Coastal Habitats

Durham Lowland Priority Habitats
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Coastal Habitats Action Plan

Priority Habitats: Maritime grasslandCoastal soft cliffs and slopes, Strandline

Priorities
1. Raise awareness of the biodiversity importance of coastal habitats including soft rock cliffs, their cliff-top habitat and the strandline.
2. Increase knowledge of the invertebrate communities of soft rock cliffs.
3. Improve the quality of maritime grasslands and cliff top habitats through appropriate management regimes.
4. Protect coastal habitats from inappropriate development.
5. Restore maritime grasslands, utilising natural regeneration or planting with native species of the appropriate provenance

Coastal Soft Cliffs and Slopes Targets
Vision Statement: To have a better understanding of invertebrate distribution on soft cliffs & slopes, and for key sites to be safegaurded through semi-natural buffers and connecting coastal strips.

Target Type Unit Value
1. To maintain the current extent of maritime cliff and slope vegetation in the Durham BAP area. maintain ha tbc
2. To expand the extent of cliff-top semi-natural habitats in the Durham BAP area. expand ha  tbc

Strandline Targets
Vision Statement: For strandline to be left undisturbed along the entire coastline, except for hand clearance of man-made litter.

Target Type Unit Value
1. To maintain the overall length of intact/undisturbed strandline along the coast of the Durham BAP area. maintain linear metres tbc

 

Strandline

The Strandline is the line of seaweeds and other debris left stranded on the beach at high water mark. The strandline moves up and down the beach in a fortnightly cycle.

Strandlines provide sheltered, moist conditions for invertebrates from both terrestrial and marine ecosystems. Rotting seaweed provides food for a great variety of animals including sandhoppers, kelp flies, beetles, small crabs and sea-slaters. There are a number of beetles which feed only on sea-soaked wood.

The presence of all these invertebrates provides an important food source for coastal birds (see Coastal Birds Action Plan). Strandline also has a role in supporting specialist and pioneer plant communities and in helping stabilise the foreshore in exposed locations, sometimes leading to sand dune formation.

Coastal soft cliffs and slopes

Maritime soft rock cliffs and slopes are a habitat that, in the past, has been largely neglected. They are widely recognised for their geomorphological interest, but less well known for supporting rich invertebrate assemblages and as a refuge for rare insect species.

In the UK twenty-eight species of insect are only found in this habitat, 22 of which are red data book species. Alongside these restricted species there are at least another 75 species that have an affinity to the habitat.

Key reasons for the importance of this habitat to invertebrates include the historical continuity of bare ground (for hunting and basking), the maintenance of early successional pioneer plant communities, especially as nectar sources for solitary bees and wasps, and local hydrological features such as freshwater seepages.

Soft rock cliffs are also important as refuges for invertebrates, as much of the semi-natural cliff top habitat behind these cliffs and slopes has disappeared in the past to arable farming or building development. At the same time, the loss of this cliff top habitat has reduced foraging areas for insects inhabiting the soft cliffs on slopes below.

Maritime Grassland

The cliff top vegetation in Durham is influenced by its magnesian limestone geology and the maritime influence of sea spray, which extends approximately 500m inland. Where it still exists this fragmented habitat consists of varied communities of calcicolous and mesotrophic species, alongside salt tolerant species such as sea plantain (Plantago maritima) and thrift (Armeria maritima). On the Durham coast the vegetation is also unusual in that species with a northerly distribution such as birds-eye primrose (Primula farinosa) and melancholy thistle (Cirsium heterophyllum), overlap with those of a southerly distribution such as yellow-wort (Blackstonia perfoliata) and pyramidal orchid (Anacamptis pyramidalis).

Threats

  • Inappropriate management of the cliff top habitat:
    •  Loss of semi-natural vegetation adjacent to soft cliffs reduces foraging areas for soft cliff inhabitants, and reduces seed availability for the recolonisation of bare ground.
    • Artificial drainage of land above cliffs disrupts the hydrological regime which provides important freshwater features for some invertebrates.
    • Agricultural or amenity practices such as ploughing, reseeding, fertilising, close-mowing, all damage or destroy species rich grassland communities.
  • Coastal defences – Any coastal defence work which defends soft cliffs against erosion will affect the maintenance of bare ground exposures and early successional communities.
  • Coastal squeeze from built development – As cliffs erode, and natural coastal processes change the shape of our coastline, the grasslands which lie behind them are slowly squeezed between the retreating cliffs and the immovable roads and houses behind.
  • Possible acceleration of coastal erosion due to climate change.
  • Increased recreational pressure – dog-walkers, caravan parks and so on, has increased nutrient load in some areas, threatening some species of plant.
  • Litter. Litter on beaches and in the sea is a threat to wildlife. It is estimated that, globally, over a million birds and 100,000 marine mammals and turtles die every year from entanglement, or ingestion of. Results from the MCS Beachwatch litter surveys indicate that, over the past 10 years, beach litter has increased by 80%. When litter is caught up in the strandline it is often seen as unsightly and leads to calls for mechanical beach cleaning.
  • Mechanical beach cleaning removes the strandline, its vegetation and invertebrate communities. It also compacts sand, reducing its aeration for burrowing organisms.
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