Saltmarsh Conference 8 October 2015

in the Suffolk Coast & Heaths Area of Outstanding Natural Beauty

Conference organised by Haidee Stephens,

Suffolk Estuaries Officer Suffolk Coast & Heaths AONB

t: 01394 445210 m: 07850 575971

Haidee.stephens@suffolk.gov.uk

Dock Lane, Melton, Woodbridge, Suffolk, IP12 1PE

suffolkcoastandheaths.org

Saltmarsh ecology: building

understanding to inform

management

Sue Rees and Graham Weaver;

Natural England

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Presentation aims

• Refresh understanding of

– saltmarsh ecology

– habitat function and dynamics

– saltmarsh as part of a wider system

• To inform effective management approaches

• Contribute to knowledge to support adaptation

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What is saltmarsh?

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“Intertidal areas of fine sediment, colonised by halophytic and other vascular plants”

Saltmarsh vegetation: a double life

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A habitat with regular phases of tidal inundation and exposure, reflected in patterns of plant distribution and interaction with other species

Interactions between intertidal zones

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Saltmarshes need marine processes

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Tides bring in nutrients & sediment, transport seeds/root fragments out Marine species can access flooded saltmarsh. Tidal exposure at low tide also influences vegetation Upper marsh may be hypersaline

…and marine processes need saltmarshes

• Role in nutrient cycling

• Provision of organic matter, role in food web

• Capture of pollutants

• Sediment store to buffer mudflat function

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These are not just any plants

• A few specialised plants

• Fleshy, succulent leaves

• Thick epidermis

• Hairy surfaces

• Salt storage cells

• Air storage cells in roots

• Tolerant to flooding and

exposure

• Annuals & perennials

• Floating seed

• Root fragments 9

Saltmarsh: where it ‘starts’ and ‘stops’

10 Succession progresses as sediment accretes: not a static system

Transitional habitats

Reality is more complex

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Saltmarsh succession

• An ongoing process with adequate sediment

• Vertical accretion can achieve 4-15mm yr-1

• Some locations dated from >5,000 years BP

• As ‘ecosystem engineers’ plants trap sediment,

attenuate wave energy & provide sediment from decay

• Phases dominated by erosion or accretion, subject to

sediment availability

• Sediment and nutrient exchange via water column

• Can change to other habitats e.g. dunes

• Can go into ‘reverse’ 12

Other factors affecting succession

• Elevation

• Drainage

• Response to grazing

management

• Wild herbivores

• Historic intervention

• Current vegetation will

influence resilience to future

change

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Importance of coastal morphology

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Different forms of saltmarsh

• Barrier beach coasts (North

Norfolk)

• Areas protected by a bay or

offshore banks (Dengie

peninsula, Essex)

• Estuarine saltmarshes

(Thames or Humber)

• Lagoonal/bar-built saltmarsh

(Poole Bay, Dorset)

• Rias or drowned river valleys

(Fal, Cornwall)

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Conditions for saltmarsh development

Essential:

• sediment exposed at low tide for a longer period than it

is exposed

• surfaces ‘sticky’ with coating of microalge/diatoms

• a supply of suitable suspended sediment available

during high tide

• water velocities that allow sedimentation at high tide

• a supply of seeds or other propagules transported in the

water column

• drainage through sediment to prevent waterlogging

• chemical and nutrient status.

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Looking for more information

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Seals to spiders: species on saltmarshes

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Habitat/niche requirements of Priority

species associated with saltmarsh

Species preferences within saltmarsh zones

Bird habitat: breeding, feeding, roosting

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Saltmarshes link marine & coastal habitats

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Extent of coastal habitats

231,880, 87%

14,545, 5%

12,800, 5%

4,495, 2%

1,649, 1%

Intertidal Mudflats and

Saltmarsh

Maritime Cliff and Slope

Sand Dunes

Vegetated Shingle

Coastal Lagoons

Transitions with the land

• Transition zones vary

• Generally truncated by sea

walls

• Natural transitions need

space

• Important for range of

species

• Sea walls support fragments

of habitat 23

Management of saltmarshes

• In general no active vegetation management essential

• Grazing history influences vegetation composition and structure

• Agri-environment option for grazing management

• Ensure maintenance of sedimentary regime

• Limit damaging activities

• Manage access

• Saltmarsh management manual EA:

– Maintain or restore conservation interest

– Managing sediment processes

– Creating new habitat to landward

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Annex I habitats

Annex I habitat Approx extent in

England

Distribution in UK

Salicornia & other

annuals colonising

mud & sand

2300ha All countries

Atlantic

saltmeadow

29000 ha All countries

Spartina swards

(not S.anglica)

<100 South east England

only

Mediterranean &

thermo-Atlantic

halophilous scrub

<100 Gibralter Point to

Chesil Beach only 25

Published guidance

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Risks to saltmarshes

• Climate change & sea level rise

• Inappropriate levels of grazing

• Coastal defences

• Ports/development

• Invasive species

• Land claim

• Discharges, pollution,

• Military use, drainage, turf cutting, harvesting.

• Renewable energy development: barrages, impoundments, cabling

• Impacts on sediment supply and wave climate (dredging, boat wash

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Key messages 1

• Saltmarshes and the marine environment are linked

• Dominated by vascular plants, with many halophytic species, that

develop in an intertidal environment and withstand regular tidal

inundation

• Variation in morphology, structure and composition depending on

age and sedimentary processes combined with anthropogenic

influences

• Saltmarshes can benefit from adaptive management that accounts

for their complexity

• The biological contribution to sediment processes is vital

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Key messages 2

• Highly productive systems which provide a range of ecosystem

services

• Valued and important for biodiversity conservation

• These habitats are scarce in England and at risk from a range of

pressures

• Gaps in knowledge but understanding is improving

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Thank you for listening

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