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GCNs and bark mulch

Printed From: Reptiles and Amphibians of the UK
Category: Herpetofauna Native to the UK
Forum Name: Great Crested Newt
Forum Description: Forum for all issues concerning Triturus cristatus
Printed Date: 15 Aug 2020 at 5:04pm
Software Version: Web Wiz Forums 11.06 -

Topic: GCNs and bark mulch
Posted By: Matt Harris
Subject: GCNs and bark mulch
Date Posted: 25 Jul 2012 at 2:30pm
Has anyone ever heard of GCNs being affected either physically or behaviourally by commercial bark mulches?

We have a developer who want to use bark mulch under shrub (Hawthorn/hazel/holly etc) planting in GCN terrestrial habitat, but I am concerned that conifer-based bark mulch (they usually stink heavily of pine oil etc) might deter or even damage the newts.

There seems to be little alternative for landscaping, apart perhaps from wood chippings, than bark mulches which seem invariably to be derived from spruce, pine, cedar, hemlock etc.

Local Authority Ecologist

Posted By: GemmaJF
Date Posted: 26 Jul 2012 at 11:45am
In a sort of reverse answer Matt I came across a consultant who was advocating using bark mulches as they were "beneficial" to newts. 

Having never observed a newt anywhere near the stuff and having similar reservations as yourself I challenged the view. The distinction being where the mulches are derived from, if it was non-coniferous bark chippings I think they could be of benefit but as you say most commercially produced materials are pretty unpleasant and are intended to suppress vegetation growth and are used to reduce maintenance.

I can't help thinking that such materials will not be in the least bit attractive to newts and could easily be detrimental to them. I would be sure not suppressing the vegetation under the shrubs and letting nature be nature would be a far better solution for the newts, if not human aesthetics.

Posted By: Noodles
Date Posted: 26 Jul 2012 at 12:36pm
The use of bark mulch as amphibian refuge is as old as the hills (well, newt mitigation anyway). It immediately simulates a loose, moist woodland floor type substrate with plenty of inverts. Ideal for 'burrowing' etc. As for its resin content i would argue that newts commonly use coniferous woodland and must subsequently crawl over and through dense mats of resinous pine needles. Moreover, i reckon that any resin content would soon deteriorate in an exposed location. Not fact of course! 

Posted By: GemmaJF
Date Posted: 27 Jul 2012 at 9:34am
Strange then after clearing dozens of sites over the years I've never recorded any of the native newt species in the stuff. Despite them being present in leaf litter immediately adjacent to piles of well aged coniferous mulch.

Just because it is recommended doesn't mean it is of any use. I would also assume those that recommended bark mulch expected people to use less toxic alternatives than commercially produced coniferous mulches. One might even assume that one would use a chipper and produce a suitable mulch from easily available materials already present on the site rather than buying in a toxic non-composting soil dressing.

But that is always the case, things go in guidelines and are then interpreted by those with practically no field experience and mistakes are made.

Other examples:

Log piles 3 inches high

Artificial hibernacula the size a suitcase

Shall I go on? Wink

If you are still not sure, try dropping a newt in a jar or turpentine and see if it is good for it. Confused

Posted By: Noodles
Date Posted: 27 Jul 2012 at 9:49am
Its good that you have comparative data from mulch piles adjacent to woodland leaf litter. How very convenient LOL

 P.S. I think its use is recommended in one of or both the GCN Conservation Handbook and GCN Guidelines. Obviously one would not use a variety with chemicals in but the fact that coniferous mulch is distressing to newts is pure conjecture. Do you have any variables on your observations. I suspect not.

Posted By: Suzy
Date Posted: 27 Jul 2012 at 9:50am
There are so many ground cover plants that would do the same weed-supressing job and be possibly more wildlife friendly.


Posted By: Noodles
Date Posted: 27 Jul 2012 at 9:55am
Good point Suzy. If in doubt leave it out.

Posted By: Noodles
Date Posted: 27 Jul 2012 at 2:10pm
From The GCN Conservation Handbook. Note the use of the word deciduous! Sourcing this appropriate material would appear to be the solution to your client's problem Matt.

Providing a deep litter layer (100mm or preferably more) of
deciduous or mainly deciduous bark mulch artificially creates a
litter layer. Composted bark mulch is even better as it
compacts well and holds moisture more effectively. Used in
association with new tree plantations it can be immediately
successful in providing habitat for newts. Mulch also reduces
growth of ground flora that competes with newly planted tree
stock. As plantations grow and are thinned, the cut poles and
branches can be left on the surface between trees as further
dead wood. By 10-15 years the plantation should provide good
quality newt habitat, as an understorey of bramble, ivy or other
plant cover develops.

Posted By: GemmaJF
Date Posted: 27 Jul 2012 at 5:40pm
I totally agree Noodles with that one word being the key here. 

You will note that the guidelines recommend deciduous bark. Stating composted bark is better.

Coniferous bark practically does not compost at all and is full of naturally produced toxic chemicals. Unfortunately what seems to happen is people read the guidellines, remember that mulching is recommended but then recommend the use of commercially produced coniferous mulch which is really not suitable. 

And it was indeed convenient to be able to compare naturally produced deciduous leaf litter to swathes of coniferous based mulch placed under ornamental plantings at a couple of sites. Not exactly a rare opportunity for those of us involved in large scale mitigations though. Along with the general 'chemical saturated' properties, it was also surprisingly dry under the surface. In fact nothing at all, including common invert species  was making any use of it as far as we could see.

When it says mulching in the guidelines it does not indicate buying commercially produced coniferous mulch at all, despite this being favoured by some landscapers and consultants. They are simply missing the rather important detail of the materials that the mulch should be formed from.

But I think I said that already in my first post........ 

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