Main Biodiversity Resources in the tidal Thames - Sites and Habitats

Introduction

A very high proportion of the area within the PLA’s jurisdiction is of value for biodiversity. In particular, a large part of the estuary is included within statutorily designated wildlife sites, and supports nationally and internationally important habitats and species (notably birds, but also including fish, invertebrates and marine mammals). There are fewer statutory sites in the upper reaches, although the entire tidal Thames and tributaries within Greater London are a Site of Metropolitan Importance for wildlife (non statutory but recognised in the London Plan and Borough development documents). The Thames Estuary Partnership has produced a useful Habitat and Species Audit for the tidal Thames between Teddington Lock and a line between the Isle of Grain and Shoebury Ness.

Sites and Habitats

Sites of Special Scientific Interest (SSSIs)

Nine SSSIs are wholly or partly within the PLA’s area of jurisdiction. As would be anticipated, the great majority of this comprises inter-tidal habitats, but additionally the whole of the PLA’s terrestrial estate at Cliffe Marshes and most of that at Allhallows is SSSI, predominantly grazing marsh. Barn Elms Wetland Centre is adjacent to, but outside the PLA's jurisdiction.

The SSSIs and their reasons for designation (as regards the PLA’s jurisdiction) are tabulated below:

Total SSSI area within PLA jurisdiction:  15,531.36 ha (1.7% of England SSSI by area).

Natural England is required to carry out a condition assessment of each unit in SSSIs as a measure of the state of the site with regard to the features for which it has been designated. Units are assessed as being in one of five condition categories: Favourable, Unfavourable Recovering, Unfavourable No Change, Unfavourable Declining, Destroyed/Part Destroyed.  These terms are defined as follows:

Favourable:  the SSSI land is being adequately conserved and is meeting its "conservation objectives". However, there is scope for the enhancement of these sites
Unfavourable Recovering:  SSSI units are not yet fully conserved but all the necessary management measures are in place. Provided that the recovery work is sustained, the SSSI will reach favourable condition in time
Unfavourable No Change:  the special interest of the SSSI unit is not being conserved and will not reach favourable condition unless there are changes to site management or external pressures. The longer the SSSI unit remains in this poor condition, the more difficult it will be, in general, to achieve recovery
Unfavourable Declining:  the special interest of the SSSI unit is not being conserved and will not reach favourable condition unless there are changes to site management or external pressures. The site condition is becoming progressively worse
Destroyed/Part Destroyed:  lasting damage has occurred to all/part of the special conservation interest of the SSSI unit such that it has been irretrievably lost

Assessments have been carried out at various times, and in some cases the available information is some years old. The table below sets out the available condition assessments for those SSSI units within the PLA's jurisdiction, with a summary of the factors affecting condition where this has been assessed as not being favourable.

Summary

Special Protection Areas (SPAs)

Four SPAs are wholly or partly within the PLA's area of jurisdiction. Three of these are predominantly (but not wholly) coincident with the SSSIs, and accordingly comprise a similar range of habitats. The fourth, the relatively newly classified Outer Thames SPA, is entirely marine. SPAs are classified under the EU Birds Directive ('Council Directive 79/409/EEC on the conservation of wild birds') to protect breeding, passage and wintering populations of birds of significance at European level.

Thames Estuary and Marshes SPA

This site is made up of the South Thames Estuary and Marshes SSSI and Mucking Flats and Marshes SSSI. Additionally, the Holehaven Creek SSSI, although not currently classified as SPA provides key habitat for black-tailed godwit and qualifies for inclusion as part of the Thames Estuary and Marshes SPA. This is recognised by Natural England and for practical purposes the site is treated as if already designated.

The principal habitats within the PLA's jurisdiction are intertidal mudflats and smaller areas of saltmarsh, but freshwater and brackish grazing marsh and open water habitats within the PLA's estates at Cliffe Marshes and Allhallows Marshes are also within the SPA.

The reasons for the site's qualification as a SPA and the species involved taken from the SPA review - The UK SPA network: its scope and content. JNCC, 2001 (opens in a new window) - are set out below:

Benfleet and Southend Marshes SPA

This site is coincident with the Benfleet and Southend Marshes SSSI. The principal habitats within the PLA’s jurisdiction are salt marshes, cockle shell banks and mudflats, providing a wide range of feeding and roosting opportunities for internationally important numbers of wintering wildfowl and waders.

The reasons for the site’s qualification as a SPA and the species involved (taken from the SPA review) are set out below:

Foulness (Mid-Essex Coast Phase 5) SPA

This site is coincident with the Foulness SSSI, and is regarded as an integral component of the phased Mid-Essex Coast SPA. The principal habitats within the PLA’s jurisdiction are salt marsh, mudflats, sand flats and cockle shell banks, supporting important populations of breeding, migratory and wintering waterbirds, notably very important concentrations of Dark-bellied Brent Goose.

The reasons for the site’s qualification as a SPA and the species involved (taken from the SPA review) are set out below:

Outer Thames Estuary SPA

This marine SPA was classified in August 2010, and qualifies under Article 4.1 of the Birds Directive as it is regularly used by 1% or more of the Great Britain population of red-throated divers (a wintering peak mean of 6,466 individuals, which is 38% of the GB population). It covers an area of 379, 268.14 hectares. 

Special Areas of Conservation (SACs)

Two SACs (Essex Estuaries and Margate and Long Sands) are partly within the PLA’s area of jurisdiction. SACs are designated under the Habitats Directive (‘Council Directive 92/43/EEC on the Conservation of natural habitats and of wild fauna and flora’) to protect a number of habitats and non-avian species of importance at European level.

Essex Estuaries SAC

The southern part of this large SAC, comprising a large proportion of the Foulness SSSI, including Maplin Sands, is within the PLA’s area of jurisdiction. It is designated for a number of habitats, set out in Annex 1 of the Directive:

Annex 1 habitats that are a primary reason for selection of this site

Estuaries
Mudflats and sandflats not covered by seawater at low tide
Salicornia and other annuals colonising mud and sand
Spartina swards
Atlantic salt meadows
Mediterranean and thermo-Atlantic halophilous scrubs

Annex 1 habitats present as a qualifying feature, but not a primary reason for selection of this site

Sandbanks which are slightly covered by sea water all the time

Margate and Long Sands candidate cSAC

Most of this candidate SAC (which was submitted to the European Commission in August 2010) is within the PLA's area of jurisdiction. It is recommended for designation for a single habitat in Annex 1 of the Directive, namely:

Sandbanks which are slightly covered by sea water all the time 

Ramsar sites

These sites are designated under the International Convention on Wetlands of International Importance especially as Waterfowl Habitat (the Ramsar Convention). As the full name of the Convention suggests there is a principal focus on waterfowl, but other wetland ecological criteria are available including aquatic invertebrate and plant interests. Within the PLA’s area of jurisdiction the boundaries of the Ramsar sites are coincident with the corresponding SPAs (although there is terrestrial habitat within the Thames Estuary and Marshes Ramsar site, outside PLA jurisdiction, that is not within the SPA). Where bird interests are the principal reason for designation there is usually significant correlation between the Ramsar and SPA interests but there may be variance in some instances, either because the Ramsar criteria differ from the SPA ones, or because the data used to justify Ramsar designation cover a different time period to those used for the SPA designation.

Marine Conservation Zones

MCZs are to be set up under the Marine and Coastal Access Act 2009 to protect nationally important marine wildlife, habitats, geology and geomorphology. A collaborative project, Balanced Seas, is working on recommendations for MCZs around south-east England, and it is expected that these will be available in June 2011. Account will be taken of this at the next review of this CMF. 

River Thames & tidal tributaries Site of Metropolitan Importance

Sites of Metropolitan Importance (SMI) are not a statutory designation as such, although nationally or internationally designated sites may be included within the boundaries of SMIs. They are sites identified as being of strategic importance for nature conservation and biodiversity across London (mostly from work published in 1994 by the former London Ecology Unit, now part of the Greater London Authority), and are afforded protection in the London Plan and Borough development documents. See also Planning and Strategic Background section.

The River Thames & tidal tributaries SMI comprises the whole of the river and its tidal tributaries within the boundary of Greater London. As well as the river channel itself, habitats within the SMI include mudflats, shingle beach, inter-tidal vegetation, islands and the river banks.

National Nature Reserve

The Leigh National Nature Reserve

Comprises 257 ha of mainly intertidal habitats, and is entirely within the Benfleet and Southend Marshes SSSI/SPA. It is managed by the Essex Wildlife Trust under an agreement with Natural England under Section 35 of the Wildlife and Countryside Act 1981.

Local Nature Reserves

Local Nature Reserves are statutory sites, designated by local authorities under Section 21 of the National Parks and Access to the Countryside Act 1949. There are three LNRs within the PLA’s area of jurisdiction:

Southend on Sea Foreshore LNR

Comprises 1088 ha of intertidal habitats, lying wholly within the Benfleet and Southend Marshes SSSI/SPA. It was declared by Southend on Sea Borough Council in 1996.

Chiswick Eyot LNR

A 0.82 ha island declared as a LNR by the London Borough of Hounslow in 1993.

Isleworth Ait LNR 

A 3.48 ha island declared as a LNR by the London Borough of Hounslow in 2003.

PLA’s Terrestrial Estate

Cliffe Marshes and Allhallows

These two estates on the Hoo Peninsula, Kent comprise principally grazing marsh and associated habitats. The whole of Cliffe Marshes and most of Allhallows are within the South Thames Estuary and Marshes SSSI and the Thames Estuary and Marshes SPA/Ramsar site (see above). More detail of their management can be found on the PLA website here.

Oliver’s Ait

This is a small island in the London Borough of Hounslow with significant biodiversity interest and potential. It is the subject of a management brief prepared for the PLA by the London Ecology Unit in July 1995, which makes a number of recommendations, most of which have not been implemented (e.g. re improving woodland structure), although some management of the breeding Canada goose population has been undertaken. The PLA currently has a partnership agreement with the London Wildlife Trust in respect of the management of Oliver’s Ait, with a view to a plan being written and signed off during 2011 to improve and maintain biodiversity on the Ait.

Canvey Estate

This is a 80 ha site on the north bank of the Thames, which has been owned by the PLA since the 1930s. 33 ha is an operating industrial area, leased to oil storage operators. The remaining 47 ha is farmland, which is likely to be of low value for biodiversity.

Rainham landfill

The PLA is the freehold owner of 75 ha of land adjoining the Thames at Rainham, in the London Borough of Havering, which was used for river dredgings disposal between 1958-1968, and subsequently for disposal of household waste. The site, with adjoining land in separate freehold ownership, is currently leased to Veolia Environmental Services (Landfill) Ltd. Potential contamination issues were identified in a report to the PLA by Willis Corroon Environmental Division (September 1995). Although the site has some limited current biodiversity interest, a key issue is the future restoration of the site after waste disposal ceases, anticipated to be in 2018. It is intended that the restored site will become part of the London Riverside Conservation Park (the Wildspace project), which includes the nearby RSPB nature reserve. The restoration will be guided by a Master Plan, to be prepared by Veolia under the terms of a Section 106 agreement, in consultation with the PLA, the RSPB and other Wildspace partners. 

Rainham Silt Lagoons

These lagoons were created by the PLA in the 1960s on land then owned by the Ministry of Defence to the north east of the Rainham landfill, with a view to providing replacement capacity for the disposal of river dredgings as the Rainham landfill site became full. Dredgings disposal led to the creation of wet conditions that were favourable for over-wintering waterfowl, notably teal, for which the site was nationally important between the 1970s and the early 1990s. This contributed to the lagoons being included in the Inner Thames Marshes SSSI, which was designated in 1986.

The much diminished use of the lagoons for disposal thereafter led to a rapid drying out and the succession of rank vegetation, with a consequent loss of the over-wintering waterfowl interest, although a locally important Thames Terrace invertebrate community has developed. The RSPB acquired the freehold to the lagoons early in 2009. Natural England has assessed the condition of this part of the SSSI as Unfavourable Declining.

Against this background, the future management of the lagoons is in question, and is the subject of continuing discussion between the PLA, RSPB, NE, EA and Westminster Dredging. More details of the sites management can be found on the PLA website here.

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