Plant Invaders on “Plants: From Roots to Riches”

Plant Invaders on BBC Radio 4 at 13:45 British Summer Time on 31 July 2014

Podcasts and Downloads from the series


The Victorians’ pride at the effortless movement of plants around the world during the late 19th century was having an unwelcome side effect. Invasive species were beginning to wipe out native populations of plants. With no natural predators to control them, one man’s flower was turning into another man’s weed.

Prof Kathy Willis hears how during the late 1800s, many invasive species from Japanese knot weed to Himalayan balsam to water hyacinth came from deliberate introductions and asks if today, trying to control them is ultimately futile?

As historian Jim Endersby explains both Charles Darwin and Kew’s director Joseph Hooker were the first to examine the impact of invasives, having noticed on the island of St Helena and Ascension Island the effect on native plants.

One of the current biggest invaders is lantana, familiar to British gardeners as a small pot plant. As Shonil Bhagwat of the Open University reveals, since its introduction to Kolkata Botanical garden in the 1870s it decimated native teak plantations. But today opportunities exist to exploit its presence for the wood, basketry and paper industries.

And Kathy Willis hears from Kew conservationist Colin Clubb on the extent to which we should view invasive plants in our ecosystems as part of a strategy to maintain resilience to environmental change in the future.


Presenter: Kathy Willis
Interviewed Guest: Jim Endersby
Interviewed Guest: Shonil Bhagwat
Interviewed Guest: Colin Clubbe
Production Coordinator: Elisabeth Tuohy
Assistant Producer: Jen Whyntie
Producer: Adrian Washbourne
Editor: Deborah Cohen


Article on invasive species in The Conversation

Invasive species: if we can’t beat them, maybe we should eat them

By Shonil Bhagwat, The Open University

What to do about invasive species, which are having a growing and generally detrimental effect on Europe’s environment and economies, is the subject of discussion in both the European Parliament and UK Parliament this week.

Invasive alien species are animals and plants introduced accidentally (or deliberately) into an environment where they are not normally found. Although estimates indicate that there are some 12,000 alien species in Europe, only 10-15% have become invasive, that is, have become damaging and of concern. However, just these 10-15% cost Europe €12 billion a year. So while the European Union has put in place its 2020 biodiversity strategy, it has not yet managed to provide a comprehensive framework to address this threat to European biodiversity.

The EU legislation pending a vote has been under discussion since September 2013 and has steadily gathered support from various European bodies and committees. The case for new legislation is persuasive, and in all likelihood it will pass and become a new EU regulation, bringing with it legal obligations on member states to ban the import, keeping, sale, exchange and so on of specific species.

But foresters and horticulturists, whose professions depend on valuable exotic plant species, have raised concerns. After all, many “alien” species of plants have long been cultivated for timber or for ornamental purposes – too broad a ban and these will be drawn into it.

Some of the poorer member states have argued that the proposed measures for surveillance, monitoring and control of invasive alien species will put a heavy burden on their already over-stretched budgets. It’s estimated that this legislation will cost the EU €560,000 between 2015 and 2021 – small change compared to the cost the damage these species cause, but an extra cost nonetheless. But, most importantly, questions remain about the results: experience from around the world suggests that the large sums of money spent on control and eradication programmes have not yielded the promised results.

Lantana camera. Pretty – for a triffid.
Joaquim Alves Gaspar, CC BY-SA

No proven response, yet

Some colleagues and I carried out a historical analysis of the spread and management of Lantana camara, wild or red sage, one of world’s top 50 worst invasive species. We found that despite many different measures – mechanical removal, chemical poisoning, biological control – Lantana continued to spread throughout subtropical regions during the 19th and 20th centuries.

It was evident that countries spent large sums of money trying to control the plant. For example, in 1973 the cost of Lantana control in Queensland, Australia was estimated at A$1 million (US$800,000) per year. In South Africa, chemical poisoning cost an estimated 1.7 million rand (US$250,000) per year in 1999. Indian estimates in 2009 put control costs at 9,000 rupees per hectare (US$200) – reaching a total of US$2.6 billion to tackle the 13m hectares where it has spread in India, a sum greater than the GDP of the neighbouring Maldives islands.

Despite all this money spent in Australia, South Africa and India, the notorious weed has continued to spread. And unfortunately it is not the only invasive species that has proved unmanageable: hundreds or thousands of others have spread across the world, defying all attempts by countries to make their borders “biosecure”.

New approach required

To deal with alien and invasive species that have already made it through porous borders and have established themselves in their new homes, we need more creative approaches than throwing mechanical excavators, chemicals, and enormous amounts of money at the problem.

With the help of NGOs, some rural communities in India have started a cottage industry of making baskets and furniture from Lantana. Other radical solutions that have been proposed to control invasive species include eating them.

A Chicago restaurant owner sells Asian carp burgers at his specialist fish shop to help the problem of this giant fish infesting North America’s Great Lakes. Others making dinner out of invasive alien species include Miya’s Sushi in New Haven, Connecticut, which has a special invasive species menu, through which they “return to the roots of sushi, meaning simply to use what we have available.” Crayfish Bob in London offers a variety of invasive crayfish dishes, providing “quality food for a better environment”.

So the new EU legislation is a precautionary measure to prevent the ecological, economic and social costs that invasive species might in future impose. This will try to ensure Europe is more biosecure through a variety of control measures at borders, tackling those species that have made it through, and efforts to eradicate those that have become a nuisance.

But the costly failures elsewhere in controlling and managing invasive species makes one wonder whether we should find more creative ways of dealing with the problem: local economies based on harvesting invasive species, or recreational hunting, fishing or foraging as a part of nature tourism, perhaps. In any case, a new approach is needed.

The Conversation

Shonil Bhagwat has received funding from Ecosystem Services for Poverty Alleviation programme of the Natural Environment Research Council, Economic and Social Research Council and Department for International Development, UK.

This article was originally published on The Conversation.
Read the original article.

Two food cultures of the Anthropocene

Cultured-Beef-01Source: Cultured beef


Source: Spatula, Spoon and Saturday

Think of these two foods – one synthetic meat, tasted in London last week, and the other made out of crayfish, an invasive species. Two very different food cultures: one ‘cultured beef‘ and the other invasivore diet. Both arise out of concern for the environment. The cultured beef promises to supply meat more sustainably as the world’s population – increasing in numbers and also in affluence – demands more and more meat. The invasivore diet, on the other hand, attempts to solve the problem of biodiversity loss by making dinner out of invasive species. Let’s call synthetic meat a technological response to the environmental concern and invasivore diet an ecological response.

The technological response to food was under media spotlight last week. The stem cell beef burger was manufactured in a laboratory and tasted in London on Monday, 5th August – a historical moment – as the media enthusiastically reported. There was excitement, even among the vegan community, because of the promise of synthetic meat to remove animal suffering all together. Numbers were shown to demonstrate that synthetic meat will also drastically reduce greenhouse gas emissions and environmental impact of cattle ranching. But there was also some skepticism about the so-called “frankenburger” and concerns that the ‘yuk’ factor in lab-made burger means it will never become popular as the inventors and funders believed it would.

Things can also be said of the ecological response, invasivore diet. ‘Biotic homogenization’ is a serious concern among ecologists and the solution proposed is the eradication of invasive species. Increasingly, the public is getting involved in identifying places where invasive species have spread and are going there to systematically remove them, usually by uprooting the weedy plants or killing animal pests that pose threat to native biodiversity. Eating invasives is a radical solution and there is now a growing movement of invasivores doing just that. There is of course no shortage of invasive species – crayfish, lionfish, Asian carps or garlic mustard, autumn olive, dandelion – all are abundant in places they have invaded. But there is also the ‘yuk’ factor in eating invasives because we are not used to eating these sorts of things, as opposed to conventional vegetables and meat.

What both these food cultures – technological and ecological – do is that they unsettle our notions of what is acceptable as food and what is not. I actually don’t mid trying either synthetic meat or invasivore diet, but must admit that this is not the sort of cuisine I find easily palatable. And I am pretty sure I am not the only one. Both food cultures demand a re-alignment of our ‘comfort zone’ of what is food and what is not. Both shake up our ideas and cognitive models of what is edible. Both are perhaps radical, even audacious, solutions to living in the Anthropocene – part of the survival kit in a brave new world?

Not to disregard the $330,000 spent on making a stem cell beef patty in the lab, personally I think invasivore diet has a lot more going for it – the idea that we can make tasty and even nutritious food out of invasive species can be a much-needed adaptation to our changing natural environment in the Anthropocene. The stem cell burger, in comparison, feels somewhat alien to taste and health. To make invasivore diet a reality, however, we will need to start a cottage industry around invasive species. George Washington Carver, a 20th-century American agronomist, said “Start where you are, with what you have. Make something of it and never be satisfied.” So while we wait for the ‘cultured beef’ to make its way into our supermarkets, we might as well start eating invasive species.

Food security in the Anthropocene


Robert and Didi’s allotment garden plot in Kirtlington, Oxfordshire, United Kingdom

Allotment or community gardens (like the one pictured above) are a common feature of many European townships. In the United Kingdom, these are collections of small plots that can be rented for a small fee by individuals to grow food. Mostly cultivated by hobby gardeners, these patches are sites of experimentation with a variety of crops – many more varieties than a conventional, commercial farm would dare to grow! Allotments are wonderful spaces of ‘agrobiodiversity’- the sheer diversity of food crops including leafy and root vegetables, fruits and occasionally cereal grains. On the day the above picture was taken, we harvested a unique variety of curly lettuce on Robert and Didi’s allotment and made delicious salad out of it.  There are other vegetables, raspberries and even a small vineyard on the plot – an impressive variety of species on a tiny piece of land in a semi-rural corner of England! Most allotment gardens are a mosaic of small plots, each very individual in its soil type, planting design and crop varieties. This inevitably means that some plots remain uncultivated at times and they can accumulate ‘weeds’ very quickly. Some of the weeds (brambles, in particular) are terribly difficult to get rid of and leave many gardeners frustrated while others are benign.

Somewhat counterintuitive to the frustration with weeds, the headline of report published earlier this week in Nature says: “Weeds warrant urgent conservation”. To many conservationists, that sounds blasphemous: Weeds and conservation? No way! But this report is based on a global analysis of ‘conservation gaps‘ in wild relatives of our 29 most important crop species. There are about 455 known wild relatives of these crops and more than half of those are underrepresented in gene bank collections like the Millennium Seed Bank at the Kew Gardens. But why worry about those so-called ‘weeds’ which grow in the wild and often end up making life difficult for gardeners and farmers. Well, these weeds are the ones that have the ‘magic formula’ to grow in harsh conditions like too little water or too high temperatures (or in case of bramble, ability to send it’s tough roots so deep in the soil that without a JCB digger, the gardener has to accept defeat!). But what is remarkable about these plants is their tenacity. And this tenacity is what might help us in the future to make our crops resilient. That is why the report says we might have to turn to ‘weeds’ to make our crops stronger. If we are successful in expanding our portfolio of crops from 29 to 455, that’s a big step in making agriculture resilient.

This reports has some important consequences for how we grow our food in the Anthropocene – a geological age of our own making. The Anthropocene demands innovative ways to tackle a variety of challenges and food security is one of the more serious ones. There is no doubt we need to increase production to feed a growing population, a proportion of which will also become more affluent. But the question is: can we continue to depend on the 29 crops or are we better off spreading the net wider and looking at their 455 wild relatives? These ‘wild cousins’ might well include some rowdy, unruly and rambunctious characters, but sooner or later we will have to look at their good qualities. To paraphrase Ralph Waldo Emerson, the 19th century American Transcendentalist, weeds are plants whose virtues have not yet been discovered. The challenge for us in the Anthropocene is to discover the virtues of these 455 wild cousins and feed 9 billion people by mid-21st century.

The Anthropocene cuisine

autumn olive goat cheese dip

Goat’s cheese and autumn olive dip and dressing (Source: 3-Foragers)

“We must mine the biodiversity in seed banks to help to overcome food shortages” urges a report published in Nature earlier this month. A very sensible plea this – not least because our entire global food system is supported by a dozen plant species while there are 300,000 other flowering plants that we can potentially use as food source. A missed opportunity? Absolutely.

This fragile food system is also starting to crack along the margins as recent food scandals have hinted at. Horsemeat might arguably be the only healthy ingredient in burgers (!), but when it sneaks into our food system through the backdoor, we are extremely upset. The truth is that the supply chain of food is getting so complex that we can’t quite trace our food properly. But even more fundamental issue is: Why are there adulterants in our food in the first place? Is it because the ‘quality’ of food has to be compromised so as to supply cheap and abundant food – the hallmark of our food system – leading inevitably to overconsumption, food waste and health problems?

I would rather eat the ‘Goat’s cheese and autumn olive dip and dressing’ pictured above than horsemeat-filled beef burgers! Autumn olive (Elaeagnus umbellate), an Asian native has become invasive in North America. The domestic goat is one of worst ten invasive species – a prolific grazer and browser, which has ravaged the countryside in many European countries for centuries. There is no way we can get rid of all goats overnight, nor can we get rid of plants like autumn olives. What better use for these than to make food out of them? Critiques say that by making food from invasive species, we are only going to increase the demand for them and make the problem worse. But we got to start somewhere when control and eradication measures thus far have not been successful. Making food out of invasives is a mighty good idea!

This is the brave new Anthropocene cuisine. An interesting piece in The Atlantic talks about a growing food movement: “Chefs are serving up invasive species like knotweed and snakehead fish – and diners are enjoying them”. The author of this piece Nancy Matsumoto (health, food, and culture writer based in New York City) argues that this food movement might also be good for the environment. Let’s call it invasivory. Not only is invasivory controlling the spread of invasive species, but it is also diversifying food, perhaps even making it more nutritious. Think of Dandelions, a somewhat annoying weed for gardeners in Europe, but Megan Saynisch in an article in Ecocentric says: “Raw dandelion greens have a crazy amount of vitamin K, necessary for blood coagulation and bone health. The greens are also a great source of vitamins A and C, and a decent source of iron, calcium, vitamin E, potassium and manganese. The leaves even have a little bit of protein.”

The Anthropocene cuisine might be good not only for the environment but also for the health.

Invasives on Nature Table


Source: Funky biodiversity

This extraordinary creature is tardigrade, affectionately called ‘water bear’. In reality, it is a microscopic creature and is known to be the only species able to survive in space! I took part in Open Space Research Centre’s Nature Table event last week with a number of colleagues and a fantastic guest speaker, Caspar Henderson, the author of The Book of Barely Imagined Beings and a fellow citizen of Oxford. Water bear features in Caspar’s excellent book subtitled ‘A 21st Century Bestiary’, bestiary being medieval encyclopedia of natural history – wonderfully illustrated with facts, observations and stories of wild animals. Water bear in Caspar’s book is perhaps the most celebrated example of resilience of life: even if all life on earth vanishes in a catastrophe of meteoric proportions, water bear will probably survive – a ‘polyextremophile‘ as Caspar described it.

Such is the resilience also of many invasive species: they may not survive in space, but they certainly survive on earth due to their sheer adaptability to no matter what is thrown at them. One ought to admire their resilience, which also makes them extremely difficult to control. Alien invasive species cost the British Economy £1.7 billion every year, estimates the Environment Agency – that’s bigger that the GDP of some of the Caribbean nations – an impressive statistic. The Environment Agency has recently announced a new smartphone app called PlantTracker. This is a great tool for people to get involved in spotting invasive species and reporting them. This ‘citizen science’ can lead to new understanding of the geography of many invasive species. But is it enough? Can we then simply go on with business-as-usual? Or do we also need to find a different way to look at this ‘alien invasion’?

It’s a tricky question, but it might be useful for us to recognize that the alien invasives have gone out of control because we have created habitat for them. Attempts to eradicate them is one way, but another is to reverse our gaze and accept that the invasives will continue to flourish alongside us. For a species of our size, we have changed the rules of the game by having a disproportionately large impact on the planet and in the process created space for other species like us. This brave new world – the Anthropocene – is beginning to be recognised. There is now even an academic journal by the same name, which usually suggests that this idea has caught on – after 13 years since the Nobel-laureate atmospheric chemist Paul Crutzen first wrote about it. In favour of ‘the Anthropocene approach’ to looking at the world, Gary Hamilton writes ‘Welcome weeds: How alien invasion could save the Earth‘ and argues that there is more good to weeds than meets the eye, while Emma Marris in her book ‘Rambunctious Garden’ argues that we should “let a little more wild” into our lives. With these new ways of looking at our natural world, something is surely changing. As Caspar described it last week, “the beginning is nigh”.

Invasives on the plate


Photo credit: Ashley Baldridge (

Mystery-snail Fettuccine anyone? Served with fruit, corn on the cob, garlic bread, slaw, and boiled rusty crayfish. Sounds appetizing, looks colourful and probably tastes delicious. It’s one of those recipes from invasive snail in North America. There are dozens of others on – welcome to a brave new world of invasive species cuisine!

Going by findings of recent research on growth in crop yields by 2050, invasive species might well have to be on the menu. This research, reported in the Guardian newspaper, shows that agriculture productivity is not rising fast enough to meet the needs of a rapidly growing world population. This was based on a study of yields of four key staple crops – maize, rice, wheat and soybeans – which supply a large proportion of the world’s diet. Some estimates suggest that 80% of global calorie intake comes from 12 plant species, eight of which are
grasses and four tubers. Imagine a scenario where a pathogen infects some of these crops – global food supply will be in deep trouble. Remember ash dieback in Europe which started in the winter of 2012? As of 17 June 2013, in the United Kingdom alone, there are 524 reported cases of ash dieback. Luckily we don’t eat ash trees! What if this was wheat or rice? Can’t even begin to imagine the catastrophe that would have caused.

The truth is that the global food system is highly ‘centralized’.  We depend on too few crops to feed ourselves. Should we seriously look beyond our 12 main crops? Yes. Wild edible plants – the weeds we often want to get rid of – might in fact have nutritional value that we haven’t recognized.  There are thousands, some of them already tried and tested as edible. Can we ‘discover’ food value in others? We might have to if we are to make our food system more resilient. The invasivores are on to something – they are experimenting with a radically different way of growing or gathering food. Such radical food movements are not new.  There are also locavores, who buy and eat only local food grown within a certain radius from where they live. And there are freegans, who are deeply unhappy about supermarket waste and go to great lengths to collect discarded food and cook dinners out of it. At the heart of these radical food movements is the dissatisfaction with the global food system and a strong statement that something needs to change.

Could ‘invasivory’ turn into a radical movement? Possibly. We might be initially suspicious of trying out food outside of our comfort zone, but we might learn to put up with it, even enjoy it. Miya’s Sushi in New Haven, Connecticut, has a special invasive species menu. They are after cuisine that “returns to the roots of sushi, meaning simply to use what we have available where we live.” Crayfish Bob in London, United Kingdom, offers a variety of invasive crayfish dishes, providing “quality food for a better environment”. There are others who are making adventurous food out of invasives and serving all sorts of things on the plate: lionfish, python and even alligator! But Chef Philippe Parola, a Californian, has the best advice of all: “Can’t beat’em? Eat ’em”!

Invasion and migration


“Invasion of the killer shrimp: Britain on high alert after ‘voracious predator’ from Eastern Europe spotted in UK waters” goes the headline of a story in Daily Mail on 5 October 2012. The main concern for Daily Mail is that this “alien shrimp” has migrated from Eastern Europe and that it could cause havoc by killing a range of native species, particularly the “British Shrimp” which forms valuable part of the UK’s marine ecosystem. It’s odd that Daily Mail has taken interest in a conservation issue, but it is the World’s Most Popular Online Newspaper reaching 45.3 million people, so surely, that’s a good thing for conservation? Potentially 43.5 million people will become aware of a serious conservation issue from this news report.

But reading between the lines, I am struck by the parallels drawn in this news report between migration and invasion. Shortly after some of the Eastern European countries joined the European Union in 2004, there was a wave of migration to Britain and tabloid newspapers launched on this issue. Apocalyptic scenarios of migration were portrayed and that created public anxiety over harmful effects of Eastern European migration on the European economy. Whether or not such migration helps or hurts an economy is debatable and I don’t want to go into that debate, but what is striking is the similarities drawn in this news report between invasion of an alien species of Eastern European origin and migration from Eastern Europe.

Indeed, the comments from the readers underneath the news report go like this: “Just one more thing from eastern europe which is not wanted here in the UK” or “This is what happen when you import too many Polish plumbers.” Even though the news report does not directly imply a connections between Eastern European invasion and migration, the readers have picked up on this perhaps unconsciously. So the ‘migration’ frame doesn’t do any favours to creating greater awareness about invasion. Instead, it only promotes Daily Mail’s somewhat xenophobic propaganda – this time pointing to non-native species.

Even more shocking are the parallels between the language used to describe eradication of invasive species and ‘ethnic cleansing’. Provoked by conservation practice in the Balkans, a former student – one of those rare conservation practitioners who reflect critically on their practice – wrote to me: “It has always troubled me that the same language we use to describe native trout populations and how to conserve them are a direct mirror of the language used to justify ethnic cleansing and genocide of human populations (i.e., ‘etničko čišćenje’ –ethnic cleansing. A genetically pure species of trout is referred to as a ‘čista populacija’ a ‘clean population’, which is the exact same language that was used to ‘cleanse’ ethnically diverse population of people–to rid them of their ‘aliens’.”

Are alien invasive species perhaps bringing out some our worst fears about our place in this world? Any sensible conservationist, I am pretty sure, will abhor ‘ethnic cleansing’  and instead celebrate living in a multicultural world. Yet, we are comfortable with those exact same words to describe invasive species management – intriguing!

Thinking invasives


I was leading the Open University’s Friday Thinker today – as I can be seen peeping out from a photo on the OU’s Facebook page captured here.

Each week an academic takes charge of Friday Thinker and poses a question to the 12,500-strong audience of the OU students taking Social Science modules. The discussion with students – who are distributed all over the UK and have various ‘day-jobs’ alongside their OU studies – was extremely interesting. I was delighted to see so many of the OU students engaging in discussion and debate.

The question I posed was about invasive species (naturally, they have been on my mind quite a lot lately!). The discussion started off by asking how we should respond to alien invasives. This sparked off some debate on whether it is our moral responsibility to make space for ‘native’ flora and fauna by removing ‘alien’ invasives, or whether we need to find new ways of living with the invasives and accepting them as part of our natural world. Some very strong views about how the natural world should look like were voiced, informed perhaps by people’s own values of nature and a slight discomfort with what is seen as not natural.

The discussion then focused on invasive species as potential source of food and exposed uneasiness about the idea of ‘eating aliens’, but it also brought up questions about the necessity of such extreme measures for global food security. Jackson Landers’ book and FAO’s report on the need for eating insects came into discussion as radical solutions for global food security. This was just around lunch time, and looking back, the thought of ‘eating aliens’ might have put several people off their lunch – oops, mea culpa!

One question that I couldn’t tackle on the Facebook forum was that of money. Substantial sums of money have been spent on eradicating invasives, but with little success. Could we use those billions of pounds, dollars, euros somewhere else? For example, education programmes, poverty alleviation programmes or healthcare provision? How can we weigh-up our moral responsibilities towards other species (native flora and fauna) and towards other human beings? These are difficult questions to answer.

Alien invasive species perhaps expose many of our own innate anxieties. The fact that they are where they shouldn’t be makes us react in some pretty visceral ways, as the emotive language we use to describe them shows. The idea of ‘eating aliens’ also exposes our anxiety about what is and what isn’t acceptable source of food. And most importantly, invasive species pose some very challenging moral dilemmas about the natural world. As one student rightly said, “[we] habitually elevate ourselves to the position of some imaginary ‘Fat Controller’, the custodian of the natural world”.

The (almost) uncontrollable nature of invasive species perhaps challenges this image we have of ourselves and leads to what Paul Robbins and Sarah Moore call ‘Ecological Anxiety Disorder’. In using the emotive language to describe them, one wonders: are we projecting our own anxieties on invasive species?

Invasive words


This is a field of red poppies in spring. In a farming village in Greece, this patch of land is one of very few that is left uncultivated. Poppy thrives on such abandoned land, keeping its ‘seed bank’ in the soil and popping up (it surely lives up to its name!) when things get warmer. It’s a prolific plant – one that grows in abundance – characteristic of a ‘weed’. Yet, most people find the appearance of this poppy field beautiful. A ‘beautiful weed’, in other words.

But not all weeds appear beautiful to us. Some of them are ‘native’ (they belong to the land), others ‘alien’ (they were brought in from outside, mostly by accident), but we openly express our anguish at these weeds. Rhododendron becomes ‘A Killer of the Countryside‘ in Britain; Himalayan Balsam is considered ‘Prohibited Noxious’ plant in Canada. Plantlife, a charity in the United Kingdom concerned about conservation of wild plants lists many other plants that are considered invasive and has launched a campaign for their eradication.

We also use emotive words to describe invasive species. “‘Dirty dozen’ invasive species threaten UK” goes the headline of a Cambridge study that identifies high-risk invasive aquatic plants and animals. The UK Environment Agency has even come up with a ‘hit list‘ of ten worst invasive species. In some parts of the world, we have ‘waged a war‘ on invasive species. In others, policymakers are encouraged to think about better bio-security to ‘guard against the threat of invaders’.

The words we use to describe these species are perhaps as invasive as the species themselves. These feelings of contempt, disgust or plain aggression we have towards invasive species are intriguing, not least because we, Homo sapiens, are – lets’ face it – perhaps the most invasive species that has ever lived.