- Chapter Nine -
and designed to maintain existing communication routes in wetter conditions (Coles
and Coles 1986). In the later Iron Age settlement was established for the first time
on the wetland itself, taking the form of an artificial palisaded island of clay mounds
at Glastonbury and seasonal settlement on clay mounds on a raised bog surface at
Meare. Pollen diagrams show that this was a time of major clearance on the dry ground,
with herb pollen accounting for 30-40 per cent and representing a fully agricultural
landscape.
Excavations at Goldcliff in the neighbouring Severn Estuary provide a further
indication of the specialized nature of iron age wetland exploitation, and the capacity
of these communities to exploit every niche of their environment. Here rectangular
wooden buildings and trackways dating to the fourth and third Be are found in a
thin peat band within marine clays (Bell 1992). The peat represents a brief period
when settlement of the wetland was possible, though for what purpose, whether
grazing, fishing or ritual activity, remains unclear. Despite the substantial nature of
these structures, their use was temporary: there were no hearths or artefacts apart
from a few bones, and the site had been subject to periodic marine inundation dur-
ing its use. In the later Iron Age, marine influence in the Severn Estuary and Somerset
Levels was reduced and in the Roman period the coastal clays were drained and pre-
sumably embanked from the sea (Allen and Fulford 1986). This Roman-inspired
drainage takes place almost a millennium before large-scale drainage and dyke
construction in the Netherlands north of the Limes, which finally insulated those
communities from the effects of all but the most severe storm surges.
British Lowland Zone
Palaeoenvironmental evidence for this period is particularly abundant in the British
Isles and has already been reviewed by Turner (1981) and Bell (forthcoming).
Current evidence indicates more widespread clearance, both before and during the
period, than on the Continent but reveals some marked contrasts between the British
Highland and Lowland Zones. The latter is the southern and eastern part of the
British Isles with mostly fertile soils, modest topography and rainfall, and much
evidence of intensive clearance before the Iron Age. This is most clearly shown on
the chalk where, for instance, the environs of Maiden Castle, Dorset (Evans 1991),
and iron age settlements on the M3 motorway (Evans and Williams 1991) were
already cleared, although some woodland regeneration occurred during an abandon-
ment phase at Danebury (Evans 1984). 'Celtic' fields show that arable agriculture was
extensive in the Iron Age and Romano-British periods and this led to soil erosion
represented by lynchets and dry valley fills (Bell 1983). Seed assemblages from iron
age sites confirm the increasing intensity of land-use during the period, with greater
use of heavier and poorly drained soils and some evidence of soil exhaustion
Gones 1981). At Danebury crop growing was taking place in a range of surrounding
habitats including the river valleys Gones 1984). By the Iron Age river valleys in the
Lowland Zone were mostly open and farmed. Tree pollen values were low in
the Thames valley, and at Farmoor seasonal occupation and grazing took place on
the floodplain, which was inundated in winter (Lambrick and Robinson 1979).
Similarly, at Fisherwick in the Tame valley, a settlement was surrounded by ditched