Studying natives and invasives

After sounding off about the plant police yesterday, I’m struck by the contrast between this attitude and a note I came across on the website of the Botanical Society of the British Isles (BSBI). Here, they list six non-native plants and remark that they seem to be “turning up more frequently than expected”. But they don’t get in a panic and warn us to rip them out in case they take over.

The BSBI has a scheme in which expert plant recorders, professional and amateur, regularly send in plant records from observations in the wild all over the British Isles. These are plotted on maps which are updated weekly, one map for each plant, native and non-native, and they’re free available online.

This scheme has been running for over 50 years and the database now contains 3.2 million records! In conjunction with earlier less comprehensive recording going back centuries, it provides an impressively accurate picture of the way in which plants increase their range and decline. That staggeringly impressive book, The New Atlas of the British and Irish Flora, was based on these records. You can access distribution maps for individual plants at the BSBI Maps Scheme website.

Even though it is now very easy to see which non-native species are increasing dramatically (not many) and which are not, in the UK too there is a certain amount of hysteria., This has been effectively skewered by David Pearman, past President of the BSBI and the moving force behind the Atlas, in a recent piece in The Plantsman entitled Don’t Blame the Aliens (which you can download here).

So what are these half dozen plants to which the BSBI directs our interest, our scientific curiosity, but not our fear?

They are: Cardamine corymbosa, Conyza bilbaoana, Euphorbia maculata, Gazania rigens, Senecio inaequidens and Yucca recurvifolia. Most, frankly, I’d never heard of. Only two of these are grown in gardens, and almost all the gazanias grown are complex hybrids rather than the wild G. rigens.

Which leaves Yucca recurvifolia, the Curved-leaved Spanish-dagger, an RHS Award of Garden Merit plant, no less and native to Alabama, Florida, Georgia, Louisiana and Mississippi. In Britain, it was first spotted in the wild in two locations between 1970 and 1986, then in twelve more from 1987 and 1999, and in twenty four since then. You can see the distribution map here. And there’s a picture of the flowers, and thoughts on eating it (that’s one way to stop it spreading) here. Interestingly, its flowers are pollinated by a moth not found in Britain.

So, what all this boils down to, I think, is that when it comes to invasives we need more research and less hysteria. And with climate change already influencing the distribution of native species on both sides of the Atlantic, and everywhere else– they may no longer be able to grow in some areas and move into others – we need an altogether less parochial, more international view of the whole issue.

Comments

[william]

Fascinating problem invasives.Once a plant is in the country, it has the potential to become an invasive. What makes a plant a potential invasive? When Japanese Knotweed was introduced, would anyone have imagined the reputation it has today - is it that bad? It is a good source of nectar for honey bees and there are drifts of Snowdrops growing amongst the old canes on the gravel at the bottom of our river here near Criccieth. There was an interesting experiment done on Snowdon in Cwm Glas Mawr where a number of 'alien' artic alpines were planted to 'beautify' the place - some are still there - the original plants and are certainly not invasive. An interesting one introduced by Alpine Garden enthusiasts in the '1900's is the diminutive creeping Epilobium brunnescens - I suspect that if you looked at its distribution today, it is far worse than Japanese Knotweed. However it does not occupy habitats where it becomes a threat to us! Most people do not notice it. I could go on and on.

[max]

... except, of course, for hybrid Narcissus.

Just kidding. I suspect, though, that the issues are quite different in Britain, which has been intensively inhabited for thousands of years, than, say, in California, where we do have serious problems with invasives, all introduce in the last 150.

[Graham Rice]

That's fascinating, William. And on the BSBI Atlas website you can compare the distribution of Epilobium brunnescens (here: http://tinyurl.com/yuwhjh), which includes most of Scotland, Wales, N. Ireland and northern England and Fallopia japonica (here: http://tinyurl.com/2b86pw) which grows just about everywhere except the Highland of Scotland.

The thing about Japanese knotweed is that becasue it's such an enormous plant it's so noticeable, and because it's distributed largely by root fragments, it tends to grow along roadsides, streams etc where it will be seen.

[Graham Rice]

Yes, Max, the situations are different. Although in Britain people have been bringing plants in from Europe for more than 500 years and many have settled down to become integrated into the natural flora without causing trouble.

And I'm not saying there are no serious problems with invasives; there are. I'd just like to see more studies on the spread of introduced plants over time based on recording in the field. If anyone can point me to such research, please do.

For example, I suspect that people get worked up over the spread of dandelions in the US because they're so often seen along roadsides where they can be spotted from passing cars. And it's the air turbulence caused by the passing cars which helps spread the wind-blown seeds.

[susan harris]

Excellent points. Less hysteria - please.