Sophia Volzke

With multiple Declared Areas nationally, offshore wind energy is poised to expand within Australia’s iconic coastal and marine environments. We argue that the central obstacle to credible environmental assessment of offshore wind is not a shortfall of effort or rigour within individual assessments, but a structural feature of how assessment is legally constituted. Australia’s principal national environmental law, the Environment Protection and Biodiversity Conservation Act 1999, protects species across their distribution, yet project-level assessments investigate impact only within or near a development’s footprint. We identify four structural problems, namely unmanaged cumulative impacts, mismatched regulatory and ecological scales, an incomplete species list, and a causal-evidence gap that project-level assessment cannot close, which limit our capacity to detect and attribute development impacts on far-ranging, long-lived marine mammals, birds, and sharks, charismatic species whose life histories make them particularly sensitive to reductions in survival and reproductive success. We recommend addressing these shortfalls through a coordinated, independent, and openly accessible national program of marine and coastal biodiversity science, funded through a pooled industry levy rather than project-by-project commissioning, and coupled to strategic environmental assessment. Australia’s offshore wind sector is at an early enough stage to build this architecture from the outset, so that renewable development and environmental stewardship advance together rather than in tension. Done well, this might help build public trust in offshore wind domestically and position Australia as a leader in international best practice in offshore environmental research and monitoring, offering a model for nations whose offshore wind sectors are emerging.

The Southern Ocean, its ecosystem, and inhabitants are vulnerable to climate‐mediated shifts in habitat conditions. These changes can affect marine predators in the long term through changes in the distribution, density, and quality of prey. To understand how these changes affect vital rates requires longitudinal studies integrating demography and environmental states. We analyzed 22 years of capture–mark–recapture data to quantify the influence of broad‐scale climate on the survival of male southern elephant seals from Macquarie Island, Tasmania, Australia. Weaning mass was incorporated as a quadratic predictor of survival to account for the known influence of maternal investment. First‐year survival was greatest for weaners weighing 160 kg. Subsequent developmental stages were grouped into juvenile, subordinate, and breeding adult states to reflect the known life history of individuals. We found increased juvenile and subordinate survival with positive values of the previous years' Southern Annular Mode. This is likely due to the northward shift of westerly winds increasing productivity and prey availability in the Sub‐Antarctic region. In contrast to females of this population, the Southern Oscillation Index did not affect male survival. In this highly polygynous mating system, sex‐dependent differences in foraging behavior may be causing the small number of successful breeding adult males to be less susceptible to external influences after reaching the minimum age and body size required to be socially competitive for mating. These extremely large bulls will breed with multiple females and thus make a disproportionate contribution to the gene pool of the next generation. Considering the susceptibility of males to climate influences is therefore highly relevant to assessing the future adaptive capability of the species.

Developmental differences in vital rates are especially profound in polygamous mating systems. Southern elephant seals ( Mirounga leonina ) are highly dimorphic and extremely polygynous marine mammals. A demographic model, supported by long-term capture–mark–recapture records, investigated the influence of sex and age on survival in this species. The study revealed clear differences between female and male age-dependent survival rates. Overall juvenile survival estimates were stable around 80–85% for both sexes. However, male survival estimates were 5–10% lower than females in the same age classes until 8 years of age. At this point, male survival decreased rapidly to 50% ± 10% while female estimates remained constant at 80% ± 5%. Different energetic requirements could underpin intersex differences in adult survival. However, the species' strong sexual dimorphism diverges during early juvenile development when sex-specific survival rates were less distinct. Maximizing growth is especially advantageous for males, with size being a major determinant of breeding probability. Maturing males may employ a high-risk high-reward foraging strategy to compensate for extensive sexual selection pressures and sex-specific energetic needs. Our findings suggest sex-specific adult survival is a result of in situ ecological interactions and evolutionary specialization associated with being a highly polygynous marine predator.

The Southern Ocean has been disproportionately affected by climate change and is therefore an ideal place to study the influence of changing environmental conditions on ecosystems. Changes in the demography of predator populations are indicators of broader shifts in food web structure, but long‐term data are required to study these effects. Southern elephant seals (Mirounga leonina) from Macquarie Island have consistently decreased in population size while all other major populations across the Southern Ocean have recently stabilized or are increasing. Two long‐term mark‐recapture studies (1956–1967 and 1993–2009) have monitored this population, which provides an opportunity to investigate demographic performance over a range of climatic conditions. Using a 9‐state matrix population model, we estimated climate influences on female survival by incorporating two major climatic indices into our model: The Southern Annular Mode (SAM) and the Southern Oscillation Index (SOI). Our best model included a 1 year lagged effect of SAM and an unlagged SOI as covariates. A positive relationship with SAM1 (lagged) related the previous year's SAM with juvenile survival, potentially due to changes in local prey availability surrounding Macquarie Island. The unlagged SOI had a negative effect on both juvenile and adult seals, indicating that sea ice dynamics and access to foraging grounds on the East Antarctic continental shelf could explain the different contributions of ENSO events on the survival of females in this population.