Dr Glen Walker is the 2001 winner of Australia's most prestigious accolade for innovation in salinity research and development - the National Dryland Salinity Program's WE Wood Award. This precis is an extract from the 2001WE Wood Memorial Lecture, presented by Dr Walker in Perth in late 2001.

Not seeing the Wood for the trees

Now nearly 80 years old, Walter Ernest Wood's landmark paper 'Increase in Salt in Soil and Streams following the Destruction of Native Vegetation (1924)' is remarkable in its clarity of understanding some seventy to eighty years ago of the processes leading to dryland salinity.

This long-term understanding seems at odds with my experience in the area of recharge research, in which a lack of understanding of the impacts of land use has led to inappropriate action.

In the late 1970s it was thought that increased recharge and hence salinity could not occur in semi-arid areas such as the Mallee, a thought which we now realise was incorrect. In the United States, similar thinking about arid areas led to storage and subsequent leaching of radioactive wastes in the soil zone near a major river.

In the Upper South East region of South Australia, the notion that mature pastures used more water than the native vegetation persisted for 50 years, sufficiently muddying the debate as to cause inaction. Even today, discussion on issues such as vegetation clearance is often based on common misperceptions, and leads to inappropriate action.

The presence of good technical information and clear understanding of processes goes some way to constraining the debate and hence the likely management actions.

The variability of landscapes across Australia makes it difficult to ensure that technical information is relevant to different regions and is used sensibly to target salinity efforts.

One of the successes in recent years in addressing this issue has been a catchment classification for salinity management. Such classifications are not new, but previous efforts have varied from state to state and even between institutions.

The National Classification (RIRDC, 1998) portrayed in a simple but effective fashion the key catchment characteristics that lead to salinity, building upon work by Shaw in Queensland and George and Nulsen in Western Australia.

This National Classification is extremely useful in communicating the variety of processes and management recommendations for different areas while at the same time, reinforcing similarities where they existed, even across State borders.

Classifications are always a balancing act between being simple enough to be useful, but portraying the complexity that actually exists. The classification has other limitations; the main one being the ability to map the catchment types.

The National Groundwater Flow Systems approach (NLWRA, 2000) is an adaptation of the National Classification that is mappable at a national scale using geology and terrain attributes.

The same approach has been used to develop maps at the regional and basin-wide scale for the Murray-Darling Basin (MDB). The MDB map is due for release in April 2002. The regional scale maps are being used to aid regional planning for salinity targets.

The salinity planning process varies across the MDB from Queensland where the potential salinity problem is beginning to be recognised, to Victoria where salinity planning has already been going on for 15 to 20 years.

The acceptance of the classification by the latter seems somewhat surprising given their existing investment in salinity planning.

Reasons for change include greater ownership achieved during the classification workshops, access to products associated with the classification approach and using the opportunity to update the planning framework.

In reviewing the classification framework for salinity management, there are some sobering aspects.

Our general understanding of salinity is based upon a small number (~30) of intensively studied catchments around Australia. For many classes within the classification, there is no more than one case study - i.e. all our knowledge of a process comes from one place in Australia.

Many of the case studies have not been properly documented or peer reviewed. In the first cut of the classification, many of the case studies were placed in the wrong class. All of this suggests that it will take some time to bed down the framework and the ongoing need for demonstration case studies to be developed in the various regions during the NAP process.

While any classification needs to be simple, there is a need to deal with some of the complexity that exists. Techniques such as the aerial geophysics program enable us to see a little more of this complexity, although at some cost.

Such complexity is seductive and it is easy to use it as an excuse for inaction, rather than as a refinement of management. The classification framework hopefully enables us to see the Wood as well as the trees.

REFERENCES

Coram, JE (1998) National Classification of Catchments for Land and River salinity Control. A Report for the RIRDC/LWA/FWPRDC Joint Venture Agroforestry Program. RIRDC Publication No 98/78

Coram JE, Dyson PR, Houlder, PA and Evans WR (2000) Australian Flow Systems contributing to Dryland Salinity, Report by Bureau of Rural Sciences for National Land and Water Resources Audit, Canberra.

Wood WE (1924) Increase in Salt in Soil and Streams following the Destruction of Native Vegetation. J. Royal Society