Wetland rehabilitation far from easy and not for the fainthearted…or ‘bankers’

27 January 2012

Wetlands are a product of their position in the landscape, and hundreds of years of development! (Photo: Bill Harding)

A recent study has reached a conclusion that wetland ecologists have known for a long time, namely that it is very difficult to re-create, restore or rehabilitate a wetland that even closely resembles what nature put there in the first place.  Wetlands are seriously multi-functional environments, their function is, in essence, derived from their complexity.  Those who think fully-functional wetlands can be rebuilt in a few years, as opposed to nature’s nurturing over hundreds, suffer from what I have long-termed ‘ego-system’, as opposed to ‘ecosystem’, management.

Wetland restoration is a billion-dollar-a-year industry in the United States that aims to create ecosystems similar to those that disappeared over the past century.  But a new analysis of restoration projects, shows that restored wetlands seldom reach the quality of a natural wetland.

“Once you degrade a wetland, it doesn’t recover its normal assemblage of plants or its rich stores of organic soil carbon, which both affect natural cycles of water and nutrients, for many years,” said David Moreno-Mateos, a University of California, Berkeley, postdoctoral fellow. “Even after 100 years, the restored wetland is still different from what was there before, and it may never recover.”

This finding supports one of the long-standing criticisms of ‘wetland mitigation banking’, a concept provided for many years ago in the USA’s laws governing wetland regulation (the Comprehensive Wetlands Conservation and Management Act of 1995).  According to this Act, mitigation banking is “wetlands restoration, enhancement, preservation or creation for providing compensation for wetland degradation or loss“.

Its is important to note that officials and specialists in the USA grappled for years to provide a comprehensive set of tools and methods and policies for wetland protection – most of which are of globally generic value.  An equally-generic limitation of these tools has been their largely technical nature – i.e. they do little to provide anything close to realistic assessments of true wetland values.  In some cases these tools have been of so arbitrary a nature and so subjective in their application, that their use has sustained wetland loss, rather than reverse it.  In countries like South Africa, instead of moving on from these available solid assessment basics, to the integration of regional and sub-regional specifics, the wheel was simply reinvented so that, bizarrely, we in this country have wetland evaluation techniques prefaced as WET- this and that, entirely similar to one’s that existed in the USA a decade or so before.  We have not moved forward an inch!

But I digress…

The concept  of mitigation banking is basically an offset system, but where it went wrong is for cases where “new” wetlands were allowed to be “created”, so that natural wetlands could be filled in for development.  The Act defines ‘Creation’ – not in the biblical sense but as “an activity that brings a wetland into existence at a site where it did not formerly occur for the purpose of compensatory mitigation”.

The intention of mitigation (for wetlands other than those already irretrievably degraded) is to:

  1. avoid adverse impacts
  2. minimize those adverse impacts that cannot be avoided and to
  3. compensate for any loss of wetland functions that cannot be avoided or minimized.

Where mitigation banking does have value is where properly funded and managed sites restore degraded systems.  I am currently directing a project where long-lost wetlands converted to dams will now see the dams removed and the water used to re-create a wetland last seen over 100 years ago.   Hopefully what we put back will still be there in 100 years time!

The Berkeley study found that from an assessment of 621 (!) sites,

show(s) that even a century after restoration efforts, biological structure (driven mostly by plant assemblages), and biogeochemical functioning (driven primarily by the storage of carbon in wetland soils), remained on average 26% and 23% lower, respectively, than in reference sites. Either recovery has been very slow, or postdisturbance systems have moved towards alternative states that differ from reference conditions. We also found significant effects of environmental settings on the rate and degree of recovery. Large wetland areas (>100 ha) and wetlands restored in warm (temperate and tropical) climates recovered more rapidly than smaller wetlands and wetlands restored in cold climates. Also, wetlands experiencing more (riverine and tidal) hydrologic exchange recovered more rapidly than depressional wetlands. Restoration performance is limited: current restoration practice fails to recover original levels of wetland ecosystem functions, even after many decades. If restoration as currently practiced is used to justify further degradation, global loss of wetland ecosystem function and structure will spread.

The key finding here is that restoration practices are probably based on the wrong approaches, i.e. too much reliance on assessment systems that try to place a value number or category (A-F for example), on a natural ecosystem.  There is a greater need for informed ecological input, expert judgement if you will, rather than spending so much time and money trying to dumb science down to valuation protocols that can be applied by the untrained and inexperienced!  This is why we keep moving backwards.  “Wetland Assessment For Dummies” is not a title we need to see!

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