Prescribed burning is used to reduce the occurrence, extent and severity of uncontrolled fires in many flammable landscapes. However, epidemiologic evidence of the human health impacts of landscape ...fire smoke emissions is shaping fire management practice through increasingly stringent environmental regulation and public health policy. An unresolved question, critical for sustainable fire management, concerns the comparative human health effects of smoke from wild and prescribed fires. Here we review current knowledge of the health effects of landscape fire emissions and consider the similarities and differences in smoke from wild and prescribed fires with respect to the typical combustion conditions and fuel properties, the quality and magnitude of air pollution emissions, and the potential for dispersion to large populations. We further examine the interactions between these considerations, and how they may shape the longer term smoke regimes to which populations are exposed. We identify numerous knowledge gaps and propose a conceptual framework that describes pathways to better understanding of the health trade-offs of prescribed and wildfire smoke regimes.
Wildfires pose significant risks to people and human infrastructure worldwide. The treatment of fuel in landscapes may alter these risks but the magnitude of this effect on risk is poorly understood. ...Evidence from Australian Eucalyptus forests suggests that mitigation of risk using prescribed burning as a fuel treatment is partial because weather and fuel dynamics are conducive to regular high intensity fires. We further examine the response of risk to treatment in eucalypt forests using landscape simulation modelling. We model how five key measures of wildfire activity that govern risk to people and property may respond to variations in rate and spatial pattern of prescribed fire. We then model effects of predicted climate change (2050 scenarios) to determine how the response of risk to treatment is likely to be altered in the future. The results indicate that a halving of risk to people and property in these forests is likely to require treatment rates of 7–10% of the area of the landscape per annum. Projections of 2050 weather conditions under climate change further substantially diminished the effect of rate of treatment. A large increase in rates of treatment (i.e. circa. 50% over current levels) would be required to counteract these effects of climate change. Such levels of prescribed burning are unlikely to be financially feasible across eucalypt dominated vegetation in south eastern Australia. Despite policy imperatives to expand fuel treatment, a reduction rather than an elimination of risk will result. Multi-faceted strategies will therefore be required for the management of risk.
► Risk of human losses from wildfires may vary in response to rate of fuel treatment. ► Fuel treatment may lead to risk reduction but not elimination in many ecosystems. ► Simulation results show that this response applies in temperate Australian forests. ► Treatment effectiveness is predicted to be further diminished by climate change. ► Cost-effectiveness may constrain the scope of future fuel treatment programs.
Large budgets are spent on both suppression and fuel treatments in order to reduce the risk of wildfires. There is little evidence regarding the relative contribution of fire weather, suppression and ...fuel treatments in determining the risk posed from wildfires. Here we undertake a simulation study in the Sydney Basin, Australia, to examine this question using a fire behaviour model (Phoenix Rapidfire). Results of the study indicate that fire behaviour is most strongly influenced by fire weather. Suppression has a greater influence on whether a fire reaches 5 ha in size compared to fuel treatments. In contrast, fuel treatments have a stronger effect on the fire size and maximum distance the fire travels. The study suggests that fire management agencies will receive additional benefits from fuel treatment if they are located in areas which suppression resources can respond rapidly and attempt to contain the fires. No combination of treatments contained all fires, and the proportion of uncontained fires increased under more severe fire weather when the greatest number of properties are lost. Our study highlights the importance of alternative management strategies to reduce the risk of property loss.
•Fire weather has the greatest effect on containment, size and distance travelled.•Suppression has a stronger effect in the initial attack phase.•Fuel treatment has a greater effect on fire size and distance travelled.•Fires impacts assets in weather when management treatments are less effective.
An understanding of the effects of climate on fuel is required to predict future changes to fire. We explored the climatic determinants of variations in surface fine fuel parameters across forests ...(dry and wet sclerophyll plus rainforest) and grassy woodlands of south‐eastern Australia. Influences of vegetation type and climate on fuel were examined through statistical modelling for estimates of litterfall, decomposition and steady state fine litter fuel load obtained from published studies. Strong relationships were found between climate, vegetation type and all three litter parameters. Litterfall was positively related to mean annual rainfall and mean annual temperature across all vegetation types. Decomposition was both negatively and positively related to mean annual temperature at low and high levels of warm‐season rainfall respectively. Steady state surface fine fuel load was generally, negatively related to mean annual temperature but mean annual rainfall had divergent effects dependent on vegetation type: i.e. positive effect in low productivity dry sclerophyll forests and grassy woodlands versus negative effect in high productivity wet sclerophyll forests and rainforests. The species composition of the vegetation types may have influenced decomposition and steady state fuel load responses in interaction with climate: e.g. lower decomposition rates in the low productivity vegetation types that occupied drier environments may be partially due to the predominance of species with sclerophyllous leaves. The results indicate that uncertain and highly variable future trends in precipitation may have a crucial role in determining the magnitude and direction of change in surface fine fuel load across south‐eastern Australia.
The regrowth of woody vegetation in cleared landscapes (i.e. revegetation) has the potential to dramatically alter the spatial characteristics of vegetation and fuels, which will potentially alter ...fire characteristics. Understanding how revegetation alters fire size and intensity will be critical in determining the social and environmental value of revegetation. We used simulation modelling to examine (i) whether increasing native woody vegetation extent across landscapes cleared for pasture (i.e. revegetation) affects fire size and median fireline intensity and (ii) whether fuel load in the pasture matrix, the initial extent of land clearing and weather conditions during a fire alter the direction and/or magnitude of the relationships between revegetation and fire size or intensity. Simulations revealed that fire size and intensity were altered by increasing woody vegetation extent, though the direction of change was dependent upon landscape context. Increased woody vegetation extent led to (i) increased fire size in landscapes with low pasture fuel load (2tha−1) regardless of the extent of land clearing, (ii) decreased fire size in highly cleared landscapes with moderate (4.5tha−1) and high (7tha−1) pasture fuel load, and (iii) little change to fire size in landscapes subjected to low levels of clearing when pasture fuel load was moderate or high. Similar patterns were observed for fireline intensity. The magnitude of change in fire size and intensity was greatest under extreme fire weather conditions. Revegetation rarely increased median fireline intensity beyond suppressible levels (i.e. 4000kWm−1), with fire weather and pasture fuel load being the main determinants of suppression potential. Our findings show that the response of fire size and intensity to revegetation will depend on landscape scale pasture management.
•Woody regrowth in cleared landscapes (revegetation) may affect fire regimes.•We use simulations to model the effect revegetation has on fire across landscapes.•When pasture biomass was low fire size increased with revegetation.•Under high pasture biomass fire size was decreased or unchanged by revegetation.•The response of fire intensity to revegetation was similar to that of fire size.
In order to quantify the risks from fire at the wildland urban interface (WUI), it is important to understand where fires occur and their likelihood of spreading to the WUI. For each of the 999 fires ...in the Sydney region we calculated the distance between the ignition and the WUI, the fire's weather and wind direction and whether it spread to the WUI. The likelihood of burning the WUI was analysed using binomial regression. Weather and distance interacted such that under mild weather conditions, the model predicted only a 5% chance that a fire starting >2.5 km from the interface would reach it, whereas when the conditions are extreme the predicted chance remained above 30% even at distances >10 km. Fires were more likely to spread to the WUI if the wind was from the west and in the western side of the region. We examined whether the management responses to wildfires are commensurate with risk by comparing the distribution of distance to the WUI of wildfires with roads and prescribed fires. Prescribed fires and roads were concentrated nearer to the WUI than wildfires as a whole, but further away than wildfires that burnt the WUI under extreme weather conditions (high risk fires). Overall, 79% of these high risk fires started within 2 km of the WUI, so there is some argument for concentrating more management effort near the WUI. By substituting climate change scenario weather into the statistical model, we predicted a small increase in the risk of fires spreading to the WUI, but the increase will be greater under extreme weather. This approach has a variety of uses, including mapping fire risk and improving the ability to match fire management responses to the threat from each fire. They also provide a baseline from which a cost-benefit analysis of complementary fire management strategies can be conducted.
Wildfires can result in significant economic and social losses. Prescribed fire is commonly applied to reduce fuel loads and thereby decrease future fire risk to life and property. Fuel treatments ...can occur in the landscape or adjacent to houses. Location of the prescribed burns can significantly alter the risk of house loss. Furthermore the cost of treating fuels in the landscape is far cheaper than treating fuels adjacent to the houses. Here we develop a Bayesian Network to examine the relative reduction in risk that can be achieved by prescribed burning in the landscape compared with a 500 m interface zone adjacent to houses. We then compare costs of management treatments to determine the most cost-effective method of reducing risk to houses. Burning in the interface zone resulted in the greatest reduction in risk of fires reaching the houses and the intensity of these fires. Fuel treatment in the interface zone allows for a direct transfer of benefits from the fuel treatment. Costs of treating fuels in the interface were significantly higher on a per hectare basis, but the extent of area requiring treatment was considerably lower. Results of this study demonstrate that treatment of fuels at the interface is not only the best means of reducing risk, it is also the most cost-effective.
•Fuel treatment in the interface zone gives the greatest reduction in risk of property loss.•Costs of managing the interface zone are comparable to landscape treatments.•Treating the interface zone is cost-effective and significantly reduces the risk of property loss.
Reducing the risk of house loss due to wildfires Penman, T.D.; Nicholson, A.E.; Bradstock, R.A. ...
Environmental modelling & software : with environment data news,
20/May , Letnik:
67
Journal Article
Recenzirano
Wildfires will continue to reach people and property regardless of management effort in the landscape. House-based strategies are therefore required to complement the landscape strategies in order to ...reduce the extent of house loss. Here we use a Bayesian Network approach to quantify the relative influence of preventative and suppressive management strategies on the probability of house loss in Australia. Community education had a limited effect on the extent to which residents prepared their property hence a limited effect on the reduction in risk of house loss, however hypothetically improving property preparedness did reduce the risk of house loss. Increasing expenditure on suppression resources resulted in a greater reduction in the risk of loss than preparedness. This increase had an interaction effect with increasing the distance between vegetation and the houses. The extent to which any one action can be implemented is limited by social, environmental and economic factors.
•Bayesian Network models provide a powerful tool for analysing fire risk scenarios.•Combining multiple data sources allow for the exploration of a range of scenarios that cannot be empirically tested.•Fire risk reduction strategies can reduce risk, but other factors limit their implementation.•Approaches used here are broadly applicable to other natural hazards.
Summary
Background On the western border of Thailand the efficacy of mefloquine in the treatment of falciparum malaria has declined while gametocyte carriage rates have increased, which suggests ...increased transmissibility of these resistant infections. We compared the following antimalarial drugs in relation to subsequent Plasmodium falciparum gametocyte carriage: mefloquine, halofantrine, quinine, and the artemisinin derivatives.
Methods Between 1990 and 1995 we assessed gametocytaemia in a series of prospective studies of antimalarial drug treatment in 5193 adults and children with acute uncomplicated falciparum malaria in an area of malarious hill forest on the western border of Thailand. Weekly parasite counts from thick and thin blood films were done during the 4-week (1990-93) or 9-week (1993-95) follow-up period. Gametocyte positivity rates and person gametocyte week (PGW) rates were calculated to measure gametocyte carriage and transmission potential.
Findings In primary
P falciparum infections the gametocyte carriage rate was significantly higher after treatment with mefloquine than after treatment with the artemisinin derivatives (PGW 34·1 95% Cl 25·2-42·9 vs 3·9 1·9-5·9 per 1000 person weeks; relative risk 8·0 4·1-15·6; p<0·0001). Recrudescent infections were associated with increased gametocyte carrier rates (relative risk 2·2 1·6-3·0; p<0·0001), but retreatment with artemisinin derivatives reduced subsequent gametocyte carriage 18·5 fold 3·5-98 compared with mefloquine retreatment and 6·8 fold (3·1-15·1) compared with quinine retreatment (p<0·001). The introduction of the artemisinin derivatives in routine treatment at this study site in mid 1994 was associated with a reduction in the subsequent incidence of falciparum malaria of 47 (25-69)%.
Interpretation Although environmental changes affect vector numbers, and hence malaria incidence, artemisinin derivatives were found to reduce the transmission potential of falciparum malaria. Widespread introduction of artemisinin derivatives in the treatment of falciparum malaria may prevent the spread of multidrug resistance.
PDF
