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The Local Area

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The Isle of Wight was separated from the mainland during the post-glacial rise in sea level about 7,500 years ago. The varied topography and natural history of the Island is largely attributable to the underlying geology which comprises a wide range of clays, sandstones and limestones belonging to the Cretaceous and Tertiary periods. The most prominent landscape feature is the chalk ridge or 'spine' running between Culver Cliff in the east and the famous sea-stacks known as the 'Needles' in the west. The southern downs between St. Catherines Point and Shanklin are generally higher than the central spine, and rise to 786' (238m) above sea level at the top of St. Boniface Down - the 'summit' of the Island. Sections of the south and north-west coastline are receding rapidly and the shape of the coastline has changed significantly over the past 100 years. Currently the Island is 23 miles (36.8km) east to west, and 13 miles (20.8km) north to south. 

Fig 1. Map to show basic Geology and River network of the Isle of Wight.

CLIMATIC DATA

VEGETATION AND SOILS

The chemical and physical characteristics of the different rock types, climatic factors and biological processes will determine the nature of the soil and, therefore, the plant and animal communities which colonise it. On the chalk, a wide range of 'calcium-loving' species (Calcicoles) may be found on the thin, nutrient poor soils known as 'Rendzinas'. The more sandy, acid soils called 'Podzols' which exist on Headon Warren, just north of Alum Bay, have developed a heathland flora with plants more tolerant of acid conditions (Calcifuge plants). To the north of the central spine of chalk, the soil is primarily heavy clay and there are sill large areas of woodland e.g. Parkhurst Forest. About 43% of the Island's woods are considered to be Ancient Semi-Natural Woodland. These woods have had continuous cover of native trees and plants since at least 1600. Much of the fertile Lower Greensand soils in the south of the Island are now intensively cultivated.

FRESHWATER STREAMS AND PONDS

The permeability of the underlying rocks will determine the type and extent of land drainage and this in turn effects the ecology of streams, ponds and wetlands. Island rivers are unusual in the respect that most rise near the south coast and flow north, being relic tributaries of the ancient river system which existed during the glacial period. They tend to be narrow and slow flowing, and unfortunately many sections of channel have been modified to cater for land drainage schemes and flood defence. Some of the streams have problems associated with hydrated iron oxide (Iron Ochre) which forms a bright orange precipitate on the river bed. This can cause problems for animal and plant life and suppress the biological diversity of the river. Ponds have declined in many areas, though all three British species of newt do still survive, and some coastal ponds on the landslipped south-west coast have African Clawed Toads (Xenopus sp.) breeding!

THE MARINE ENVIRONMENT

The Solent Estuarine System is internationally important for its reserves of benthic invertebrates which provide a food resource for over-wintering wading birds, ducks and geese. The whole of this wetland system supports a peak winter population of 150,000 waterfowl including 8% of the 1.3 million wading birds which over-winter in Britain, the fourth largest number in British estuaries. The Newtown River, West Yar estuary and the River Medina have saltmarshes which are also important for a variety of wildlife other than birds.

In marine biogeographical terms, the Isle of Wight is at a boundary between the colder Boreal waters which flow down from the north and the warm-temperate Lusitanian seas which flow from the south-west. Some of these warm-water species reach their easterly limits in the Channel near here, such as the barnacles Chthamalus montagui and Balanus perforatus, the limpets Patella ulyssiponensis and P. depressa, the snakelocks anemone Anemonia viridis and the Peacock's tail seaweed Padina pavonica.

ISLAND SPECIALITIES

Despite being an Island, separation from the mainland appears not to have been long enough to enable the evolution of endemic species. However, there are some species which exist here at the northern edge of their European range and are not present on mainland Britain The protected Glanville Fritillary butterfly Meltiaea cinxia is one such example and breeds on the south coast. The Wood Calamint plant Calamintha sylvatica survives in a small woodland on the chalk. The native Red Squirrel Sciurus vulgaris finds refuge here from the alien grey squirrel, and breeds successfully.

HUMAN IMPACT

Human influence within the Island's countryside can be dated back to the initial clearance of the great wildwood which covered most of the Island 7000 years ago. In 2001, the population of the Island was 133,000 and growing by about 1000 per annum. The landscape is still largely agricultural, and in the fertile Arreton Valley, modern farming methods have led to the clearance of woodland and hedgerow and the drainage of damp species-rich meadows and wetlands. The use of fertilisers and leakage of farm silage and slurry has periodically led to a rise in nutrient levels in water courses and ponds with risk of eutrophication.

Tourism accounts for 20% of employment on the Island and each year the Island has to cope with about 2.7 million visitors (Isle of Wight Tourism). During the main holiday season there is tremendous pressure upon the Island's water supply and treatment works and major investment has been necessary to improve and update existing plants. Since 2002 most of the Islands sewage has undergone secondary treatment and pumped into the sea off Sandown, on the south-east coast. Abstraction of groundwater during peak periods in high summer has led to concerns for our natural wetland habitats, and the canalisation of water courses and abstraction of groundwater has led to concerns for our natural wetlands.

The development of Fawley oil refinery on Southampton Water has increased the probability of oil pollution in the Solent and around the Island's shores. The discovery of oiled seabirds such as Guillemots and Razorbills is not uncommon, especially during the winter months. The rise in popularity of yachting in the Solent has led to an increase in the development of marinas and berthing facilities. Associated pollution, such as the leakage of oil and diesel, has seriously degraded some harbours. The use of tributyltin (TBT) antifouling paints resulted in the decline of the dog-whelk around our coast and near extinction from the Solent. Since legislation in 1986, there has been a recovery on some shores. Fears have been expressed that the dredging of shingle from the Solent and off the south coast is accelerating the rate of coastal erosion. The shingle spit at Newtown has been badly disturbed in the past and the rare Little terns which used to nest there no longer do so.

Alien species from distant seas brought into the Solent on ship's hulls are a real threat to native marine life. In 1971, the prolific Japanese brown alga Sargassum muticum was discovered at Bembridge and has since spread right along the English Channel, though any major ecological damage arising from its introduction has not been confirmed.

Fig 2. The Solent Estuarine System



CONSERVATION

People may also choose to improve and conserve the environment. Fig. 3 illustrates the location of Local Nature Reserves (LNR) owned by the Isle of Wight Council and a selection of Sites of Special Scientific Interest (SSSIs) which are appointed by Natural England, the government body responsible for nature conservation in England. The 1981 Wildlife and Countryside Act increased Natural England's ability to designate such areas, although even greater legislative powers are required to fully protect these valuable sites. Being of exceptional quality, in 1995, much of the Newtown Estuary and surrounding woodland and marshes was declared the Island's first National Nature Reserve, and is managed jointly by Natural England and the National Trust. Other designations such as Heritage Coast, Area of Outstanding Natural Beauty (AONB) and the Environmentally Sensitive Areas (ESAs) are made in conjunction with the Countryside Commission.

European legislation is becoming increasingly important and two Special Areas of Conservation (SACs) have been designated, encompassing virtually the whole of the Island's coast, and some inland sites where the nature conservation interest is considered exceptional in a European context. In the UK, however, only 6% of UK territorial waters have been designated SAC (JNCC, 2007).

Locally, the National Trust owns and manages much of the undeveloped coastline, and Wight Wildlife, a partnership between the Hampshire & Isle of Wight Wildlife Trust and Isle of Wight Natural History & Archaeological Society also works to conserve our natural heritage. The Countryside Section of the Isle of Wight Council is involved in the management of Local Nature Reserves and provides advice to planning authorities, landowners and developers.

With the threat of increased residential provision and industrial development, greater vigilance is necessary if we are to conserve what remains of the Island's natural heritage. To understand how to manage its future, an understanding of the ecology of the Island is essential.

Fig 3. Nature Reserves and SSSIs (Shaded area) on the Isle of Wight.