Scrub never sleeps

Natalie Hunt

This was written by one of our alumni, Natalie Hunt, as part of her placement at Ainsdale Sand Dunes National Nature Reserve (NNR) in 2017.

The Sefton Coast Landscape Partnership said in a recent post, ‘Scrub never sleeps’. Never have truer words been spoken! Until I started my volunteer placement, I did not appreciate how much time over the winter months (December to February inclusive) is spent by the reserve staff and the volunteers removing scrub on both the open dune habitat and within the pine plantation coupes.

The reasons behind the scrub clearance relate to Natural England’s responsibilities in managing and protecting the designated features of the Sefton Coast SSSI and SAC which fall within the boundaries of the Ainsdale Sand Dunes NNR. The aim is to maintain these features in ‘favourable condition’. The standards for ‘favourable condition’ are defined by a selected set of expected attributes and indicator species (as part of the Habitat Regulations) and if the SSSI feature meets these criteria, then it is classed as in ‘favourable condition’1.

The SSSI and SAC designated features that fall within the reserve are mobile fore dunes and yellow dunes, embryonic shifting dunes, white dunes, acid, calcareous and calcifugous dune grassland, fixed dunes, dunes slacks, dune heath, salt marsh and mud/sand flats1.

Sand dunes with grass and trees in the background
Fixed dune habitat with willow scrub (source: Natalie Hunt)
Beach sand dunes
Volunteers searching for scrub (source: Natalie Hunt)
Natural England staff working on sand dunes
Sally and Dave from Natural England doing a bit of chain sawing and herbicide application (source: Natalie Hunt)

The Sefton Coast SSSI is made up of 31 units. Within the Ainsdale Sand Dunes NNR, the Ainsdale Foreshore is classed as in ‘favourable condition’, however, the Ainsdale Hills, Ainsdale Open Dunes, Ainsdale Foredunes and Ainsdale Dune Restoration are all considered to be in ‘unfavourable – recovering condition.

Reading the condition assessment comments from the last time each of these areas were assessed, the presence of scrub is cited as one of the main issues, with <5% scrub cover a target for ‘favourable condition’2. The reference to ‘recovering’ does acknowledge however that active management is in place.

The main scrub culprits, are birch Betula spp. and sea buckthorn Hippophae rhamnoides, and to a lesser extent bramble Rubus fruticosus, Japanese rose Rosa rugosa and pine Pinus spp3. The latter is rather ironic, the pines seed freely onto the open dunes but natural regeneration is slow where you want it within the pine plantations! Even more confusing, creeping willow Salix repens is a positive indicator species for the dune slack community, however, a feature can also fail if this species is too dominant and too tall. Creeping willow, as its name suggests, is supposed to be a low-growing shrub, but in this area, it grows to heights far in excess of what is expected and has to be controlled in places as a result4. This might be to do with excess nitrogen in the dune system, some of which, no doubt, comes from sea buckthorn nitrogen-fixing nodules as well as atmospheric deposition5.

So why is the presence of scrub so terrible? It’s negative impact on an open dune habitat is far reaching. As a starter for ten, its rapid, dense growth shades out the underlying ground, reduces the amount of open sand areas, upsets the hydrological regime, increases substrate nutrients, and can stabilise a dune system. These have significant knock-on effects on the survival of specialist, light-demanding dune flora that need open conditions for successful regeneration and on the fauna that relies on the unique habitats a dynamic dune system provides. The dune slacks alone support some 250 vascular plant taxa, including 47 species of conservation importance, 7 that are nationally rare and 5 nationally scarce3.

Scrub reduces water availability in the dune slacks6 which affects the formation of suitable breeding ponds for the natterjack toads and great-created newts, both designated SSSI species1. The reduction of open sandy areas impacts on the favoured habitat of the rare sand lizard Lacerta agilis7 and northern dune tiger beetle Cicindela hybrida8. It also affects the highly-specialised niche requirements of the vulnerable sandhill rustic Luperina nickerlii moth by outcompeting its food source9. Rarely seen without a magnifying glass and a lot of patience is the nationally scarce petalwort Petalophyllum ralfsii (typically 2mm across) which resembles a mini lettuce. This liverwort has made the Ainsdale Sand Dunes NNR its home and relies on light trampling, short damp turf and bare patches3.

The above is just the tip of the iceberg (couldn’t resist the petalwort pun) and the importance of scrub clearance for this nature reserve cannot therefore be overemphasised. Given the size of the site and the small Natural England team tasked with its management, this activity couldn’t be done without the dedication of the volunteers who give up their time on a regular basis to partake in a bit of ‘birch and buckthorn bashing’. The Sefton Coast Landscape Partnership estimates that within the last five years, volunteering activities contributed £49,500 worth of time above the original figure estimated for the scheme10.

During my placement, I have been out several times with a very productive volunteer group who meet twice a month and they are hard to keep up with. In exchange for nothing more than cups of tea, they clear vast areas of scrub at a time, rain or shine, and take great pride in keeping the dunes clear. The task has the added benefit of acting like a ‘green gym’, I ache more than I’ve ever ached before and I think I have muscles on muscles!

The scrub is cut by hand using shears and bow saws and if we get defeated by any of the larger birch trees, the reserve manager brings out the chainsaw.

We pile the brash in a suitable location and burn it on a bonfire. To try and prevent their regrowth, the cut surfaces of the remaining birch stumps are treated with herbicide (the only time this is used on the reserve).

A woodland fire
Brash burning – forgot to bring the marshmallows! (source: Natalie Hunt)
Two woodland tree stumps with herbicide treatment on
Birch stumps treated with herbicide (source: Natalie Hunt)

The creeping willow is too extensive to cut by hand so the reserve managers use a brush cutter where necessary to keep it in check. This technique is also used for bramble encroachment in pine plantation coupes where new tree saplings are trying to establish.

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