Climate-driven expansion of blanket bogs in Britain during the Holocene
Blanket bog occupies approximately 6 % of the area of the UK today. The Holocene expansion of this hyperoceanic biome has previously been explained as a consequence of Neolithic forest clearance. However, the present distribution of blanket bog in Great Britain can be predicted accurately with a sim...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-01-01
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| Series: | Climate of the Past |
| Online Access: | http://www.clim-past.net/12/129/2016/cp-12-129-2016.pdf |
| Summary: | Blanket bog occupies approximately 6 % of the area of the UK today. The
Holocene expansion of this hyperoceanic biome has previously been explained
as a consequence of Neolithic forest clearance. However, the present
distribution of blanket bog in Great Britain can be predicted accurately
with a simple model (PeatStash) based on summer temperature and moisture
index thresholds, and the same model correctly predicts the highly disjunct
distribution of blanket bog worldwide. This finding suggests that climate,
rather than land-use history, controls blanket-bog distribution in the UK
and everywhere else.
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We set out to test this hypothesis for blanket bogs in the UK using
bioclimate envelope modelling compared with a database of peat initiation
age estimates. We used both pollen-based reconstructions and climate model
simulations of climate changes between the mid-Holocene (6000 yr BP, 6 ka)
and modern climate to drive PeatStash and predict areas of blanket bog. We
compiled data on the timing of blanket-bog initiation, based on 228 age
determinations at sites where peat directly overlies mineral soil. The model
predicts that large areas of northern Britain would have had blanket bog by 6000 yr BP,
and the area suitable for peat growth extended to the south after
this time. A similar pattern is shown by the basal peat ages and new blanket
bog appeared over a larger area during the late Holocene, the greatest
expansion being in Ireland, Wales, and southwest England, as the model
predicts. The expansion was driven by a summer cooling of about 2 °C,
shown by both pollen-based reconstructions and climate models. The data
show early Holocene (pre-Neolithic) blanket-bog initiation at over half of
the sites in the core areas of Scotland and northern England.
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The temporal patterns and concurrence of the bioclimate model predictions
and initiation data suggest that climate change provides a parsimonious
explanation for the early Holocene distribution and later expansion of
blanket bogs in the UK, and it is not necessary to invoke anthropogenic
activity as a driver of this major landscape change. |
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| ISSN: | 1814-9324 1814-9332 |