Dryland Salinity: New Knowledge with Big Implications

David Pannell

Professor, School of Agricultural and Resource Economics, University of Western Australia

In 1910 my grandfather moved, with his parents, from rural England to rural Western Australia, where they purchased an area of uncleared land near the wheatbelt town of Wickepin. Grandpa spent much of his teenage years with an axe in his hands, chopping down trees to clear land for wheat production. This made him as strong as an ox and he went on to become a champion oarsman and a member of the WA rowing crew that won the Kings Cup in 1927.

Three years before that, Walter Ernest Wood had published an explanation of the increasing salt levels in streams in Western Australia. He said 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 am moved by the irony of the situation. Because of the incredibly hard physical work that he did in his youth, my grandfather unknowingly helped to kick off a process of salinisation that I am now trying to address through my research.

W.E. Wood’s general explanation for salinity has stood the test of time, but the science of salinity has come a long way. Science, of course, is constantly in a state of change and growth, but occasionally there is a dramatic burst of new knowledge in a field, and that is what has happened with salinity over the past 10 years. A number of the recent findings are important and some are quite surprising.

I’d like to outline some of the new knowledge about salinity, and explain why it has such big implications.

But first, some background. Australia is naturally a very salty place. Some of the salts have been released from weathering rocks, but most fell with the rains. We think of rainwater as being fresh, but it does contain a little salt, and where conditions are right, this has accumulated over thousands of years, sometimes to amazingly high levels.

When Europeans arrived, there was relatively little salt at the soil surface. To establish agriculture, they cleared large areas of the native vegetation, much of which is perennial.  This means it is alive and using water all year round. The replacement crops and pasture plants are mainly annuals, and use water for only part of the year. The leftover water enters the soil and carries the salts to places where we may not want them.

We’ve known all that for a long time, but what have we learnt recently?

For a start we have come to recognise the full diversity of costs and impacts from salinity. Apart from reducing agricultural production, salt can also do harm to rivers, to natural ecosystems, and to infrastructure, particularly roads.

Having recognised the diversity of impacts, we can begin to get smarter about the way we try to manage it. The best approach tends to vary depending on the type of asset that is under threat. It also depends on local conditions that determine how rapidly groundwater moves, and on social and economic circumstances. We’ve learnt that it is important to account for these things when planning for salinity management, and that good planning is not a simple task.

It is actually not very long since the whole issue did seem much simpler. For many years, people believed that the obvious solution to salinity was to undo the effects of the clearing we’ve done, by planting trees and perennial pastures that use more water. Perennial plants are still an important part of the solution, but not in every case, and getting them in place will require an approach that is different from the ones we’ve mainly been using.

Before I say how the approach should change, I’ll explain why it needs to.

First and perhaps foremost was the discovery that the area of perennial vegetation needed to prevent salinity is often much greater than we once thought. As one example, the CSIRO looked at part of the Eyre Peninsula in South Australia, and they found that by putting trees and perennial pastures on half of the total farm area, they could prevent about 6% of the farm going salty. But why would farmers suffer losses on half of their land to protect a twentieth of it? They wouldn’t do it unless the perennials they could plant were economically attractive.

There has recently been a review of the economics of trees and perennial pastures in cropping areas across Australia. The conclusion was that currently available perennial pastures are economically viable in many cropping regions, but generally only on a scale that is too modest to get on top of the salt problem.

This is a crucially important finding. It means that, as things stand, we don’t have sufficient perennial plants for wide-scale planting. A suitable range of economically productive plants just doesn’t exist, at least not yet.

Another important new insight is that, in some situations, putting perennial pastures and trees onto farms is not the solution at all. In fact, there are cases where planting perennials would actually make matters worse. In some higher rainfall areas, planting trees would reduce the discharge of saline groundwaters into the river in the long run, but at the cost of reducing fresh surface water flows almost immediately. The rivers would have less water and be more salty!

Planting perennial plants on farms is also not relevant to many of the country towns that are suffering from rising saline groundwaters. In these towns, the problem is not coming from surrounding farm land, but from excess water within the towns themselves. If they don’t have good drainage systems, towns are even more prone to rising water tables than are farms, because so much of them consists of roads, footpaths, and roofs in place of any form of vegetation. If their watertables have already risen to near the surface, pumping them out is the most effective strategy, although that is expensive and probably could not be justified in every town.  If trees have a role to play in protecting these towns, it is by planting them within the town boundaries, not on the surrounding farms.

Rural towns are one example of the general increase in awareness and use of engineering approaches for dealing with salinity. Other examples include some environmental assets – such as pumping to protect Toolibin Lake in Western Australia – some stretches of river – the Murray Darling Basin Commission is spending tens of millions on pumping and evaporation basins – and even some farms – many farmers are using deep open drains to reclaim salt-affected land. These drains work well in some locations, but not all, and there is concern and uncertainty about their potential downstream impacts on waterways, receiving water bodies and wetlands, as well as on other farms. This has become quite a contentious issue in some regions, and it will need strong leadership to resolve.

If you were familiar with programs like Landcare in the 1990s, there is an important recent finding that may surprise you. There has been a widespread misconception that farmers always need to cooperate in their efforts to control salinity. But we now know that there are many cases where this is not true. Many farmers can do things to manage their watertable locally and not have their efforts thwarted by groundwaters coming from their neighbours. This may be either because groundwater systems are localized, or because ground water moves very slowly in flat landscapes.

The final point of relatively new knowledge that I want to mention is that it has become much clearer that much of the impending salinity will not be prevented. This can be either because it is physically not preventable, or not practically preventable without spending more than it’s worth. This seems to be a pill that some people find particularly hard to swallow. We might wish it were otherwise, but it is the reality. Still, it is not as much of a catastrophe as it is sometimes portrayed. Salinity has always been part of the Australian environment, so our approach needs to strike a balance between preventing high-impact damage, and living with salinity, profitably and sustainably.

Given all of those research findings from the past decade, what are the implications for our national salinity program, the National Action Plan for Salinity and Water Quality?

The first clear implication is that we need to be patient about achieving outcomes. We have tended to rush into using all the money to fund on-ground works, but given the limited range of treatment options currently available, this is clearly not the best approach. We are strongly reliant on R&D to provide new types of perennial trees, shrubs, pastures and crops, and this R&D is in its early stages. It will take some time to deliver.

Another argument against rushing in to spend the money is that the groundwater processes underlying salinity are often slow, sometimes very slow. The time lags between revegetation and the delivery of off-site benefits can be decades or even centuries, so there is really no need to be rushed into action before we have the knowledge to do it right or the tools to do it at all. This is true everywhere in Australia, but particularly in those areas of the Murray Darling Basin that have large-scale groundwater systems. So let’s be patient, and do things well.

The second implication is that we need to get much smarter about the way we target funds for salinity works. Given that very large areas of perennials are needed to be effective in salinity prevention, it is all too easy to spend money in ways that won’t make much difference to the impacts of salt. It is not sensible to spread the money thinly like vegemite across lots of small projects. That would connect with the largest number of farmers, which might be politically desirable, but it would achieve little or nothing against salinity because controlling it in a particular location requires large areas of perennial vegetation, not little bits. Realistically, we can use grants to prevent salinity effectively only in quite small areas, and only if we concentrate the funds. Obviously they would need to be carefully selected as the highest priority cases.

The current national salinity program does target the funds to some extent but, in practice, the targeting is often not tight enough or clever enough. I think we are currently trying to do about ten times too much with the available funds, and as a result we will actually achieve less than we could.

Thirdly, the discussion about needing to wait for R&D begs the question, why not use some of our salinity program funds to accelerate the research that is developing new and better tools for management, including perennial plants that can be profitable while using all the available water, salt-tolerant plants, and improved engineering methods? At the moment, funding for this R&D is outside the salinity program, and is not secure, even though it is pivotal to our chances of dealing well with the problem.

Funding R&D to develop new salinity management tools is also important for ensuring that something can be done in the great majority of salt-affected areas that will not qualify for funding for on-ground works. Tight targeting of funds, while necessary for effective use of the resources, inevitably means that most agricultural areas will miss out. Developing new tools is the best way to empower farmers to take action for themselves. If we don’t do this, we can’t expect farmers to bear unrealistic costs, sweetened a little by grants that are generally too small to really make a difference.

A fourth implication is that we can’t rely on the two approaches that currently dominate the National Action Plan: providing farmers with information, and with grants. It is clear that lack of information by farmers is usually not the problem, it is lack of good management options, and that grants will not achieve worthwhile outcomes unless they are targeted very cleverly to small areas. We have the scientific capacity to do that targeting, but the program is not using it much yet. To get that happening, the regional bodies that are responsible for developing investment plans will need stronger support with scientific data and economic analysis.

We’ve learned a lot about salinity from research over the past decade. The future of the National Action Plan is currently being considered, so we have a great opportunity now to update our national and state salinity policies to catch up with the science. If we can do that, we can build a much more productive and effective salinity program that will really deliver positive outcomes, just as farmers since about my grandfather’s time have used research to develop more productive farm businesses.

Further reading

Bathgate, A. and Pannell, D.J. (2002). Economics of deep-rooted perennials in southern Australia. Agricultural Water Management 53(1): 117-132.

Pannell, D.J. (2001). Dryland Salinity: Economic, Scientific, Social and Policy Dimensions, Australian Journal of Agricultural and Resource Economics 45(4): 517-546.

Pannell, D.J. (2005). Farm, food and resource issues: politics and dryland salinity, Australian Journal of Experimental Agriculture 45: 1471-1480.

Pannell, D.J. and Ewing, M.A. (2006). Managing secondary dryland salinity: Options and challenges, Agricultural Water Management 80(1/2/3): 41-56.

Ridley AM and Pannell DJ (2005). SIF3: An investment framework for managing dryland salinity in Australia. SEA Working paper 1901. CRC for Plant-based Management of Dryland Salinity, University of Western Australia, Perth. http://www.crcsalinity.com.au/newsletter/sea/articles/SEA_1901.html

This article was broadcast on ABC Radio National's Ockham's Razor program on 18 December 2005 .