Jim Densham, Senior Land Use Policy Officer with RSPB Scotland, gets us up to speed with the wonders of mud.
Glorious Mud – homes for nature, protection for people
In February 2003 mechanical diggers broke two large holes in the sea wall at RSPB Scotland's Nigg Bay reserve in the Cromarty Firth and flooded the land. But, this wasn’t a case of wanton vandalism, this was Scotland’s first ever managed coastal realignment project to restore saltmarsh – a habitat rapidly disappearing beneath the waves.
We have much less saltmarsh and intertidal habitats (the wet muddy bits) around our coasts than we used to have 200 years ago. In the past, many areas were walled in, drained and used for agriculture – this is what happened at Nigg Bay. If you look at the Ordnance Survey map from 1872 the project site, known as ‘Meddat Marsh’, was marked as marshland and mudflats with the description ‘liable to floods’. In the 1950s an embankment was erected to keep the sea out and the resulting field was used as grazing land.
Other areas of our coastal saltmarsh have been developed for industry or homes – think of the huge Grangemouth complex on the Forth or the oil terminal and fabrication yard just round the corner in Nigg Bay. More universally threatening is sea level rise, squeezing saltmarsh habitats by lessening the space for them between the tide and hard defences – a situation which will only get worse. Between 1946 and 1997 Nigg Bay lost 36 per cent of its intertidal habitats.
This week we published on our website a report about the success of the realignment project at Nigg Bay and the importance of it for wildlife and people; we also posted a video online. In the same week that the tides were allowed back onto Wallasea island in Essex as part of a huge new RSPB managed realignment project, it’s good to look at the success at Nigg Bay and what might happen on the Essex coast in the next decade.
Ten years after the tides returned the whole field has changed from grassland to saltmarsh and mudflat increasing the area of saltmarsh in the whole of Nigg Bay by 30 per cent. The colonisation of the site by saltmarsh plants and mud-dwelling invertebrates (snails, worms and shrimps) via the tides has been quicker than expected.
It goes to show that making space for the sea in this way allowed nature to come back in quickly and recharge the habitat. The success has been there for water birds too. In the first winter after the breach, three waterbird species used the site but this jumped to 19 species in the second winter and now stands at 25 species. On occasions, the site becomes internationally important for bar tailed godwits as well as a favoured area for whooper swans, scaup and redshank.
Perhaps the greatest value of the new saltmarsh area is that it is one of the last areas in the whole of Nigg Bay to be covered by seawater on the incoming tide. It provides birds with valuable extra space and time for feeding as the tide comes in and safe roosting areas at high tide. During windy conditions and in high spring tides it is an essential refuge for up to 2,000 waterbirds.
So a resounding success for birds but what about for people? Sea level rise is inevitable even if we turn off our carbon pollution today, so flooding remains a risk for land, property and life near our coasts. Moving sea defences inland and allowing saltmarsh to buffer them reduces the cost of building and maintaining those sea defences or embankments. Saltmarsh reduces the power of waves as they roll in from the sea and therefore makes them less destructive during storms.
Scotland’s first ever managed realignment project has been a success. More managed realignment projects are needed around our coasts to recreate essential saltmarsh habitat for birds and for communities in the face of sea level rise and extreme storm threats. This is what we will be telling Government and local authorities in the coming months and using our Nigg Bay reserve as an example of how it can be done and the difference it can make.