WEBVTT
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(gentle music)
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This is Gibraltar Point National Nature Reserve
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on the northwest corner of the Wash in Lincolnshire.
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It's incredible to think that this entire landscape
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has formed as result of deposition
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in just a few hundred years.
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Gibraltar Point lies at the southern end of a sediment cell
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that stretches from here all the way to Flamborough Head,
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116 kilometres to the north.
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A sediment cell is a stretch of coastline
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in which sediment can move around,
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but sediment rarely enters or leaves the area of that cell.
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Much of the Lincolnshire coastline has receded
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by between 400 and 800 metres over the last 500 years.
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The Holderness Coast, to the north of Gibraltar Point,
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is the fastest receding coastline in all of Europe.
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Much of the sediment that's eroded
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up at the Holderness Coast is transported south
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by longshore drift,
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and it's deposited right here,
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where the orientation of the coastline changes,
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creating the sheltered environment of Gibraltar Point.
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All this deposition has created
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a five square kilometre area of land,
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comprising of a well-developed ridge and runnel foreshore,
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sand dunes, and salt marshes.
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(bright, happy music)
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Twice a day the tide moves across this beach,
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by up to 7 meters on the highest spring tides.
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At low water, you can see exposed a very large beach,
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a wide beach,
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and also, offshore, some large sandbanks.
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The wide beach that we can see here, and the offshore banks,
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show us just how much sediment deposition
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is taking place here at Gibraltar Point.
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This beach is a very important source
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of sediment for dune development.
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The sand is picked up by the wind,
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and bounced across the beach surface
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by a process known as saltation.
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(bright, happy music)
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That sediment that's been carried
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up the beach by saltation
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starts to get deposited around here,
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just above the high-water mark,
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and this is where sand dune development begins.
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In the first stage of sand dune formation,
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the wind comes into contact with an obstacle,
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like this driftwood, a rock, a shell, or even some litter.
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The wind slows down, deposits its sand,
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and it starts to build up against these obstacles.
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This spiky little plant is Prickly Saltwort,
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and it's a pioneer species on this sand dune,
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which is helping to build up and stabilise
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the sand in which it's growing.
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Most plants would die in this environment
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but the Prickly Saltwort,
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with the help of its waxy leaves and deep roots,
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are able to get the nutrients that it needs
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out of this sandy soil and saltwater environment.
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The Prickly Saltwort is helping to stabilise
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the sand on the sand dune here,
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and also it acts as a shield that slows down more wind,
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causing more sand to be deposited,
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and the sand dune to grow.
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These small, delicate sand dunes are called embryo dunes.
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They are right next to the beach,
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and they're the youngest sand dunes
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that we get along this coastline.
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These embryo dunes here have probably formed
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in the last few months or so.
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(bright, happy music)
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Just inland from the embryo dune is this foredune,
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where sand is really starting to accumulate.
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We have these salt-tolerant vegetation species,
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like Sand Couch Grass,
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and Lyme Grass,
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and they're really starting to take hold.
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(bright, happy music)
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Just beyond the foredune,
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this first main ridge of dunes are called yellow dunes.
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These yellow dunes have been here for 30 or 40 years,
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so they're really well-established in terms of vegetation.
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Marram Grass is really common on yellow dunes,
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and this stuff is really good
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at stabilising the dune and trapping sand.
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These dunes are called yellow dunes
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because of the sand that they're made of,
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which gives them a yellow colour.
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But as we start to go inland, this all starts to change.
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(bright, happy music)
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Further from the coast the dunes are more protected
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from the inundation of seawater,
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and so we start to see more and more vegetation.
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And what's more, that vegetation is changing.
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Whereas before we had a lot
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of salt-tolerant species like Marram Grass,
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here it's not as salty,
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and so more species are able to grow,
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like this Sea Buckthorn,
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and perennial species like Dewberry, which we have here.
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(digging)
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We call these grey dunes,
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and you can see why when you
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look at the colour of the soil.
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This is a sample of sand that we collected
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from the yellow dune,
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which is much closer to shore,
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and you can see just how yellow that is,
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in comparison to this sample,
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which we've collected from the grey dune.
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You can see that in this grey dune
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there's much more organic matter and humus,
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and if you compare the two samples side by side,
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you can really see the contrast in colour
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between the yellow dune and the grey dune.
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Mosses and lichens like these,
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which are growing on the surface of the dune,
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also help to give the dunes their grey colour.
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Embryo dunes, foredunes, and yellow dunes
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are all known as mobile dunes,
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because they can be disturbed
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or even destroyed by severe storms.
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But these grey dunes here are much more fixed and permanent.
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They're in a well-sheltered location
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and they're far away from the influence of the sea.
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(happy, bright music)
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The oldest sand dunes here are found
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over a kilometre inland,
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far from the influence of the sea
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where the sand dune system reaches its climax.
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The environment here is completely changed:
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we've got heath covered in shrubs
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with more Sea Buckthorn and Hawthorn,
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and we've got deciduous woodland here
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with mature trees such as Oak, Maple, and Ash.
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The ground here is different as well.
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There's a lot more organic matter
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and humus contained in the soil,
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and it's also very moist,
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and that's because the water table here
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is very close to the surface.
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The dunes here at the climax are over 250 years old,
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dating back to the mid 18th century.
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(happy, bright music)
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Today, we can see the succession of vegetation,
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from pioneer plants all the way up to climax species,
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creating a changing environment
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as we travel through these sand dunes.
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(upbeat music)
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The landscape here at Gibraltar Point
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is an incredible place to visit,
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to see the processes of a depositional
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coastal landscape at work.
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However, this environment is very sensitive to disturbances.
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The area is designated a Ramsar wetland site,
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which means it is carefully managed
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to preserve the landscape and ecosystems.
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School groups wishing to visit the area can do so
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by contacting the National Nature Reserve Office
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using the contact details shown below this video.
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(upbeat music)