Conservation and Environment

Salinity and Climate Change

Increasing salinity is a major problem facing many areas of Australia (and the world), in particular agricultural regions that have been extensively cleared. Increased salinity can have direct toxic effects on both plants and animals or reduce reproduction and growth rates, and limit the geographical range of species. Wetlands, as low areas in the landscape, are particularly vulnerable to increased salinity levels through the direct effects of high water tables and through saline water management regimes. Non-riverine wetlands have been a particular focus for salinity research at ARI. They are important ecosystems because they are often a major, or even the only, source of surface water in many of Australia’s landscapes and they have important economic, social and cultural values. Importantly, non-riverine wetlands are also “hotspots” for biodiversity. The effect of climate change upon the distribution of plants and animals is potentially severe. Increasing our understanding of how salinity and climate change impacts on biodiversity will allow for better management of these processes.

Key projects

Wetlands, Biodiversity and Salt Assessing the Risks of Salinity on Biodiversity Salinity and the Flora of Temporary Freshwater Wetlands Climate Change and Victorian Plant Communities

Details of these projects are given below.

Wetlands, Biodiversity and Salt Secondary salinisation, or human-induced changes to natural salinity regimes, is a major threat to non-riverine wetlands. Over the past several years the effects of secondary salinisation on wetlands and their biodiversity, has been under investigation. Field study sites were selected in various areas of western Victoria within priority regions identified under the National Action Plan for Salinity and Water Quality (NAP). The study involved mathematical modelling, field observation and experimentation, resulting in a significant, new knowledge base that will directly influence the management and conservation of these important ecosystems. Considerable community and agency interest, input and support was enlisted throughout the study. Community perceptions of wetland management are critical because the majority of non-riverine wetlands are on private property. At the initial stages of the study, predictive models were developed to help conceptualise the relationship between biodiversity and salinity while taking into account wetland stability, resilience and seasonality. Specifically, the models predict that the response of biodiversity to secondary salinisation in non-riverine wetlands will be mediated by the wetlands pre-threat condition, such that wetlands will respond in a few particular ways. Experiments indicate that certain wetlands may be harder to restore after secondary salinisation. Reducing salinity levels may need to be supplemented by biodiversity manipulation (for example, “seeding” of certain wetland species or providing pathways for movement of animals around the landscape) if wetland restoration is to be successful. A wide range of wetland taxa were studied, including microscopic zooplankton, large aquatic plants(macrophytes), riparian vegetation, frogs, and birds, to identify salinity thresholds and possible indicator species. Field-based research has shown that species are affected differently by salinity – but mostly negatively. Salinity thresholds were identified for a range of taxa and, for macrophytes, a way of determining critical salinity levels for these plants’ emergence, growth and diversity. Macrophytes are important in wetlands because they create structural complexity and are integral to a range of ecosystem processes, such as primary production. For further information contact Belinda.Cant@dse.vic.gov.au A series of Wetlands, Biodiversity and Salt fact sheets have been produced with project details and current results; see the ARI Brochures and Fact Sheets page. The following journal articles are also available: Smith, M.J., Schreiber, E.S.G., Kohout, M., Ough, K., Lennie, R., Turnbull, D., Jin, C., Clancy, T. (2007) Wetlands as landscape units: spatial patterns in salinity and water chemistry. Wetland Ecology and Management 15(2):95-103 Smith, M.J., Schreiber, E.S.G., Scroggie, M.P., Kohout, M., Ough, K., Potts, J., Lennie, R., Turnbull, D., Jin, C. and Clancy, T. (2007) Associations between anuran tadpoles and salinity in a landscape mosaic of wetlands impacted by secondary salinisation. Freshwater Biology 52: 75-84 Page Top
Assessing the Risks of Salinity on Biodiversity A range of published and unpublished data exists on the salt tolerance of Victoria’s plants and animals. This information can be used to develop quantitative Salt Impact Models that predict the effects of increasing salinity on the biodiversity of a particular area. The use of these models has two major aims; to reduce the subjectivity in decision making, and to provide a framework for incorporating estimates of uncertainty into assessments of the risks of salinisation on particular plants and animals. This project is funded by the National Action Plan for Salinity and Water Quality and the National Heritage Trust and involves compiling various sources of information to produce a database of the salt tolerance of Victorian organisms. The project is also developing modelling tools and decision-frameworks for assessing the risks of salinity on selected organisms. Exploring alternative techniques is also vital in predicting the salt tolerance of organisms, such as using a ‘vital attributes’ approach, where particular features about an organism (e.g. whether it lays soft or hard shelled eggs) may affect its ability to survive in salty systems. This project will link with similar projects and salinity management tools. An extensive consultation process with regional stakeholders and an external review of the initial stage of the project have been completed; the results of which are being used to refine the modelling approach taken. The next stages of the project involve the collection of salt sensitivity information, including researching targeted case studies, and the production of refined salt impact models. The following fact sheets and reports provide more details: Assessing the Risks of Salinity Fact Sheet - Salinity Risk Framework (PDF - 86 KB) Assessing the Risks of Salinity Fact Sheet - Probability Bounds Analysis (PDF - 79 KB) Assessing the Risks of Salinity Fact Sheet - Murray Hardyhead (PDF - 277 KB) ARI Technical Report 162 - A framework for assessing the biological risks of increasing salinity in Victoria (PDF - 772 KB) ARI Technical Report 163 - The use of probability bounds analysis for characterising and propagating uncertainty in species sensitivity distributions (PDF - 308 KB) ARI Technical Report 164 - Uncertainty propagation in population level salinity risk models (PDF - 1.9 Mb) Page Top
Salinity and the Flora of Temporary Freshwater Wetlands Aquatic plants are generally conspicuous and defining features of wetlands, and the presence and type will have profound effects on the wetland system. They underpin many wetland processes and dictate the presence of other biota. Aquatic plants are also thought to be sensitive to increases in salinity, so to avoid detrimental levels of wetland salinity, it’s important to know what those salinity levels are. An investigation is underway to identify levels of salinity that threaten the floristic biodiversity of temporary freshwater wetlands. The study is focussed on non-riverine wetlands of the Victorian Riverina, an area vulnerable to rising salinity levels. A series of glasshouse experiments were designed to emulate secondary salinisation and establish the impact of increases in salinity on the various life history stages of aquatic plants. Sediment collected from wetlands within the study area was inundated at a range of salinities, and plant responses monitored. Increased salinity reduced the abundance of individuals and species, and simplified species composition. Overall, emergence from the seed-bank, growth and reproduction all declined as salinity increased, but the response of individual species varied from very sensitive to largely unaffected. One of the more salt-sensitive species was Azolla filiculoides, a common and conspicuous floating fern. New modelling techniques are being developed to allow comparison of the critical levels of salinity between species and between life-history stages. These relative sensitivities can then be used for predicting the outcomes of salinity increase scenarios, setting salinity maxima limits for wetlands, and identifying species potentially suitable as early warning indicator of declining wetland health caused by increased salinity. This knowledge will facilitate preventative, rather than reactive, wetland management. This research, funded by a DSE scholarship and National Action Plan for Salinity and Water Quality grant, is being undertaken as a PhD study through Deakin University. For further information contact Keely.Ough@dse.vic.gov.au Page Top
Modelling the Potential Effects of Climate Change upon Victorian Plant Communities Several years ago ARI undertook a series of pilot studies on the potential effects of climate-warming upon selected Victorian plant species and vegetation communities. This work was collaborative effort of DSE staff, and input from Dr. Roger Jones, CSIRO Marine and Atmospheric Research, and from Dr. Peter Griffioen of Acromap Pty. Ltd. The first phase of this project created a series of ‘climate surfaces’ covering Victoria that integrated into the ANUCLIM suite of software. These climate surfaces incorporated a combination of different climate scenarios (i.e. different levels of global warming modelled using several different global and regional climate models) from 1990 to 2100. The utility of this data was that it allowed, for the first time, a modelling approach to examine the likely changes to bio-climates (i.e. surrogates of the distribution of individual species) of several different plant species/communities. This work was essentially ‘proof-of-concept’ in its nature, but was successful in identifying the practicality of the approach, as well as identifying areas where the approach can be improved. A second phase of this work the approach was broadened to cover the whole of the Australian continent, and a broader suite of species. Output from these analyses was presented as animated maps, showing the predicted change in distribution of a species over the selected time frame. While the results from this work have provided excellent insights into the trajectory of ‘bioclimates’ across Australia over the next 100 years, they have also highlighted the need for more sophisticated models that incorporate the other factors that influence the distribution of plants and animals. These include biophysical data such as soil characteristics, and the distribution and arrangement of remnant vegetation. Climate change is unlikely to impact biota directly, or in the absence of other disturbance effects, for example, fragmentation. ARI continues to work to refine the scientific methods required to realistically anticipate what effects a rapidly changing climate may have on the State’s biota. For further information contact Graeme.Newell@dse.vic.gov.au Page Top