Abstract from BTO Research Report No 331:

Banks, A.N., Burton, N.H.K., Musgrove, A.J. & Rehfisch, M.M. (2006)

Lappel Bank and Fagbury Flats Compensatory measures Site Suitability for Waterbirds: Phase I Extension.
ISBN: 1-904870-82-1

Executive Summary

1. Lappel Bank and Fagbury Flats held important numbers of feeding and roosting waterbirds prior to port development, which was completed in 1994/95. Under the EU Habitats Directive, compensatory measures are to be provided to accommodate birds displaced by the developments. In this report six candidate sites are reviewed as potential replacements for the loss of habitat. Three sites lie on the Blackwater Estuary, two on the Crouch-Roach Estuary, and one on the Swale Estuary.

2. Possible numbers of waterbirds attracted to replacement sites are predicted using BTO and WeBS datasets. These predictions are used in conjunction with adjacent area bird densities and other site information, including geographical and ecological variables, to assess the suitability of the six sites as compensatory areas. The approach used to make these predictions does not take into account site-specific hydrological or morphological variation.

3. To make a preliminary assessment of the value of the proposed sites and their ability to compensate for losses at Lappel Bank and Fagbury Flats, the predictions of bird numbers are compared against the following two provisional waterbird abundance compensation targets:

• Target 1 - The number of birds recorded feeding at Lappel Bank and roosting at Fagbury Flats prior to completion of port developments.
• Target 2 - Number of feeding birds only at Lappel Bank and Fagbury Flats prior to completion of port developments.

4. According to this preliminary analysis the six candidate sites will support between 16% and 35% of the compensation target for feeding and roosting birds and 31% to 66% of the target for feeding birds alone, based on predicted mean values. Maylandsea consistently represented the best location overall and is estimated to support 35% of feeding and roosting birds, and 66% of the target for feeding birds only, whilst Weymarks and Nagden Marshes may support 29% of the target for feeding and roosting birds, with an estimated fulfilment of 54% of the feeding birds target. The latter two sites are more exposed and may be subject to sandier sediment and thus reduced infaunal biomass, which may make it less likely that they will reach the predicted percentage of these targets. Low densities of waterbirds on the adjacent parts of the Crouch-Roach suggest that both Wallasea options may not meet their predicted percentage of the targets, whilst Mell Farm is only predicted to hold 16% of the feeding and roosting target, and 31% of the feeding birds target.

5. When the final preferred compensation sites(s) is/are identified it is recommended that further detailed simulation modelling be carried out, to ensure that the number and range of waterbird species displaced through the loss of Lappel Bank and Fagbury Flats can be compensated for by the short-listed compensatory site(s) over a period of at least 50 years.

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