Dale G. Nimmo’s research while affiliated with Charles Sturt University and other places

Aim The term ‘megafire’ is increasingly used to describe large fires worldwide. We proposed a size‐based definition of megafire—fires exceeding 10,000 ha arising from single or multiple related ignition events. A recent perspective in Global Ecology and Biogeography argues against a size‐based definition of megafire and suggest that the term is too emotive for scientific use. We highlight that many scientific terms originate from common terms. These terms are often defined once they enter the scientific lexicon, enhancing both scientific understanding and public communication. We argue that standardised definitions facilitate better prediction, preparation, and management of fire events. Location Worldwide. Time Period 2022–2023. Methods We conducted an updated structured review of the term ‘megafire’ and its use and definition in the peer‐reviewed scientific literature, collating definitions and descriptions and identifying the criteria frequently invoked to define the term. Results We demonstrate an increase in the use of ‘megafire’ in the scientific literature since our original definition in 2022, with many studies adopting the > 10,000 ha size‐based criterion. Main Conclusions We contend that abandoning the term is neither practical, possible, nor beneficial. Instead, consistent usage underpinned by clear definitions is essential. Adopting a clear, size‐based definition of megafire strengthens clarity and comparability across research and management practices globally. Precision in terminology is crucial for advancing research, improving communication, and informing effective fire management and policy.

Habitat destruction is the most pervasive threat to global biodiversity, leading to widespread population declines and range reductions. Land clearing can leave small, isolated populations persisting in remnant habitat, where demographic factors may erode genomic diversity and diminish adaptive potential. We compared the genomic structure, diversity, inbreeding and effective population sizes of fragmented populations on farms to nearby populations in large, continuous tracts of vegetation (national park) for three terrestrial lizard species in south-eastern Australia. Due to the small spatial scale of the study, observed levels of genomic differentiation among sampling locations were typically very low (FST < 0.1). The farm locality of one species, the painted dragon (Ctenophorus pictus), showed substantially more differentiation to national park localities (FST > 0.05) than the national park localities showed to one another (FST < 0.01), suggestive of genetic isolation due to the agricultural matrix. Genomic diversity and effective population sizes were lower in farm populations compared to national parks for two of the three species, the exception being shrubland morethia (Morethia obscura), where genomic diversity was similar across site types. Inbreeding coefficients were generally comparable between farm and national park populations. Our findings highlight the genetic consequences of land clearing including low population size, low genomic diversity and higher risk of inbreeding depression. Despite these challenges, habitat fragments can maintain high biodiversity value, which can be maximised by management initiatives such as translocations and establishing habitat corridors.

Habitat loss and fragmentation are leading threats to biodiversity and have been implicated in population declines worldwide. In agricultural landscapes where natural habitat has been extensively modified, remnant patches can preserve species richness and diversity. However, the persistence of some organisms is dependent on a species' ability to move between habitat patches. The effects of habitat loss and fragmentation on reptiles in semi‐arid agricultural landscapes, and the relative impact of cropping and grazing, are poorly described. We aimed to investigate the effect of habitat fragmentation on semi‐arid reptiles by comparing species richness and diversity between continuous habitat and patches embedded within different land use types (cropping and grazing). Reptiles were surveyed using pitfall traps, funnel traps and active searches across 20 sites stratified by site, vegetation and land use type. Twelve sites were established in remnant mallee woodland patches embedded within an agricultural matrix, and eight sites were established in a private conservation reserve on the same property. Generalised linear models were used to explore relationships between reptile species richness and diversity and design variables. A total of 480 individuals from 31 species were recorded. Reptile species richness was significantly higher in the reserve compared to patches. However, these differences were driven more by reductions in species richness in patches embedded within a grazing matrix, which had fewer species than patches embedded within a cropping matrix. Sites within sand plain vegetation had higher diversity than sites within dune mallee vegetation. Our findings suggest semi‐arid reptile species are sensitive to habitat loss and fragmentation associated with land clearing. Therefore, protecting large areas of intact habitat on private property is required to maintain reptile diversity in semi‐arid landscapes subject to land use change. Managing patches of remnant vegetation within the agricultural matrix through grazing exclusion may also serve to retain reptile diversity.

Context Invasive mammalian predators have caused population declines and extinctions of wildlife worldwide. Many of these species exhibit some form of prey naïveté, which heightens their vulnerability to novel predators. In Australia, introduced feral cats (Felis catus) and red foxes (Vulpes vulpes) have had a particularly negative effect on native fauna, with the impacts of cats on mammals and birds well documented. Although feral cats are known to regularly prey on Australian reptiles, little is known about the behavioural responses of reptiles to cats, including whether native reptiles can recognise cats as a predation risk, and if so, which cues they use. Aims We investigated behavioural responses of two Australian lizard species, the shrubland morethia skink (Morethia obscura) and eastern striped skink (Ctenotus robustus), to the visual cues of feral cats in semiarid, south-eastern Australia. Methods We used arena trials to test lizards for predator recognition by using visual cues of an alien mammal predator (taxidermied cat, Felis catus), a native mammal predator (taxidermied western quoll, Dasyurus geoffroyi) and a mammal non-predator (taxidermied European rabbit, Oryctolagus cuniculus), as well as a procedural control (bucket) and a negative control (nothing). Key results We found little evidence of behavioural change when lizards were exposed to the taxidermied cat. Morethia obscura basked less when exposed to all treatments and C. robustus increased vigilance when in the presence of the taxidermied cat, but overall responses were similar among treatments. Conclusions Our findings suggest that stationary visual cues of cats do not trigger behavioural responses in these two lizard species. Implications Future research should assess behavioural responses to combinations of cat cues (e.g. movement, scent). Developing a deeper understanding of predator recognition systems and prey naïveté in reptile communities will be crucial for conservation of Australian reptiles that are negatively affected by feral cats.

In a warming and rapidly changing world, biodiversity is increasingly threatened by more frequent, severe, and larger fires. Variation in the life history attributes and habitat preferences of species mean that they may be affected differently by fire, and hence, decision makers must account for this. Understanding how fire affects the distribution of important areas of habitat and refuges for biodiversity can help guide appropriate conservation and management actions. In 2019-20 Australia suffered widespread and devastating megafires, known as the Black Summer, and the East Gippsland region in state of Victoria was heavily affected. To estimate impacts of the fires on fauna within the region, we used a joint species distribution model fitted to data from 967 camera trap sites to estimate variation in the occurrence for 40 native and invasive animal species. We focused on the influence of the fire regime, lethal control of introduced red foxes (Vulpes vulpes), timber harvesting, precipitation, and soil gradients, on wildlife. We then predicted the spatial distribution of each native animal species in the dataset for three time periods: 1) in 2017 prior to the Black Summer megafires, 2) in 2022 following the 2019/2020 wildfires and 3) in 2030. This allowed us to estimate changes in the patterns of occurrence for each species attributable to fire. Finally, we used spatial conservation prioritisation to identify priority conservation areas (‘fire refuges) and identify where potential threats (e.g. invasive species) might co-occur with these areas. We found that fire regime variables, including time since fire and repeat short-interval fires, influence occurrence patterns for ~50% of species and this meant that the megafires influenced predicted occurrence patterns. Half of the mammal species (mostly small and medium-sized ground-dwelling mammals) were positively associated with a topographic wetness index, as were four bird species. Spatial conservation prioritisation also suggested that while there were some shifts in the location of fire havens due to the megafires, some large areas of high-conservation value persisted after fire. These areas were disproportionately likely to be long-unburnt (>= 80 years) with fewer repeat burns, have high fox baiting intensity, and low probabilities of introduced red fox and feral cat (Felis catus) occurrence. This suggests maintaining older vegetation in landscapes and managing predation pressure by invasive predators will be important to maintaining the identified high priority refuges. Our study presents a useful approach for guiding fire management before and after large disturbance events, and could be expanded to test the response of species and communities to forecasts of future fire regime scenarios. Predictive approaches such as this study will be essential for managers to understand the possible outcomes of management actions on biodiversity during a time of rapid global change.

Camera traps are widely used in wildlife research and monitoring, so it is imperative to understand their strengths, limitations, and potential for increasing impact. We investigated a decade of use of wildlife cameras (2012–2022) with a case study on Australian terrestrial vertebrates using a multifaceted approach. We (i) synthesised information from a literature review; (ii) conducted an online questionnaire of 132 professionals; (iii) hosted an in-person workshop of 28 leading experts representing academia, non-governmental organisations (NGOs), and government; and (iv) mapped camera trap usage based on all sources. We predicted that the last decade would have shown: (i) exponentially increasing sampling effort, a continuation of camera usage trends up to 2012; (ii) analytics to have shifted from naive presence/absence and capture rates towards hierarchical modelling that accounts for imperfect detection, thereby improving the quality of outputs and inferences on occupancy, abundance, and density; and (iii) broader research scales in terms of multi-species, multi-site and multi-year studies. However, the results showed that the sampling effort has reached a plateau, with publication rates increasing only modestly. Users reported reaching a saturation point in terms of images that could be processed by humans and time for complex analyses and academic writing. There were strong taxonomic and geographic biases towards medium–large mammals (>500 g) in forests along Australia’s southeastern coastlines, reflecting proximity to major cities. Regarding analytical choices, bias-prone indices still accounted for 50% of outputs and this was consistent across user groups.Multi-species,multi-site and multiple-year studies were rare, largely driven by hesitancy around collaboration and data sharing. There is no widely used repository for wildlife camera images and the Atlas of Living Australia (ALA) is the dominant repository for sharing tabular occurrence records. However, the ALA is presence-only and thus is unsuitable for creating detection histories with absences, inhibiting hierarchical modelling. Workshop discussions identified a pressing need for collaboration to enhance the efficiency, quality and scale of research and management outcomes, leading to the proposal of a Wildlife Observatory of Australia (WildObs). To encourage data standards and sharing, WildObs should (i) promote a metadata collection app; (ii) create a tagged image repository to facilitate artificial intelligence/machine learning (AI/ML) computer vision research in this space; (iii) address the image identification bottleneck via the use of AI/ML-powered image-processing platforms; (iv) create data commons for detection histories that are suitable for hierarchical modelling; and (v) provide capacity building and tools for hierarchical modelling. Our review highlights that while Australia’s investments in monitoring biodiversity with cameras position it to be a global leader in this context, realising that potential requires a paradigm shift towards best practices for collecting, curating, sharing and analysing ‘Big Data’. Our findings and framework have broad applicability outside Australia to enhance camera usage to meet conservation and management objectives ranging from local to global scales. This review articulates a country/continental observatory approach that is also suitable for international collaborative wildlife research networks.

Earth’s old animals are in decline. Despite this, emerging research is revealing the vital contributions of older individuals to cultural transmission, population dynamics, and ecosystem processes and services. Often the largest and most experienced, old individuals are most valued by humans and make important contributions to reproduction, information acquisition and cultural transmission, trophic dynamics, and resistance and resilience to natural and anthropogenic disturbance. These observations contrast with the senescence-focused paradigm of old age that has dominated the literature for over a century yet are consistent with findings from behavioral ecology and life-history theory. Here, we review why the global loss of old individuals can be particularly detrimental to long-lived animals with indeterminate growth, increasing reproductive output with age, and those dependent on migration, sociality and cultural transmission for survival. Longevity conservation is needed to protect the important ecological roles an ecosystem services provided by old animals.

Climate change is increasing the frequency and severity of short-term (~1 y) drought events—the most common duration of drought—globally. Yet the impact of this intensification of drought on ecosystem functioning remains poorly resolved. This is due in part to the widely disparate approaches ecologists have employed to study drought, variation in the severity and duration of drought studied, and differences among ecosystems in vegetation, edaphic and climatic attributes that can mediate drought impacts. To overcome these problems and better identify the factors that modulate drought responses, we used a coordinated distributed experiment to quantify the impact of short-term drought on grassland and shrubland ecosystems. With a standardized approach, we imposed ~a single year of drought at 100 sites on six continents. Here we show that loss of a foundational ecosystem function—aboveground net primary production (ANPP)—was 60% greater at sites that experienced statistically extreme drought (1-in-100-y event) vs. those sites where drought was nominal (historically more common) in magnitude (35% vs. 21%, respectively). This reduction in a key carbon cycle process with a single year of extreme drought greatly exceeds previously reported losses for grasslands and shrublands. Our global experiment also revealed high variability in drought response but that relative reductions in ANPP were greater in drier ecosystems and those with fewer plant species. Overall, our results demonstrate with unprecedented rigor that the global impacts of projected increases in drought severity have been significantly underestimated and that drier and less diverse sites are likely to be most vulnerable to extreme drought.