On the loss of saltmarshes in south-east England and the relationship with Nereis diversicolor
R. K. A. Morris, English Nature, Northminster House, Peterborough PE1 1UA, UK (e-mail: Roger.Morris@English-Nature.Org.UK).
- 1Two papers, Hughes & Paramor (2004) and Paramor & Hughes (2004), published in Journal of Applied Ecology are discussed. These papers suggest that saltmarsh erosion is linked to bioturbation, and concentrate on the role of the ragworm Nereis diversicolor. The authors also suggest that new saltmarsh will not develop in realignment sites because bioturbation will prevent the establishment of saltmarsh plants. We dispute their analysis and offer evidence that inferences derived from their experimental work are erroneous.
- 2Experience from the current range of managed realignment sites in the UK shows that saltmarsh communities are developing, and include the lower marsh Salicornia communities that they suggest are vulnerable to the effects of bioturbation and grazing by N. diversicolor.
- 3Further evidence of the benefits of managed realignment, even in situations where realignment sites lie below existing seaward mudflat levels, is provided by the saltmarshes that developed on sites that were not re-enclosed after the 1953 flood in eastern England.
- 4We highlight the importance of maintaining positive sediment budgets in order that saltmarshes may continue to adjust to sea level rise and to ensure that sufficient sediment exists to allow realignment sites to warp up to levels at which pioneer saltmarsh may develop.
- 5We also draw attention to a range of initiatives that seek to maintain sediment levels within estuaries in south-east England, and highlight the broader conceptual approach that looks upon dredged sediment as an important resource and not a waste material. None of these is designed to change permanently the estuarine tidal prism, as suggested by Hughes & Paramor (2004).
- 6Synthesis and applications. We present evidence to show that coastal realignment is effective in managing and reversing saltmarsh erosion. We dispute the conclusions presented in the recent papers by Hughes & Paramor (2004) and Paramor & Hughes (2004). We suggest that infauna play an essential role in saltmarsh ecology and that N. diversicolor does not play a destructive role in saltmarsh establishment. In the broader context of coastal management, the long-term benefits of managed realignment in sea defence and in delivering nature conservation benefit are quite clear. Sustainable sediment management will play a key role in sustaining saltmarsh habitats in the future.