Occurrence Of Large Wildfires Research Articles

Near-term fire weather forecasting in the Pacific Northwest using 500-hPa map types

Background Near-term forecasts of fire danger based on predicted surface weather and fuel dryness are widely used to support the decisions of wildfire managers. The incorporation of synoptic-scale upper-air patterns into predictive models may provide additional value in operational forecasting. Aims In this study, we assess the impact of synoptic-scale upper-air patterns on the occurrence of large wildfires and widespread fire outbreaks in the US Pacific Northwest. Additionally, we examine how discrete upper-air map types can augment subregional models of wildfire risk. Methods We assess the statistical relationship between synoptic map types, surface weather and wildfire occurrence. Additionally, we compare subregional fire danger models to identify the predictive value contributed by upper-air map types. Key results We find that these map types explain variation in wildfire occurrence not captured by fire danger indices based on surface weather alone, with specific map types associated with significantly higher expected daily ignition counts in half of the subregions. Conclusions We observe that incorporating upper-air map types enhances the explanatory power of subregional fire danger models. Implications Our approach provides value to operational wildfire management and provides a template for how these methods may be implemented in other regions.

Psychotropic Medication Prescriptions and Large California Wildfires

Wildfires, intensified by climate change, have known effects on physical health but their effects on mental health are less well characterized. It has been hypothesized that the residential proximity to a large wildfire can exacerbate underlying mental health conditions as evidenced by increased prescriptions of psychotropic medications. To evaluate the association between the occurrence of large wildfires and the prescription rates of psychotropic medications immediately following the start of the fire. This cohortstudy used an interrupted time-series analysis to compare psychotropic medication prescriptions in the 6 weeks before and after each of 25 wildfires. The setting was California counties within metropolitan statistical areas (MSAs) experiencing large wildfires from 2011 through 2018. Participants included individuals residing in California MSAs with prescriptions of psychotropic medications recorded in the Merative MarketScan Research Database (MarketScan) during the study period. Statistical analysis was performed for these 25 large wildfires occurring between September 2011 and November 2018. Residential proximity to large wildfires that burned more than 25 000 acres occurring in a California county within an MSA. Prescriptions of psychotropic medications, including antidepressants, antipsychotics, anxiolytics, hypnotics, and mood-stabilizers, with statins as a negative control outcome. For the study period, prescription data and patient-level attributes were extracted for 7 115 690 unique individuals (annual mean [range]: 889 461 [455 705-1 426 928] individuals) enrolled in MarketScan and residing in fire-affected MSAs. This study found a statistically significant increase in prescriptions of antidepressants (rate ratio [RR], 1.04 [95% CI, 1.01-1.07]), anxiolytics (RR, 1.05 [95% CI, 1.02-1.09]), and mood-stabilizing medications (RR, 1.06 [95% CI, 1.01-1.13]) in the fire period compared with the prefire baseline. However, the prescriptions of antipsychotics, hypnotics, and the negative control outcome, statins, showed no significant association. In this cohort study of large California wildfires, the occurrence of wildfire was associated with increased mental health burden as reflected in increased prescription rates of certain psychotropic medications. The findings underscore the need for further scientific examination into the mental health effects of wildfires and the allocation of mental health resources in disaster responses. California experienced a substantial burden of wildfires from 2011 to 2018, and as wildfires become more intense and frequent in the context of anthropogenic climate change, it is increasingly important to understand and address their mental health effects.

The effect of broadleaf forests in wildfire mitigation in the WUI – A simulation study

The increasing occurrence of large wildfires in Southern European countries calls for the adoption of more effective measures of fire prevention, to protect people and infrastructures, namely in the Wildland-Urban Interface (WUI). Previous research suggests that broadleaf forests could mitigate the effects of these wildfires due to their lower flammability. However, few attempts have been made to investigate the possibility of using broadleaf-based green firebreaks to protect infrastructures, as an alternative to current less ecologically and economically sustainable fuel reduction techniques. Here, we assess the relevance of a broadleaves fuel model in reducing fire hazard in the WUI, by analyzing a set of six Industrial Zones (IZs) in Central Portugal, severely affected by wildfires during the catastrophic fire season of 2017. We developed alternative scenarios for the spatial simulation of fire behavior, using a factorial combination of weather conditions (standard and extreme), buffer around each IZ (distances of 100 m and 500 m) and land cover (current and broadleaves fuel model). The simulations were grounded on real-world data obtained from reconstructed fire front isochrones and fieldwork. Our results suggest that replacing the flammable vegetation present in the WUI with broadleaf forests could reduce fireline intensity by up to five times, even under extreme weather conditions. This reduction occurs subtly as the broadleaf cover interface is expanded from 100 m to 500 m. Our results show that fires that exceed the suppression capacity in pine and eucalypt forests (>4 m flame length) can be effectively suppressed in broadleaf forests under extreme fire weather (1.4 m flame length) and easily suppressed in broadleaf forests in standard weather (0.8 m flame length). Due to significant changes in land use and extreme weather events, future large wildfires could occur again in Portugal. In this regard, our results corroborate the urgent need to discuss forest management in the country, which has already proven to be insufficient to prevent fire disasters in the WUI.

Increased wildfire hazard along South-Central Chile under the RCP8.5 scenario as revealed by high-resolution modeling

Among Mediterranean regions, the South-Central Zone of Chile (SCZCh) portrays a landscape where wildfires constantly and historically occur, many times damaging ecosystems, lives and livelihoods. Since 2010, this zone has entered a period of unprecedented drought that has contributed to wildfire rising trends. Wildfire occurrence and intensity in this zone can be associated with three main factors: climate and land cover as conditioning factors, and human activity as a triggering factor. This paper evaluates wildfire hazard for the SCZCh, based on environmental susceptibility to wildfire occurrence, using numerical regional climate and wildfire modeling for the 2002–2005 historical period and for the mid and late 21st-century under the RCP8.5 climate change scenario. Results indicate high skill in matching spatial patterns of fire spot occurrence and density in the historical period, as well as the ability to simulate seasonal behavior in wildfire environmental susceptibility, consistent with national historical statistics. The fire hazard in SCZCh will slightly increase in all seasons for both 2041–2050 and 2091–2100 periods, especially southward, with a long-term spatial homogenization of medium levels of hazard in Central Valley and Coastal Range, between 0 and 1000 m a.s.l. These results combined with the current homogeneous extensive exotic species plantations dominated by inflammable tree species in SCZCh might facilitate the occurrence of large wildfires under the projected 21st-century climate regime.

Vegetation Recovery Patterns in Burned Areas Assessed with Landsat 8 OLI Imagery and Environmental Biophysical Data

Vegetation recovery after the large wildfires that occurred in central Portugal in 2017 is assessed in the present study. These wildfires had catastrophic consequences, among which were human losses and a vast extent of forest devastation. Landsat 8 OLI images were used to obtain the land use and cover (LUC) classification and to determine the Normalized Burned Ratio index (NBR) for different times. NBR results were used to determine the difference between the NBR (dNBR) before the fire (pre-fire) and after the fire (post-fire), and the results obtained were cross-checked with the LUC. The dNBR results were cross-referenced with biophysical data to identify the characteristics of the most important burned areas in need of vegetative recovery. The results showed the spatial differentiation in vegetation recovery, highlighting different factors in this process, in particular the type of vegetation (the predominant species and bank of seeds available), the biophysical characteristics of burned areas (for example, the soil type in burned areas), the continentality gradient, and the climate conditions. The vegetation recovery was differentiated by time according to the species present in the burned areas pre-fire. In general, shrubland recovery was faster than that of tree species, and the recovery was more marked for species that were regenerated by the rhizomes after fire. The recovery process was also influenced by the season in the study area. It was more efficient in the spring and at the beginning of the summer, highlighting the importance of optimal conditions needed for vegetation regeneration, such as the temperature and precipitation (soil humidity and water availability for growing plants). The results of this research are important to forest planning: the definition of the strategies for the ecosystems’ recovery, the adoption of preventive measures to avoid the occurrence of large wildfires, the modification of anthropogenic practices, etc.

Land-Use Type as a Driver of Large Wildfire Occurrence in the U.S. Great Plains

Wildfire activity has surged in North America’s temperate grassland biome. Like many biomes, this system has undergone drastic land-use change over the last century; however, how various land-use types contribute to wildfire patterns in grassland systems is unclear. We determine if certain land-use types have a greater propensity for large wildfire in the U.S. Great Plains and how this changes given the percentage of land covered by a given land-use type. Almost 90% of the area burned in the Great Plains occurred in woody and grassland land-use types. Although grassland comprised the greatest area burned by large wildfires, woody vegetation burned disproportionately more than any other land-use type in the Great Plains. Wildfires were more likely to occur when woody vegetation composed greater than 20% of the landscape. Wildfires were unlikely to occur in croplands, pasture/hay fields, and developed areas. Although these patterns varied by region, wildfire was most likely to occur in woody vegetation and/or grassland in 13 of 14 ecoregions we assessed. Because woody vegetation is more conducive to extreme wildfire behaviour than other land-use types in the Great Plains, woody encroachment could pose a large risk for increasing wildfire exposure. Regional planning could leverage differential wildfire activity across land-uses to devise targeted approaches that decrease human exposure in a system prone to fire.

Drought in Portugal: Current regime, comparison of indices and impacts on extreme wildfires

In Portugal, drought characterizes the climatic variability, contributes to the increase of fire risk and its duration and intensity are expected to increase in future climate. Surprisingly, the quantitative and objective analysis to characterize the drought regime in current climate conditions as well as its influence on the occurrence of large wildfires (LW) has never been done for Portugal, which are the main objectives of this study. We assessed drought regime for recent past climate conditions (1981–2017), using four different drought indices, namely SPI, SPEI, RDI and VCI, and assessed the influence of drought in LW occurrence. Results include the characterization of drought number, duration, severity, intensity, extension, intra- and inter-annual variability for different classes of severity and the space-time distribution of LW in drought periods and affected area. Our main findings include 67% of the study period were drought months; regions with higher drought duration and severity assessed with SPI and SPEI for general drought conditions evolves from north to south with the increase of drought assessment period; drought characteristics present low intra - annual and inter - annual variability but are clearly associated to the temporal and spatial distribution of LW. In fact, all LW occurred during drought assessed with SPI or SPEI, almost all LW (97% to 95%) and corresponding burnt area (98% to 97%) occurred during drought assessed with SPI and SPEI. The relationship between drought and fire incidence is statistical significant for 3 - month SPI, 3 - and 6 - month SPEI, and is particularly strong for Moderate and Severe drought. 85% and 87% of LW occurred in area affected by drought assessed with SPI or SPEI, respectively. It is not clear which is the best index, but drought plays a fundamental role in the occurrence of large wildfires in Portugal.

A weekly, continually updated dataset of the probability of large wildfires across western US forests and woodlands

Abstract. There is broad consensus that wildfire activity is likely to increase in western US forests and woodlands over the next century. Therefore, spatial predictions of the potential for large wildfires have immediate and growing relevance to near- and long-term research, planning, and management objectives. Fuels, climate, weather, and the landscape all exert controls on wildfire occurrence and spread, but the dynamics of these controls vary from daily to decadal timescales. Accurate spatial predictions of large wildfires should therefore strive to integrate across these variables and timescales. Here, we describe a high spatial resolution dataset (250 m pixel) of the probability of large wildfires ( > 405 ha) across forests and woodlands in the contiguous western US, from 2005 to the present. The dataset is automatically updated on a weekly basis using Google Earth Engine and a continuous integration pipeline. Each image in the dataset is the output of a random forest machine-learning algorithm, trained on random samples of historic small and large wildfires and represents the predicted conditional probability of an individual pixel burning in a large fire, given an ignition or fire spread to that pixel. This novel workflow is able to integrate the near-term dynamics of fuels and weather into weekly predictions while also integrating longer-term dynamics of fuels, the climate, and the landscape. As a continually updated product, the dataset can provide operational fire managers with contemporary, on-the-ground information to closely monitor the changing potential for large wildfire occurrence and spread. It can also serve as a foundational dataset for longer-term planning and research, such as the strategic targeting of fuels management, fire-smart development at the wildland–urban interface, and the analysis of trends in wildfire potential over time. Weekly large fire probability GeoTiff products from 2005 to 2017 are archived on the Figshare online digital repository with the DOI https://doi.org/10.6084/m9.figshare.5765967 (available at https://doi.org/10.6084/m9.figshare.5765967.v1). Weekly GeoTiff products and the entire dataset from 2005 onwards are also continually uploaded to a Google Cloud Storage bucket at https://console.cloud.google.com/storage/wffr-preds/V1 (last access: 14 September 2018) and are available free of charge with a Google account. Continually updated products and the long-term archive are also available to registered Google Earth Engine (GEE) users as public GEE assets and can be accessed with the image collection ID users/mgray/wffr-preds within GEE.

Short-term effects of spring prescribed burning on the understory vegetation of a Pinushalepensis forest in Northeastern Spain

Since the 1970s, fire regimes have been modified in the Northern Mediterranean region due to profound landscape changes mostly driven by socioeconomic factors, such as rural abandonment and large-scale plantations. Both fuel accumulation and the increasing vegetation spatial continuity, combined with the expansion of the wildland-urban interface, have enhanced fire risk and the occurrence of large wildfires. This situation will likely worsen under the projected aridity increase resulting from climate change. Higher fire recurrences, in particular, are expected to cause changes in vegetation composition or structure and affect ecosystems' resilience to fire, which may lead to further land degradation. Prescribed burning is a common fuel reduction technique used for fire prevention, but for conservation and restoration purposes as well. It is still poorly accepted in the Mediterranean region since constrained by critical knowledge gaps about, in particular, its effects on the ecosystems (soil, vegetation). We studied the short-term (10months) effects on the understory vegetation of a spring prescribed burning conducted in a Pinushalepensis forest in Mediterranean climate (Northeastern Spain). Our results show that the understory plant community recovered after the burning without short term significant changes in either species richness, diversity, or floristic composition. Most vegetation structural characteristics were modified though. The burning strongly reduced shrub height, shrub and herbaceous percentage covers, and aerial shrub phytomass; especially its living fine fraction, thus resulting in a less flammable community. The treatment proved to be particularly effective for the short term control of Ulexparviflorus, a highly flammable seeder species. Moreover, the strong reduction of seeder shrubs frequency in relation to resprouters' likely promoted the resilience to fire of this plant community. From a fuel-oriented perspective, the burning caused a strong reduction of spatial continuity and surface fuel loads, leading to a less fire-prone fuel complex.

The normal fire environment—Modeling environmental suitability for large forest wildfires using past, present, and future climate normals

We modeled the normal fire environment for occurrence of large forest wildfires (>40ha) for the Pacific Northwest Region of the United States. Large forest wildfire occurrence data from the recent climate normal period (1971–2000) was used as the response variable and fire season precipitation, maximum temperature, slope, and elevation were used as predictor variables. A projection of our model onto the 2001–2030 climate normal period showed strong agreement between model predictions and the area of forest burned by large wildfires from 2001 to 2015 (independent fire data). We then used downscaled climate projections for two greenhouse gas concentration scenarios and over 30 climate models to project changes in environmental suitability for large forest fires over the 21st century. Results indicated an increasing proportion of forested area with fire environments more suitable for the occurrence of large wildfires over the next century for all ecoregions but less pronounced for the Coast Range and Puget Lowlands. The largest increases occurred on federal lands, while private and state lands showed less. We calculated fire rotation periods for the recent historical and current climate and examined the relative differences between them and our modeled large wildfire suitability classes. By the end of the century, the models predicted shorter fire rotation periods, with cooler/moister forests experiencing larger magnitudes of change than warmer/drier forests. Modeling products, including a set of time series maps, can provide forest resource managers, fire protection agencies, and policy-makers empirical estimates of how much and where climate change might affect the geographic distribution of large wildfires and effect fire rotations.

Relative importance of climate and mountain pine beetle outbreaks on the occurrence of large wildfires in the western USA.

Extensive outbreaks of bark beetles have killed trees across millions of hectares of forests and woodlands in western North America. These outbreaks have led to spirited scientific, public, and policy debates about consequential increases in fire risk, especially in the wildland-urban interface (WUI), where homes and communities are at particular risk from wildfires. At the same time, large wildfires have become more frequent across this region. Widespread expectations that outbreaks increase extent, severity, and/or frequency of wildfires are based partly on visible and dramatic changes in foliar moisture content and other fuel properties following outbreaks, as well as associated modeling projections. A competing explanation is that increasing wildfires are driven primarily by climatic extremes, which are becoming more common with climate change. However, the relative importance of bark beetle outbreaks vs. climate on fire occurrence has not been empirically examined across very large areas and remains poorly understood. The most extensive outbreaks of tree-killing insects across the western United States have been of mountain pine beetle (MPB; Dendroctonus ponderosae), which have killed trees over >650,000km2 , mostly in forests dominated by lodgepole pine (Pinus contorta). We show that outbreaks of MPB in lodgepole pine forests of the western United States have been less important than climatic variability for the occurrence of large fires over the past 29years. In lodgepole pine forests in general, as well as those in the WUI, occurrence of large fires was determined primarily by current and antecedent high temperatures and low precipitation but was unaffected by preceding outbreaks. Trends of increasing co-occurrence of wildfires and outbreaks are due to a common climatic driver rather than interactions between these disturbances. Reducing wildfire risk hinges on addressing the underlying climatic drivers rather than treating beetle-affected forests.

Linking landscape futures with biodiversity conservation strategies in northwest Iberia — A simulation study combining surrogates with a spatio-temporal modelling approach

The most prominent factors inducing landscape change in the rural regions of south west Europe are depopulation and the associated socio-ecological modifications. The aim of this work was to assess the future implications of these processes on land use/land cover and biodiversity in northwest Iberia. To achieve our goal, we developed a virtual spatially explicit dynamic model to simulate regional socio-ecological dynamics. For the period between 1960 and 2040, we tested four different environmental scenarios ranging from small decreases in conifer forest and a stabilization of agricultural areas and shrublands to more radical shifts, substantial decreases in agricultural areas and massive expansion of eucalyptus stands. The model considers also fire, whose role increased significantly in the scenarios of expanded forests. Bird assemblages, which we used as a surrogate for biodiversity, showed complex patterns although with overall decreases in richness and abundance. Species with narrow niche and from Mediterranean open habitats were particularly sensitive to the ongoing changes simulated. Our results suggest that landscape management actions and planning assessments designed for conserving biodiversity should focus on the maintenance of the traditional agricultural mosaic combined with a regulatory legislation limiting the expansion of fast growing tree forests (e.g Eucalyptus stands). This strategy can contribute to maintaining a diversity of land use/land cover in a heterogeneous landscape and the prevention of the occurrence of large wildfires, fundamental for the implementation of national biodiversity strategies and action plans.

Regional modeling of large wildfires under current and potential future climates in Colorado and Wyoming, USA

Regional analysis of large wildfire potential given climate change scenarios is crucial to understanding areas most at risk in the future, yet wildfire models are not often developed and tested at this spatial scale. We fit three historical climate suitability models for large wildfires (i.e. ≥ 400 ha) in Colorado and Wyoming using topography and decadal climate averages corresponding to wildfire occurrence at the same temporal scale. The historical models classified points of known large wildfire occurrence with high accuracies. Using a novel approach in wildfire modeling, we applied the historical models to independent climate and wildfire datasets, and the resulting sensitivities were 0.75, 0.81, and 0.83 for Maxent, Generalized Linear, and Multivariate Adaptive Regression Splines, respectively. We projected the historic models into future climate space using data from 15 global circulation models and two representative concentration pathway scenarios. Maps from these geospatial analyses can be used to evaluate the changing spatial distribution of climate suitability of large wildfires in these states. April relative humidity was the most important covariate in all models, providing insight to the climate space of large wildfires in this region. These methods incorporate monthly and seasonal climate averages at a spatial resolution relevant to land management (i.e. 1 km2) and provide a tool that can be modified for other regions of North America, or adapted for other parts of the world.

Seasonal reversal of the influence of El Niño–Southern Oscillation on very large wildfire occurrence in the interior northwestern United States

AbstractSatellite‐mapped fire perimeters and the multivariate El Niño–Southern Oscillation index were used to examine the impact of concurrent El Niño–Southern Oscillation (ENSO) phase on very large fire (VLF) occurrences over the intermountain northwestern United States (U.S.) from 1984 to 2012. While the warm phase of ENSO promotes drier and warmer than normal conditions across the region during winter and spring that favor widespread fire activity the following summer, a reduction in VLFs was found during the warm phase of ENSO during summer concurrent with the fire season. This paradox is primarily tied to an anomalous upper level trough over the western U.S. and positive anomalies in integrated water vapor that extend over the northwestern U.S. during summers when the warm phase of ENSO is present. Collectively, these features result in widespread increases in precipitation amount during the summer and a curtailment of periods of critically low‐fuel moistures that can carry wildfire.

Impacts of repeated wildfire on long-unburned plant communities of the southern Appalachian Mountains

The infrequent occurrence of large wildfires in the southern Appalachian Mountains over the last several decades has offered few opportunities to study their impacts. From 2000 to 2008, five wildfires burned a large portion of the area in and surrounding the Linville Gorge Wilderness in North Carolina. Areas were burned either once or twice. The response of acid cove and thermic oak plant communities (structure, cover, richness, diversity) was measured in 78 vegetation monitoring plots, established in 1992 and remeasured in 2010–11. Fire altered forest structure in both communities, resulting in the mortality of larger trees and increases in the abundance of smaller (<5 cm diameter at breast height (DBH)) stems. Burning twice decreased stem counts for mountain laurel (Kalmia latifolia) in both communities, whereas oaks (Quercus spp.) responded positively to burning twice in the thermic oak community. Table Mountain pine stem counts increased in acid cove and thermic oak communities burned once. Fire appears to promote princesstree (Paulownia tomentosa) invasion. Herbaceous species cover responded positively to fire (once or twice; both communities), with concurrent increases in woody species richness and diversity. Tree species composition in acid cove plots was not affected by burning, although some slight changes occurred in thermic oak plots burned twice.

Spatial and temporal drivers of wildfire occurrence in the context of rural development in northern Wisconsin, USA

Most drivers underlying wildfire are dynamic, but at different spatial and temporal scales. We quantified temporal and spatial trends in wildfire patterns over two spatial extents in northern Wisconsin to identify drivers and their change through time. We used spatial point pattern analysis to quantify the spatial pattern of wildfire occurrences, and linear regression to quantify the influence of drought and temporal trends in annual number and mean size of wildfires. Analyses confirmed drought as an important driver of both occurrences and fire size. When both drought and time were incorporated in linear regression models, the number of wildfires showed a declining trend across the full study area, despite housing density increasing in magnitude and spatial extent. Fires caused by campfires and debris-burning did not show any temporal trends. Comparison of spatial models representing biophysical, anthropogenic and combined factors demonstrated human influences on wildfire occurrences, especially human activity, infrastructure and property values. We also identified a non-linear relationship between housing density and wildfire occurrence. Large wildfire occurrence was predicted by similar variables to all occurrences, except the direction of influence changed. Understanding these spatial and temporal drivers of wildfire occurrence has implications for land-use planning, wildfire suppression strategies and ecological goals.

Climate change and growth scenarios for California wildfire

Large wildfire occurrence and burned area are modeled using hydroclimate and landsurface characteristics under a range of future climate and development scenarios. The range of uncertainty for future wildfire regimes is analyzed over two emissions pathways (the Special Report on Emissions Scenarios [SRES] A2 and B1 scenarios); three global climate models (Centre National de Recherches Meteorologiques CM3, Geophysical Fluid Dynamics Laboratory CM2.1 and National Center for Atmospheric Research PCM1); three scenarios for future population growth and development footprint; and two thresholds for defining the wildland-urban interface relative to housing density. Results were assessed for three 30-year time periods centered on 2020, 2050, and 2085, relative to a 30-year reference period centered on 1975. Increases in wildfire burned area are anticipated for most scenarios, although the range of outcomes is large and increases with time. The increase in wildfire burned area associated with the higher emissions pathway (SRES A2) is substantial, with increases statewide ranging from 36% to 74% by 2085, and increases exceeding 100% in much of the forested areas of Northern California in every SRES A2 scenario by 2085.

Modelling the effect of fire-exclusion and prescribed fire on wildfire size in Mediterranean ecosystems

There is a debate on which factor, fuel accumulation or meteorological variability, is the fundamental control of the occurrence of large fires in Mediterranean-type ecosystems. Its resolution has important management implications, because if the fuel hypothesis proves to be right, then fire-exclusion would enhance the occurrence of large wildfires, and prescribed-fires would be a useful tool to fight them. On the other hand, if large fires were just a direct consequence of some extreme weather situations, neither fire-exclusion nor prescribed fire would have any influence on the size of wildfires. Here we present a simple model of vegetation dynamics and fire spread over homogeneous areas intended to treat quantitatively this issue. In particular, we wanted to address the following questions: (1) What is the effect that different fire fighting capacities have on the total area burnt and, especially, on large fires? (2) What is the effect that different levels of prescribed fire have on the area burnt in wildfires and, especially, in large fires? The model incorporates meteorological variability, different rates of fuel accumulation, number of ignitions per year, fire-fighting capacity, and prescribed burning. The model was calibrated with fire regime data (mean fire size, annual area burnt, and fire size distribution) of Tarragona (NE Spain) and Coimbra (Central Portugal), and it accurately reproduced both data sets, while allowing for multiple behavioural models and prediction uncertainties within the GLUE methodology. Results showed that for a given region, with its particular characteristics of climate, number of ignitions, and vegetation flammability, there was a fairly constant annual area burnt for different fire-fighting capacities. However, higher fire-fighting capacities resulted in a slightly higher proportion of large fires. There was also a quite constant annual area burnt (prescribed and wild fires together) for different prescribed fire intensities in each region. However, the total amount and proportion of large fires decreased as the prescribed burning intensity increased. So, according to the model, it seems that the total area burnt will be more or less the same despite any effort to reduce it by extinguishing fires or by using prescribed burning. Nevertheless, the effect of the fire exclusion policy slightly enhances the dominance of large fires, whereas the use of prescribed fires greatly reduces the importance of large fires.

Landscape changes and breeding bird assemblages in northwestern Portugal: the role of fire

Fire is a major driving force of landscape change in the Mediterranean region. The objectives of this paper were to explore the implications of landscape change and wildfires in a region of northwestern Portugal for the diversity of breeding birds. Land use cover for the years 1958, 1968, 1983 and 1995 was obtained from aerial photography for a study area of 3700 ha. Breeding bird assemblages in each of six land use categories were characterized in 1998 using point counts. The main landscape changes in the study area across the 40 years were a decrease in the area of agricultural land and low shrublands (respectively 29% and 48%) and an increase in forests and tall shrublands (both over 95%). Bird assemblages showed increased richness and diversity across the gradient: low shrublands → tall shrublands → conifer → mixed → deciduous → agricultural areas. Many of the species with narrow niche breadth (specialists) were associated with agricultural areas and deciduous forests. In spite of the low diversity of burned areas (mostly shrublands) a few specialist species depend on this habitat. Thus, the current fire regime probably contributes to maintaining bird diversity at the landscape level. There was an inverse relationship between landscape diversity and estimated bird diversity across the last 40 years. Landscape management actions to preserve bird diversity should focus on the maintenance of agricultural land and deciduous forests. In parallel, a wider use of prescribed burning and grazing is suggested. This would contribute to maintaining low shrublands in the landscape, useful both as an habitat for some bird species and as fuel breaks for preventing the occurrence of large wildfires.