Salinity In Australia Research Articles

Adapting to extremes: Reconstructing evolution in response to changing climate over time and space in the diverse Australian plant genus Acacia

AbstractAimMacroevolutionary analysis is increasingly being used to study biodiversity responses to climate change, for example by using phylogenetic node ages to infer periods of diversification, or phylogenetic reconstruction of traits to infer adaptation to particular stresses. Here we apply a recently developed macroevolutionary method to investigate the responses of a diverse plant genus, Acacia, to increasing aridity and salinity in Australia from the Miocene to the present. We ask whether increase in tolerance of aridity and salinity coincided with periods of aridification, and if it allowed the radiation of Acacia into a wide range of niches.TaxonAcacia.LocationAustralia.MethodsWe applied the Niche Evolution Model (NEMo), which combines environmental (or ecological) niche modelling (ENM) with phylogenetic comparative methods (PCMs) in a single statistical framework, to a large database of Acacia presence‐only records and presence–absence survey sites in order to infer current environmental tolerances of Australia Acacia species and reconstruct the evolution of environmental tolerance to increasing aridity and salinity.ResultsWe find that patterns in evolution of Acacia, over time and across different habitat types, are consistent with the aridification history of Australia and suggests substantial ability to adapt to high aridity and salinity.Main conclusionsOur results suggest that many Acacia lineages have been able to exploit new environments created during the aridification of Australia through evolution of environmental tolerance, resulting in their current dominance of many habitats across the continent. This study demonstrates that phylogenetic studies of the evolution of responses to changing environment can move beyond the application of simple trait‐based models, allowing the underlying processes of speciation, adaptation and dispersal to be explicitly modelled in a macroecological and macroevolutionary context.

Effect of Naturally Occurring Salts on Tensile and Shear Strength of Sealed Granular Road Pavements

Areas affected by dryland salinity in Australia are predicted to more than double over the next 40 years as a result of land use and climatic changes. This presents a significant risk to road asset managers because the concentration of salts within road pavements has been shown to cause damage to pavements and surfacings. The present study explores the impact of dryland salinity on road pavements by assessing the effect of naturally occurring salts on the tensile and shear strength of a sealed granular pavement. Microstructure analysis techniques using scanning electron microscopy and mercury intrusion porosimetry were employed to analyze tested specimens to explain the physical mechanisms that occur as a result of salt concentration. The presence of natural salts was found to have a positive effect on granular pavements but a negative impact on bituminous surfacings. While in solution, salts were found to have a very small positive effect on the tensile strength of the pavement material, which is likely related to clay chemistry interactions. Upon crystallization, salts were observed to form bonds within the pores of the pavement material, which led to a significant increase in tensile strength and a moderate increase in shear strength. However, at the interface between the surfacing and the pavement material, whisker-shaped crystals were observed to grow from the bitumen. Interestingly, the chemical composition of the two types of crystals observed was found to be completely different, despite occurring within the same specimens, under the same conditions. The implications of these findings for road pavements in high-saline areas are also discussed.

Piloting a systematic framework for public investment in regional natural resource management: Dryland salinity in Australia

The Salinity Investment Framework (SIF3) is designed to help environmental managers make better policy decisions about protecting key assets under threat of dryland salinity, a major degradation problem in Australia. This study reports results from applying SIF3 in partnership with two regional organizations (in the states of Victoria and Western Australia) with contrasting institutional powers and structures. We also engaged relevant policy makers with a view to influencing national policy. Available knowledge, science, and data were used to develop region-specific recommendations for public investment in salinity management. SIF3 proved easy to apply, requiring minimal changes from its original version. Establishing trust and credibility with stakeholders was extremely important. More time was required to be spent on communicating what SIF3 was and what it would mean for stakeholders than in applying it in the catchments. In both regions, recommendations included making a clear distinction between localized assets (such as a particular wetland) and dispersed assets (such as agricultural land as a whole); more targeted investment in spatially identified localized assets; using a broader range of policy tools; basing recommendations on the levels of public and private net benefits; anticipating the adoptability of sustainable land-management practices; and formally integrating relevant scientific, economic and social information with community values. The differences between current action and recommendations were significant in both regions, particularly in Victoria. As a result of our work both regions have decided to implementing a similar asset-based approach covering various environmental threats in addition to dryland salinity. The research indicates that it is feasible to use decision frameworks such as SIF3 to improve the rigour of decision making by community-based environmental management organizations. A broader range of policy tools are needed for dryland salinity, with less reliance on extension and small grants, and more emphasis on intervention around key assets and investment in technology development. We have influenced policy makers to some extent at state level and nationally through discussion of SIF3 in a national inquiry, preparation of a policy paper for peak multi-government policy committees, briefings and provision of advice on policy design. Despite this, achieving significant policy change at the state and national levels remains difficult for a number of reasons. Governments give limited signals to environmental managers to achieve environmental outcomes, being more concerned with community participation objectives and political considerations. We hope for significant policy change with increased scrutiny about sound decision making and public accountability.

A line spacing compression method and an improved minimum curvature operator for grid interpolation of airborne magnetic surveys

We have modified the minimum curvature gridding method to cope with various flight line gaps, by employing a line spacing compression technique. The line spacing compression method was applied to magnetic data from a survey in northern Canada and was able to smoothly interpolate across the unevenly spaced lines without creating false anomalies. We have also derived a new, longer minimum curvature operator to handle flight lines of various lengths. The longer operator was applied to South Australia Salinity Project data and it removed the artificial boundaries at changes in flight line spacing and smoothly interpolated anomalies even over wider flight line gaps.

A comparison of the water use of tree belts and pasture in recharge and discharge zones in a saline catchment in the Central West of NSW, Australia

Planting trees has been proposed as part of the solution to dryland salinity in Australia. The best location in the landscape and the spatial arrangement of trees however, is difficult to determine. This paper presents a case study of a field experiment that compared the water use of tree belts with that of pastures in recharge and discharge areas of a first order catchment in the Central West of NSW, Australia. The recharge tree belt and both pasture sites used very similar amounts of water but the discharge tree belt used double the water of the other three land uses by accessing groundwater. The discharge tree belt operated in an energy-limited environment, transpiring at a rate equivalent to atmospheric demand whereas the other three land uses were all water-limited. From a land management point of view, the establishment of more trees on the discharge site would have the biggest impact on reducing saline discharge and the least impact on the agricultural operations.

Economic returns from environmental problems: Breeding salt- and drought-tolerant eucalypts for salinity abatement and commercial forestry

Remediation of agricultural landscapes affected by salinity requires modification of land use practices to re-establish water balance at the catchment scale. Forest plantations established throughout the landscape, from recharge to discharge areas, have the potential to play an important role in this regard given their deep rooting habit, high perennial water use and low leakage of rainfall below the rootzone relative to annual crops. However, areas affected by salinity in Australia often present environmental conditions challenging to commercial growth. In 1996, the XylonovA R&D Syndicate commenced a collaborative breeding program to combine the salt and drought tolerance of Eucalyptus camaldulensis, with the growth rate, stem form and wood properties of the commercial species Eucalyptus grandis and Eucalyptus globulus. These hybrids exhibited heterosis under saline irrigated conditions, with the mean stem volume of hybrids at 85 months exceeding the best pure species parent by 140–252%. Gains in stem volume based on the mean of a commercial selection of hybrid clones ranged from 287 to 481%. Gains were more modest under non-saline, medium to low rainfall conditions (531–707 mm/year). Hybrid population means were similar to alternative pure species, but the hybrids were more stable across sites. Gains in mean stem volume from selection of the top 10% of hybrid clones over the best performing pure species ranged between 40 and 45%. The opportunity for commercial plantations of improved eucalypt hybrids integrated with agriculture in medium to low rainfall areas to address salinity and sustainability is discussed.

A review of a community-based approach to combating land degradation: dryland salinity management in Australia

Degradation of farmland caused by salinisation is a major environmental issue in Australia. To combat salinisation a community-based approach has been adopted. This paper reviews the nature and effectiveness of this approach, describing its rationale, strengths and weaknesses. The community-based approach is shown to have been highly successful in raising awareness and providing education about the problem of dryland salinity in Australia, and has encouraged group participation in managing the problem. The approach has allowed some internalisation of the externalities associated with dryland salinity, with peer group and community pressure helping to address some salinity problems. However, the approach has not greatly lessened the threat of salinisation. Community and regional groups continue to receive the bulk of salinity management funding yet it is funding for development of new innovations, technologies and policies that is also critical to combating salinity. A conclusion is that there may have been an over-investment in the community-based approach and under-investment in the development of skills and research infrastructure required to develop innovative solutions to lessen the cost of salinity.

Integrating physical, biological, social and economic sciences for dryland salinity management and policy

The earth sciences have made major contributions to the diagnosis and management of dryland salinity in Australia, and have influenced policy directions in a number of ways. However a well-balanced response to salinity requires the integration of information from a range of disciplines, including physical, biological, social and economic sciences. This paper discusses dryland salinity management and policy, bringing together key issues from each of those disciplines. At the farm level, beyond being consistent with hydrogeological knowledge, proposed responses need to be sufficiently economically attractive in the long term, and ideally should have other characteristics that promote widespread adoption among the farming community. At the policy level, the same farm-level issues are relevant to the selection of appropriate policy tools and the design of programs, and the issue is further complicated by the diversity of bio-physical and socio-economic circumstances that must be addressed, by the diversity of policy tools available, and by a number of other specific challenges that have emerged in recent years. We present a framework that has been developed to integrate the relevant information and allow improved investment decisions by catchment managers and policy makers in relation to dryland salinity. Application of the framework indicates the need for a number of important changes to Australia's national policy directions for salinity.

Farming carbon: an economic analysis of agroforestry for carbon sequestration and dryland salinity reduction in Western Australia

The widespread removal of native trees from the agricultural zone and replacement with annual crops and pastures is a major cause of dryland salinity in Australia. It has been recognised that a large proportion of the landscape needs to be replanted to trees to prevent further salinisation. However, for much of the agricultural zone, agroforestry is not an option due to lack of species that can viably generate the products currently demanded by the market. The emerging carbon market may provide a new agroforestry option for landholders, through carbon sequestration. This analysis assesses the viability of growing trees for the purpose of selling carbon credits, from a landholder’s perspective. Benefits of trees in preventing the onset of dryland salinity are accounted for. Two regions in Western Australia; a low rainfall (330 mm/year) region and a medium rainfall (550 mm/year) region, are analysed. At the expected carbon price of A$15/tCO2-e, growing trees for carbon is not a viable alternative for landholders in the low rainfall region, due to low sequestration rates. In the medium rainfall region, growing trees for carbon and timber is a viable alternative; however the opportunity costs of land mean the carbon price would still need to be higher than expected for growers to choose this alternative. Accounting for the salinity prevention benefits makes growing trees a more attractive investment for landholders in both regions. However in both regions, even after accounting for salinity benefits, the price of carbon would need to be A$25–A$46/tCO2-e higher than expected to make growing trees a worthwhile investment.

Prologue: Amending agricultural water use to maintain production while affording environmental protection through control of outflow

The long-standing debate about the problem of dryland salinity in Australia has been increasingly well informed. We chart here the deepening understanding of the processes involved in how plants use water and what this means for flows in the regolith, from the introduction of the idea of the soil–plant–atmosphere continuum 50 years ago, through the comparative patterns of water use by annual and perennial vegetation and the variety of their hydrological effects in different landscapes, to the realisation, as demonstrated by many of the papers in this special issue of AJAR, that the era of unviable simplistic solutions to dryland salinity is behind us. The mood now is one of cautious optimism that we will be able to develop a wide range of options for maintaining economically viable farming systems that protect the environment by controlling outflow well enough to arrest the spread of dryland salinity.

The role of livestock in the management of dryland salinity

Management of dryland salinity in Australia will require changes in the design and utilisation of plant systems in agriculture. These changes will provide new opportunities for livestock agriculture. In areas already affected by salt, a range of plants can be grown from high feeding value legumes with moderate salt tolerance through to highly salt tolerant shrubs. A hectare of these plants may support between 500 and 2000 sheep grazing days per year. The type of plants that can be grown and the subsequent animal production potential depend on a range of factors that contribute to the ‘salinity stress index’ of a site, including soil and groundwater salinity, the extent and duration of waterlogging and inundation, the pattern and quantity of annual rainfall, soil texture and chemistry, site topography and other site parameters. Where the salinity stress index is high, plant options will usually include a halophytic shrub that accumulates salt. High salt intakes by grazing ruminants depress feed intake and production. Where high and low salt feeds are available together, ruminants will endeavour to select a diet that optimises the overall feeding value of the ingested diet. In areas that are not yet salt affected but contribute to groundwater recharge, perennial pasture species offer an opportunity for improved water and salt management both on-farm and at the catchments. If perennial pasture systems are to be adopted on a broad scale, they will need to be more profitable than current annual systems. In the high rainfall zones in Victoria and Western Australia, integrated bioeconomic and hydrological modelling indicates that selection of perennial pasture plants to match requirements of a highly productive livestock system significantly improves farm profit and reduces groundwater recharge. In the low to medium rainfall zones, fewer perennial plant options are available. However, studies aiming to use a palette of plant species that collectively provide resilience to the environment while maintaining profitable livestock production may also lead to new options for livestock in the traditional cropping zone.

A model for knowledge transfer and adoption: a systemic approach to science communication

Abstract This article describes a new model for science communication relevant to natural resource management as well as any other sector with the need to integrate and find pathways through an extensive body of information. The model comprises a hardcopy resource directory and a companion interactive CD-ROM. Together, the approach represents the first integrated and readily accessible repository of information on dryland salinity in Australia, and probably in the natural resource management sector more generally, and targets the many thousands of catchment managers. The advice of more than 150 people involved in salinity research and management informed the structure and content of the resource materials. This article discusses the strengths and limitations of the approach and its potential for broader application, the need for adaptive management and on-going learning, and some prospects for further investment.

The role of plants and plant-based research and development in managing dryland salinity in Australia

The roles of plant-based systems and plant-based research and development for management of dryland salinity in southern Australia vary over a range of biophysical and socio-economic conditions, and differ according to the resources at risk (protection of water resources, biodiversity, infrastructure, dispersed assets such as agricultural land, and salt-affected land). Recommended responses are sensitive to a range of biophysical and socio-economic conditions. Extension and incentives to promote currently available perennials or salt-tolerant plants are only appropriate as the main policy response in a minority of cases. Regulation or permits to limit planting of perennials can be justified in certain areas of high-water-yielding catchments. For the majority of agricultural land that is at risk or is contributing to dryland salinity, the most logical policy response is to invest in development to improve salinity management technologies, including research and development into new plant-based systems. Situations where plant-based R&D for profitable farming systems is the best option include: (i) to reduce salinity impacts on water resources where groundwater systems are responsive and the dependence on fresh runoff for consumptive use is low; (ii) to protect infrastructure and biodiversity where there is relatively high responsiveness of groundwater and the urgency of response is low; (iii) to protect dispersed assets (e.g. agricultural land, most remnant vegetation on farms, flood risk mitigation) where profitable perennial plant options are lacking; and (iv) for land that is already salt affected.

Lessons from agri-environmental policies in other countries for dealing with salinity in Australia

Approaches to environmental policy for the agricultural sector have involved education programs, direct regulations, and market mechanisms. The effectiveness of these policies has varied depending on the characteristics of the environmental issue and incentives facing producers. This paper reviews, and provides examples of, agri-environmental policy options and points out the scenarios under which the instrument would be most effective. The paper concludes with recommendations on determining the policy solutions to the problem of salinity in Australia.

Integrating spatially referenced social and biophysical data to explore landholder responses to dryland salinity in Australia

Researchers attempting to integrate socio-economic data in watershed planning often draw on nationally collected census data. However, there are critical limitations to the usefulness of this type of data for decision makers operating at the watershed scale. In this paper we demonstrate the relevance of spatially referenced socio-economic data collected using mail surveys to random selections of rural landholders. The issue explored was dryland salinity management in two large watersheds in the Murray-Darling Basin of south-eastern Australia. Contrary to the assumptions underlying public policy in Australia, but consistent with the literature on farmer knowledge, comparisons of expert maps and landholder identified salinity sites suggested that landholders in these watersheds had excellent knowledge of the current extent of salinity on their property. Our research also suggested that salinity education was a sound investment by governments. At the same time, the expert maps failed to predict half of the saline affected sites identified by landholders. Accurately mapping the extent of salinity would seem a first step in addressing this nationally significant land degradation issue.

Salinity and the discharge of salts from catchments in Australia

Discharge of soluble salts from catchments following clearing of native vegetation for dryland agriculture is a serious environmental and economic problem affecting soil and water resources in Australia. The fundamental challenges are: To identify areas of soil at risk of becoming saline. To relate soil and water salinity risk to options for management of land in the area that contributes to the risk, and thereby contribute to the evaluation of management options. These challenges are faced in an environment where native vegetation has roots that extend to depths of order 10 m in soil profiles that are formed by in situ weathering of granitic rocks and dolerite dykes to depths of about 20 m. The profiles typically contain 1–100 kg m −2 of salt (primarily sodium chloride) in solution in the pore water. The distribution of soluble salts, and the movement of water within most of the unsaturated zone of these soils results from a combination of matrix flow and flow through remnant root channels and larger-scale structures with geologic origins. Recognized options for management of salinity risk, or to reduce existing areas of saline soil, are revegetation of part of the cleared land with alternative species, pumping to lower the watertable in selected areas, and construction of ditch drains for control of surface water and shallow groundwater. All options are constrained by the economics of dryland farming, and pumping or drainage is further constrained by possible environmental impacts of disposal of saline water. Application of soil physics/hydrology to salinity in Australia has contributed to understanding, but generally it has proven to be inadequate to aid the development of effective management strategies. A classic approach to soil water movement at the primary catchment scale (areas of order 10 6 m 2 or more) will always be limited by errors of measurement at each site within the catchment, those arising from the method of estimation of soil characteristics between measurement sites, and those arising from the method of integration to predict whole-catchment behaviour. The cost and effort of such an approach, and the errors that must eventuate, should be compared with the costs and errors of alternatives for characterization at a whole catchment scale.

Economics of deep-rooted perennials in western Australia

Much of the hoped-for success of deep-rooted perennials in reducing the eventual extent of dryland salinity in Australia will depend on the farm-level economic performance of the available perennial-based farming systems. A diverse range of factors contributes to this economic performance, including short-term production-related issues, dynamic factors, sustainability factors, risk factors and whole-farm factors. Although some examples of profitable perennial-based farming systems can be identified, they are limited to particular niches in particular regions, which tend to be higher rainfall regions. For the great majority of land that is at risk of salinisation, no profitable perennial plant options are currently available. The benefits of perennials for on-farm salinity prevention are likely to be of secondary importance in determining their economic attractiveness to farmers. A case study is presented for lucerne ( Medicago sativa L.) in the southern region of Western Australia. Lucerne appears likely to be profitable in suitable environments, even without considering salinity-related benefits. However, further improvements to its economic performance are needed if it is to be adopted voluntarily on a scale that would address the bigger, catchment-level problems such as river salinity and flooding risk. Policy implications of these findings are discussed.

Developmentalism and its Environmental Legacy: The Western Australia Wheatbelt, 1900 – 1990s

The Western Australia Wheatbelt contains the largest area of dry‐land salinity in Australia with major economic, social and environmental consequences. In recent years salinity has been widely recognised as the State's worst environmental problem. Yet, the historical record shows that this crisis, which has taken half a century to fully materialise, was largely foreseen by contemporary agricultural scientists. In examining the origins of the salinity crisis, the article examines the reasons why this scientific advice was ignored. It locates the schemes to open up the area for agriculture in the period 1900‐1980s within the ideology of developmentalism which became the major plank in the policy of successive governments. The article identifies the key elements in the way developmentalism was applied to agriculture and discusses its populist appeal; the separation of science from policy; and the institutionalisation of the developmentalist ethos in the administrative arms of government.

Improving the management of dryland salinity in Australia through the national airborne geophysics project

A comprehensive evaluation of the application of airborne geophysics to the management of dryland salinity is currently underway in Australia. Known as the National Airborne Geophysics Project (NAGP), it is a joint initiative of the Commonwealth and State Governments designed to assess the value-added contribution that can be made by time domain EM, frequency domain EM, magnetics and radiometrics to those data (including topography, soils and satellite imagery) already in use for salinity management. The project will concentrate on five selected catchments in Queensland, New South Wales, Victoria and Western Australia.The focus of the project will be to define the geological characteristics, to measure three-dimensional variability in conductivity in the regolith system, and to determine the spatial variability in soil characteristics. The analysis will allow the derivation of products such as maps showing salinity hazard, water resource target, soils, regolith conductivity and thickness, and geological interpretation. These derived products will be integrated with other datasets to specifically assist with the development of land management plans at appropriate scales and to contribute to the understanding of hydrogeological processes. The project will also produce cost/benefit analyses and confidence level estimates associated with the use of airborne geophysical and other data (Woodgate et al., 1998).

Cereal and wool production in the Esperance Sandplain area of Western Australia: The need for a systems approach for sustainable agriculture

AbstractThe problems facing farmers in the Esperance Sandplain region of Western Australia—salinity, herbicide resistance, wind erosion, and plant disease—are highly interrelated. Unless the biological, economic and social aspects of the problems are examined in an integrated way, no sustainable system will be found. Similarly, agricultural teaching and research must become much more integrated if they are to address agricultural and environmental problems satisfactorily. This will require changes in the structure of university and research institutions and in the rewards for research and teaching.