Plant Migrations

Hugh Warwick, direct action against GM crops

With human civilisation comes ecological engineering. Over 10,000 years we have changed the world in increasingly dramatic ways. Many of these changes have been deliberate. Many have been the unintended consequences of our unquenchable curiosity and our anthropocentric thinking.

How soon did early modifications of grasses in the fertile crescent of our imagination become commodities? At what moment in time did our capacity to store an excess of grain result in a trade more complex than barter? If we want to examine the unintended consequences of our relationship with plants we can go a long way back.

The dawning of civilisation was only possible because an alternative to hunting and gathering became viable. From that step emerged the first civilisations: da Vinci, Turner and the Internet all trace their heritage back to the early trade in plants and plant products. It would have been a brave Mesopotamian who prophesied such things as the eight Neolithic founder crops were tended in those fecund hills: emmer wheat, einkorn, barley, flax, chickpea, pea, lentil and bitter vetch.

The first agrarians lit the fuse which travelled through time until the explosion when plants began to scatter around the globe. The Columbian Exchange began with Christopher Columbus in 1492. The collision of the Old and New World populations led to what Simon Lewis describes in Nature as an ‘unprecedented homogenization of the Earth’s biota’. Much of this exchange was deliberate. Maize, tomatoes, potatoes and tobacco came from the New to the Old, and in return were sent rice, wheat, onions and bananas.

At this point, human progress accelerated dramatically, and as Lewis argues in Nature, the year 1610 could be seen as the dawn of the Anthropocene, the new human-defined geological epoch. This date coincides with a 2,000-year low in CO2 concentrations in the atmosphere, brought on by the near cessation of farming and burning on the American continent, which in turn was the result of the extirpation of 90% of the native population through war and disease.

The speed at which plants and seeds can hitch around the world has accelerated, and with that has come a massive increase in the potential for the unforeseen. Looking back at the explosion of plant movement, I do wonder if while Western Europeans thought they were busy colonising the world, taking their vision of civilisation to the remotest regions, there was a subtler game being played. Have we been tamed by plants rather than the other way around? That would be the ultimate unintended consequence of our actions.

Hugh Warwick Invasive species

In 1994 I took part in a protest at the site of the M3 extension through Twyford Down. Before tempers were roused and fences cut I had taken a walk along the River Itchen and thrilled at the sight of kingfisher and water vole. The sun beat down heavily on the motley crew who confronted the diggers and police and I returned home a day or so later exhausted. The next morning I woke with a disturbing pain on my left knee, which over 48 hours grew the most alarming blister. With a wound 5 cm long and 2 cm deep I was restricted to wearing shorts and decided I ought to get medical help. Turns out that Genesis were right. Their song ‘The Return of the Giant Hogweed’, charts the arrival of this regal plant in the care of a Victorian collector who had gone exploring in Russia. And it explains how ‘they are invincible, immune to all our herbicidal battering’ – ‘around every river and canal their power is growing’.

They are majestic plants; five metres tall with beautiful umbels. But they have a sap that causes phytophotodermatitis and I must have unwittingly brushed against a plant along the river and ended up with massive localised sunburn. I still have the scars. The giant hogweed is just one of many on the list of undesirables to be found at the Non-native Species Portal, though not all the species found on that portal are undesirable. The vast majority have been benign. However, the scale at which they have been arriving could be considered alarming by anyone wanting to preserve our island in floral aspic. Between 1600 and 1799, less than one new species, on average, arrived and established itself in Britain each year. These came to meet commercial needs, not least the demands from new Georgian gardens. The European Grand Tour inspired new ways of laying out the land. Ha-has created new form, shrubberies required new plants.

Many were introduced by Joseph Banks who travelled the world, accompanying Captain Cook on the Endeavour, collecting plants as he went. These specimens were housed at Kew where most have reproduced, sustained by the pampering they need. Today the quest for the new is unabated; since 1950 ten species have arrived here per year.

Britain has 1,400 native plant species, but thanks to the accidental and deliberate movement of plants, we now have 1,500 non-native species as well.

Consider this. Britain has 1,400 native plant species, but thanks to the accidental and deliberate movement of plants, we now have 1,500 non-native species as well. The vast majority made it to our shores through the trade in ornamental plants. That is how the giant hogweed arrived, and other plants that plague those trying to manage our semi-wild spaces. In 1981 the Wildlife and Countryside Act was passed in an attempt to exert control over these. If you would like to see the full list of horrors, check out Schedule 9 Part 2.

Which has to cause a pause. What would our land look like without these alien species? Clearly not all the incomers are on the list of undesirables. Some that are, like giant hogweed, are well known. And some of these cause a lot of money to be spent in pursuit of their eradication.

Many of the biggest problems started in the nineteenth century, a time of fundamental shifts in our understanding of our place on earth; the erosion of God with the arrival of science. It also marks the point of acceleration of ecological change. Thanks to the Industrial Revolution, we could engineer the environment like never before.

Though it was not just humans doing the engineering. Rhododendron were recorded in the wild in 1894. Until then there were relatively delicate examples in gardens. Collectors brought them to Britain from mainland Europe, North America and the Far East. Here was the ‘rose tree’ with over a thousand different species; vibrant colour in spectacular flowers. But still, they remained behind the garden wall. Until clever gardeners selected the ‘best’ characteristics, rapid growth and abundant flowers, and created a new plant. A vigorous chimera was set to leap the polite confines of the tranquil regime and make for the hills. Which it has done with extreme efficiency; according to The Wild Things, Rhododendron x superponticum now occupies nearly 70% of all 10 km squares in Britain.

Hugh Warwick 2 Invasive species

Why the concern? We have, as George Monbiot puts it, ‘sheep-wrecked’ the uplands of Wales. So perhaps vigorous plant growth should be welcomed? If only things were so simple. Trevor Dines, Botanical Specialist at the conservation organisation Plantlife, shifted my view of these effective plants. Looking from above it is easy to see how good the rhododendron are at outcompeting everything else. Almost no ground visible beneath them; they grab all the light, so nothing else gets a chance to grow. Added to this they have a chemical defence in their leaves that is toxic to most insects which, when the leaves fall to the ground, also prevents native seeds germinating.

These flouncy flowers, the result of the magnificent meddling of Victorian horticulturists, share something with the engineers of that time. While lacking the stovepipe hat, rhododendron is a plant that has the rare honour of being described as an ‘ecosystem engineer’. They can completely alter the land in which they settle. Just like us. Though, in their defence, these ecological engineers are making merry only where we have already undermined the indigenous vegetation’s capacity to thrive. Is this a lesson we can learn from the invasive non-natives? The lesson being that they will thrive where we destroy?

People are less squeamish about the control of invasive plants than they are of unwelcome animals. And so the battle-lines are set, and slashing, burning, drilling and dousing are the order of the day. When carried out vigorously, whole hillsides can return to their previous form, but the reality is we will never be rid of this Victorian invention.

And what are we trying to return to? We can’t go back to the floristic diversity of 10,000 years ago. So where is the line to be drawn? Clearly there are some plants we want out, but perhaps this is not specifically to do with their non-native status. The year 1825 saw the arrival of the Japanese knotweed which soon became a star in Victorian gardens before it too made the great leap to freedom. Though, unlike the conventional sexiness of hogweed or the engineered hybrid of rhododendron, she is a very different plant. The pronoun is deliberate. The original plant that arrived in 1825 was female. She has now spread to cover 75% of Britain’s hectads. Every shoot of tarmac-splitting plant is a clone of the original mother. Is this the largest individual wild plant in the world?

Our indignation should be aimed not at the plants but at the environment that allows them to flourish.

I have watched conservation volunteers heap knotweed onto bonfires and as their backs were turned, hands warmed by the flames, spikes of new growth appeared on the hard-won land.

I remember the delight of Himalayan balsam. As any child would, when confronted by turgid pods that explode most satisfyingly on the gentlest of contact, I assisted its spread. Trevor Dines told me that when it was being promoted as a garden plant following its arrival in 1839, claims were made that it could grow to ‘Herculean proportions’ and was blessed with ‘splendid invasiveness’.

Again, while the tendrils of British interest were reaching into the remotest corners of the world, the results were being unleashed at home with a complete unawareness of the potential fallout. Ecological engineers, with the capacity to transform our green and pleasant land. But is it always bad? The balsam does smother and has used our network of roads and canals to spread all the further. But it is an annual and dies back each year. And it is a plant that supplies nectar and pollen to insects that have found their traditional supplies, in the now cauterised meadows, gone.

The simplistic binary argument does not hold. Righteous indignation at malevolent foreigners is misplaced. It is possible that the indignation should be aimed not at the plants but at the environment that allows them to flourish, an already diminished, weakened and impoverished landscape.

We need to shift our perspective, and someone doing a great job at helping twist our stubborn heads to face a different way is the journalist Fred Pearce. In his latest book, The New Wild: Why Invasive Species Will be Nature’s Salvation, he argues that we have conflated the ecological threat of these plants with the impact they have on our sense of well-being. ‘It is sometimes hard to remember that most of the … alien species in England are benign, and generally add colour and variety to the landscape. Thanks to them, the biodiversity of the British Isles is probably greater than it has ever been.’

Edward Chell, installed artworks at the Horniman Museum, September 2015 Invasive species

Pearce forces us to think differently. There is no original, untouched, British Flora. We have been in a state of floral flux since the ice retreated. He calls on us to enjoy the stories of these adventurous organisms.

‘The seeds of hoary cress were transported in straw-filled mattresses that carried home the wounded from the Napoleonic wars two centuries ago, and were subsequently spread when the straw was given to a local farmer. A taxidermist’s stuffed bird conveyed the hairy-stemmed Canadian fleabane …’

Even the ivy-leaved toadflax, so at home that it is currently creeping across the stairs of the shed from which I write, arrived here in the packaging of imported Italian statuary in the early seventeenth century, according to Richard Mabey in Weeds.

But why is Pearce so relaxed in the face of the supposedly massive bills we pay to keep these unruly plants in check? It transpires the ‘massive’ figure of £166 million per year for knotweed destruction is something of an extrapolation. Is CABI, the former government agency Commonwealth Agriculture Bureaux International that gave us this figure, a reliable source? Pearce points out that CABI’s figures help justify the organisation’s work developing biological control agents for knotweed.

Rather than attacking the aliens for invading, perhaps we should look at how we treat our natives.

And how much is really being spent? The biggest land manager in the country, the Environment Agency, spends around £2 million a year tackling Japanese knotweed. Which goes to show there is a real problem, but probably not on the scale suggested by CABI, which went on to argue that the cost to the British economy of all invasive non-natives was £1.7 billion a year. This eye-watering figure should be cause for concern, but again Pearce unpicks it and includes 40 million rabbits, each of which is said to inflict £5 of damage to the economy.

Rabbits re-raise the interesting question of what we are aiming for with our control. In Britain we set one line at 1492, and any plant that was around before then is considered to be an archaeophyte, an ancient plant. Arrivals after that, plants that benefited from the Columbian Exchange and beyond, are neophytes. Rabbits first arrived with the Romans and then settled with the Normans, so should be classified as ‘old’.

There are three key features of an invasive non-native: the factors that constrained them in their original range are lacking (e.g. pathogens and herbivores); they grow fast, either with prolific seed production or vegetatively; the recipient environment is disturbed or degraded, allowing them to take a hold while the native plants wonder what is going on.

We can’t do much about the first two, but the third is clearly important if we look at where invasive plants become established. Rhododendron flourishes where sheep have wrecked the hills; knotweed is most frequently found on disturbed ground, pushing up through cracks already there in the concrete. Oxford ragwort, another escapee, originating from the volcanic slopes of Sicily, arrived in the city’s Botanic Gardens around 1690, and made itself at home, being ‘very plentiful on almost every wall in and about Oxford’ according to a professor of botany writing in 1794. It was not until the arrival of the railways that it broke for freedom, the unpromising clinker of the tracks’ substrate being an efficient analogue of its volcanic motherland.

Edward Chell, installed artworks at the Horniman Museum, September 2015 Invasive species

Rather than attacking the aliens for invading, perhaps we should look at how we treat our natives. We have destroyed 97% of our wildflower meadows in the last 70 years; we maintain a farming landscape that is often little more than an ecological desert. There are plants that can help feed our remaining wildlife, but they may not be native.

We know that the majority of alien species are benign. But this does not mean we can ignore the threat completely, just put it into perspective. We have to make a judgement on each and every one. Viral, bacterial and fungal diseases can all arrive hidden in foliage. In particular, plants aimed at the tropical fish market present a risk, as any escapes could cause havoc for our amphibians. Sometimes an unruly element ‘kicks off’ and it is necessary to try to remove them. Gone is the freedom to roll up on our rocks with a bundle of exotic plants and let them loose.

We need the eco-police, but should not exaggerate the risks. There are many good plants that come from elsewhere and perhaps ecosystems are rather more adaptive than we once thought. Maybe species that can work together do not need to have evolved together. Certainly Pearce thinks so. He visited Ascension Island in the tropical South Atlantic to see Green Mountain in all its glory. Nearly 200 years ago it was bare. Today it is a fully functioning ecosystem, a rich cloud forest consisting of plants brought in from all over the world. ‘This confected cloud forest was prime evidence in a growing movement among ecologists to reconsider many of their nostrums about how ecosystems function. It suggested that species with no previous contact can get along with each other much more intimately than assumed.’

Whatever the future holds it will not be the same as now. The changes that accelerated from foot to flight have a different engine now; the climate is changing too and with that a whole range of novel plant communities will appear, adapt, flourish or perish. In the end, there will be plants after we have gone. What we panic about now is the impossibility of keeping things the same. We are attempting to hold in a tight embrace a completely fluid system. Things change, they always will.

We are entering a new era of plant trade. This time exotics are being created in the laboratory.

But there are changes we are witnessing now that we do have the capacity to control. We are entering a new era of plant trade. This time exotics are being created in the laboratory. There have been several decades without dramatic incident in the field of genetically engineered crops, which might lead the naïve to assume all is right. The industry shills spin tales of great success, but beneath the scientists’ intentions is an economic model that has made a mess.

The vast majority of GE crops have not been engineered to be more productive or better; just tolerant of the herbicide glyphosate, a chemical that kills weeds and other things too. Monsanto, the company that unleashed this chemical on the world, which is also a leading producer of GE seeds, has spent a long time saying how safe glyphosate is, though it is known to negatively affect aquatic invertebrates.

The unintended consequences of this new wave of organisms will be far reaching. If you apply the same herbicide to fields of crops every year you get a build up of resistant weeds. And this is what is happening. Charles Benbrook, research professor at Washington State University, is a rare voice in the call for science and sanity to be applied to the claims of the GE industry. In Environmental Sciences Europe, he writes:

‘Contrary to often-repeated claims that today’s genetically engineered crops have, and are reducing pesticide use, the spread of glyphosate-resistant weeds … has brought about substantial increases in the number and volume of pesticides applied.’

Attempts to engineer the good PR gene into GE crops have so far failed, not because, as the advocates would have you believe, evil environmentalists have thwarted their attempts. No, it is because things like ‘Golden Rice’ don’t work yet – even according to the International Rice Research Institute which is trying to develop the technological solution to a serious problem – vitamin A deficiency.

It is possible that one day there will be a component of sustainable agriculture made up of genetically engineered crops, but at the moment that is just a fantasy. For now, given the unintended consequences that have erupted wherever the technology has taken hold, I think we should be far more cautious.

We can think about plants as combatants in a battle between invasive and archaeophyte species, or as representatives of a balance between commodity, food production and the environment. We can also see them as ornamental contrivances for landscape gardens and the aesthetic seed images informing visual taste that evolved through porcelain imports from China and their European ceramic equivalents. As specimens, they are discrete elements that can be understood, collected, catalogued, photographed and pictorialised in their own right. Above all, plants form the stage and setting for everything we do.


This essay was originally published in Bloom,published in November 2015 by Horniman Museum and Gardens to accompany Edward Chell’s exhibition of the same name. The book also includes essays by Chell and The Learned Pig contributor Anna Ricciardi.

Bloom is at Horniman Museum and Gardens until 6th December 2015.

(By coincidence, Bloom is also the title of a recent book by artist Ben Cave, extracts of which we have published elsewhere on The Learned Pig.)

Image credits (from top): 1-2. Hugh Warwick; 3-4. Edward Chell, installed artworks at the Horniman Museum, September 2015


The Learned Pig

Hugh Warwick

Hugh Warwick is an ecologist and writer with a particular fondness for hedgehogs. His first book, A Prickly Affair, remains the only book to have accolades from both Jeanette Winterson and Ann Widdecombe on the cover. The Beauty in the Beast was published in May 2012 and takes him on a journey in search of other animals. In November 2012 he returned to hedgehogs with a book about the iconography of the animal. He is currently working on a new book, The Linescapes of Britain.