lot, there were 3 different types of invasive sea squirts that I found clinging to the seaweed frond.

Non-natives around the Kent coast are ubiquitous and ever-increasing, and unfortunately, many other places have similar conditions. The question now is only "what can we do about them?"

Do we leave our shores to be smothered and overrun by plants and animals that may take over from loved and charismatic native shore life?

It's a difficult question. An incredibly difficult question, with few answers.

I find it hard to believe the attitude of "they're here now so learn to live with them" that Rotherham appears to have.

We need to act early against alien invasives because we don't know the long term effects of these alien species on our native wildlife. Although not a clear cut case, just look at the situation between our native red squirrel and the introduced grey. When these were introduced I'm sure that those responsible would never have envisaged the problems that exist now between these two species. If they had of known would they have tried to eliminate the problem they had caused?

On the show Rotherham stated that we will not be able to get rid of Himalyan balsam. This incredibly invasive plant attracts our native insects to it in preference to our native plants therefore there are pollination concerns. It grows incredibly rapidly along river banks to the detriment of our native plants, they can get shaded out and locally eliminated. Then once it dies off and rots away at the end of it's season it leaves bare river banks that can suffer intense erosion in our winter floods whereas our native plantlife tends to bind the banks together and reduce erosion.

Can it be eliminated? YES, very easily. We are involved in a partnership project along the River Alyn in north Wales. This is our third year and we have already seen a dramatic reduction in Himalayan Balsam numbers along the river. We envisage that in just a few more short years we will have eliminated this plant from the upper stretches to the benefit of our environment and our native wildlife. The main workforce behind this work are local volunteers! It takes a lot of man hours but it's all worthwhile.

It's never too late to take a stand against these alien invasives, but we really do need to take a stand against them and to act sooner rather than later!!

We are campaigning to stop DEFRA's Monk Parakeet eradication programme. Do you have a view on this bird's presence in small colonies? As far as we can tell after a lot of research it does no harm, contrary to DEFRA's assertions. Please see for more info.

Certainly, both marine and freshwater alien invasives can be absolutely devastating and they spread insidiously and rapidly. The international dimension of such invasions can make effective control problematic.

With Himalayan Balsam, it is certainly possible to control it at a local and even a regional level - if we are prepared to put resources in. Cornwall County Council for example has fulltime trained officers who provide advice and undertake control. I actually help mnay local groups and networks in coordinating both Balsam and Knotweed control programmes - on the urban River Don a group called SPRITE who carry out sterling work, and south of Sheffield the Moss Valley Wildlife Group. We have hauled out tons of Balsam from our SSSI river, the Moss Brook.

BUT I have interviewed entire families whose lives are dedicated to actively spreading Balsam seeds around Britain and across Europe - because they like it. Nobel Prize-winning scientist Sir Hans Krebs, in the 1940s and 1950s, spread Balsam seeds throughout the River Sheaf and west into the Peak National Park, as a sort of therapy from his work. It takes about 10,000 person hours to clear a few hectares of nature reserve woodland of Balsam, but only a few minutes for the seeds to be spread over hectares of new ground. Don't stop trying - but the control will be management that happens for a very long time. Present government policy and finance do not look promising for long-term measures.

Muntjac Deer for example, are spread by enthusiasts carried up the A1 in the backs of vans to release to new areas.

The Red Squirrel / Grey Squirrel debate is fascinating and my research suggests that urban people growing up with Greys love them, but rural folk and those in Red Squirrel areas hate the Greys. Peter Coates has written some amazing stuff about attitudes to the two species. It is also worth remembering that Red Squirrel was formerly considered a pest, with a bounty on its head and clubs formed dedicated to its eradication. It became extinct in many areas and was reintroduced with European, non-native genetic stock.

To be effective we need to look at coordinated long-term controls of PEST species -old-fashioned land management - and that has to be paid for. Like it or not many exotic species have already become cornerstones of our accepted ecologies and others will no doubt follow. Simply not being considered as native is not a reason for control or attempts at eradication.

Finally, a big issue is that the decisions to control or to intervene or not, are often based%

Continued from 4)

Finally, a big issue is that the decisions to control or to intervene or not, are often based on subjective opinions and not on scientific evidence or reasoning. The Buddleia (from China, late 1800s) is loved by most conservationists but causes huge structural damage to buildings and railway lines etc - we don't hear calls for eradication. Ring-necked Parakeets are the subject of objections by some people but are now loved by others as an exotic addition to our avifauna. The Wild Boar, was a keystone native mammal that was hunted to extinction but which, reintroduced and spreading rapidly, is considered to be an alien, the Eagle Owl was almost certainly once native......!!?


Ian Rotherham

I'm an American alien living in GB. Should I leave?

I agree very much with Ian Rotherham's comments (4 and 5). Many aliens are with us whether we like it or not. Though we have used our goats at Kent Wildlife Trust to help of get rid of buddleia on some sites, I seem to remember!

What is considered native is a thorny question. What do we take as a baseline? Is a 1900 fauna and flora "native"? Is something from 1500? What about 1000? What likelihood is there now that we could reintroduce something used to the climatic and marine / terrestrial conditions of today?

Some alien species simply are too entrenched into our ecosystems to try and eradicate. However, we should remain to be alert to new invasions, ones that we can possibly control or manage. For example, down in Kent, we are trying to control the spread of the Pacific oyster into a site of European importance for its coastal habitats and wildlife, and we're doing that by eradicating many of the oysters on one section of the coast. We'll never get rid of the oysters, but we can hope to control their spread!

By coincidence of a PhD choice in 1982 I happen to follow both macrofungi and Collembola (springtails), and would just like to add the observation that both these groups have thrown up numerous examples of alien species appearing in the UK, almost always in highly human-controlled habitats and with what looks like an increase in rate over the last 30 years. I put up a page about some of these alien toadstools a few years ago - see



- but confess that I have rather failed to update the research, which pleads for PCR/barcoding. Similarly the UK is experiencing an almost invisible invasion of tiny alien springtails, at least one of which appears (according to the world expert Penny Greenslade) to be a new genus to science. See



for one of these, whose name has been verified.

What to make of this? The same invasions are almost certainly occurring in most other groups of organisms, whether or not anyone is monitoring them. I think that we have little choice but to monitor carefully and go with the flow (though limits on the international horticultural trade might slow down this international hitchhiking). Like Sika DNA in Scotland, it's out there and we can like it or lump it.

This is an old story - I checked collections of Collembola from St Helena for Howard Mendel (NHM) a few years ago - and every springtail from St Helena was a UK garden/flowerpot species. Almost certainly these aliens had been introduced accidentally with flowerpots, then escaped and wiped out numerous endemics.

Over on my Transatlantic Gardener blog - - I picked up on David Pearman's piece entitled The Alien Invasion Myth in the December issue of the RHS magazine The Garden. In North America there's an enthusiastic (fanatical at times) pro-native/anti-alien movement and serious research on the behavior of new arrivals is often hampered by the fact that they're removed before they can be studied.