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two centuries ago
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one in every four or five hectares of
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land in ireland
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was covered by bog a wild
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and wonderful type of landscape
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underlying by anything up to
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15 meters of peace a very limited
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agricultural value
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but a vital source of fuel in a country
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that had lost
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almost all of its woods between the 16th
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and the 19th century now
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almost all of that has disappeared
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mostly as a result of large-scale
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industrial harvesting of peat and all
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we're left with
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are a few small remnant fragments
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precious fragments such as this
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the conservation of which is an
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important conservation priority
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but perhaps even more important
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is the restoration to as
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great an extent as possible to those
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now degraded peatlands which have been
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stripped
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of their great reserves of peat
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to a state of biological diversity
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and to a state where something is
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restored of their ability to sequester
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carbon
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so what we're going to do or try to do
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in this short series of videos
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is to tell very briefly the story
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of the raised bogs of how they came to
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be here in the first place
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of how they came to be the wild and
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wonderful places they once
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were to tell the brief
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chapter of how they disappeared and most
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importantly
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what we can do to restore as much as is
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possible
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of what has been lost
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towards the end of the ice age 12 or 13
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000 years ago
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a great lake formed in the midlands
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between two melting ice masses
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that had begun to split apart and were
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moving away from each other
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one of them was anchored in place on
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sleeve bloom to the south
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and the other was retreating north
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westwards
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over time great quantities of sand and
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gravel
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carried in melt water streams in tunnels
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at the base of the ice
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were washed into this lake and deposited
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as
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deltas and fans along the margins of the
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lake
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and it is these deposits that in time
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came to become
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the winding ridges and waves of the
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eskers
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which are such a distinguishing and
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characteristic feature
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of the landscape of the midlands
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the great size of some of the boulders
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in the eskers gives us some idea of the
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power
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of the meltwater rivers flowing beneath
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the ice
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elsewhere a more general blanket of
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mixed rocky debris was dumped on the
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land
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rock debris that had been entombed in
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the moving glaciers and left behind when
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the retreating ice finally melted
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when the ice had all melted away a
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network of lakes replaced the one great
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lake of the late glacial period
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then when conditions became warm enough
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for life to return
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the lakes were colonized by vegetation
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and animal life
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and it was these lakes that over the
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course of time became the templates
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for the formation of peat peat
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is an organic soil that forms where
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conditions are waterlogged
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and therefore anaerobic inhibiting
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decomposition of dead plant material
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which therefore builds up over time
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where the many meters of peat have been
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stripped away from the bogs
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we can see with our own eyes and examine
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the evidence
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for this first chapter in the story of
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the bogs
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so this is what we find underneath all
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those many meters of peat
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this white limey deposit which is known
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as marl
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and the marble is made up largely of the
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remains of the plants that were growing
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at the bottom of these
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early post-glacial lakes particularly
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stonewarts
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which have a limey skeleton and in fact
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there are still some stonewarts actually
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growing in the drain
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here are some so
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the limey skeletons of these building up
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year by year
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is what largely went to the composition
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of the marl
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and if we examine the mild more closely
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we can see that it also contains
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numerous remains of lots of different
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species of freshwater snails
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many of them similar to species that are
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found in limestone lakes in the midlands
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today
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and others which have since disappeared
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from ireland
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so that's the mall and sometimes in some
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places
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the mile can accumulate or has
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accumulated to a depth of several meters
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and if we take a look now at what is on
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top of the mall what comes immediately
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after the marl
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you can see this is the lowest piece
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here okay the lowest pin it will take
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take some of that away
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and have a look at that
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because it's very crumbly and
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it breaks into kind of flat plate like
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bits
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this is reed swamp or reed marsh
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peat and it's made up largely
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of the remains of reeds
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that were growing on the margins of the
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lake and if you look
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more closely you can actually still see
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the flattened remains of the leaf stems
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you see how easy it breaks because it's
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breaking parallel
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to those flat
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stems of the reeds
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so those are flattened reed stems
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basically that's a good example see
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okay so that's reed swamp peat and again
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in some places
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that reed marsh reed swamp pete can
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accumulate to a depth of several meters
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then on top of that
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here it's not as deep as that it's maybe
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two-thirds of a meter here but on top of
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that you'll see
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the peat
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becomes much more crumbly
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becomes much more crumbly there are no
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reed stems in this but there are present
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are little twigs
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you see bits of twigs present here that
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and if you look at those more closely
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those little twigs are going to be
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mainly birch or alder
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this is this crumbly black peat is fen
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peat
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which accumulated as the advance of the
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reed marsh into the lake squeezed out
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the open water all together
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and conditions became suitable for a a
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woody
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swamp-like habitat in which this
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thin piece accumulated again for many
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hundreds of years
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over the course of time then the reeds
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extended further and further out into
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the deeper waters of the lake
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giving rise to large areas of reed swamp
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eventually squeezing the open water out
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altogether and accumulating
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as reed swamp peat sometimes to a depth
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of several meters
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although the plants growing in these new
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fen habitats had an abundant supply of
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minerals
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limited soil aeration and water-logged
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conditions continue to inhibit
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decomposition
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resulting in continued peat formation
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but in time the growing thickness of
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peat
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raised the surface beyond the reach of
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groundwater and its nutrient supply
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giving the advantage to new communities
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of plants that could thrive without that
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source of nutrients
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these communities of bog plants now
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replaced those of the fen
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plants that had evolved a variety of
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different strategies which enable them
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to survive
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independently of groundwater nutrients
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the marl here can be as much as several
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meters deep
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but down below the marl there is often
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an
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older and very different sort of clay
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this older clay formed in the great lake
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that lay across the midlands towards the
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end of the ice age
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the same lake into which the sands and
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gravels of the eskers were swept
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and deposited along the margins long
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before
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conditions became warm enough for any
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vegetation to grow
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or for the marl to form
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but this was the finest sediment
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which drifted out into the deeper waters
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of that great lake
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where it settled slowly year by year
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forming a finely laminated clay each
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narrow band recording a single year of
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seasonal deposition
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this older clay which is very dense and
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heavy
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sticky in texture and blue gray in color
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is the material from which the yellow
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bricks that are such a distinctive
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feature of offaly's architecture were
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made
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from the 17th century onward
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in the 19th and early 20th centuries
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bricks from this clay
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were made on a modestly industrial scale
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along the brosnan and its claudia
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tributary
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where the same blue grey late glacial
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play occurs extensively under the
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callows
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but they were made on a smaller scale
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from clay under the bog in many
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localities
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the bricks were made by hand one by one
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using timber molds
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and since the kiln in which they were
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burnt was made of the bricks themselves
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nothing remains at the site of these
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kilns today but the telltale signs of
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scattered broken brick
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they were especially fashionable for
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framing windows and doors
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but in areas close to the bogs entire
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houses were often made of brick
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and rough stone from the glacial moraine
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this brief look at how the bogs came to
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be here in the first place
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is the first part of a tree act drama
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which is the story of the raised bogs
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in the second act we will look at how
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the bogs grew to be the wild and
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wonderful places they once were
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and at how they disappeared as we
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exploited their great reserves of peat
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for
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energy for fuel and for horticultural
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use
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in the third act we will look to the
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future
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at what we need to do in particular
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uh to restore to these now degraded
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areas of peatland
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that have been stripped of their great
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reserves of peat
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of as much as we can of their lost
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biological diversity
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and their ability to sequester carbon
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you
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