NATURE NOTES HEADON Warren, above Alum Bay, and Ventnor Down, overlooking Luccombe, are splendid this year in the purple of their late summer plant cover.
They are the two main areas of heathland on the Island, comprising communities of ericaceous plants — heather, ling, and gorse — which require an acid soil low in nutrients for their survival.
Lowland heath has become comparatively rare in England, having declined in area by some 70 per cent since the middle of the 19th century; this loss caused by urban development and agricultural improvement for crops.
Consequently, much surviving lowland heath is now protected and the Island’s two main areas have been designated Sites of Special Scientific Interest by the government’s nature conservancy agency, Natural England.
The origins of most areas of lowland heath lie in the clearance of natural tree cover by the first farmers some 5,000 years ago.
Archaeological evidence suggests that the forest covering these areas was already vulnerable due to the unstable soils overlying certain types of rock, making clearance relatively easy for agriculture.
But once the tree cover had been removed, the soils quickly broke down further into sandy or peaty deposits, from which any nutrients rapidly seeped away rendering the areas almost useless for growing crops.
Abandoned by the farmers, the poor soils were colonised by those heathland plant types we see today and which are tolerant of these dry, nutrient-poor conditions.
The resulting heathland took on a new role as a support system for the farming communities, providing bracken and heather for animal bedding and gorse for firewood, as well as some rough grazing for hardier animals.
This situation continued for hundreds of years until, in the 18th century, soil improvement techniques were developed leading to the enclosure of much of England’s large open heathland areas into new field systems.
Later the urban expansion of towns and cities began to encroach onto remaining areas of relatively cheap heathland for house and factory building.
The heaths at Headon Warren and Ventnor Downs, are similar in the composition of their plant communities and associated wildlife but they do have a marked and important difference concerning the underlying geology.
Headon Warren is a classic South — of England heath, being formed on acidic sandstone rock but the Ventnor Down heath is a national rarity being formed on alkaline chalk rock — it is the peaty capping on top of the down which creates the right conditions for the development of a heathland plant community. Heath on chalk is a real scarcity.
As well as being protected by law, these two sites are owned by the National Trust, which is carrying out sympathetic management to enhance the quality of the wildlife habitat and encourage public access.