Environmental Engineering Reference
In-Depth Information
along the Murray, but increased nutrients in the Mississippi. In these situations
it is difficult to decipher the principal causative agent of change.
Regional integration
A better understanding of the nature and timing of wetland changes more
widely may emerge from the integration of site studies into regional databases.
This is occurring for lake studies across Europe with the compilation of
the 'Euro-limpacs' database (Battarbee et al.
2007
). Within Australia the records
of limnological change are being integrated within the OZPACS network
(Fitzsimmons et al.
2008
) that is integrating multiple palaeoenvironmental
records to understand human impact on ecosystems across the continent.
It is becoming clear that, relative to the pre-industrial baseline, most wetlands
across southeast Australia are impacted to a moderate to serious level and
are in states unprecedented in their history. Most changes can be most easily
attributed to catchment change inspired by agricultural development but
direct hydrological change, through drainage schemes and inter-basin transfers,
are also implicated. In many instances, the degraded nature of the wetland
was not fully recognised and only revealed from sediment-based approaches.
Were the acid test of 'good ecological condition' from the WFD applied to this
region then no wetland would conform. Further, given the critical economic
importance of the MDB to Australia's gross domestic product, it would be likely
that the derogation clause would be invoked in this hypothetical scenario
and managers would be directed to merely 'work towards' good condition. In
the Mississippi River lakes, where degradation of condition was identified and
mitigation measures put in place during the twentieth century, such impro-
vements are already evident. Here too, as evident in the record of mercury
accumulation in the lake's sediments, the path to restoration can be followed
by reference to the long-term baseline available in the sediment record.
Which baseline?
Clearly, within the MDB and the Mississippi River, wetlands and rivers are
severely impacted. Also, in both regions, it is clear that the changes to this
impacted condition occurred early in the development of industry. In these
neo-industrial landscapes, these sediment-based records of the nature and
timing of change make a powerful contribution to the understanding of the
challenges for restoration. It is not unreasonable for society, armed with the
knowledge that a wetland was 'naturally' in better condition than anecdote
or Ramsar listing would lead us to believe, to demand that action be taken
to return it to its original condition even if that was 100 years ago. The longer
sediment record, however, poses higher questions of the appropriate baseline
to be used as a restoration target. In environments with longer settlement
histories such as Denmark it is clear that even very early industry had an
