Modelling the spatial extent of post-fire sedimentation threat to estimate the impacts of fire on waterways and aquatic species

Aim: Fires can severely impact aquatic fauna, especially when attributes of soil, topography, fire severity and post-fire rainfall interact to cause substantial sedimentation. Such events can cause immediate mortality and longer-term changes in food resources and habitat structure. Approaches for estimating fire impacts on terrestrial species (e.g. intersecting fire extent with species distributions) are inappropriate for aquatic species as sedimentation can carry well downstream of the fire extent, and occur long after fire. Here, we develop an approach for estimating the spatial extent of fire impacts for aquatic systems, across multiple catchments. Location: Southern Australian bioregions affected by the fires in 2019–2020 that burned >10 million ha of temperate and subtropical forests. Methods: We integrated an existing soil erosion model with fire severity mapping and rainfall data to estimate the spatial extent of post-fire sedimentation threat in waterways and in basins and the potential exposure of aquatic species to this threat. We validated the model against field observations of sedimentation events after the 2019–20 fires. Results: While fires overlapped with ~27,643 km of waterways, post-fire sedimentation events potentially occurred across ~40,449 km. In total, 55% (n = 85) of 154 basins in the study region may have experienced substantial post-fire sedimentation. Ten species—including six Critically Endangered—were threatened by post-fire sedimentation events across 100% of their range. The model increased the estimates for potential impact, compared to considering fire extent alone, for >80% of aquatic species. Some species had distributions that did not overlap with the fire extent, but that were entirely exposed to post-fire sedimentation threat. Conclusions: Compared with estimating the overlap of fire extent with species' ranges, our model improves estimates of fire-related threats to aquatic fauna by capturing the complexities of fire impacts on hydrological systems. The model provides a method for quickly estimating post-fire sedimentation threat after future fires in any fire-prone region, thus potentially improving conservation assessments and informing emergency management interventions

Range-wide population genetics study informs on conservation translocations and reintroductions for the endangered Murray hardyhead (Craterocephalus fluviatilis)

1. Freshwater ecosystems worldwide harbour disproportionately high numbers of endemic species under threat from human activity, particularly accelerated habitat fragmentation. The Murray–Darling Basin in south‐eastern Australia, one of the country's largest and arguably its most vulnerable freshwater ecosystem, is inhabited by a number of small‐bodied fishes that are threatened with imminent extinction. 2. Here an extensive microsatellite dataset was used, supplemented by additional allozyme and mitochondrial DNA analyses, to assess the genetic diversity, population structure and contemporary migration patterns in the Murray hardyhead Craterocephalus fluviatilis, one of Australia's most threatened fishes. 3. Genetic diversity estimates, primarily based on 413 fish collected during the latter period of intense drought (1997–2010) from 23 sites and genotyped at 14 microsatellite loci, were higher than those previously detected for other regionally co‐occurring small‐bodied freshwater fishes. 4. Population structure analyses identified a subtle primary split between ‘lower Murray’ (lower river reaches) versus ‘upstream Murray’ (upper river reaches) and a total of nine genetically similar sub‐populations. This includes unexpected sub‐population differentiation in the Lower Lakes, a region at the terminus of the Murray–Darling Basin that most often has inter‐connected habitat. 5. Very low levels of contemporary migration were detected between most inferred populations (<2%) during the drought, with all exceptions involving moderate levels of migration from an upstream sub‐population into an adjacent downstream sub‐population. 6. This article describes how these genetic data have guided translocation and reintroduction efforts in recent years. We advocate the use of assisted gene flow as a central component of continuing efforts to rescue this species from imminent extinction.Samantha Thiele, Mark Adams, Michael Hammer, Scotte Wedderburn, Nick S. Whiterod, Peter J. Unmack, Minami Sasaki, Luciano B. Beheregara

Regional extinction, rediscovery and rescue of a freshwater fish from a highly modified environment : the need for rapid response

There are high rates of regional and global extinctions among freshwater species and few chances for recovery. We report here on the rediscovery after 30. years of a small fish, the southern-purple spotted gudgeon (Mogurnda adspersa), once widespread in the southern Murray-Darling Basin of south-eastern Australia. The rediscovery was in a region, the Lower Murray, where temperate riverine and wetland habitats are modified by a broad spectrum of changes including intensive flow regulation and diversions. There was some doubt whether the rediscovered population was a true remnant or a recent introduction, particularly as there was a translocated population in a nearby artificial habitat. Fortunately, a non-government organisation acted to rescue into captivity about 50 specimens as the remaining wetland habitat dried completely, soon after rediscovery, as a consequence of a decade-long drought and water diversions. We describe the habitat and ecology of fish in the rediscovery site, and provide genetic data, both nuclear (50 allozyme loci) and mtDNA (1141 base pairs; two genes), to show that they were true remnants of the regional native population. This information allows clear planning for future recovery including reintroductions, and is a case study that provides strategies, and hope, for conservation and management concerning other modified habitats. Specifically, it highlights the need for a rapid response to conserve threatened species, the recognition of remnant natural values in altered environments, and the treatment of new finds as native until there is alternate evidence.10 page(s

Rapid assessment of the biodiversity impacts of the 2019–2020 Australian megafires to guide urgent management intervention and recovery and lessons for other regions

Aim: The incidence of major fires is increasing globally, creating extraordinary challenges for governments, managers and conservation scientists. In 2019–2020, Australia experienced precedent-setting fires that burned over several months, affecting seven states and territories and causing massive biodiversity loss. Whilst the fires were still burning, the Australian Government convened a biodiversity Expert Panel to guide its bushfire response. A pressing need was to target emergency investment and management to reduce the chance of extinctions and maximise the chances of longer-term recovery. We describe the approach taken to rapidly prioritise fire-affected animal species. We use the experience to consider the organisational and data requirements for evidence-based responses to future ecological disasters. Location: Forested biomes of subtropical and temperate Australia, with lessons for other regions. Methods: We developed assessment frameworks to screen fire-affected species based on their pre-fire conservation status, the proportion of their distribution overlapping with fires, and their behavioural/ecological traits relating to fire vulnerability. Using formal and informal networks of scientists, government and non-government staff and managers, we collated expert input and data from multiple sources, undertook the analyses, and completed the assessments in 3 weeks for vertebrates and 8 weeks for invertebrates. Results: The assessments prioritised 92 vertebrate and 213 invertebrate species for urgent management response; another 147 invertebrate species were placed on a watchlist requiring further information. Conclusions: The priority species lists helped focus government and non-government investment, management and research effort, and communication to the public. Using multiple expert networks allowed the assessments to be completed rapidly using the best information available. However, the assessments highlighted substantial gaps in data availability and access, deficiencies in statutory threatened species listings, and the need for capacity-building across the conservation science and management sectors. We outline a flexible template for using evidence effectively in emergency responses for future ecological disasters