Prediction of the probability of large fires in the Sydney region of south-eastern Australia using components of fire weather.

The probability of large-fire (\u3e= 1000 ha) ignition days, in the Sydney region, was examined using historical records. Relative influences of the ambient and drought components of the Forest Fire Danger Index (FFDI) on large fire ignition probability were explored using Bayesian logistic regression. The preferred models for two areas (Blue Mountains and Central Coast) were composed of the sum of FFDI (Drought Factor, DF = 1) (ambient component) and DF as predictors. Both drought and ambient weather positively affected the chance of large fire ignitions, with large fires more probable on the Central Coast than in the Blue Mountains. The preferred, additive combination of drought and ambient weather had a marked threshold effect on large-fire ignition and total area burned in both localities. This may be due to a landscape-scale increase in the connectivity of available fuel at high values of the index. Higher probability of large fires on the Central Coast may be due to more subdued terrain or higher population density and ignitions. Climate scenarios for 2050 yielded predictions of a 20-84% increase in potential large-fire ignitions days, using the preferred model

CHD4 slides nucleosomes by decoupling entry- and exit-side DNA translocation

© 2020, The Author(s). Chromatin remodellers hydrolyse ATP to move nucleosomal DNA against histone octamers. The mechanism, however, is only partially resolved, and it is unclear if it is conserved among the four remodeller families. Here we use single-molecule assays to examine the mechanism of action of CHD4, which is part of the least well understood family. We demonstrate that the binding energy for CHD4-nucleosome complex formation—even in the absence of nucleotide—triggers significant conformational changes in DNA at the entry side, effectively priming the system for remodelling. During remodelling, flanking DNA enters the nucleosome in a continuous, gradual manner but exits in concerted 4–6 base-pair steps. This decoupling of entry- and exit-side translocation suggests that ATP-driven movement of entry-side DNA builds up strain inside the nucleosome that is subsequently released at the exit side by DNA expulsion. Based on our work and previous studies, we propose a mechanism for nucleosome sliding

Addressing inequities in maternal health among women living in communities of social disadvantage and ethnic diversity.

The response to the coronavirus outbreak and how the disease and its societal consequences pose risks to already vulnerable groups such those who are socioeconomically disadvantaged and ethnic minority groups. Researchers and community groups analysed how the COVID-19 crisis has exacerbated persisting vulnerabilities, socio-economic and structural disadvantage and discrimination faced by many communities of social disadvantage and ethnic diversity, and discussed future strategies on how best to engage and involve local groups in research to improve outcomes for childbearing women experiencing mental illness and those living in areas of social disadvantage and ethnic diversity. Discussions centred around: access, engagement and quality of care; racism, discrimination and trust; the need for engagement with community stakeholders; and the impact of wider social and economic inequalities. Addressing biomedical factors alone is not sufficient, and integrative and holistic long-term public health strategies that address societal and structural racism and overall disadvantage in society are urgently needed to improve health disparities and can only be implemented in partnership with local communities

What do the australian black summer fires signify for the global fire crisis?

The 2019–20 Australian fire season was heralded as emblematic of the catastrophic harm wrought by climate change. Similarly extreme wildfire seasons have occurred across the globe in recent years. Here, we apply a pyrogeographic lens to the recent Australian fires to examine the range of causes, impacts and responses. We find that the extensive area burnt was due to extreme climatic circumstances. However, antecedent hazard reduction burns (prescribed burns with the aim of reducing fuel loads) were effective in reducing fire severity and house loss, but their effectiveness declined under extreme weather conditions. Impacts were disproportionately borne by socially disadvantaged regional communities. Urban populations were also impacted through prolonged smoke exposure. The fires produced large carbon emissions, burnt fire-sensitive ecosystems and exposed large areas to the risk of biodiversity decline by being too frequently burnt in the future. We argue that the rate of change in fire risk delivered by climate change is outstripping the capacity of our ecological and social systems to adapt. A multi-lateral approach is required to mitigate future fire risk, with an emphasis on reducing the vulnerability of people through a reinvigoration of community-level capacity for targeted actions to complement mainstream fire management capacity

Addressing inequities in maternal health among women living in communities of social disadvantage and ethnic diversity

The response to the coronavirus outbreak and how the disease and its societal consequences pose risks to already vulnerable groups such those who are socioeconomically disadvantaged and ethnic minority groups. Researchers and community groups analysed how the COVID-19 crisis has exacerbated persisting vulnerabilities, socio-economic and structural disadvantage and discrimination faced by many communities of social disadvantage and ethnic diversity, and discussed future strategies on how best to engage and involve local groups in research to improve outcomes for childbearing women experiencing mental illness and those living in areas of social disadvantage and ethnic diversity. Discussions centred around: access, engagement and quality of care; racism, discrimination and trust; the need for engagement with community stakeholders; and the impact of wider social and economic inequalities. Addressing biomedical factors alone is not sufficient, and integrative and holistic long-term public health strategies that address societal and structural racism and overall disadvantage in society are urgently needed to improve health disparities and can only be implemented in partnership with local communities

Simple models of pattern and process

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Mortality and resprouting responses in forest trees driven more by tree and ecosystem characteristics than drought severity and fire frequency

Increases in tree mortality linked to drought and fires have been reported across a range of forests globally over the last few decades. Forests that resprout epicormically/aerially should be the most resistant and resilient to changes in fire regime, yet they may be at risk of increased mortality, demographic shifts and changes to species composition due to the compounding effects of drought and fire. Despite this, the synergistic effects of drought and fire frequency on resprouters has received less attention than for obligate seeder tree species. Our study examined the effects of drought severity and fire frequency on the fire resistance of eucalypts (i.e., including Eucalyptus, Angophora and Corymbia) that can resprout epicormically. Following large-scale wildfires and drought in 2013, we conducted field surveys of temperate eucalypt forests in the Sydney Basin Bioregion, focusing on two major Eucalyptus forest assemblages: dry ridgetops and wet gullies. We measured tree size, previous fire damage (i.e., fire scars), bark type, mortality and resprouting position (e.g., canopy, stem, base) of reproductive-age trees. We used a Bayesian modelling approach to derive bounded estimates of response probabilities for trees sampled in each combination of drought severity (mild/moderate versus severe) and fire frequency (low versus high), as well as bounded estimates of differences between trees with and without fire scars, different bark types and drought/fire histories. Eucalypt populations in both vegetation types were resilient to increases in mortality and changes in resprouting position under severe drought and frequent fire, and mortality and resprouting position varied substantially with tree size, fire scar presence/absence and among bark types. Tree mortality and changes in resprouting position were considerably more likely in smaller trees with fire scars. Species with non-compact bark (e.g., fibrous, stringy, rough) were less resilient to lowering in resprouting position, e.g., from canopy to stem. Populations dominated by species that have small stem diameters, thin/non-compact bark and previous fire damage are likely at elevated risk of mortality and changes in resprouting position under future climate change

Changes in the resilience of resprouting juvenile tree populations in temperate forests due to coupled severe drought and fire

Elevated tree mortality and reduced recruitment of new trees linked to drought and fires has been reported across a range of forests over the last few decades. Forests that resprout new foliage epicormically from buds beneath the bark are considered highly resilient to disturbance, but are potentially at risk of elevated mortality, demographic shifts and changes to species composition due to synergistic effects of drought and fire. Despite this, the effects of drought-fire interactions on such forests remain largely unknown. We assessed the effects of drought severity and fire frequency on juvenile mortality, post-fire seedling recruitment and replacement of juvenile trees (balance of recruitment minus mortality) following fire. We compared dry ridgetops and wet gullies (i.e. two forest types that inhabit different topographic positions in the landscape) across a temperate forest in southern Australia. Both forest types experienced higher rates of fire-induced juvenile mortality in areas that had experienced severe drought compared to moderate drought, though mortality rates were generally low across all drought and fire combinations (e.g. < 15%). This result indicated that topographic position did little to reduce juvenile mortality when exposed to severe drought plus fire. In wet forest, severe drought also reduced recruitment and replacement of dead juveniles by post-fire seedlings compared to moderate drought. In dry forest net-negative replacement increased with the severity of drought. Across both forest types, the total pool of juveniles was reduced under severe drought (by 16–79 in DSF; 5–11 in WSF). Future increases in the frequency of coupled severe drought and fire could potentially increase the susceptibility of resilient temperate forests to major changes in structure and function