Himalayan Balsam - bash or not

[naturallandscapes]

We strim hb before it flowers, this seems to control it very well, done miles of it for the woodland trust and environment agency.

[PeterJL]

Could anyone post a link or reference to peer-reviewed academic research which concludes
that HB is usually threat to native vegetation wherever it occurs?

I understand the impression it gives covering river banks in some places but that really isn't sufficient evidence for giving UK wide eradication advice is it?

[PeterJL]

I think someone needs to talk to them and explain the definition of ecosystems. I certainly won't be joining an organisation that is so ignorant of such issues. Honestly, you couldn't make it up, could you?

I wonder whether it is ever sensible to publish a policy about a plant however invasive you might think it is. We have national policies forbidding the propagation of Cirsium arvsense and other ramapant natives and they make no difference whatsoever.

No organisation like the one you quote would ever have the resources to make an impact and in any case all private landowners would have to co-operate. Unless a policy could lead to desirable action which can be supported by research then it's probably a waste of time - all you get is a paper policy which the plants just refuse to read.

[Paul mabbott]

I think it is, actually. Wherever it establishes, it becomes a monoculture therefore wherever it appears it should be eliminated.

Originally Posted by PeterJL

............
that HB is usually threat to native vegetation wherever it occurs?

I understand the impression it gives covering river banks in some places but that really isn't sufficient evidence for giving UK wide eradication advice is it?

What intrigues me is the sudden recent increase in abundance and distribution. I had not seen it in Sheffield until about three years ago when one or two appeared along the Sheaf, this year it constitutes about 50% of plant cover.
I mentioned the banks of the Irwell in another thread - miles an miles of it interrupted only by the occasional giant hogweed, Japanese Knotweed and bracken - not just around water level but well up the hillside ....

[poschiavanus]

British Wildlife's April 2007 issue (vol. 18, p. 289) refers to 2 peer-reviewed papers on HB.
These are: Hulme & Brenner (2005). J. Appl. Ecol. 43, 143-152 & Hedja & Pysek (2006). Biol. Conservation 132, 143-152.

I have not read either, but I believe that the general argument is that HB is not as evil as often alleged.

In the literature, which I have read, there seem to be 3 apparent threats: 1) Monocultures of HB result in increased erosion of river & stream banks, because bare earth is left during the winter; 2) HB is preferred as a nectar source to native plants by bees, and therefore may compete preferentially for pollinators; 3) elimination of habitats for native plants & animals. (1) is clearly important in other areas of the world where HB is an alien (e..g, British Columbia, Pacific NW of USA), but whether it is significant in the British case I don't know. (2) may be dubious reasoning, after all more food for bees should mean more bees, and therefore more pollinators. (3) as others have said in this thread, the main plants which return after HB has been removed are things like Nettle & Cleavers, which are doing quite nicely thank you. There may be specific cases: I think the shingle habitats of the 5-spot ladybird in Wales may be one such example. So the general threat may be less than would appear.

HB appears to be grazed to a limited extent by slugs and snails, and I certainly notice plenty of froghoppers on young plants. The ecoflora of the British Isles records an aphid and a fly which feed only on HB, but I have not been able to find any more about these.

As for the question, elimination is probably impossible, and the effort required is probably much better directed elsewhere. Control is feasible particularly if it is targeted. It is certainly a good idea to keep it from spreading, but water courses will form a reservoir for its return. I suspect that a significant factor in its spread is mud adhering to animals, people & equiment: so keen balsam-bashers may be exacerbating the problem!

poschiavanus

[svenrufus]

Originally Posted by poschiavanus

In the literature, which I have read, there seem to be 3 apparent threats: 1) Monocultures of HB result in increased erosion of river & stream banks, because bare earth is left during the winter; 2) HB is preferred as a nectar source to native plants by bees, and therefore may compete preferentially for pollinators; 3) elimination of habitats for native plants & animals. (1) is clearly important in other areas of the world where HB is an alien (e..g, British Columbia, Pacific NW of USA), but whether it is significant in the British case I don't know. (2) may be dubious reasoning, after all more food for bees should mean more bees, and therefore more pollinators. (3) as others have said in this thread, the main plants which return after HB has been removed are things like Nettle & Cleavers, which are doing quite nicely thank you. There may be specific cases: I think the shingle habitats of the 5-spot ladybird in Wales may be one such example. So the general threat may be less than would appear.

Always good when someone gives us the references to look in more detail at a subject, thanks for that. HAving said that, I haven't read them either, and no time to do that at the moment, but added to my list of things to do.

I actually just wanted to comment of your comments to the three main strands of objections to HB. On point 1 - If it is acknowledged as a problem in other parts of the world, then there is no reason to assume that it will not be the case here. Although our rivers may well be more managed than is the case for the other countries, we do still have areas where it can have that effect, so the criticism is valid on that point. Point 2 - I would agree with you. But point 3 - the plants that come back after HB has been removed are not the same as those that are lost as it takes hold, therefore the fact that nettles and cleavers are doing well, is not relevant, it is the loss of other bankside vegetation, the sedges, sweet grass, many flowering plants and so on, wiped out by the brutal over-competitiveness of HB that is the problem. So this strand of criticism is valid in general, not jsut in specific cases such as the 5 spot ladybird you mention.

I also agree that eradication may not be possible - I still voted for it as an aspiration, if not as a realistic proposition.

[PeterJL]

To quote one of these refs:

Impatiens glandulifera (Balsaminaceae) is a widespread invasive riparian weed, yet few quantitative assessments of its impact on natural vegetation exist. ..............

The approach adopted in this study highlights that although Impatiens reduces native species diversity in open and frequently disturbed riparian vegetation, many of the species negatively influenced by Impatiens are widespread ruderal species. Furthermore, management may lead to a compensatory increase in the abundance of other non-native species and thus fail to achieve desired conservation goals.

It was AlanS who pointed us towards the idea that perhaps not enough study had been done and this particular peer-reviewed paper seems to say the same thing.

I'm not a fan of Impatiens glandulifera but even less of a fan of knee-jerk conservationists who suggest "magagement" or "eradication" as a result of local observation of the change in habitat but no scientific backing evidence of whether their proposals would make things better or worse.

[poschiavanus]

Originally Posted by svenrufus

...snipped...
But point 3 - the plants that come back after HB has been removed are not the same as those that are lost as it takes hold, therefore the fact that nettles and cleavers are doing well, is not relevant, it is the loss of other bankside vegetation, the sedges, sweet grass, many flowering plants and so on, wiped out by the brutal over-competitiveness of HB that is the problem. So this strand of criticism is valid in general, not jsut in specific cases such as the 5 spot ladybird you mention.
...snipped...

Thanks for these remarks. I had not meant to imply that HB is only a threat in a limited number of cases. The 5-spot ladybird was the only one which came to mind after a busy morning pulling HB!

To try and place this in a broader context: I would say that in some environments HB is a threat to native vegetation, and their dependent fauna, whereas in others it is not. We can take a guess at which habitats might fall into each category, with the ruderal nitrogen-rich communities where nettles & cleavers replace HB being an obvious candidate for the latter category. However, these are still GUESSES. Despite HB having been flagged as a potentially serious threat to native species for at least 20 years, we still don't really know if it is. This is also true in Germany, as well as in the Pacific Northwest.

The German web-page also highlights that the available literature on HB in the Himalayas is confusing & inconsistent. For instance, it is not clear whether it is native in Nepal (the on-line flora of Nepal has the following entry "Himalaya (Kashmir to ?Nepal), naturalised in Europe."). According to this site its native habitats include damp confer forests, clearings, road-side ditches and field edges, but it is rare by mountain streams and not seen by rivers. So its not just invasiveness which is poorly researched.

I better shut-up, as the more I look, the more aware I am that there are many more opinions available on this subject than decent sets of observations.

So one last observation: the Ellenberg numbers for HB (these are indicators of environmental conditions derived from the plants growing in an environment) for HB suggest that it lives in a wider range of conditions than the usual mega-nitrophiles (nettle etc.). The numbers are: Nitrogen - 7; Light - 6; Moisture - 8; pH - 7; Temperature - 7; Continentality - 1 to 3. All on scale of 1 to 9. Nettle is 9 & Cleavers 8 on the nitrogen scale. Using these indicator values may help in identifying locations where balsam-bashing will most beneficial.

poschiavanus

PS. If you want to translate the german text, "jumping herb" = "Springkraut" which should be translated as "Balsam".

[PeterJL]

I better shut-up, as the more I look, the more aware I am that there are many more opinions available on this subject than decent sets of observations.

Agree - when what research there is points in different directions it's a clue that we humans don't yet understand the ecology. I have to say that some conservationists do sometimes remind me of Daleks:

E-x-t-e-r-m-i-n-a-t-e

[Hornbeam]

Not wanting to repeat myself or prolong what is proabably a futile argument, but I am appalled by the expressed views that it is ok to use chemical weedkillers on plants such as HB. Especially when such views are expressed by those flaunting their "Green" credentials.

All that is needed to control HB is to CUT IT. Mow it or strim it before it seeds. Yes, I do know that it is a perennial, but if you cut it before it seeds you will prevent a new generation and will seriously weaken the present one. Cut it again and yet again - after three consecutive cuts you will have prevented the established plants from photo-synthesysing and prevented future seedlings. It's not rocket science and no more expensive than futile bashing and horrendous poisoning of the wetlands. Don't tell me that your brand of poison is relatively harmless and degradeable. All poisons are harmful, not just to the target and other more desirable plants, but to the insects and invertebrates that live in the water and the soil and the food chain.

HB cannot compete with reeds, flags, nettles and similar native "thugs". If you can't recognise HB as a truly magnificent and not very invasive alien that is now an enlivening part of the British flora - cut it down , but don't poison the land that you are supposed to be CONSERVING!