Environment, Natural resource management

26 – Dryland salinity in Australia

Dryland salinity is a major problem affecting Australian agriculture. Here is an overview of the main issues, some changes in our understanding of it, and some insights into how policy can best address it. 

In 1910 my grandfather moved with his parents from rural England to rural Western Australia. They purchased an area of uncleared land near the town of Wickepin. Imagine the culture shock. Grandpa was only 11 years old when he arrived, but he had vivid memories of those early days when he talked to me about them eighty years later. He spent much of his teenage years chopping down trees with an axe to clear land for wheat production. This made him as strong as an ox, and he ended up being a champion rower, including being a member of the WA crew that won the Kings Cup in 1927.

Three years before that, Walter Ernest Wood became the first person to publish a correct explanation of the cause of the increasing salinity in streams in rural Western Australia. Basically it was due to rising groundwater tables on land that had been cleared for agriculture by people like my Grandpa.

When I see the saline land around Wickepin these days, I can’t help but be moved by the irony of the situation, because the incredibly hard physical work that my grandfather did in his youth kicked off a process of salinisation that my own research has been trying to help manage.

W.E. Wood’s general explanation for salinity has stood the test of time, but in many respects, the science of salinity has come a long way. Science is always in a state of change and growth, with new ideas and new knowledge constantly coming forward. But occasionally there is a dramatic burst of new knowledge in a field that means we have to rethink an important issue. Sometimes it means we have to reorganise and redesign government policies for that issue, and that is exactly the point we have reached with salinity in non-irrigated areas.

I’d like to explain the recent changes in our knowledge, and why they have such big implications.

Firstly, some background. Australia is naturally a very salty place. Some of the salts have been released from weathering rocks, but most have been carried inland from the oceans on the wind. We think of rainwater as being fresh, but in fact it contains somewhere between 20 and 200 kg of salts per ha per year, and where conditions are right, salts have accumulated is soils over many thousands of years, sometimes to amazingly high levels. In some regions 15,000 tonnes of salt per ha in the underground soil is not unusual. When we cleared the perennial native vegetation, we replaced it with annual plants that don’t use up all the rain that falls, and it’s this excess rainfall that is carrying the salts that were there already to places we don’t want them, and causing all the problems.

One of the changes in our knowledge of salinity is that we now recognise a wider diversity of impacts, not just impacts on agricultural production. The National Land and Water Resources Audit in 2000 quantified risks to water resources, biodiversity and infrastructure.

For many years people believed that the simple and obvious solution to the salinity problem was to undo what we’ve done by replanting trees and converting annual pastures into perennial pasture species that use more water. We now have a more sophisticated understanding. Perennial plants are still an important part of the solution, but not everywhere, and getting it to happen will require a different approach than we’ve been using, as I’ll explain.

Another key change in salinity knowledge has been that the area of perennial vegetation that you need to plant to prevent salinity is much greater than was previously guessed. For example, computer modelling was conducted by CSIRO to test out revegetation strategies for part of the Eyre Peninsula of South Australia.

They found that to prevent salinisation of about 6% of the land in that catchment over the next 20 years, trees and perennial pastures would need to be established on over 50% of the total area of the catchment. Think about that from the point of view of a farm business. The farmer can choose to bear a moderate cost from loss of land to salinity, or cop a vastly greater cost from conversion of huge areas of productive crop land to much less profitable land uses. Taking such drastic action to prevent salinity may be good for their souls, but it would put the viability of their whole businesses under threat.

When such huge changes in management are suggested, their economics become particularly important. There has recently been a review of the economics of trees and perennial pastures in cropping areas across Australia. The authors concluded that increasing areas of perennial pastures seems economically viable in many cropping areas, but only up to a point. Unfortunately that point is not nearly enough to get fully on top of the salt problem.

Now jump to the current national salinity program, the National Action Plan for Salinity and Water Quality. This aims to prevent salinity, mainly by providing information and grants to farmers. Based on the research I’ve already described, the level of funding that would be needed to secure uptake on the scale needed would be vastly greater than the existing $1.4 billion program. Not that I am arguing for more funding. The $1.4 billion is enough to achieve a lot, but we can spend it a lot more cleverly if we make some key changes to the program.

One crucial change is to be more patient about achieving outcomes. We should not rush into using all the money to fund on-ground works, but should allocate a significant part of it to research and development to bring on new types of trees, shrubs and perennial pastures, and to better inform priorities for future on-ground works..

The new plants need to be profitable enough to be competitive with current farming options in the medium to long term. That seems to be the only way we can conceivably get uptake of these land-uses on a scale that will actually get control of salinity. We need to tackle it by exploiting the commercial drivers of farm business managers, rather than by expecting them to bear unrealistic costs, sweetened a little by small grants.

Another finding of recent modelling research has been that the time lags between revegetation and the delivery of off-site benefits is long – often decades and sometimes centuries. This is particularly relevant to protecting rivers in large areas of the Murray Darling Basin, which have large-scale groundwater systems. Longer time lags make it harder to justify current spending, as the cost of interest on up-front expenses has to be considered. Anyone with a housing loan knows how dramatically interest can accumulate over the long term, and the same logic applies to up-front costs of salinity works.

The recent research findings have a really obvious consequence for the way that governments spend money to encourage farmers to change their farm management: If the approach is to hand out grants, it is not sensible to spread the funds thinly like vegemite across lots of small projects in many areas. That would connect with the largest number of farmers, but it would achieve little or nothing against salinity because, controlling it in a particular location requires a lot of perennial vegetation, not little bits. This means that we can only use grants to prevent salinity effectively and economically in quite small areas, and only then if we concentrate the funds. Obviously, they should be carefully selected, high priority cases, such as key infrastructure or environmental assets.

In other agricultural areas, the best solution is often to put funding into R&D to provide farmers with better options for salinity management, rather than giving them grants that are too small to really make a difference.

Another realisation that has come out of recent research is that the nature of the salinity problem is remarkably different in different parts of Australia. It is different in the types of assets affected – land, biodiversity, water or infrastructure – in the way that groundwaters respond to management, and in the socio-economic context.

In some situations, putting perennial pastures and trees onto farms is not the solution at all. For example, in some of the country towns that are suffering from rising saline watertables the problem is not actually coming from surrounding farm land, but from excess water within the towns themselves. Water collects on roads, footpaths, roofs and bare ground, and if it is not collected and directed away in drains, groundwaters can rise rapidly. If the problem is urgent, pumping the water out is the most effective strategy, although it is expensive and can only be justified in some cases. If trees have a role to play in protecting these towns, it is usually by planting them within the town boundaries, not on the surrounding farms.

The heavy-engineering approach of using mechanical pumps is at least part of the best response in some other cases as well. It is appropriate for some environmental assets – there is some serious pumping happening to protect Toolibin Lake in WA – it is used for some stretches of river – the Murray Darling Basin Commission is spending tens of millions on pumping and evaporation basins – and even for some farms – many WA farmers are experimenting with large-scale deep open drains to try to reclaim salt-affected land. Where it works, engineering is quick acting, but the expense means that the economics have to be carefully weighed up.

In the case of deep open drains, there are some serious challenges for the WA government. On the one hand, there is inadequate scientific information about their performance and their downstream impacts. On the other hand, the approach has some passionate and well-organised supporters who are calling for the construction of very expensive channels to collect and carry the drainage waters away from farming regions. It has become a politically charged issue, and the government has been unwilling or unable to resolve it.

One positive message about salinity to emerge recently is that, if geological conditions are in your favour, locally targeted engineering works can be effective, locally. They won’t necessarily be swamped by groundwaters from neighbouring land.

Even on agricultural land, we are now able to identify plenty of cases where the impacts of revegetation are mostly localised. This is important because it avoids the need for multiple farmers to coordinate their salinity control efforts in order to be successful. The supposed need for farmers to cooperate and collaborate in salinity control has been emphasised in the past in policy approaches like Landcare and Integrated Catchment Management, but we now know that technically it is simply not true in many cases.

Another research finding that has been much discussed lately is that, among the huge diversity of circumstances we need to address, there are some cases where planting trees or perennial pastures will actually make maters worse. This applies to some higher rainfall areas where fresh water running off into a river helps to dilute salty water coming from groundwaters. Planting trees or perennial pastures in this situation will reduce the groundwater problem in the long run, but at the cost of reducing fresh surface flows in the short run.

The loss of surface water is a double whammy, because it means we miss out on the desirable dilution we were getting, and also that there is less water in the river for downstream users or the environment. This highlights just how clever and careful we need to be in dealing with the diversity of impacts and circumstances for salinity management.

A pill that some people find particularly hard to swallow is that some salinity will not be prevented – it is physically not preventable, or not practically preventable without spending vastly more than it’s worth. There are millions of hectares of agricultural land that are already salt-affected, or destined to become so. We should not be over-dramatising this outcome, as there are options for productive use of much of this land, and plenty of scope to develop even better options. There is a rapid growth in the area of salt-tolerant plants used for grazing, and efforts are underway to develop new salt-tolerant crops and trees. In some places deep open drains are working well to reclaim saline land. The basic point is that salinity is not a death sentence to agriculture. For most farmers, it is far from being the most serious of their concerns.

Back then to government policy. There is a huge amount of public and private money at stake here, so we need to update our national and state salinity policies to catch up with the science, or much of that money, and lots of energy and effort will be wasted. It will not be that hard to improve things, but it will require a much more patient and analytical approach than we’ve seen so far.

To finish, then, here is an eight-point plan to bring salinity policy up to date and compatible with the new science.

  1. Use different policy approaches for different types of salinity impact (water, infrastructure, biodiversity, land), rather than the current one-size-fits-all approach.
  2. Put more effort into developing options for making productive use of saline land and water.
  3. For those impacts that can be managed with highly targeted localised revegetation or engineering, concentrate the funding onto a few, top-priority areas. Base these choices much more on science and economics, and take a more systematic and analytical approach to selecting them.
  4. Be more realistic about what can be achieved through provision of information. In most cases overcoming information shortages won’t solve the main problem, which is lack of good salinity management options.
  5. Don’t expect too much of grants to encourage land use change. For impacts that require really broad-scale planting of perennials, forget about spending money to directly encourage that planting. The amount of money available won’t touch the sides.
  6. Sort out the science needed to make sensible decisions about deep open drains in Western Australia, and then deal with it decisively.
  7. Direct more funds into creation of profitable new perennial plant options, including R&D and perhaps infrastructure. In the long run, this approach will be much more effective over much greater areas. It will also have spin off benefits for other environmental problems, and for rural communities.
  8. Most importantly, don’t primarily set priorities at the regional scale, as we are currently doing. In many cases priorities and actions should be handled at the state or national scale.

The case for these changes is compelling. It is time now to start making them.

David Pannell, The University of Western Australia

Further reading

Ridley, A., and Pannell, D.J. (2005). The role of plants and plant-based R&D in managing dryland salinity in Australia, Australian Journal of Experimental Agriculture, 45: 1341-1355. Full journal paper (127K pdf)

Pannell, D.J. (2001). Dryland Salinity: Economic, Scientific, Social and Policy Dimensions, Australian Journal of Agricultural and Resource Economics 45(4): 517-546. Final journal version (212K pdf file) also available via the Journal homepage: http://onlinelibrary.wiley.com/doi/10.1111/1467-8489.00156/abstract