QUESTION SUBMITTED LIVE:
Not a question but just to share: RSPB sustainable shores project: https://www.rspb.org.uk/our-work/conservation/projects/sustainable-shores/ of relevance to saltmarsh
Thanks for that Emily. Yes, i had heard about that sustainable shores project. I like it.
@Martin (Saltmarshes) - Could you use rates of sediment supply and sea-level rise etc. to produce 3D numerical forward models to simulate the rate and spatial distribution of saltmarsh backstepping?
Yes, exactly, you can do that. It's really interesting idea and we've been playing a bit with it. Mainly, marshes responde to a certain elevation level and if sediment supply gets the substrate to that elevation, then marsh plants will colonise it (unless hydrological forcing is too great, of course).
@Martin, how much of the change in salt marsh size is linked to poor land management upstream, and increased erosion of terrestrial soils? If we factor in improved catchment management what might we expect to happen in salt marsh?
That is a good quutestion, which is a bit more difficult to answer for Wales, and the UK, as we have only looked at this indirectly. The East coast of the USA, this is an extremely relevant question (marshes tehre wouldn't be as big as they are, had it not been for catchment disturbance of land which injected sediments into the coast, for marshes to grow on). We've looked at sediment load in rivers and not found any strong correlation of marsh area changes with that across the UK. It will be most important in the south-east. Here in Wales, and much of the west coast, we have inwelling of post-glacial sediment supplies, and my feelign is taht present day changes of marshes are less driven by terrestrial runoff.
Martin - can you clarify your comment about cattle and redshank please. I assume that is the physical impact during the breeding season not impact on habitat so it is not cattle per se but timing of cattle being present/
Neil. Nice question. There are at least two ways in which grazing can affect redshank breeding success. First, there is the direct nest trampling. Elwyn Sharp's work has shown that even very light livestock densities causes nest mortality, and in a futher paper he shows that is because livestock movement concentrates in the same areas as nest preferences for redshank (cattle also prefer the type of vegetation that redshank like to nest close to). In addition, grazing opens up the landscape, so there is a very strong increase in nest predation. Basically, grazing, even at low levels, open up the access to predators. You should check Elwyn Sharp's papers (in reference list at the end of my Powerpoint - if you get stuck, email me from my Bangor University address).
Really interesting presentation Martin. What do you think the marine plan could do more of to support managed realignment/saltmarsh expansion?
Hi Clare. That is a really nice question which is not an easy one to answer, so i'll give a relatively superficial answer to it. I think we should be looking for easy wins - Perhaps smaller scale managed realignment opportunities, that don't require large budgets. I'm all for an opportunistic approach, which is perhaps less easy to build into the marine plan. I think we need to also think on the very large scales about what we want. Of course, that's what planning is all about, but what i mean is: which marshes and which regions are important for delivering which ..elements (services and other) that we need and want to deliver. Take SMPs as an exemplar: for some issues and services it's sensible to think about a network of sites, for others it will only be certain key sites that we want; do we want many small ones, or a few large ones? The answer to that depends very much on the services in question, right. AND, we need to understand what leads to the delivery of different services. For instance, take recreational use of marshes; during lockdown we've seen how some sites (e.g., Snowdon) become hotspots where people want to go. We need to understand more about how the spatial distribution of sites relate to peple's interaction with them, and what drives that choice that people make.
Oh, and i should have mentioned the word 'connetivity' there: how marshes link up and how marhes link up to other habitats, for wildlife habitat, flood protetion, the provisioning of recreational space, the works.
Cara Wilson, Llais y Goedwig , South West:
thank you all, very interesting presentations.
I work as a groups support offcer for Llais y Goedwig - community woodlands in Wales - perhaps other projects might mention the part coastal woodland may play? I am just here in case!..
I think that's a good point Cara. I think we don't always have enough consideration for how habitats link up, and how that affect restorational successes. CHeck Cwm Ivy, if you haven't already. There is a beautiful example of how the shore enviormment link up with coastal woodland, in a beautiful continuum, which is crucial to some wildlife, and is also very attractive to human recreation.
How do we promote managed realignment to communities whose natural responses to global sea-level rise and increased storm surges is to build even higher walls ?
As mentioned in the talk itself, i think that is a crucial question to ask, when we come to roll out managed realignment. Key is to showcase the good stories emerging from managed realignment (e.g., search for accounts of the managed realignment site at Medmerry in south England. You can also start with this publication, and go from there, which particularly exemplifies successes, and failures, in a Dutch/Belgian setting: https://www.researchgate.net/publication/259200820_Ecosystem-based_coastal_defence_in_the_face_of_global_change)
Question for Martin Skov - you mentioned, given space, marshes can adapt to Climate Change - are they showing they can adapt to the speed of Anthropogenic Climate Change, if space is made available?
Yes, we have quite good and convincing evidence of that now: marshes can keep pace IN NATURAL CONDITIONS. Even in a 'step-change' scenario wtih sea-level rise - of course, up to an extent, but with the current predicted levels of relative sea level rise by teh end of the centuary, marshes can keep pace. Things that diminish marsh ability to keep pace is marked reductions in natural sediment supply (a global problem tied to anthropogenic activity), subduction of land, etc. I think, with the current predictions for sea level rise, the key question is not whether marshes can grow vertically in pace with sea level rise, but whether they will have land up-shore to move on to. They need that, but often we have dikes, sea walls or even natural topography blocking the way: coastal squeeze is the big worry.
Martin - I may have misunderstood the point you were making about the North South divide. Published data eg ONS and SCAs state net loss of salt marsh across UK countries not justS England. Are you saying your data is contrary to this?
The north-south divide is, of course, punctuated: within every region in the UK, you can find marshes that are expanding and marshes that are eroding. The study i referred to looked at very long time scales - much longer than any other study: we went back to the mid 1800s. Since that time, marshes have been expanding. Even in areas like the SOlent, where there is much current concern about marsh loss, we actually have more marsh area than we did in the mid 1800s. The current estimate we have of net changes to marshes are strongly driven by marshes in the south east. Now, some of the larger marshes occur there, but for much of the rest of the UK, we have actually seen an increase in marsh area.