title: Tasmanian coastal saltmarsh ecology and conservation
Creators: name: Prahalad, VN
Publisher: name: University of Tasmania
Year: 2019

description: Coastal saltmarshes of sub-tropical and temperate Australia are in decline and have been listed as a ‘threatened ecological community’ under the Australian Federal Environment Protection and Biodiversity Conservation Act 1999. Tasmanian coastal saltmarsh wetlands are recognised as ‘vulnerable’ under this listing. There is a growing body of international and Australian literature on saltmarsh ecosystem functions and services, exposure of saltmarsh to increasing pressures from development and global change, and models and tools to support conservation. Basic information on ecology, distributions, key threatening processes and conservation needs have been inadequate in Tasmania. The overarching aim of this thesis is to identify and fill those critical gaps in Tasmanian coastal saltmarsh ecology and advance its conservation through additional information, models and tools. The following were the research objectives: • What is in Tasmanian saltmarshes? (ecological components) • What are their spatial and biogeographic arrangements? (spatial distributions) • How are Tasmanian saltmarshes changing? (key threatening processes) • What conservation actions are needed? (conservation needs) In achieving these objectives, a collaborative, multi-stakeholder driven, ecosystem based and outcome oriented approach has been employed. Key stakeholders were engaged in expanding capacity. Connections were made with ecosystem based management. Models and tools were developed for immediate application in saltmarsh conservation. Gaps were identified through literature review in curating a more context-specific and up-to-date list for Tasmanian saltmarsh birds and plants. The list includes a preliminary coding to indicate the dependence of the species to saltmarsh habitat and provides the basis for site-specific data collection. Methods suitable for ‘citizen science’ monitoring of birds and plants in Tasmanian saltmarshes have been outlined and lists of birds and plants in saltmarsh were developed using citizen science inputs. The ever-decreasing capacity of managers to collect scientific data and to undertake long term monitoring of habitats can be mitigated in some situations by community efforts under the auspices of citizen science. High-resolution aerial imagery and extensive field validation were combined to inventory 58.6 km2 of saltmarshes as part of 61 mesoscale complexes. The complexes were classified into three broad saltmarsh groups. Mean annual rainfall was most significant in predicting saltmarsh extent, plant community composition, presence of salt pans and the three saltmarsh groups. Mean annual daily minimum temperature and saltmarsh area best predicted obligate plant distributions. Projected changes in rainfall and temperature by 2100 are unlikely to severely affect these distributions, while stochastic disturbances may continue to play a greater role at local scales. A case-study approach was used in evaluating the role of key threatening processes of direct human impacts and sea level rise effects. The north-west of Tasmania was selected as being one of the single largest expanses of saltmarshes in the state (~25% of total extent) and known previously to be most impacted by these threatening processes. Human impacts had caused an absolute loss of 219 ha since 1952, and a further 752 ha (65%) was associated with one or several of land-based human impacts. The study underscores the importance of considering functional health (i.e. habitat fragmentation) in addition to simple extent measures in conservation planning. The effects of sea level rise were most prevalent in areas of saltmarsh exposed to higher energy wind waves than those that were more sheltered. A simple cartographic wind-wave fetch model provides a useful planning tool in identifying those parts of saltmarsh shores where erosion is most likely or least likely to occur. Sea level rise is expected to alter future extent of saltmarsh as they will need to retreat into nearby low lying areas. Such refugia for saltmarsh retreat will also need to be formally included under the land-use planning and approvals processes. A planning overlay map was developed for eventual inclusion within the new 2017 State-wide planning system. To gauge the potential for saltmarsh repair, fish in north-west Tasmania were selected as a proxy. Eleven species were caught, including fish that are important to commercial and recreational fisheries. The mean density of &gt; 72 fish per 100 m2 was the highest yet reported from Australia and suggest that restoring basic saltmarsh structure through tidal re-connection will deliver substantial benefits for fish productivity through habitat expansion. Fish are also a compelling subject with broad resonance and can be used as a surrogate for the broader values of ecosystem services that saltmarshes provide. Overall, through an ecosystem based approach and collaboration with stakeholders, several outcomes have been generated that creates pathways for saltmarsh conservation and a scientific base for further exploration to fill in current and emerging research needs.