From: Planet Earth Online, by Adele Rackley
A new approach to assessing coastal management strategies could give us a much more accurate picture of the long-term costs and benefits than has previously been possible, say scientists.
Salt marsh in Salcott Creek, Blackwater Estuary.
The new process applies a price to the benefits these coastal zones give us – be it biodiversity or recreational space – through a carefully defined sequence of steps. It also takes account of the specific characteristics of each site as well as the effects over a wider geographical area and longer timescale, whereas previous approaches have taken more of a 'one size fits all' approach.
Applying an economic value to these ecosystem services allows planners to take them into account in a measureable way, alongside the easily quantifiable aspects like land value and sea-defence construction costs.
With the world's coasts increasingly threatened by erosion, silting and sea-level rise resulting from natural and man-made changes in the environment, finding economically viable ways of managing these valuable resources is increasingly urgent.
To find out how their process might work, the researchers tested their process on 'managed realignment' (MR) schemes, which deliberately breach existing sea defences to flood the land behind and restore salt marshes. As well as the obvious benefits to biodiversity and recreation, the marshes provide a more sustainable flood defence as they help to dissipate wave energy.
The UK has been losing its salt marshes through something called coastal squeeze, where inter-tidal zones are gradually squashed between rising sea levels and defensive sea walls.
'MR is controversial because it sacrifices previously reclaimed land, usually agricultural,' explains Dr Tiziana Luisetti from the University of East Anglia, who led the study.
So these costs and benefits have to be carefully weighed up for policy-makers to be certain it's a good way forward in the long term.
I could see exactly how the numbers matched up with what people had said to me.
Dr Tiziana Luisetti, University of East Anglia
In their study the researchers, from the University of East Anglia and Queen Mary University, London, used models to apply their system to MR schemes in the Humber and Blackwater estuaries on the east coast of England, an area prone to major flooding. Their findings are published in Ocean and Coastal Management.
They took into account the precise characteristics of individual MR areas, which allows much more detailed prediction of the effects of the schemes across a wider area.
'You can't assume that MR is good everywhere for ever,' says Luisetti.
'We also took account of non-linearities – where a change doesn't necessarily lead to the effect you would expect. For example, if a MR scheme brings benefits at a certain scale, you can't assume that increasing the scale will increase the benefits in direct proportion,' she continues.
A key feature of the new method is its avoidance of 'double counting', by separating out the ecosystem services from the benefits they provide. For example, a wetland can provide a service by storing pollutants, which consequently provides the benefit of cleaner water for downstream users such as recreational anglers. To avoid double counting it is only legitimate to quantify the value of the anglers' benefit.
Separating out these aspects gives a more realistic idea of the total 'benefit' derived from different aspects of the ecosystem.
The team then interviewed different groups of people, including students, retired people and commuters, to find out how much more council tax they would be prepared to pay for the recreational use of restored salt marsh. By using a sophisticated questionnaire they were able to derive deeper insights into people's motivations and to more accurately compare their general perceptions and feelings with the detailed data collected from a sample of around 1000 people.
'It was so interesting to know what people were thinking when they made their choices' says Luisetti, 'and once we'd run our models I realised how well the numbers matched up with what people had said to me.'
The results showed that MR schemes were efficient for both the Humber and Blackwater estuaries, but only at carefully selected sties. Interestingly, MR schemes in the Blackwater were economically efficient across all time periods but for the Humber this was only the case over the longer term.
Following this new method should give a much more accurate and site-specific prediction of the benefits of MR schemes in different areas. The researchers point out in their paper that it's not appropriate to simply assume that MR schemes will be economically efficient across similar sites in a different estuary.
Tiziana Luisetti, R Kerry Turner, Ian J Bateman, Sian Morse-Jones, Christopher Adams, Leila Fonseca. 2011. Coastal and marine ecosystem services valuation for policy and management: managed realignment case studies in England. Ocean & Coastal Management, 54, 212-224
