Boscombe Cliff and Overcliff

BOSCOMBE CLIFF AND OVERCLIFF

OUTLINE MANAGEMENT PLAN

March 2004

INTRODUCTION

Bournemouth’s sea cliffs extend for approximately 8km from the Borough of Poole boundary east to the Point House café in Southbourne. Including the overcliff, they cover an area of approximately 45 hectares.

Generally the cliffs and overcliff are known to support a diverse and interesting flora and fauna with a number of rare species present.

In recognition of this fact and because of the presence of some important geological exposures, areas of the cliffs are designated as Sites of Special Scientific Interest (SSSI).

The majority of the area outside of the SSSIs is designated as a Site of Nature Conservation Interest.

A vegetation survey of the cliffs was carried out in 1993 by the Dorset Ecological Consultancy (Walls 1993) and a sand lizard Lacerta agilis survey of the cliffs between the piers was undertaken in 1994 by the Herpetological Conservation Trust (Corbett 1994). Otherwise there has been little formal ecological monitoring on this valuable resource.

It is widely recognised that some major active habitat management is required to maintain the ecological interest of the cliffs and overcliff.

This is particularly the case in respect of the increasing prevalence of invasive, non-native plant species such as hottentot fig Carpobrotus edulis.

A small area of cliff to the west of Boscombe Pier is currently managed by the Herpetological Conservation Trust as a Nature Reserve.

Following discussion with various groups and individuals and because of the varied ecological interest of the cliff and overcliff in the vicinity of Portman Ravine, it has been resolved that a management plan be produced for this site. The site location is shown on Map 1.

SUMMARY

This outline management plan sets out to describe and evaluate the area and to prescribe a workable management programme.

While it is taken into account that the area has a high amenity and recreational value, the plan is geared towards conservation management.

The plan is divided into three stages:

Description – a brief description of the site providing a general background on which to base a management policy.

Ecological evaluation and objectives – a summary evaluation from an ecological perspective and an account of the principle management objectives.

Prescription – describes the actual managements of the site and how these will be put into practice.

1DESCRIPTION

1.1General information

Portman Ravine is situated approximately 1.3km east of Boscombe pier midway between Shelley Park and Fishermans Walk.

The area covered by the management plan comprises both cliff face and overcliff as shown on Map 2 and is approximately 5.7ha in extent.

It is owned by the Leisure and Tourism Directorate with the overcliff the responsibility of Leisure Services and the cliff the responsibility of Seafront Services.

1.2Environmental information

1.2.1Physical

The cliffs are composed of soft Tertiary sands and clays of the Bracklesham and Bagshot series. In places such as the overcliff there is a thin topping of plateau gravels and wind-blown sand.

1.2.2Biological

1.2.2.1Habitat types and associated species (see map 3)

Scrub

The predominant scrub species is common gorse Ulex europaeus, but there ae also significant areas of bramble Rubus fruticosus and holm oak Quercus ilex. A number of garden shrub species are well established including Hebe, Griselinea, Escallonia and Duke of Argyll’s tea tree.

Ruderal and short grass

The light, sandy, free-draining soils support an interesting community of annuals and drought-resistant plants. Characteristic plants include squirrel-tail fescue Vulpia bromoides, early hair-grass Aira praecox and stag’s-horn plantain Plantago coronopus.

A range of nationally rare and scarce species is present including hairy bird’s-foot-trefoil Lotus subbiflorus, mossy stonecrop Crassula tillea and some of the scarce clovers Trifolium spp.

Again a number of garden plant species are established such as stonecrops Sedum spp, AlyssumAlyssum saxatile and candytuft Iberis sempervirons.

Dune grasses

On both the cliff and the Overcliff are areas dominated by marram Ammophila arenia and lyme grass Leymus arenarius. These are typical early colonists of loose sand and play an important role in stabilisation, paving the way for colonisation by other species.

Wet flush/seepage

There is a seepage line to the east of the Portman Ravine zigzag created by an impervious layer in the strata. Here water reaches the surface and an interesting plant community has developed. Of particular interest is the royal fern Osmunda regalis a plant made scarce by over-collecting in Victorian times.

Bare ground

The more vertical sand cliffs tend not to be vegetated and are a valuable habitat in their own right, particularly for a range of burrowing insects and nesting sand martins. Other less steep areas of open sand provide suitable habitat for a variety of invertebrates and are particularly important as egg laying sites for sand lizard Lacerta agilis, green lizard L. viridis and wall lizard Podarcis muralis.

The stone walls of the zigzag path are utilised by wall lizards. They live in the crevices between the stones and can often be seen basking on the walls themselves.

1.2.3Present management

Management of the cliff face has been minimal and certainly no specific habitat management work has occurred in this area.

The overcliff has been quite intensively managed for amenity purposes with most of the grassland regularly mown.

Several tarmac footpaths traverse the site and these are kept clear of encroaching vegetation.

Benches are situated throughout as are waste bins.

2Ecological evaluation and objectives

2.1Evaluation

A range of habitat types are represented that support a diverse flora and fauna. In recognition of this, the overcliff and a large part of the cliff are designated as a Site of Nature Conservation Interest (SNCI). See Map 4.

A number of rare species (both plant and animal) occur and the site is particularly interesting because of its reptilian fauna.

Common lizards Lacerta vivipara are numerous and there are populations of both wall lizard and green lizard. The latter 2 species are not native to mainland Britain and have evidently been introduced to this site although it is not clear when the introduction occurred or whether it was deliberate or accidental. Both species are thriving here and there is evidence of successful breeding. Although they are not expected to have any negative impacts on native wildlife, the populations will need to be carefully monitored, especially in respect of sand lizard status.

There have been recent sightings of sand lizard and appropriate habitat management would provide suitable conditions for this rare animal.

To date there has been no formal surveying of other animal groups but general observation has revealed a diverse fauna.

Several species of bird breed in the area including meadow pipit Anthus pratensis, stonechat Saxicola torquata and Dartford warbler Sylvia undata. A small colony of sand martin Riparia riparia nest in a sand cliff to the east of Portman Ravine.

Butterflies are a feature of the area with species recorded including Essex skipper Thymelicus lineola, common blue Polymmatus icarus, marbled white Melanargia galathea and clouded yellow Colias croceus. Portman Ravine was in fact the first UK location where clouded yellow were observed to breed and to survive the winter in 1998/99. Eggs, larvae and an emerging adult were also observed in December 2002/January 2003.

Surveys would undoubtedly reveal a diverse invertebrate fauna but casual observation has already revealed some less common, localised species such as long-winged conehead Conocephalus discolour, grey bush-cricket Platycleis albopunctata and the bee killer wasp or bee wolf Philanthus triangulum. The possible presence of the rare cliff tiger beetle Cicendela germanica requires confirmation.

The predominantly acid free-draining soils coupled with harsh and variable climatic conditions and other environmental factors such as salt spray and unstable slopes have resulted in the development of specialist plant assemblages. These include some nationally rare plants as described previously. Unfortunately, these natural plant communities are being damaged and, in some areas, displaced by introduced plant species.

2.1.1Alien plant species

A whole range of non-native plant species thrive on the cliffs and many coexist with the native flora with no particular detrimental impact. However, there are others that are thriving at the expense of the native wildlife. Hottentot fig Carpobrotus edulis is becoming a dominant feature over large areas where it is completely overwhelming all other vegetation and is even encroaching over sand cliffs.

Several non-native tree and shrub species have become well established such as holm oak and garden privet Ligustrum ovalifolium. These tend to form dense stands under which nothing is able to grow.

2.1.2Native shrub species

The presence of native shrubs such as gorse is problematic in some areas, especially close to paths, because of the inherent fire risk. In addition, the dominance of gorse can be at the expense of other native plants.

2.2Objectives

1. To initiate surveys and monitoring programmes in respect of plant and animal communities.

2. To reverse the current trend of native habitat loss to invasive alien species and to re-establish natural vegetation. This will involve the eradication of hottentot fig and the removal of a significant amount of non-native shrub and tree species.

3. To encourage the development of larger areas of marram/lyme grass on the overcliff by reducing the area currently mown.

4. To initiate a gorse management programme with an initial reduction in the area and subsequently a system of rotational coppicing.

5. To ensure the zigzag path walls continue to provide suitable habitat for the wall lizard colony. This will be achieved by not replacing any missing pointing unless absolutely necessary in localised areas for health and safety purposes.

6. To educate site users about the ecological importance of the site through appropriate signage.

7. To encourage dog owners to dispose of their dogs’ waste in the bins provided.

3Prescription

3.1Working compartments

To facilitate reference and description, the area has been divided into 6 working compartments as shown on Map 5. On the overcliff, paths have generally been used to demarcate the compartment boundaries. However, the eastern and western extremes of the cliff compartment are more arbitrary and can essentially be taken to follow a line from the overcliff extremities.

For each compartment a brief description is given and the required management is then discussed. This is shown in map form with Map 6 showing the desired state of the site and Map 7 giving a summary of the management required to achieve this state.

3.1.1Compartment 1

Description

This is the area between the cliff top fence and the main central footpath to the west of Portman Ravine zigzag. It largely comprises open grassland that is mown and tends to be heavily trampled. There are some areas of gorse especially towards the eastern edge of the compartment along with further small blocks of oak and privet scrub. Towards the western edge of the compartment, the central path is bordered by marram and lyme grass.

There are 4 commemorative benches within the compartment.

Most of the scrub areas are used by common and green lizards as is the dense marram and lyme grass on the path edge. This was also the location of the most recent sand lizard sightings.

In places the grass is very worn and sparse creating the ideal habitat for burrowing wasps and solitary bees. Of particular note is a colony of bee wolf.

Management

It is proposed to cease any mowing operations with a view to encouraging the spread of marram and lyme grass and other associated grass and herb species.

This will provide additional habitat for reptiles such as sand lizard as well as for a range of invertebrate species. It is important though that some short sward areas are retained as these support rare annuals and burrowing bees and wasps as previously described. Almost undoubtedly such habitat will be maintained by trampling and it may be necessary to use temporary fencing to allow the development of areas of taller vegetation.

Where gorse abuts the main path, it will be cut back approximately 2m from the path edge to reduce the fire risk.

If possible it would be beneficial to move benches presently located towards the centre of the compartment to the periphery.

3.1.2Compartment 2

Description

This is a small area towards the centre of the site surrounded by tarmac paths. The majority of the area comprises sparse, low growing gorse interspersed with short grass and bare earth. The western edge is dominated by a stand of dense mature gorse and the southern edge is fringed by marram and lyme grass.

Common, wall and green lizard occur here and grey bush-cricket was recorded in 2003.

Management

The mature gorse block will be removed to encourage the spread of tall grass and herb species.

Where other gorse is growing to the path edge it will be cleared to a width of approximately 2m.

It may be necessary to periodically cut back other gorse to retain areas of bare earth and short grass.

3.1.3Compartment 3

Description

This is the area between the clifftop fence and the main central footpath running eastwards from comp. 2. Its eastern boundary is an arbitrary line running to the cliff top fence from the junction of the main footpath and the linking path to the main road immediately east of Dingle Road.

The whole area is open grassland, the majority of which is a short-mown sward. However, an area adjacent to the clifftop fence has been left unmown allowing the development of a marram/lyme grass dominated sward. This provides a link with the marram-dominated cliff face at this point and is ideal habitat for sand and green lizard and for a variety of invertebrate species, in particular orthopterans.

There are 2 commemorative benches, one of which is situated in the centre of the compartment.

Management

Mowing of the grass will cease to encourage the spread of the well established dune grasses. There may be a requirement for some temporary fencing to prevent trampling during the initial stages of establishment.

Ideally, the bench in the centre should be moved the periphery.

3.1.4Compartment 4

Description

This is essentially the whole cliff area including the Portman Ravine zigzag between the cliff top fence and the beach promenade wall. The eastern and western boundaries are not readily definable but approximate to those of the overcliff.

The cliff has a complex and dynamic assemblage of habitats that are difficult to relate to recognised plant communities except over small, isolated areas. This is largely due to the presence of a range of non-native species of herbs, shrubs and trees.

There are considerable areas of bare ground especially on the steeper slopes which in some cases are practically vertical. One of these vertical cliffs is a nesting site for sand martin.

Dartford warbler successfully bred here in 2003.

In parts the bare ground grades into sparse vegetation cover with discrete areas of taller marram and scattered gorse, but generally scrub is tending to dominate at the expense of this desired habitat structure. The scrub is dominated by common gorse but there are substantial stands of non-native species such as garden privet, Griselinea and holm oak.

To the east of the zigzag is an area of wet flush dominated by common reed with several plants of royal fern.

Throughout, there are substantial areas of hottentot fig that are rapidly spreading to the detriment of any native vegetation and even bare ground.

The zigzag path is flanked on either side by stone/concrete block walls. The southerly facing walls provide ideal habitat for a thriving population of wall lizard especially where sections of pointing are missing providing crevices between the stones.

Management

The 2 main priorities are:

1. To eradicate the hottentot fig and the non-native shrubs.

2. To reduce the area of gorse by approximately 50%.

The hottentot fig can be treated with a glyphosate-based herbicide and removed from site when completely dead. This process will create large areas of bare ground that will eventually recolonise naturally. However, the option of seeding with appropriate species could be investigated if thought necessary.

There will be a phased removal of the scrub, concentrating initially on the non-native species.

The desired state is an area dominated by marram grass and associated herb species contiguous with a similar habitat on the seaward edge of the overcliff. There should be areas of bare ground and short vegetation and scattered gorse scrub. It would be expected that ericaceous species would also become established to a limited extent.