Restoring a mixed grassland habitat for the Common Blue butterfly (Polyommatus icarus) on the slumps at Castle Hill LNR in Newhaven
In February, the sun-splashed, salt-stunted
grassy slumps beneath the cliffs at Barrow Head are largely absent of human activity.
The occupation by hordes of barbecue-brandishing sun worshippers and their competing
beat boxes are still five and a half months away; for now only the occasional
dog walker ventures off the ribbon of vegetative shingle onto the slumps. The
rabbits and voles need concern themselves only with the fox and the kestrel
amongst their daily anxieties.
The Barrow Head rabbits are a depleted race;
once numerous enough, perhaps, for the headland name to have been
re-Christened in their name as their burrows became the noticeable
feature following the geological demise of the barrowland. The rabbits
have melted away themselves over the decades and
their nibbled turf has become neglected so that the few remaining burrowers cannot
compete with the advance of successional vegetation: the slithering bramble and brittle-boned elder
which have slowly and ominously emerged the victors in a turf war across the
slumps. The salt-laden Channel winds do their best to slow the advance, but these are winds which lack the fury of an Atlantic or North Sea
gale. Channel winds are soft in a way which the Welsh writer Edward Thomas understood in his 1909 book The South Country:
South is tender and will harbour anyone; her quiet people resent
intrusion quietly, so that many do not notice the resentment. These are
the "home" counties. A man can hide away in them. The people are not
hospitable, but the land is.
Common Blue (Polyommatus icarus)
The slumps are a habitat in
flow, particularly so in February. The chalk cliffs of Barrow Head are topped
with layers of change: London and Woolwich clays, sands, raised beach, lignite
and a rendzina crowned with short-cropped fescue and thrift. These flow, perhaps in
emulation of the Ouse river a stone's throw to the east, from
the clifftop downwards in a glacial dance onto and into the slumps, plump with
the weight of the winter's rain. Castle
Hill's barrows, after which the small headland is named, have long
since melted away into the slumps below, noticed or not by the eyes of
man. But the flow is not always glacial in character, a
smooth progression of melting clay or fossilised oyster bed dancing across deep time;
it is seasonal, sudden and catastrophic and some February inspections reveal the
gashes and scars of a sudden night time slip or collapse of sandstone.
Wild thyme and trefoil
The sandy, ligneous soil forming the slumps is
well drained and offers a suitable habitat for Sedum: biting and white stone-crops which flower sulphur and white in the summer. This two-tone
tableau carpets the exposed soils, filling the gashes and scars of winters past. Amongst these one can find
burrowing invertebrates such as solitary bees and wasps, beetles and hunting
spiders. Their exposed habitat relies on change. If the flow from above was to
cease, the barren ribbon of soils would engage in a succession of the grasses
and sedges which can be found a little lower down the slumps and, as their
roots take hold of the soils, rhizomes of bramble would sneak in and begin to suffocate the lower plants and their denizens. The burrowing
insects would be replaced by cone-heads and Roesel's bush-crickets, which
already chirrup and drone further down the hill, but the loss of the
marginal habitat and its tenants would be very difficult or impossible to
replace once it is gone and the character of the place would become more
uniform, less diverse.
It is a mistake to look upon the Barrow Head
slump and see only a wasteland of slipped ground, useful only as a site for
disposable barbecues, a resting place of windblown litter or to utilise as an outdoor latrine. There are contoursof life
here: narrow bands of neighbouring communities which exploit ribbon-like bio-halines.
These specialist niche-dwellers of the slumps collectively amount to the richest biological
community anywhere within the Castle Hill Local Nature Reserve. The resident
stonechat pair seem to know this. These ribbons require a well-considered eye
and hand to ensure they are performing well. The suffocating tangle of bramble
must be held in check and this is the reason why our work-party is visiting today.
We arrive with our tools, down them and stand in
a cluster to ponder the landscape. The slumps' grassland areas have been choked
by encroaching bramble during recent years and it came to our notice the
previous year when numbers of butterflies experienced a significant decline.
The grassy undulations, now smoothed by crowns of bramble, were in previous
years host to a colony of common blue butterflies, which laid their eggs on
bird's-foot trefoil. Mixed clovers fed the Mother Shipton and Burnet Companion
day-flying moths; countless noctuid moth species nibbled away at grass roots
and, as adults, they shared the shelter of the grass tussocks with foreign
visitors such as Silver Y and Rush Veneer. The loss of grass and flowers means
also the loss of the invertebrates which rely upon them. The birds which are
fed by their lower trophic levels shelter in the bramble perhaps less certain
of their next meal.
Our group of friends have pondered how to tackle
the thicket. We debate the need for sheep - their grazing power would do the trick! To fence the sheep in would be a simple and satisfying task, but fencing out humans and their dogs is considered by all to be an impossible goal. Everything growing before us has endured despite the behaviour and activity of many people and their pets and any livestock, howeverlookered, would be placed in a precarious situation, however optimistic or diligent we may be.
Sedum, sulphur and white growing above the Barrow Head slump
We agree to leave in place a protective skirt of bramble a few
metres thick along the cliff bottom and to remove anything below it. There are
some considerations and negotiations to be made: what will happen to the
cherished colonies of Roesel's bush-cricket and long-winged cone-head, which we
recorded around the thicket the previous summer? We agree that the next
generation of these species will emerge from their protective grasses as nymphs
and, if desired, shall migrate slightly uphill to the remnant bramble. Where
shall we have a fire? Must we scorch and lose another patch of grassland? After
much debate and concern about the practicalities of carrying a prickly
cumbersome mass of bramble down to a remote fire site and the prospect of
sacrificing a remaining patch of grass to a fire, we agree to cut a patch of
bramble and build the fire on the exposed ground. How should we actually cut
the bramble? It appears to be more involved than lopping and sawing through the
scrub of gorse, blackthorn, hawthorn and sycamore on the northern slope of the reserve.
We decide to learn through doing and get to work.
We agree to leave in place a protective skirt of bramble
Burning the tangled, rolled fleeces is a pleasurable affair
It quickly becomes apparent that cutting bramble
is hard work. One has to adopt a crouching posture, so as to work at the level
of the lower stems, but also to ensure a reasonable working distance from the
thorns. Legs and arms are not as protected as hands and, soon after cutting
commences, as body temperature rises and layers are cast off, they are protected less still. A few explorative
snips with a lopper persuade me that progress can only be made with a less
discriminatory set of shears: several cable-thick stems may be cut at
once instead of a single stem at a time. I swap tools and progress through the
stems. We learn that the best method for removal is to imagine we are shearing
a sheep and begin working with a partner, cutting and rolling, cutting and rolling, one shearing through the spinous
fleece, bristling with thorns, the other rolling the cut fleece over,
pulling it back to enable the next cut.
The hard work takes its toll and my forearms tire
too quickly. The slashes of my shears slow, soften and cease. The lactic acid
burn would penetrate so deeply into seldom-used muscles that I would not enjoy
full use of my aching arms for six full days. When I stop and sit by a cleared
patch I notice for the first time just how much new habitat we have created. If
the potential for blue butterflies could be measured in satisfaction, we had
enjoyed a very satisfying morning of hard work. The resident stonechats,
perched almost within an aching arm's reach behind me, clack in appreciation.
Burning the tangled, rolled fleeces is a pleasurable
affair. The flames take hold of the brambles with enthusiasm. I stand a
distance from the heat and imagine that the potential for harm held within
each thorn can be measured as a unit of energy. As the flames sweep through
the newlyadded bundles, the crackles and pulses of flame mark the demise of
one thorn after another. No longer shall they catch hold of my boot or pierce
my skin; no longer shall their stems and leaves shade the trefoils and their
butterflies from the sun.
enjoyed a very satisfying morning of hard work.