Managed realignment in the UK – the first 5 years of colonization by birds

Abstract

With current losses of saltmarsh running at > 100 ha per year in the UK, creation of new intertidal habitats through managed realignment is likely to be increasingly used. Potentially, this has biodiversity as well as engineering benefits. However, assessing the conservation value of many of the current UK schemes is difficult as the biological monitoring has been generally poor, with a few notable exceptions. At the Tollesbury and Orplands realignment sites, Essex, bird communities were dominated by terrestrial species during the first year of inundation and waterbird communities rapidly developed during the second and third years. Five years after the initial breach in the sea wall, communities were similar to surrounding mudflats but with some notable exceptions. Dunlin Calidris alpina and Common Redshank Tringa totanus that prey on the early colonizing Nereis and Hydrobia used the sites in the first 2 years. Eurasian Oystercatcher Haematopus ostralegus did not occur on the realignment site as there were no large bivalves, whereas Red Knot Calidris canutus used the site after 4–5 years coincidentally with the appearance of Macoma balthica. The differences in the bird communities occurred because UK sites are often small, enclosed and poorly drained. If at a suitable height in the tidal frame, UK managed realignment sites are successful in that they have developed saltmarsh and biologically active mudflats but they may lack the full range of biodiversity found in surrounding natural intertidal habitats, even decades after inundation.

Travelling through a warming world: climate change and migratory species

“…Coastal habitats have long suffered from human use (Lotze et al 2006), and existing habitat will be further threatened as it is increasingly squeezed between rising waters and the land, especially where it is protected by 'hard' man-made defences (Atkinson et al 2004). Replacement habitat is unlikely to be extensive (and may take many years to develop), as low-lying areas often provide the most fertile agricultural land and are home to millions of people.…”

“…Very little is known about the migratory behaviour of invertebrates; most attention has focussed on pest species, or the charismatic Lepidoptera, although most groups, particularly larger insects, cephalopod molluscs and marine crustacea, have representatives that can be considered migratory. 7: 87-99, 2009 waterbirds (Rehfisch et al 2004) and of, already scarce, haul-out sites that seals use for breeding, nurseries and resting (Baker et al 2006). In the Arctic and Antarctic, the predicted substantial contraction in sea-ice cover will reduce the breeding and feeding habitat of species such as seals and polar bears Ursus arctos in the Arctic (Barber & Iacozza 2004) and seabirds in the Antarctic (Croxall et al 2002).…”

“…In contrast, 'managed re-alignment' of coastal defences, selectively allowing sea-defences to be breached to create a new land -sea interface, has the potential to create habitat. Although plant and invertebrate communities are slow to respond to such habitat creation, near-natural assemblages of more mobile species, such as migratory birds and fish, can be restored in remarkably short periods of time (Atkinson et al 2004).…”

Ecoengineering with Ecohydrology: Successes and failures in estuarine restoration

“…Ecological success is often measured in the size and type of habitats re-created or restored (e.g., size of intertidal mudflat) against the targets (if any) set by the developers or nature conservation bodies. The functional capacity of created intertidal habitats to mimic the ecological roles of nearby natural sites is a better indication of success and is widely used to evaluate success in restoring saltmarshes (Mossman et al, 2012), invertebrate communities (Mazik et al, , 2010 and estuarine bird communities (Atkinson et al, 2004, Mander et al, 2007.…”

Saltmarsh Conservation, Management and Restoration

“…Accretion rates were high averaging 23 mm per year, ranging from 8 mm to 258 mm. Four years after inundation, the bird populations were still evolving (Atkinson et al 2004). By October 2002 ( Figure 51) the vegetation consisted mainly of Invertebrate colonisation of the site was rapid, with 14 species recorded after only two months of tidal inundation and between 18 and 19 species, thereafter with the number remaining constant.…”