Biological Impacts of a Severn Barrage Les Batty.
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Transcript of Biological Impacts of a Severn Barrage Les Batty.
Biological Impacts of a Severn Barrage
Les Batty
Biological Impacts of a Severn Barrage
Les Batty
OutlineOutline
A. How important is the Severn? B. The features of an estuary C. What would change with a
barrage? D. What would be the biological
effects? E. Would it matter?
A. How important is the Severn? B. The features of an estuary C. What would change with a
barrage? D. What would be the biological
effects? E. Would it matter?
A. How Important is the Severn Estuary?
A. How Important is the Severn Estuary?
One of largest intertidal zones in UK Ranks 15th in the UK for birds Covered by a suite of international
nature conservation designations
One of largest intertidal zones in UK Ranks 15th in the UK for birds Covered by a suite of international
nature conservation designations
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Designated conservation areasDesignated conservation areasMap 14: Designated Conservation Areas
Wetland of International Importance
(Ramsar Convention)
Wetland of International Importance
(Ramsar Convention)
Important run of migratory fish - salmon, sea trout, lampreys, allis shad, eel
One of most diverse fish communities in UK
Internationally important for birds
Important run of migratory fish - salmon, sea trout, lampreys, allis shad, eel
One of most diverse fish communities in UK
Internationally important for birds
Special Protection Area(EU Birds Directive)
Special Protection Area(EU Birds Directive)
Internationally important population Annex 1 species - Bewick’s swan
And other species: White-fronted Goose, Shelduck, Gadwall, Pintail, Dunlin, Redshank
Internationally important assemblage (>70,000)
Internationally important population Annex 1 species - Bewick’s swan
And other species: White-fronted Goose, Shelduck, Gadwall, Pintail, Dunlin, Redshank
Internationally important assemblage (>70,000)
Special Area of Conservation(EU Habitats & Species Directive)Special Area of Conservation(EU Habitats & Species Directive)
Estuary, Saltmarshes, Intertidal flats;
Sabellaria alveolata reefs;
Shads and lampreys.
Estuary, Saltmarshes, Intertidal flats;
Sabellaria alveolata reefs;
Shads and lampreys.
B. The features of an estuary
Physical features
B. The features of an estuary
Physical features
Mudflats and their ecologyMudflats and their ecology
Most productive habitat in estuary
High water content, even at low tide
Organic matter from detritus, phytoplankton, benthic algae, saltmarshes
Most productive habitat in estuary
High water content, even at low tide
Organic matter from detritus, phytoplankton, benthic algae, saltmarshes
Mudflat faunaMudflat fauna
Mudflat food webMudflat food web
SaltmarshesSaltmarshes
Stabilize margins of estuary Important source of primary production Invertebrate fauna Habitat for fish and birds
Stabilize margins of estuary Important source of primary production Invertebrate fauna Habitat for fish and birds
C. What would change?Tides
C. What would change?Tides
Tidal range & velocities reduced by 50%
Low water at present mid tide level
High water level reduced by c.1m
Possible increase in high water stand.
Tidal range & velocities reduced by 50%
Low water at present mid tide level
High water level reduced by c.1m
Possible increase in high water stand.
ProcessesProcesses
Longer period of wave action at HW
Reduced turbidity/ more light
Change in erosion/ accretion patterns
Redistribution of sediments
Longer period of wave action at HW
Reduced turbidity/ more light
Change in erosion/ accretion patterns
Redistribution of sediments
ZonesZones
Saltmarsh - erosion in some places, expansion in others
Intertidal zones - decrease
Subtidal - more soft sediment
Saltmarsh - erosion in some places, expansion in others
Intertidal zones - decrease
Subtidal - more soft sediment
So . . .So . . .
The estuary would be altered . . . But it would still be estuarine
The estuary would be altered . . . But it would still be estuarine
D. What would be the biological effects?
Changes in flora
D. What would be the biological effects?
Changes in flora
More phytoplankton (more light)
More eelgrass (Zostera)
More deep water seaweeds
More phytoplankton (more light)
More eelgrass (Zostera)
More deep water seaweeds
Changes in faunaChanges in fauna
More zooplankton and suspension feeders, eg.mussels, oysters, scallops
Changes in fish community
More fish-eating birds (clearer water)
Potentially fewer shorebirds
More zooplankton and suspension feeders, eg.mussels, oysters, scallops
Changes in fish community
More fish-eating birds (clearer water)
Potentially fewer shorebirds
So . . .So . . .
There would be an impact on the designated conservation areas
The biological communities would change, but biodiversity may increase
There would be an impact on the designated conservation areas
The biological communities would change, but biodiversity may increase
E. Does it matter? E. Does it matter?
If a significant effect on a Natura 2000 site (SPA/SAC) is likely
And the proposal goes ahead for “imperative reasons of over-riding public interest”
If a significant effect on a Natura 2000 site (SPA/SAC) is likely
And the proposal goes ahead for “imperative reasons of over-riding public interest”
According to legislation . . .
Measures must be secured to “maintain the coherence of the Natura 2000 interest” (i.e. compensatory habitat provided)
According to legislation . . .
Measures must be secured to “maintain the coherence of the Natura 2000 interest” (i.e. compensatory habitat provided)
But what do you think?But what do you think?
How could you find compensatory habitat for the Severn estuary?! and . . .
From an ethical standpoint . . . Does it matter if the Severn estuary and its ecology changes as the result of a barrage?
How could you find compensatory habitat for the Severn estuary?! and . . .
From an ethical standpoint . . . Does it matter if the Severn estuary and its ecology changes as the result of a barrage?