Who are the 'thugs' in British woods?
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.
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.
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.