Area: 603.46 hectares.
The site overlaps two Nature Conservation Review Sites and is mostly within the Cornwall Area of Outstanding Natural Beauty.
Description and Reasons for Notification:
The Fal Estuary is a ria, a deeply incised river valley which has been ‘drowned’ by rising sea levels. The estuary, whose lower section is an important natural deep-water harbour, opens to the sea near Falmouth on the south coast of west Cornwall. The upper reaches which constitute this site are, for the most part, sediment-filled, with mudflats backed by low rocky cliffs. They are of major importance for the wintering wading birds and for the ancient semi-natural woodlands which clothe much of their banks.
Of particular importance and rarity are the relatively undisturbed transitions from tidal mud through saltmarsh and scrub to woodland at the upper limits of tidal influence. On a high proportion of estuaries, such transitions have been destroyed by drainage and subsequent agricultural activity or by development.
The mudflats within the site support nationally important numbers of Black-tailed Godwit Limosa limosa during autumn and winter. They are also important feeding grounds for large populations of a number of other wintering waders and wildfowl. In particular, the site supports curlew Numenius arquata, dunlin Calidris alpina, shelduck Tadorna tadorna, redshank Tringa totanus and golden plover Pluvialis apricaria. On the Tresillian River there are habitats which support greenshank Tringa nebularia, spotted redshank Tringa erythropus, little grebe Tachybaptus ruficollis and kingfisher Alcedo atthis. Small but growing numbers of little egret Egretta garzetta now occur within the complex. The site is important for grey herons Ardea cinerea and there is a major heronry.
Saltmarsh communities have developed in a number of localities within the complex, most notably near the limit of tidal influence at Ruan Lanihorne and on the Tresillian River. In addition extensive beds of common reed Phragmites australis have developed in some places. Typically the saltmarshes in these upper reaches are characterised by sea club-rush Scirpus maritimus and creeping bent Agrostis stolonifera, common saltmarsh-grass Puccinellia maritima, red fescue Festuca rubra and sea rush Juncus maritimus.
On the transitions from saltmarsh to woodland isolated young trees grow over the upper marsh and eventually, despite the area being subjected to flooding with brackish water on extreme tides, more extensive scrub invades and extends across the entire alluvial valley floor. Alder Alnus glutinosa is the major component of these woodlands, forming a closed canopy of well grown, characteristically multi-stemmed trees at a height of around 15 metres. In places willow Salix spp. forms a boundary against mature oak woodland.
This transition zone supports over 100 species of flowering plants and ferns, many not normally associated with maritime situations. These include greater tussock-sedge Carex paniculata, hemlock water-dropwort Oenanthe crocata, lesser pond-sedge Carex acutiformis, yellow iris Iris pseudocorus, common nettle Urtica dioica, hemp-agrimony Eupatorium cannabinum and meadowsweet Filipendula ulmaria. On the drier areas on the estuary sides there is a transition to oak-dominated woodland.
The upper estuaries and these transitional zones are important for Otters Lutra lutra.
Extensive stands of ancient semi-natural woodland occur within the site and on the eastern shores these are virtually continuous. They lie on steep slopes rising to 80m and upon soils which are acidic and generally free draining.
Sessile oak Quercus petraea is generally the dominant tree of these valley side woodlands, although there are variations, notably on damp valley floors where sessile oak with ash Fraxinus excelsior and hazel Corylus avellana occurs and on well-drained slopes, where silver birch Betula pendula -- sessile oak woodland is present. Pedunculate oak Quercus robur also occurs within these woodlands and hybridisation between the two oak species is thought to have taken place.
Much of the oak woodland was coppiced between 40 and 90 years ago resulting in even-aged stands with a closed canopy, though in inaccessible valleys areas of standard trees occur.
Two types of ground flora are widespread within the woodland:
A bramble Rubus fruticosus dominated community with honeysuckle Lonicera periclymenum, bluebell Hyacinthoides non-scriptus, Dryopteris ferns and creeping soft-grass Holcus mollis occurs typically on the higher, gentler slopes which permit good soil-depth and fertility. Closer to the estuary a bilberry Vaccinium myrtillus, greater woodrush Luzula sylvatica, hard fern Blechnum spicant community is more common. Heather Calluna vulgaris is frequently abundant where the lower slopes give way to low rocky cliffs. A number of notable plants are found within the woodlands including the nationally rare wild leek Allium ampeloprasum and the nationally scarce bastard balm Melittis melissophyllum. Other species of note are wild madder Rubia peregrina, imperforate St John’s-wort Hypericum maculatum, greater burdock Arctium lappa and hard rush Juncus inflexus. Spindle Euonymus europaeus, alder buckthorn Frangula alnus and Cornish elm Ulmus cornubiensis occur within the underwood.
A number of mosses and liverworts typical of ancient woods in the southwest occur including big shaggy moss Rhytidiadelphus triquetrus, common tamarisk moss Thuidium tamariscinum, common haircap Polytrichum commune and mouse tail moss Isothecium myosuroides. The fern flora includes common polypody Polypodium vulgare, hart’s tongue fern Asplenium scolopendrium, golden male fern Dryopteris affinis and an abundance of soft shield fern Polystichum setiferum. Despite the dense shade of the canopy, and the comparative youth of the coppiced stems, the trees support a range of epiphytic lichens including two nationally scarce species Opegrapha corticolaand Schismatomma niveum which are found on old oak bark.
The invertebrate fauna of these woodlands is also rich. Particularly notable species include the ground-living spider Hahnia helveola and the beetle Rhizophagus nitidulus, a species confined to ancient woodlands.
The site is also of high marine interest. On the extensive area of coarse intertidal sediment at Turnaware Point, a number of interesting communities have developed largely associated with beds of seagrass Zostera marina. A rich algal flora includes Cladosiphon zosterae, slender wart weed Gracilaria verrucosa and mermaid’s tresses Chorda filum. Further communities of particular interest occur at Tom’s Rock within the King Harry Reaches where the steep rocky shores are dominated by egg wrack Ascophyllum nodosum. On the lower shores a particularly luxuriant growth of sponges has developed which includes Hymeniacidon perleve and Halichondria panicea.