Planet Earth Online

Aliens descend on Britain

Helen and colleagues from CEH, Mark Hill and Chris Preston, tell us what invasive species are, how they got here and what scientists are doing about them.

Later, we'll find out more about the harlequin ladybird: what to do if you spot one, how to be sure it's a harlequin and what you can do to help scientists keep track of their spread across Britain.

Helen has a keen interest in invasive species like the harlequin ladybird, muntjac deer and Buddleia and spends much of her time looking at how they affect native plants and animals.

She coordinates the UK Ladybird Survey, and is working on a project to produce a comprehensive information portal on non-native species in Britain. She leads a European study group within the International Organisation for Biological Control on the Risks and benefits of Exotic Biological Control Agents.

At a later date, we'll hear about Helen's plans for the invasive species information portal project and find out why scientists like Helen are so excited about it.

How you can help monitor invasive species

Helen Roy

Chinese muntjac deer, Chinese mitten crab, zebra mussels, tree-of-heaven, American skunk-cabbage and creeping water-primrose are at the centre of a new website launched today called 'Recording Invasive Species Counts'.

They're quite an assorted bunch, but they all happen to be invasive non-native species that are established in Britain. Through this project scientists hope to improve their understanding of the ecology and distribution of these species, and also to highlight the importance of monitoring them.

The project has been developed collaboratively by the Biological Records Centre at the Centre for Ecology & Hydrology, the National Biodiversity Network Trust, the GB Non-native Species Secretariat, and other national societies which run recording schemes for plants and animals.

The website is based on the hugely successful Harlequin Ladybird Survey, described in an earlier blog, which has tracked the rapid spread of the invasive harlequin ladybird across Britain since the first recorded sighting in 2004.

The British public has reported sightings of these insects to the Harlequin Ladybird Survey and gone on to look for all species of ladybird, contributing enormously to ladybird recording. There is no doubt that the arrival of the harlequin ladybird has encouraged many people to get involved in recording all ladybird species through the Ladybird Survey. The survey has received a staggering 60,000 records over five years. Scientists are hoping for a similar response for the six species selected for the RISC project.

Why these six species?

The six species scientists have selected are easy to identify and are seen reasonably often, so they are excellent candidates for a project that aims to get wide participation across Britain. The information gathered will increase our understanding of the distribution and ecology of these invasive species and the extent of the problems they pose.

Recording these six species through the new website will be closely linked to key national organisations that lead biological recording for particular groups of species (the Botanical Society of the British Isles, Marine Life Information Network, the Conchological Society, the Mammal Society and the People's Trust for Endangered Species).

We're hoping that people who record when they see any of the six selected invasive species will also be encouraged to get involved with recording sightings of other wildlife species, contributing widely to scientists' understanding of biodiversity in Britain (and beyond). Just as has been the case with the Harlequin Ladybird Survey.

How can you get involved?

The new website is part of the Great Britain Non-native Species Information Portal (described in an earlier blog). You can find both on the internet through the Non-Native Species Secretariat website:

The RISC project web pages feature lots of information about the six species and a form for you to complete if you have seen any of them. You will also have the opportunity to upload a photo. It'll be easy to take photos of some of the species, but for others, it might not be so easy – but even a shot of the tail of a muntjac deer as it leaps from view would still be helpful.

What will scientists do with this data?

Each record will be checked by an expert from one of the societies linked to the project, who will then provide feedback on the record. The verified record will then be added to a database of distribution information about each species and sent to the National Biodiversity Network Gateway.

The Gateway acts as a 'data warehouse' for biodiversity information. Once the data is on the Gateway it will appear on the relevant species pages on the website and so will be visible to everyone visiting the site.

The data will be extremely useful to recording schemes and societies, scientists, policy makers and many other people, because it will provide valuable information about where these species are and what they are doing.

For example, the effects of the American skunk-cabbage aren't known in Great Britain; so information gathered through this project will contribute to our basic understanding of this species and its interactions with others.

There are many questions that we will be able to address using this data. Some have a very practical basis – for example, are there some habitats that are more at risk, because of the threat of invasive species than others? Others fascinate invasion biologists across the globe, like what is the role of 'invasion meltdown' in the threat posed by invasive species?

Invasion meltdown

This is a theme that fascinates me as a community ecologist (someone interested in the intricate relationships between species). It is a dramatic term for a dramatic concept. Invasion meltdown describes the way in which the negative effects of an invasive non-native species on an ecosystem are made worse by interactions with other non-native species existing or arriving within that ecosystem.

There is very little information about invasion meltdowns, but the fantastically named yellow crazy ant (Anoplolepis gracilipes) provides a good example. This invasive ant was introduced to Christmas Island in tropical Australia and when an exotic scale insect arrived on the scene the crazy ant's population exploded.

Unfortunately this large ant population devastated the population of native red crabs (Gecarcoidea natalis) and resulted in a dramatic increase in forest undergrowth because of reduced grazing by the crabs. It is also predicted that the huge decline in red crabs will make Christmas Island more vulnerable to the arrival of new invasive non-native plant species.

The RISC website will help us to assess populations of these six invasive species in considerable detail. The Great Britain Non-Native Species Information Portal project will gather information on many more non-native species. We can link these datasets to the wealth of biodiversity data we hold at the Biological Records Centre at the Centre for Ecology & Hydrology to explore hypotheses, such as invasion meltdown, in the context of communities of species existing within a changing landscape.

These are exciting times for invasion biologists. The biological signals we detect through the wealth of data gathered by people across Britain will prove indispensable in addressing key questions in this fascinating area of science.

Posted on 22 March 2010 | Comments (2)

Keeping track of non-native species in Britain

Helen Roy

There are 3808 non-native species in Great Britain: 43 bony fish, 44 mammals, 326 birds, 1821 flowering plants, 64 crustacea, 865 insects... and many more. Or so we think. It is extremely difficult to work out precisely how many non-native species are resident in a country and, in some cases, equally difficult to predict whether or not a particular species will be invasive, that is, have an ecological impact.

Indeed some non-native species arrive, establish small populations and seem to be unproblematic years after arrival, but then something changes and these so-called 'sleeper species' become invasive, or a threat to biodiversity.

Oxford Ragwort, Senecio squalidus, is a sleeper species with a distinguished history. It was introduced from Paris to the Duchess of Beaufort's garden at Badminton between 1700 and 1702. Sometime before 1719 it was transferred from Badminton to the Oxford Botanical Gardens. It was then recorded as an 'escapee' from the gardens in 1794 and noted only at a scattering of localities in Oxford until 1850.

By 1879 Oxford Ragwort reached the Oxford railway and from there it spread rapidly across the rail network. This species grows on the soils derived from volcanic ash on Mount Etna in Sicily and the railway system provided a perfect substitute. Fortunately Oxford Ragwort is not considered to be an invasive species because it is a benign addition to the British landscape.

There are a number of non-native species that have restricted distributions because climatic constraints limit their population growth. For example, an isolated colony of the Mediterranean termite, Reticulitermes grassei, was found in Devon in 1994 behind some skirting board. Thousands of individuals were present which suggested the colony had been thriving for some years but had failed to spread from the house. It is widely accepted that climate warming could help termites and many other species currently limited by British temperatures spread.

Non-native species have become such a problem that policymakers have come up with a plan of attack. The most crucial part of this plan is to detect non-native species as soon as they arrive in the country and rapidly assess the risk they pose to biodiversity. Although Britain has well-established monitoring schemes for many taxonomic groups (many coordinated through the Biological Records Centre within the Centre for Ecology & Hydrology), non-native species tend to be under-recorded in part because native species are the primary interest of most researchers.

Coordination of data collection and data-holding mechanisms for non-native species is a high priority and this is where the GB Non-Native Species Information Portal comes in.

What is the Portal?

The portal, commissioned by Defra, essentially contains information on all the non-native plants and animals in Great Britain and so far includes 3808 species. For each we are gathering as much information as possible. This process is in its early stages. First we are asking taxonomic experts to check the species we have listed in the central database of the portal.

For some groups there will be more species to add (particularly the less charismatic species) but there will also be some species that should not be on the list because they are considered native or naturalised (having arrived using their own natural dispersal mecahnisms from a country in which they are native).

The next step will be to add more information about each non-native species on the list: How did it get here? When did it arrive? Where did it come from? What do we know about its ecology? Of course, we don't always know the answers to these questions. Some species (especially the very small ones) just appear mysteriously, and no one knows how they got here.

For 300 species, detailed information, pictures and distribution maps will be available through the portal. There are currently 20 fact sheets already available. Why not click on the link to see which species are already in the portal.

Some non-native species will be deemed to require particularly close surveillance and monitoring and accordingly designated as 'alert' species. Alert species include: high-risk invasive species not yet present in Britain but which might enter in the future; sleeper species; invasive and non-native species for which there is a special concerted effort to provide better quality distribution information, particularly if direct action is being taken to control the species.

One of the current alert species is the Carpet Sea-squirt, Didemnum vexillum, which is a highly invasive non-native marine animal (originally from Japan) that could threaten conservation, fishing and the shellfish industry. It has recently been found in England and Wales and it is very likely to spread further. The portal lists this and other alert species so that anyone can provide nformation on sightings (or indeed a new arrival not on the alert list) by sending details and ideally a photo to: non-native_alert@ceh.ac.uk.

Linking to this will be a participatory project in which people will be invited to record their sightings of a selection of easily recognisable invasive species. More on that later.

How will the information in the Portal be used?

Anyone wanting to know about a particular non-native species will be able to access information through the portal. This comprehensive resource is primarily being designed to help policy makers take a coordinated approach to non-native species. However, it will also provide a powerful research tool.

We will be able to explore the portal to address key questions in non-native species biology. For example, are there characteristic traits of non-native species that can be used to predict invasiveness? And do some habitats have more non-native species than others?

There is no doubt that invasive species pose a considerable threat to biodiversity. The portal will be a core element of the non-native species surveillance strategy in Great Britain and will provide a dynamic interface to other initiatives across Europe and beyond. The accurate and detailed information it contains will provide a foundation on which to base decisions, and will ultimately contribute to safeguarding biodiversity - whether it be non-native or native.

Posted on 26 February 2010 | Comments (0)

Aliens in the attic

Helen Roy

"Ladybird knocks spots off the squirrel's migration" (The Times, 7th February 2008); "Invading ladybirds breed up ecological storm for UK species" (Guardian, 30th June 2009); "Harlequin ladybird threat to 1000 species" (Mirror, 30th June 2009); "Beware the plague of smelly ladybirds" (Daily Express, 27th October 2009)

These are just a few of the many headlines for stories about the arrival and spread of the harlequin ladybird (Harmonia axyridis). Indeed the press has been instrumental in highlighting research on the harlequin ladybird; last year alone there were more than 200 press items about the harlequin ladybird. But what is the story behind the headlines?

The invasive alien harlequin ladybird, Harmonia axyridis was introduced into continental Europe in the 1980s as a biological control agent. It's a voracious predator of scale insects (small sap-sucking insects, so called because they produce an umbrella-like waxy coating or 'scale' over their soft bodies) and aphids. Never intentionally introduced into Britain, it arrived in the county of Essex in 2004 and its spread across the country has been spectacular - approximately 100 kilometres per year.

The harlequin ladybird is particularly abundant in the southeast of England, but there are many records from central and northern England, Wales and also a few records from Scotland, as far north as Orkney. In the last month we heard that the ladybird is now breeding in Scotland.

This precise information on the distribution of the harlequin has been achieved because of the staggering response from people contributing to the harlequin section of the UK Ladybird Survey website which was launched in 2005 as a collaborative project between the Centre for Ecology & Hydrology, the University of Cambridge and Anglia Ruskin University.

People across the country have recorded their ladybird sightings and uploaded photographs, and this has resulted in an impressive and unique dataset documenting the movement of an alien species since its arrival in Britain.

Research behind the scenes of the ladybird survey has also been very productive. We have asked key questions to unravel the story of this alien invader. Perhaps the most important, but difficult to answer, is: how will this species affect native biodiversity?

Laboratory studies have demonstrated that the harlequin can eat native ladybird species such as the 7-spot, Coccinella septempunctata, and the 2-spot, Adalia bipunctata while these native ladybirds do not eat the harlequin. Further experiments have shown the ladybird also eats other insects such as the green lacewing, Chrysoperla carnea and even butterflies. In all of these cases it is usually the immature stages (larvae) that are attacked.

But what is happening outside the laboratory in the wider countryside? How can we address this challenging question? Every year ladybird numbers vary dramatically. Many people remember the year of 1976 when 7-spot and 11-spot, Coccinella unidecempunctata, ladybirds were extremely abundant. The summer of 2008 was bleak for all ladybirds but then last summer numbers were high.

So how can we tease out whether or not the harlequin is having an impact on native ladybirds against this backdrop of fluctuating numbers? One answer is: with difficulty! However, a more constructive response is to use standard survey methods to monitor ladybirds (and other insects) in various habitats throughout the year. Such systematic field surveys are indicating that the niche of the harlequin overlaps with a number of herbaceous and arboreal insect species.

These results allow us to assess the status of native species using ecological models which can include other factors such as habitat and climate. We can integrate the data received through the online survey to strengthen these models. In addition, the photographs from contributors to the UK Ladybird Survey indicate the potential for antagonistic interactions between the harlequin and other species (people have recorded H. axyridis eating larvae of many species, from ladybirds to lacewings and even moth larvae) and we can use these to refine our research questions.

Information of this kind is being gathered not only in Britain but also across Europe. Indeed, collaborative effort is essential to further our understanding of this conspicuous invader. So in September this year scientists from Europe, United States, Japan and South Africa met in Switzerland to share their findings.

The main conclusion so far is that the arrival of the ladybird in Europe poses a risk to native biodiversity, but we are not yet in a position to say how big this threat is. There is an early indication that the small 2-spot ladybird is being found less frequently than in previous years. Is this a consequence of the harlequin or was the species already in decline? This species will be the focus of extensive analysis over the coming years.

Each autumn the UK Ladybird Survey receives reports of very large numbers of harlequins, when the insect enters buildings to find suitable overwintering sites. The autumn of 2009 was no exception; the survey received approximately 800 records a week during October.

The 2-spot ladybird also favours buildings for overwintering and so now is an ideal time to look for these two species. Window frames and attics often harbour large aggregations and it would be very useful if people could send in photos of the ladybirds they see in their houses this winter using the online survey or perhaps their mobile phones (text* "ladybird" to 83040). How many harlequins are living in your house? How many 2-spots?

We are often asked what will stop this invader? We do not recommend anyone killing the harlequins they see because they are easily confused with other species and such action would have minimal impact on the overall harlequin ladybird population at large. Also, we do not yet have a full understanding of the threat posed to biodiversity by the harlequin.

There are a number of parasites that attack native ladybirds and this year we have the first evidence that they are beginning to turn their attention to harlequin ladybirds. This is a research theme that we will be expanding over the next year when we will be encouraging people to report their sightings of some of the parasites that exploit ladybirds. At the end of last year I received an exciting package - some harlequin ladybirds infected with an insect pathogenic fungus. This is the first such report from Britain but I am sure it will not be the last.

So to conclude, the harlequin ladybird is often reported as an invasive non-native species with far-reaching ecological impacts, and there is no doubt that it could threaten biodiversity. However, it is critical that we gather evidence to give us a thorough understanding of the extent of any effects it will have on other species. We have a unique opportunity to monitor this species through public participation and to study this species within a community context through extensive biological recording in the field.

*Texts will be charged at your standard network rate. Internet browsing costs will be subject to your tariff but should not be more than 20 pence.

Posted on 1 February 2010 | Comments (1)

Invasive non-native species in Britain and beyond

Helen Roy, Mark Hill & Chris Preston

The Millennium Ecosystem Assessment published in 2005 designated invasive non-native species, alongside climate change, habitat destruction, pollution and overexploitation, as one of the main causes of biodiversity loss.

Over the last century there has been a dramatic increase in the arrival of non-native species around the world as a consequence of international trade and travel. So what are invasive non-native species and what threats do they pose?

Non-native (or alien) species are ones that people introduce, intentionally or unintentionally, to a new region of the world. One example is the muntjac deer (Muntiacus reevesi), which comes from China. This species was introduced to Woburn Safari Park in southeast England in 1894. In 1901 it was released into neighbouring woods.

Muntjac deer are now widespread in central England but also occur in northern England and Wales, and have recently been reported in Scotland and Ireland. Where muntjac deer occur in high numbers they can devastate woodland plants and prevent tree regrowth. They also damage vegetables and roses in suburban gardens.

Most non-native species are not a threat: the tens rule

As a rule of thumb, only ten percent of non-native species arriving in a new place will survive and reproduce (we refer to these as "established"), and only ten percent of those established species will cause any harm. Harmful non-native species that spread rapidly are called "invasive". Muntjac deer reproduce prolifically in Great Britain and are now an established invasive species.

An audit, published in 2005, concluded that there were 2721 non-native species in England. The total for Great Britain is now estimated to exceed 3500 species. The tens rule suggests that only about 35 of these will harm native animals and plants. But we reckon that about 50 of them are in fact invasive. The rest are innocuous.

Some non-natives are attractive. The southern oak bush cricket, Meconema meridionale, recently arrived in southern England. It cannot fly and is thought to have arrived on fruit and vegetables. It is a beautiful species and is not expected to harm other British animals. Indeed it has been widely welcomed by entomologists.

Those non-native species that harm native species may not necessarily affect the overall functioning of the ecosystem. For example, the non-native harlequin ladybird, Harmonia axyridis, feeds on aphids. We expect it to displace a number of native species that also feed on aphids.

The dynamics of ecosystems are complex and the harlequin may have far-reaching effects beyond aphid regulation. Rigorous, objective research is essential if we are to find out.

We live in a dynamic world

The British landscape is not static; nor are the species that live in it. Ecosystems change and species adapt. The Jurassic landscape was very different to the one we see today, with completely different species. 20,000 years ago, much of Britain was covered in ice. Less extreme change occurs over much shorter timescales. Species move. A number of species, particularly warmth-loving insects such as butterflies, are now reported further north than fifty years ago. Scientists think climate change is behind this.

So does it matter if we have a mix of native and non-native species?

To some extent no. Many of the non-native arrivals are interesting or desirable additions to our native flora and fauna. But the rate of change is worrying. The number of non-native species arriving in countries around the world has increased dramatically and is showing no signs of slowing.

In 1800 there were about 600 non-native plant species in Europe, in 1900 about 1000 non-native plant species and by 2000 a staggering 2500 non-native plant species. This escalation in the rate of arrival exceeds the natural rate of colonization by two orders of magnitude. This can not be considered an evolutionary process.

Invasive species are only a small fraction of the total non-native influx but may do much harm. The Chinese mitten crab (Eriocheir sinensis) damages riverbanks. The large and aggressive signal crayfish (Pacifastacus leniusculus) not only out-competes native white-clawed crayfish but also carries a disease which has devastated white-clawed crayfish (Austropotamobius pallipes) populations in Europe. Other invasives cause economic damage. Buddleia (Buddleia davidii) is abundant on railways and has to be cleared from the tracks at substantial cost. Rabbits (Oryctolagus cuniculus) are thought to cost the Australian economy $200 million a year (but in Britain rabbits plays a valuable role in many habitats as a grazing animal or prey for predatory birds). Many invasive non-native species cause both economic and ecological harm.

International obligations

European countries have obligations in relation to non-native species; for example countries must: "strictly control the introduction of non-indigenous species" (Bern Convention on the Conservation of European Wildlife & Natural Habitats) and "eradicate those alien species which threaten ecosystems, habitats or species" (UN Convention on Biological Diversity).

But to do this, the first step is to document the non-native species already present in countries as well as those likely to arrive (perhaps because they have been introduced into a neighbouring country).

DAISIE (Delivering Alien Invasive Species Inventory for Europe), a European project led by the Centre for Ecology & Hydrology, highlights the non-native species that are of concern in Europe through a list called "100 of the worst". The Non-Native Species Secretariat provides information on non-native species in Great Britain and has developed a process of risk assessment to underpin action.

Now scientists face the challenge of gathering data about where in Great Britain these non-native species are found and providing a portal to deliver this information to policy-makers, other scientists and many other interested parties. This is being achieved through a Defra-funded "Great Britain Non-native Species Information Portal". More on that in a later blog.

Concluding remarks

In conclusion, non-native species have a bad reputation, but actually probably only ten per cent of new arrivals will survive in Britain and only ten per cent of these are likely to be problematic (so only one per cent of total species). It is critical that we gather evidence on the effects of invasive species on native biodiversity so that we have a thorough understanding of the problems these new arrivals will cause.

Posted on 26 January 2010 | Comments (1)