Wednesday, 27 May 2015

Havergate Island - adapting to climate change

When the tidal surge of December 2013 hit Suffolk, 1.5 million cubic metres of water poured over the sea walls into Havergate Island, flooding everything bar the tops of the hides and huts.  It is widely acknowledged that the flooding of the island saved other land around the estuary from a similar fate.  Damage was severe to some parts of the walls and it took a month or so to drain out the water to suitable levels. But ultimately, the flooding caused very little damage to the ecology of the island and may even have been beneficial.  Under climate change predictions, such events will increase in the coming years.  So where do we go with Havergate in the future?

Havergate Island used to be 'Avocet Island' but although large numbers of Avocets still feed on the lagoons, very few now breed.  In recent years the complex of saline lagoons on the island have been colonised by 1000s of pairs of Lesser Black-backed and Herring Gulls.  Now, nice as large gulls are, they have the potential to all but eliminate smaller 'seabirds' (gulls, terns and waders) by their sheer density of occupation and their habit of predating the chicks. Whereas 20,000+ pairs of LBBG used to nest in the adjacent Orfordness, a rapid decline to just a few hundred has occurred due to predation by Foxes and disturbance.  Evidence from colour-ringed birds shows that these displaced Orfordness gulls now nest widely.   There were 2,070 pairs on Havergate in 2014. Although the gulls may be squeezing out the Avocets, the island is still favoured by Spoonbills and in other locations they are quite happy to nest amongst large gulls.

The surge tide damage to the island has now been repaired. The section of wall that was all but washed away has been re-built but is now slightly lower and re-profiled.  The aim is to lower and re-profile further sections of wall and install more water control sluices.  The lowering and re-profiling will allow future surge tides to flow in more smoothly without damaging the walls, so will both reduce repair work and maintain the wider flood defence benefits of allowing the island to flood.  The additional sluices will allow quicker discharge of the floodwater to restore optimum water levels.  The island will be managed for wintering and passage waterbirds, breeding gulls, Spoonbills and specialist lagoonal invertebrates such as the Starlet Sea-anemone.  But what of the displaced Avocets?

On the ‘mainland’ of Suffolk the aim is to ‘roll back’ and create new freshwater and brackish lagoon habitat behind the seawall.  The project at Hollesley (as previously described) is already highly productive for breeding Avocets and other waders.  New areas are also being planned at nearby Boyton to add to the existing wet grassland habitat.  The aim is to adapt to climate change, where possible providing benefits both for wildlife and for people at the same time.

Photos: above: Havergate aerial, just after the surge, Avocets in a fluster.
Below: damaged sea wall, Starlet Sea-anemone, Hollesley aerial.


Chris McGregor said...

Are you still blogging Grumpy? I have found your posts very useful and entertaining. Hope all is OK.

Grumpy Ecologist said...

Very kind of you. Just been very busy recently! Will return soon.

Julian Merson said...

I've just found your site. Fantastic. I particularly like this post on Havergate Island. I write my own sailing blog: I was wondering whether you would mind me using your aerial view of the Island in my blog - with appropriate acknowledgement, naturally. It's fascinating seeing aerial views of locations I have frequently anchored alongside, and often wondered what went on over the marsh wall.

Grumpy Ecologist said...

Hi Julian, thanks for your comments. Great pics on your blog! If you use the aerial shots please credit 'RSPB'