Fire!
Fire was an important part of the bog
ecosystem. The same types of plants have grown on the
bog since around 8160 years ago (328 cm) –
plants like heather, other heath plants, Sphagnum
bog moss, some sedges and grasses. But how much and
where each grew changed because different plants
respond differently to burning. Fires may have
helped heather to become established or expand on the
bog between 9870 and 9550 years ago (394-386 cm) and
again at 8160 years ago (328 cm) by creating openings
of disturbed ground enriched with ash. Since then,
fires often helped heather and perhaps heath to grow
more abundantly. In contrast, crowberry is sensitive
to severe fires and so seems to have been more common
when there was less burning.
Burning
heathland © SNH
Pollen and microscopic charcoal
fragments show us that burning happened but they
can’t tell us what started the fires. There are
many possible things that may have caused burning
– drier conditions on the moss caused by changes
in the water table, lightning storms, a drier
climate, deliberate or accidental fires started by
people. Perhaps it was a combination of all of these
factors at different times!
Palynologists (pollen analysts) often
see a similar pattern between the amount of heather
pollen and the number of charcoal fragments. So
did heather just catch fire very easily?
Ecologists and palynologists still debate this
question, but modern heathland fire regimes are so
strictly controlled by people that it is hard to tell
what other factors can cause heathland fires and how
often these happened in the past.
There is evidence from the far north
and west of Scotland that heather fires were more
common when the climate was drier, espoecially around
8800-5800 years ago. In these areas of Scotland this
is the time when heathland and blanket peat were
spreading, so fire could be linked with the growth of
heather. A lot of detailed work is still needed
before we can tell if heather fires at Greenhead Moss
were controlled by the climate. To do this, the
records of fire and heather pollen will be compared
with all available palaeoclimatic (past climate),
pollen and charcoal records from central Scotland and
the borders. This will show us if there is a regional
pattern in heather and burning which could be linked
to climatic changes over this area.
In the Highlands today patches of
burnt heather are common on the hillsides. Most of
this is part of modern heathland management
programmes known as muir-burn.
Regular burning helps keep a wider range of species
and stops trees from invading. It also keeps the
variety of habitats that grouse birds need to survive
and provides more young, tender shoots for sheep
grazing the hill pastures.
In the pollen diagram heather,
charcoal and plants indicating farming occur together
from around 3630 years ago (120 cm), giving us a good
indication that people were responsible for at least
some of the fires.
A Bronze Age farm with a
view: pastures new>
From country to industry: the Dark Ages to the
Industrial Revolution>
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