One thing is clear from the past two years leaving the beach unmanaged, Spartina anglica is taking a strong hold, it's a salt marsh perennial, non native and highly invasive grass.
Saltmarshes are not simple ecosystems, a lot of thought needs to go into the pros and cons of salt marsh development, and that doesn't seem to be happening enough. Sand engineering as the alternative on Hoylake Beach would also need researching.
Scientific research into the exchange of GHGs ( greenhouse gases) between the atmosphere and salt marsh ecosystems is known as ‘flux’.
Recent studies in China, USA and very recently in Japan have shown unexpected results about CO2, CH4 & NO2 emissions.
Unfortunately, the UK is lagging behind in researching the carbon cycle of saltmarshes.
The United Nations Environment Programme World Conservation Monitoring Centre (UNEPWCMC) based in Cambridge still advocates the benefits of saltmarsh for biodiversity, and its function serving as a nesting nursery and feeding ground for numerous species of birds, fish, molluscs and crustaceans, some of which are endangered species. It also notes that saltmarshes are a potential source of GHG, if disturbed.
The exact amount of blue carbon stored in saltmarsh ecosystems is still an active area of research, and GHG emissions from salt marsh is also under- researched especially in this country. They are only just realising more studies are needed on coastal eco system emission risks.
UNEPWCMC in their Marine Ecosystem Series section say:
"This report builds on these and other efforts to bring to light the important sequestration potential of coastal wetlands and the significant and largely unaccounted for GHG emissions resulting from disturbance, drainage and conversion of these natural coastal carbon sinks for agriculture, tourism and other coastal development."
So, it’s not straightforward and management is very important to monitor all risks and look at the carbon balance in the habitat, alongside assessing social and economic impacts as well as environmental and social safeguard risks.
The large salt marsh at Neston could benefit from some flux data research to help inform decisions taken for North Wirral Foreshore.
The UN Climate Change Conference (COP26) will be held in Glasgow from 31 October-12 November. This will be where more data will appear relevant to decisions made in 2022 for our beach area. New scientific evidence is emerging, which is more relevant to our area.
The photo below shows brown Spartina, when it's dormant (not growing) during the winter season which is when new studies have discovered higher emission levels, not picked up in previous data taken during the summer.
Spartina is a pioneer plant for marsh development. Initially it grows vigorously, during its growing phases it stores carbon. When it’s not growing in the cold months it gives off CO2 & methane. After it's vigorous growth as the marsh accumulates more sediment other plants then become established . At this point its growth slows and then it becomes susceptible to dieback, where vast swathes of it just die off. This causes collapse and breakup of the plant and a loosening of the roots and sediments, thus allowing longer periods of GHG emissions .
'Die back' appears to be part of its natural cycle. So we would expect this to happen at Hoylake . Recent flux results coming from towers erected in saltmarshes in China, the carbon storage benefits are shown to be greatly compromised by Spartina’s instability and dieback GHG emissions.
Early stages to die back
The report with the graph below shows the different stages:
Green grass =s Co2 sink when the grass is growing.
Brown grass ==s GHG emissions when grass the is dormant or starting to die. (dieback)
Report Abstract: Salt marshes are large carbon reservoirs as part of blue carbon ecosystems. Unfortunately, there is limited information about the net ecosystem (NEE) and methane (CH4) exchange between salt marshes and the atmosphere to fully understand their carbon dynamics.
Reference:
Authors: Alma Vázquez-Lule, Rodrigo Vargas,
Biophysical drivers of net ecosystem and methane exchange across phenological phases in a tidal salt marsh,
Agricultural and Forest Meteorology,
Volume 300,
2021,
108309,
ISSN 0168-1923,
https://doi.org/10.1016/j.agrformet.2020.108309.
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