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Who are the 'thugs' in British woods?

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Matt Walker Matt Walker | 09:01 UK time, Friday, 3 June 2011

Broadleaf forests are a key British habitat (image: Niall Benvie / NPL)

Broadleaf forests are a key British habitat (image: Niall Benvie / NPL)

If you go into the woods today, you might be in for a big surprise.

Because within these woods lurk a bunch of thugs.

These “thugs” are plant species that bully others, take over the landscape and destroy ecosystems. While it’s perhaps unexpected to hear of plants acting this way, that is not the surprise.

What is surprising is that these so called thugs are home-grown.

We usually assume that species wrecking havoc this way are exotic aliens; invasive "outsider" species that have colonised our land and which now hold dominion over our somehow more natural, vulnerable wildlife.

Think of the grey squirrel, imported from the US, and now dominating our reds. The American signal crayfish, that is killing off our white-clawed variety. When it comes to plants we decry the rhododendron and its sprawling bushes that are strangling our native trees, pushing them out of park and forest.

But the thugs I am talking about are natives; plants we might consider to be quintessentially British.

Blackberrys or brambles (image: Henryk T Kaiser)

Blackberrys or brambles: fruity or thuggish? (image: Henryk T Kaiser)

A new research study published by scientists in the Kew Bulletin fingers three native species of particular concern: brambles, bracken and ivy.

In fact, these three species, according to the study, may do more damage to British woodlands than either rhododendron or sycamore, which are both invasives.

That’s worth repeating: the humble and very British bramble (also known as the blackberry), bracken or ivy harms British woodlands more than rhododendron – a plant that Scottish Natural Heritage has identified as the biggest threat to natural habitats in Scotland.

The idea is not new. David Pearman of the Botanical Society of the British Isles first coined the phrase “thugs” in 2004 to describe these species and their potential impact.

But now Professor Rob Marrs of the University of Liverpool and colleagues have quantified that impact for the first time.

He tells me that they used a base-line study of the plants growing in native British broadleafed woods, effectively a MORI poll of ground vegetation. They then used some complex maths to analyse this data, which allowed the scientists to work out which environmental factors, such as climate, soil, or land management, were important in controlling the composition of these species.

Taking these factors into account, the research showed that, on a nationwide scale, “thugs” such as bramble, bracken and ivy appear to influence what vegetation grows in our woods more than rhododendron or sycamore. They actually cause four times the variation in natural flora compared to the aliens.

The BBC has discussed before how we might need to learn to embrace some weeds. Burdock, for example, can be used with dandelions to make both a traditional drink and cake.

Rhododendrons (image: Paul Hobson / NPL)

Rhododendrons were introduced to Britain in the late 18th century (image: Paul Hobson / NPL)

But the fact that in some places, the worst “weeds” or invaders of all may actually be home grown does offer a fresh perspective on the whole issue of invasive species.

Generally alien species are considered to be a major threat to native wildlife, and a considerable amount of resource is spent trying to eradicate them.

Alien invasives are damaging of course, and we shouldn’t deny the impact they have, or question without serious consideration the efforts to roll them back.

For example, rhododendron grows voraciously, and excretes chemicals that prevent other plants growing in the same soil. The once favourite ornamental is now pushing other species out of woodlands, parks and gardens. And north of the border, it may well have a much more significant impact than brambles or ivy.

But brambles too can be hard to eradicate.

So to borrow the title of Prof Marrs and his colleagues’ study: Aliens or natives: who are the ‘thugs’ in British woods?

According to the scientists, the surprise is that it could be the natives. And we should start paying them more attention, as these plants are potentially more damaging to native woodlands than any alien invader.


  • Comment number 1.

    All of the issues surrounding native plants in Woodlands can be solved by managing the land as per a sensible coppice-rotation.

  • Comment number 2.

    Virtually all the British landscape is man-made anyway. Where do you draw the line? Should we exterminate rabbits and pheasants? Re-introduce wolves?

    Personally I prefer the rhododendron-clad valleys of north-west Scotland to the barren grouse moor, deer "forest" and rough sheep grazing that blight much of the land.

  • Comment number 3.

    Ivy intrigues me, as in days of old when knights were .... OK so about 20 years ago, people out walking would cut Ivy low down, in fact I was brought up to do this ..... until they changed the law prohibiting us mere mortals carrying pen knifes!

  • Comment number 4.

    Consider yourselves blessed not to have poison ivy in this group. It's just awful in the US.
    And thank you for this article.I had no idea rhododendron could be invasive.

  • Comment number 5.

    I'm going to Perry Wood near Faversham tomorrow, a place that boasts about its rhododendrons! Are they right or wrong to do so?

  • Comment number 6.

    We'll take our squirrels and crayfish back if you'll take back your blackberries and ivy but we'll keep the rhodendrons, we rather enjoy them.

  • Comment number 7.

    It's one particular species of Rhododendron, in fact probably one strain of R. ponticum that's causing problems. Don't mislead people into thinking all the hundreds of beautiful Rhododendron species and cultivars are villains.
    And I can see that brambles and bracken can out-compete young trees, but am sceptical about ivy - does no harm to healthy plants, important habitat for insects and birds.

  • Comment number 8.

    In North America, Native Americans burnt the forests for 8000 years .. to keep down undergrowth, to foster hunting visibility, to foster new growth, to drive animals in a hunt, to make the land more friendly for food producing plants, etc. In a book titled America's Ancient Forests, the author shows that Native Americans burnt the continent about every 5 years to make it friendly to human habitation and use. This lasted until the late 1500s, early 1600s, when European diseases decimated the native populations. Transplanted Europeans fell in love with the open forests with huge trees, and we've been trying (and failing) to maintain what Native Americans left us with out using the tools they used for 8000 years. It's almost funny in a very sardonic way.

    Britain and Europe probably developed the same way --- burning as an agricultural and hunting tool. The big difference is the iron age came along a lot earlier in Britain and Europe, and population expanded rapidly at a much earlier time.

    So question: using pond coring techniques to measure frequency of burning, and forest and grassland species composition --- did Britain/Europe use fire as a tool as Native Americans did? I ask, because this controlled burning is what controlled brambles, and ivy from becoming the big nuisances that they often are. The other thing your article doesn't mention is that brambles such as blackberry, are part of the "old field" stage of ecological succession. Brambles (and ivy) don't do well in mature forests nor in maintained fields and pastures.

    So, if you explain more completely, where do these brambles and ivy and bracken show up in the ecological succession of your nation?

    thanks .......

  • Comment number 9.

    Bramble does grow quick and may strangle other plants if left unmanaged - however it also supports a huge variety of invertebrate life, and these are a vital part of the lower food chain to our diversity of native species. I have seen more insects and bugs on a single bramble than I've ever seen on any oak tree. That's not to say I want to see fields of bramble, just that sometimes it's best not to clear everything away so that to human eyes it looks more tidy.

  • Comment number 10.

    Brambles at least provide food and shelter for other species which rhododendron don't. When I was doing some small mammal trapping last year, the only place I caught bank voles were in brambles - conclusion - the brambles provided cover for them against predators. The sycamore issue has long been contended - there is some evidence that it may be a native after all, as at Hardwick Hall in Derbyshire there are some very old sycamore trees and it may be a case that they were less common at one point but a change in the environment meant that they could spread more easily, making it appear that they are a non-native invader.

    Bracken really only takes over if woodland has been cleared and the bracken then allowed to go rampent. Ivy is an indicator species for ancient woodland, so I would think that the biggest threat to woodlands aren't the "invasive" native species they hold but the fact that woodlands have been cut up into fragmented pockets that are isolated from each other, meaning that the natural processes that would allow the ecosystem to be in balance are disrupted.

  • Comment number 11.

    Rhododendrons is a green desert, destroying everything it gets near and giving nothing back until it seeds. It is unbelievable that people still plant it on their own land. The foul stuff should be banned and eradicated before it is too late.
    Unfortunately it seems to be be attractive to people with big gardens.

  • Comment number 12.

    The simple fact is we need to manage our woodland.

  • Comment number 13.

    I'm sorry but I find this article ridiculous.

    I fine example .... "But brambles too can be hard to eradicate."

    As it has been made clear in the article those three species of ‘thugs’ are native plants, none of them need eradication?! I completely understand that sympathetic management is sometimes needed, i.e. managing a heathland it can be necessary to control bracken/bramble/shrubs so natural succession doesn’t eventually turn the area to woodland. This is only needed as the natural balance of habitats changing over decades/centuries has been broken by humans, so certain habitats/species have become rare and need maintaining.

    It has already been pointed out by other comments plants like bramble are very good for invertebrates and a whole range of other creatures (including for example vital varying vegetation structure / edge habitat for basking reptiles), same with bracken. These plants (and the species that rely on them) get enough trouble with people finding it necessary to tidy them out of gardens, parks and even nature reserves without this research bad mouthing them anymore.

    I could understand if this post was on a gardening website, but a bbc nature blog?

  • Comment number 14.

    Whatever happened to survival of the fittest? If certain species are more successful at reproducing, even at the expense of others, then so what? The notion of ecosystems being destroyed is surely a subjective one (and not without a tinge of romanticised nostalgia, I don't doubt). Trying to keep ecosystems in a state of suspended equilibrium goes against Nature (capital intended).

    BTW, I'm not sure I fully agree with this, just throwing this into the mix as a bloody-minded idea.

  • Comment number 15.

    Any plant is capable of becoming dominant where conditions permit. The problem in this case is not the plants mentioned, but the ecological condition of the woodland.
    A healthy and natural woodland ecosystem would have large herbivores to browse/graze young ivy and bramble (and trample bracken). Atmospheric nitrogen deposition and diffuse pollution from inorganic fertilizer and farm slurry also contribute to the problem by enriching woodland soils allowing 'competitior' species such as those mentioned and including other species such as nettles to proliferate at the expense of 'stress-tolerant' species more associated with woodland flora e.g. bluebell and primrose.

  • Comment number 16.

    Ivy is not just a problem in woodland areas. There are many magnificent trees planted in and around towns by the Victorians (particularly Giant Redwoods), and it is very sad to see so many of these blighted by the dreadful stuff. Ivy has its place, and it may be useful to some wildlife, but we humans also have a right to have some of our ornamental trees visible without it smothering them!

  • Comment number 17.

    What should be considered when making statements about so-called Native Thugs of the woodland is that these plants carry out a vital role within the UK ecology.

    They are of major importance as a late summer source of food to lots of UK mammals, and Pollinating insects including the Bee’s, enabling them to make it through the winter.

  • Comment number 18.

    The article and the comments mention ivy as though there is only one type in the UK. Am I the only person reading this article who has more than one species of ivy growing in their garden? [rhetorical].

    There is one specimen with smallish very dark green leaves that has invaded [no other word will do] my back garden and is working it's way to the front via a wall. The other is a variegated cream and green monster, the leaves of which grow larger and larger when left unchecked and if allowed to grow up a tree trunk into the canopy it will eventually strangle the tree. I have a laburnum that is now very weak on one side because of an ivy attack a couple of years ago. The ivy got up into the tree on a side unsighted from the garden, one of the main boughs died off and if the ivy had not been cut down at the root when it was, the whole tree would have died - it may still do that.

    Both of these plants crept into my garden up and over the wall, under fences and underground from neighbouring gardens and common land on one side. So yes, I consider some ivies to be thugs.

  • Comment number 19.

    I simply do not understand! Why is man trying to play God (or for the non-believers, master of nature)? Basically for millions of years, we had ent entire continents of Europe and North America with probably ivy, bramble and other aggressive species. It is not like every other plant species went dead! I think human beings should leave nature alone. I hate this idea of "managed forests", with the justification given that without our (human) intervention these forests would all be overgrown and wild.....Errm....is'nt that the idea of a forest? Leave the forests alone. That is how they are supposed to grow...without our intervention! I mean look at the forests in Africa, Amazon, India and even Japan. Apart from the tribals which live in these forests, humans do not go walking in with tools and equipment saying - Oh, I think this forest needs to be managed by me, otherwise it is going to get destroyed.

  • Comment number 20.

    Man is like to play with god but god will teach a good lesson for those kind of bad guys.




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