Yung En Chee (Waterway Ecosystem Research Group, University of Melbourne) & Rhys Coleman Waterways and Wetlands Research Manager, Melbourne Water)
Ecological modelling and waterway management prioritisation in greater Melbourne
Partnership: Melbourne Water (MW) is a statutory corporation owned by the Victorian State Government. MW manages thousands of kilometres of rivers, creeks and drainage systems throughout the ~12,780 km2 Port Phillip and Westernport region. MW’s vision is ‘Enhancing Life and Liveability’ and their goal is to improve the quality of life and prosperity of the region by providing safe, secure and reliable water services, desirable urban spaces and thriving natural environments supported by healthy waterways and bays. MW works together with and stakeholders to enhance liveability against a setting of population growth, increased urban density, a changing and variable climate, natural resource scarcity and community expectations for affordable services.
The Waterway Ecosystem Research Group (WERG) is a world-leading multidisciplinary group of researchers at The University of Melbourne that has partnered with MW to create the Melbourne Waterways Research-Practice Partnership (MWRPP). The MWRPP studies the interactions of urban and rural landscapes and freshwater ecosystems and develops knowledge and tools to improve land, waterway and biodiversity management. The multidisciplinary research of this innovative partnership has delivered leading edge research, substantial new knowledge and solutions, coupled with extensive capacity building. We describe this below.
Like other cities around the world, there is increasing pressure on our freshwater ecosystems from impacts such as urban growth and climate change. To halt and reverse the degradation of our rivers and creeks it is essential that decision-making is underpinned by best available science. Critical to this, is sound knowledge of current ecological status, key threats, likely future condition, and an understanding of the types of management actions most likely to protect or improve the health of waterways given expected challenges.
We developed and applied an innovative approach to identifying waterway management priorities for Melbourne’s new Healthy Waterways Strategy 2018. Central to this was the use of quantitative habitat suitability models for instream values (aquatic macroinvertebrates, fish, platypus) that drew on >20 years of biological monitoring data. These models allowed us to estimate the current status of biotic values at 8,000+ stream reaches across the region, make predictions of how those values are likely to change under projected future scenarios of urban growth and climate change, and quantify expected benefits of specific management actions or combinations of actions. These models helped us identify the most cost-effective management action at any given reach. We then analysed this map of cost-effective actions with spatial conservation prioritisation software (Zonation) to rank all 8,000+ reaches showing where we should optimally act first to protect and improve aquatic biodiversity.
Model outputs informed multiple co-design workshops with a broad range of stakeholders where predictions were combined with local knowledge and expertise to agree on priority actions and 50-year environmental outcome targets. This project demonstrated how spatially-explicit quantitative habitat modelling, action prioritisation and a whole-of-landscape approach can help us strategically understand threats and identify actions to give us the best chance of protecting our waterways for future generations.
Impact: This project successfully applied a novel approach to management action prioritisation using ecological model predictions, analyses and maps in stakeholder workshops that co-designed spatially-explicit priority actions and 50-year targets for Melbourne’s Healthy Waterways Strategy (HWS) 2018.
MW manages thousands of kilometres of waterways across greater Melbourne. The region has substantial climatic and physiographic variability, and land use varies from natural and intact, to rural and urban, so streams range from near-pristine to highly degraded. MW’s challenge was to strategically plan for sustainable management given expected urban growth, climate change, land use change and community aspirations for healthy waterways. The HWS sets out the plan for stakeholders and community to work in partnership to maintain and improve the environmental, social, cultural and economic condition of waterways across Melbourne.
In co-developing the HWS, MW needed to:
• account for climate and land use changes in strategic planning to optimise stream biodiversity and waterway health
• identify the most cost-effective action for supporting stream biodiversity at any given reach
• strategically prioritise investment in interventions across the region, given landscape (spatial) variation in stream biodiversity patterns, threats of warming and drying and urban development, and costs of candidate management actions
Together, the Melbourne Waterways Research-Practice Partnership (MWRPP) co-developed and applied a suite of interlinked spatial and quantitative tools. Specifically, we:
1. developed a GIS stream network representing 8,000+ reaches, hydrologically delineated watersheds for each reach, and ecologically-relevant environmental data to enable comprehensive, multiscale characterisation and modelling of stream conditions and values across the region
2. used ~20 years of georeferenced biological data and our environmental stream reach data to develop habitat suitability models (HSMs) for 59 macroinvertebrate families, 13 native fish species and platypus
3. used the models to make fine-grained, spatially-explicit predictions of current and future habitat suitability across the full stream network, including impacts of climate change and urban growth
4. used the models for scenario analyses—such as quantitative predictions of the benefits of key management actions, like riparian revegetation, stormwater management and removal of instream fish barriers, in any required combination
5. combined predicted benefits of management actions for all modelled animals, along with associated costs, in order to prioritise actions (using the conservation planning software, Zonation)
These new tools provided powerful analytical capacity to explore strategic concerns for long-term planning at the management-relevant scale of stream reaches. It also allowed the use of detailed, stream-level data in whole-of-landscape prioritisation analyses. Outputs of plausible future scenarios and predicted benefits of mitigating actions were quantified, summarised, mapped and shared with stakeholders.
These products supported stakeholder deliberations on issues, opportunities and trade-offs in their catchment of interest. This process ultimately informed priority actions and spatially-explicit target-setting for aquatic macroinvertebrates, native fish species and platypus objectives in Melbourne’s Healthy Waterways Strategy 2018.
Importantly, the spatial environmental data and individual species habitat suitability models provide a framework for quantifying spatially-explicit ecological outcomes in the form of a change (i.e. gain/loss) in habitat suitability measure. Changes in habitat suitability for each taxa in response to environmental conditions and/or implemented actions can also be compiled for any set of streams of interest to provide a measure of stream ecological condition as indicated by taxa representing multiple trophic levels.
These measures are being designed into MW’s Monitoring, Evaluation, Reporting and Improvement (MERI) framework and detailed Monitoring Evaluation Plan (MEP) for rivers. As the HWS is implemented, these measures (alongside others) will be used to track and report progress in actions, status/condition of environmental variables and stream ecological objectives.
Communication: Project research outcomes have been communicated to practitioners, stakeholders and the broader community in a number of different ways, including
• the published Healthy Waterways Strategy [https://www.melbournewater.com.au/about/strategies-and-reports/healthy-waterways-strategy]
• the published Co-designed Catchment Programs for the Werribee, Maribyrnong, Yarra, Dandenong and Westernport & Mornington Peninsula regions, respectively [see e.g. https://www.melbournewater.com.au/media/6316/download]
• the Healthy Waterways Monitoring, Evaluation, Reporting and Improvement, MERI Framework version 1.1 [https://yoursay.melbournewater.com.au/healthy-waterways/MERI-survey]
• the forthcoming Monitoring and Evaluation Plan (MEP) for rivers
• in MW Annual Reports
• a peer-reviewed conference proceedings paper on ‘Benefits and challenges of incorporating spatially-explicit quantitative modelling and action prioritisation in Melbourne Water’s Healthy Waterways Strategy’ at the 9th Australian Stream Management Conference (Hobart, Aug 2018) [https://tinyurl.com/y33syo5g]
• a MWRPP Technical Report on ‘Habitat Suitability Models, Scenarios and Quantitative Action Prioritisation (using Zonation) for the Healthy Waterways Strategy 2018: A Resource Document’ (Chee et al. 2020) [https://wp.me/a3ZzWm-Nb]
• at scientific/practitioner conferences nationally, internationally and virtually, e.g. 9th Australian Stream Management Conference (Hobart, Aug 2018), Ecological Society Australia Conference (Launceston, Dec 2019), joint Australian-New Zealand Freshwater Sciences Society (AFSS-NZFSS) Conference (Waurn Ponds, Dec 2019), 5th Symposium on Urbanisation and Stream Ecology (Austin, Texas, Feb 2020), Society of Conservation Biology Greater Melbourne Chapter Twitter Conference (#SCBMelb20, July 2020, https://tinyurl.com/yyogov4c)
Papers for publication in peer-reviewed international journals are in preparation.
Robust databases and reproducible workflows and code are in development for existing spatial and biological datasets, planned monitoring datasets, models and scenario analyses. Collectively, these resources will provide a sound and durable foundation for the ecological knowledge and evidence base required to support management across institutions and collaborating organisations and community groups.
Research outcomes from ongoing work relating to the HWS will continue to be shared and promoted to practitioners, stakeholders and the broader community as it becomes available.
Broader outcomes: Our development and application of spatially-explicit quantitative modelling and mapping of species habitat suitability and action prioritisation across greater Melbourne has contributed to, and advanced freshwater conservation planning and waterway management in Australia in a number of ways. It has:
• provided greater rigour and detail in characterising instream biodiversity patterns throughout the greater Melbourne region
• substantially enhanced MW’s capabilities for exploring concerns of strategic importance for long-term planning
• enabled clear communication of stream biodiversity patterns, future impacts under different scenarios and benefits of actions to multiple audiences
• produced useful insights that have deepened and enriched deliberations within MW, in HWS community co-design workshops and amongst natural resource management stakeholders (e.g. state government, local government councils, CMA environmental water managers, and environmental consultants)
• provided a valuable set of quantitative tools for tractable, defensible, data-based decision support
Some specific examples of benefits for industry and the community include:
• better use of biological data: from discrete, point data to spatially continuous estimates of instream biodiversity across all Melbourne’s waterways
• fine-grain mapping of stream biodiversity patterns helped alert stakeholders to values, constraints and opportunities they had been unaware of
• ability to model strategic considerations such as different aspects of climate change impacts (e.g. warming, drying), land use change and their interactive effects
• ability to incorporate a degree of ecological realism with respect to taxa/species-specific connectivity requirements
• ability to quantify the expected difference made by management actions, and to account for costs so that action planning can be based on cost-effectiveness
Demonstration of this approach and its numerous benefits for stream biodiversity and health across greater Melbourne provides an exemplar for stream management in other regions. We believe our exemplar has the potential to contribute to broader outcomes in enhancing the scale and/or quality of larger scale freshwater conservation efforts national and internationally.