Monday 17 October 2016

Non-native invasive species. Friends or foe?

I've been thinking a great deal over the last few years about 'non-native invasive species' and wondering whether some might actually be more 'friend' than 'foe'.

Species like the Asian hornet are clearly a great threat to diversity because if they establish a foothold in the UK, they have the potential to wreak havoc on our bee population which, as well as being a concern in its own right, will of course have a knock on effect on the plants our native bees currently pollinate and the eco systems these plants support.

But what about other recent arrivals? What about Ivy bees and Tree bumblebees? Unlike the Asian hornet these species are not 'predators' nor have they arrived via human agency. But could they be competing with our existing population of bees (and other insects) for foraging and habitat? Do we know yet if this is the case? Does it matter? If not, why not? Maybe these and other new species arriving from Northern Europe will prove better equipped to deal with an ever changing landscape and climate that our existing bee species might struggle with in the future. 

And then there's Himalayan balsam. This plant is vilified by most, but having established itself is now providing much needed late season nectar and pollen for our native pollinators. Maybe, in time, it will turn out to have other benefits that we don't yet know about? Perhaps it will be better able to cope with climate change, rising temperatures and flooding than some of our native plants? And what would be the consequences to the eco systems it now helps to support if we were to pull it all up and completely eliminate it? I don't know the answers to these questions, but can't help wondering.

Food for thought.... and as an aside, I think we would do well to remember that we, the human race, cause more damage to biodiversity than all the invasive plants put together. When human beings talk about 'invasive species', the expression 'pots and kettles' springs to mind.

Against this backdrop of our (innate?) fear of non native invasive species taking over our countryside, is the current trend for more and more people to keep honeybees in towns and cities. I find myself unable to reconcile the fear of the former with the acceptance and encouragement of the latter.  Do those who set up new hives plant more pollen and nectar rich plants to help sustain their increasing honeybee populations? If not, and if natural resources are limited, do these hives then need to be routinely fed on sugar water over winter? And how do native bumblebees, solitary bees and other pollinators cope when tens of thousands of extra (managed) honeybees are suddenly introduced to an area where the existing floral resources are already depleted?

I ask these last questions (about bees) because where I live in Shaftesbury, North Dorset, I have seen a huge increase in the number of honeybee hive being kept by local beekeepers over the last couple of years. Where these colonies are at their most dense I am now noticing that bumblebees are conspicuous by their absence on sedum and other plants popular with the honeybees, whereas further out of Shaftesbury, in surrounding villages where there are not so many beehives, the sedum, at least, is covered in bumblebees and butterflies in the autumn. 

So many questions, but not many answers.  On balance, I have to say I am no longer sure what to think, per se, about non-native invasive species.... especially when I am noticing, first hand, our native wild bees being outcompeted on some flowering plants by the increase in popularity for keeping honeybees.

If you are interested in exploring these questions further, you might like to read The New Wild by Fred Pearce. A very thought provoking book!

Also, check out this post on Biff Vernon's Blogspot.

With many thanks to twitter friend @dolly_and_dj for allowing me to use her beautiful photograph x

P.S. I should add (in case it appears that I am picking on beekeepers) that my partner and I have a few hives ourselves and are fortunate enough to be able to keep our bees out of town in an area where there are very few other beekeepers.


  1. Thanks for this interesting blog. I dont have any firm information to add but recently when I was watching ivy bees on large stands of ivy I got the distinct impression that if the ivy bees took a liking to one clump of ivy they were able to out compete the other species (hoverfly and wasp) who stayed away. But this didnt matter as there was a lot of ivy about.

    1. Thank you for your observations Philip. It will be interesting to see how it all pans out in the long run....

  2. 'Where do Camels Belong?' is also well worth reading on the subject of so-called 'invasive' species. The damage that these species appear to cause is often really provoked by environmental degradation, climate change and other human caused problems.
    Best wishes