Coastal wetlands at greater risk from man than from sea level rise

30 December 2013


Coastal wetlands can cope with sea-level rise, providing man allows them to (Photo: Bill Harding)

While man is deemed to be  the most intelligent life form on earth (debatable but there it is…), man also is responsible for wilfully destroying the environment of this sphere that we live on.  This assault on our natural capital is particularly, but not exclusively, relevant to the ecosystem services provided by coastal wetlands.

A recent article in Nature reveals that while coastal wetlands have in-built mechanisms to allow them to compensate for rising sea levels, they cannot attenuate the impacts of land-based and marine eutrophication (nutrient enrichment) and, obviously, physical impacts from development – the latter including the reduction in transport of sediments to wetlands.  Authors Kirwan and Megonigal observe that “…observations of wetland drowning are infrequent because of the fascinating interactions between plants and soil that allow wetlands to actively engineer their position within the intertidal zone in ways that enhance ecosystem persistence“.

Phosphorus! food iconThis ability to compensate is, inter alia,  affected by man’s manipulation of wetlands (or their proximal environments), developing too close to them – precluding their ability to expand landwards and the ever-increasing scourge of eutrophication – which alters wetland plant communities and cripples their capacity to cope with changing water levels.  As Droplets has stated, ad nauseum, local and national efforts to attenuate nutrient enrichment of vital land and marine water resources is abysmally inadequate.  This is true for South Africa and many other countries.  The central argument against doing anything meaningful remains the issue of costs – blindly ignoring what the future costs will be once we approach a threshold of loss of ecosystem functioning that will irrevocably threaten man’s very existence on this planet.


Regretfully the true value of wetland ecosystems remains elusive – with “economic” evaluations leaving much to be desired – if it is indeed possible to value priceless ecosystems that have taken millennia to develop (but who said man is not arrogant in his presumptive ability to manage nature?).  Kirwan and Megonigal conclude that “Coastal population growth and accelerating rates of sea-level rise will intensify the tight interactions between society and coastal wetlands.  The effect of decisions that determine how governments and landowners conserve wetlands and defend uplands from rising seas may dwarf the effects of sea-level rise alone“.

IMG_8620Droplets Viewpoint: The bottom-line is that all too little is known about how these complex environments operate to presume to be able to ensure their longevity and functionality against the challenge of socio-economic development.  A lot of what poses as wetland science, often associated with EIA assessments, is naive and based on a very limited understanding of complex and interlinked ecosystem processes.  Humans, as a collective, do not yet adequately appreciate the value of wetlands.  Wetland scientists still have a lot to learn!



Source: Tidal wetland stability in the face of human impacts and sea-level rise. Kirwan ML and JP Megonigal.  Nature Vol 504:53-60.

Leave a Reply

Your email address will not be published. Required fields are marked *