How fire interacts with habitat loss and fragmentation

Biodiversity faces many threats and these can interact to produce outcomes that may not be predicted by considering their effects in isolation. Habitat loss and fragmentation (hereafter 'fragmentation') and altered fire regimes are important threats to biodiversity, but their interactions have not been systematically evaluated across the globe. In this comprehensive synthesis, including 162 papers which provided 274 cases, we offer a framework for understanding how fire interacts with fragmentation. Fire and fragmentation interact in three main ways: (i) fire influences fragmentation (59% of 274 cases), where fire either destroys and fragments habitat or creates and connects habitat; (ii) fragmentation influences fire (25% of cases) where, after habitat is reduced in area and fragmented, fire in the landscape is subsequently altered because people suppress or ignite fires, or there is increased edge flammability or increased obstruction to fire spread; and (iii) where the two do not influence each other, but fire interacts with fragmentation to affect responses like species richness, abundance and extinction risk (16% of cases). Where fire and fragmentation do influence each other, feedback loops are possible that can lead to ecosystem conversion (e.g. forest to grassland). This is a well-documented threat in the tropics but with potential also to be important elsewhere. Fire interacts with fragmentation through scale-specific mechanisms: fire creates edges and drives edge effects; fire alters patch quality; and fire alters landscape-scale connectivity. We found only 12 cases in which studies reported the four essential strata for testing a full interaction, which were fragmented and unfragmented landscapes that both span contrasting fire histories, such as recently burnt and long unburnt vegetation. Simulation and empirical studies show that fire and fragmentation can interact synergistically, multiplicatively, antagonistically or additively. These cases highlight a key reason why understanding interactions is so important: when fire and fragmentation act together they can cause local extinctions, even when their separate effects are neutral. Whether fire-fragmentation interactions benefit or disadvantage species is often determined by the species' preferred successional stage. Adding fire to landscapes generally benefits early-successional plant and animal species, whereas it is detrimental to late-successional species. However, when fire interacts with fragmentation, the direction of effect of fire on a species could be reversed from the effect expected by successional preferences. Adding fire to fragmented landscapes can be detrimental for species that would normally co-exist with fire, because species may no longer be able to disperse to their preferred successional stage. Further, animals may be attracted to particular successional stages leading to unexpected responses to fragmentation, such as higher abundance in more isolated unburnt patches. Growing human populations and increasing resource consumption suggest that fragmentation trends will worsen over coming years. Combined with increasing alteration of fire regimes due to climate change and human-caused ignitions, interactions of fire with fragmentation are likely to become more common. Our new framework paves the way for developing a better understanding of how fire interacts with fragmentation, and for conserving biodiversity in the face of these emerging challenges.

Landscape management of the mahogany glider (Petaurus gracilis) across its distribution: subpopulations and corridor priorities

Key threatening processes to biodiversity include habitat loss and fragmentation, with populations restricted to small fragments of habitat being more prone to extinction. The mahogany glider (Petaurus gracilis) is endemic to sclerophyll woodland forests between Tully and Ingham in north Queensland and is one of Australia’s most endangered arboreal mammals due to these processes. The aim of this study was to identify the degree of habitat fragmentation of the remaining remnant vegetation of the mahogany glider, identify subpopulations within its distribution and identify key wildlife corridors for restoration to facilitate the movement of this species within and between subpopulations. Ten glider subpopulations, spread over 998 habitat fragments, were identified, of which only five subpopulations may currently be considered to be viable. To assist in providing habitat connectivity between and within the subpopulations, 55 corridors were identified for restoration that had an average length of 8.25 km. The average number of gaps greater than 30 m was 3.4 per corridor, with the average length of these gaps being 523 m. This study confirmed a high degree of habitat fragmentation across the distribution of the mahogany glider and highlighted the need to strengthen the remaining subpopulations by restoring habitat connectivity between the remaining habitat fragments.

Growth and development of the Mahogany Glider (Petaurus gracilis)

The growth and development of the endangered Mahogany Glider (Petaurus gracilis) was monitored in a captive population at Burleigh Heads, Queensland, Australia. Video surveillance confirmed that the gestation period for this species was 16 days. Morphometric data and developmental milestones were recorded from 10 Mahogany Gliders from birth to weaning. Growth curves were developed for head length, ulna length, tail length, and body weight. Weekly inspections of female pouches revealed the young's eyelid margins were visible by Day 21, the first hair erupted on the bridge of the nose at Day 30, pigmentation of the body developed at Day 63, and they started detaching from the teat intermittently, and the body was covered in short fur by Day 70. The young were left in the nest alone from Days 84 to 87, their eyes opened between Days 84 and 94, and there was a rapid increase in length and density of fur from Day 98 onwards. At Days 101 to 105 of age the young left the nest box with its mother as back young. Weaning occurred from 184 to 187 days. Typically, the reproductive rate was two young per annum per pair, but one pair produced five young in 19 months. Females produced young from 12 months to 7 years of age, males up to 9.4 years of age. The average longevity of Mahogany Gliders in the studbook in 2018 was 11.6 years. This study provides data on the reproductive biology of the Mahogany Glider that will assist in its captive breeding, management, and conservation.

Extensive range contraction predicted under climate warming for a gliding mammal in north-eastern Australia

We used MaxEnt to model the current distribution of the yellow-bellied glider (Petaurus australis) and to predict the likely shift in the species’ future distribution under climate-warming scenarios in the Wet Tropics (WT) Bioregion in north Queensland and in the South-eastern Queensland (SEQld) Bioregion, which encompasses south-eastern Queensland and north-eastern New South Wales. Bioclimatic layers were used to generate models from 57 independent records in the WT and 428 records in SEQld. The modelled distribution of core habitat under current climate showed a good fit to the data, encompassing 91% and 88% of the records in each area, respectively. Modelling of future warming scenarios suggests that large contractions in distribution could occur in both bioregions. In the WT, 98% of core habitat is predicted to be lost under low warming (1°C increase) and 100% under high warming (2−3°C increase) by 2070. In SEQld, 80% of core habitat is predicted to be lost under low warming and 90% under high warming by 2070. These results suggest that this species is highly vulnerable to climate warming and highlight the importance of focusing conservation efforts at the bioregional scale. There is also a need to identify potential thermal refuges and ensure habitat connectivity.

A review of home-range studies on Australian terrestrial vertebrates: adequacy of studies, testing of hypotheses, and relevance to conservation and international studies

Describing the spatial requirements of animals is central to understanding their ecology and conservation needs. I reviewed 115 studies describing the home ranges of Australian terrestrial vertebrates that were published during 2001–12. Understanding the features that characterise best practice can guide future studies. I aimed to: evaluate the adequacy of these studies, examine the use of current analysis techniques, examine the application of home-range knowledge to species’ management, and examine hypotheses that seek to explain the size and location of home ranges. The reviewed studies were unevenly distributed across taxa with a majority (68%) involving mammals compared with birds (12%), reptiles (19%) and frogs (1%). Many studies had various shortcomings, suggesting that they had not fully described home ranges; many (41%) involved 10 or fewer individuals, ≤50 locations per individual (44%), and spanned periods of ≤3 months (46%). Studies of short duration risk underestimating home-range area and overlooking seasonal habitat use. Global positioning system telemetry was used in 10% of Australian studies. Many were also of short duration. Despite frequent criticism in the literature, the Minimum Convex Polygon was the most frequently used home-range estimator (84% of studies), followed by the Fixed Kernel (45% of studies). Applying knowledge of home ranges appears to be underappreciated, with only 39% of studies explicitly aiming to address management or conservation issues. Only three studies tested hypotheses that may explain home-range characteristics. Resource (food and shelter) distribution and, in one case, its heterogeneity, shaped home-range characteristics. I found that most studies use the term ‘home range’ in an indiscriminate way. Only 11% of studies within the international literature used qualifying terms (e.g. seasonal, annual). Tracking period is shown to influence home-range estimates. Therefore, I recommend that qualifying terms be used more frequently to avoid confusion when referring to animal home ranges.