Summer Wildfires Research Articles

Rapid Assessment of Hillslope Erosion Risk after the 2019–2020 Wildfires and Storm Events in Sydney Drinking Water Catchment

The Australian Black Summer wildfires between September 2019 and January 2020 burnt many parts of eastern Australia including major forests within the Sydney drinking water catchment (SDWC) area, almost 16.000 km2. There was great concern on post-fire erosion and water quality hazards to Sydney’s drinking water supply, especially after the heavy rainfall events in February 2020. We developed a rapid and innovative approach to estimate post-fire hillslope erosion using weather radar, remote sensing, Google Earth Engine (GEE), Geographical Information Systems (GIS), and the Revised Universal Soil Loss Equation (RUSLE). The event-based rainfall erosivity was estimated from radar-derived rainfall accumulations for all storm events after the wildfires. Satellite data including Sentinel-2, Landsat-8, and Moderate Resolution Imaging Spectroradiometer (MODIS) were used to estimate the fractional vegetation covers and the RUSLE cover-management factor. The study reveals that the average post-fire erosion rate over SDWC in February 2020 was 4.9 Mg ha−1 month−1, about 30 times higher than the pre-fire erosion and 10 times higher than the average erosion rate at the same period because of the intense storm events and rainfall erosivity with a return period over 40 years. The high post-fire erosion risk areas (up to 23.8 Mg ha−1 month−1) were at sub-catchments near Warragamba Dam which forms Lake Burragorang and supplies drinking water to more than four million people in Sydney. These findings assist in the timely assessment of post-fire erosion and water quality risks and help develop cost-effective fire incident management and mitigation actions for such an area with both significant ecological and drinking water assets. The methodology developed from this study is potentially applicable elsewhere for similar studies as the input datasets (satellite and radar data) and computing platforms (GEE, GIS) are available and accessible worldwide.

Identifying Local-Scale Weather Forcing Conditions Favorable to Generating Iberia’s Largest Fires

The Mediterranean region is characterized by the frequent occurrence of summer wildfires, representing an environmental and socioeconomic burden. Some Mediterranean countries (or provinces) are particularly prone to large fires, namely Portugal, Galicia (Spain), Greece, and southern France. Additionally, the Mediterranean basin corresponds to a major hotspot of climate change, and anthropogenic warming is expected to increase the total burned area due to fires in Mediterranean Europe. Here, we propose to classify summer large fires for fifty-four provinces of the Iberian Peninsula according to their local-scale weather conditions and fire danger weather conditions. A composite analysis was used to investigate the impact of local and regional climate drivers at different timescales, and to identify distinct climatologies associated with the occurrence of large fires. Cluster analysis was also used to identify a limited set of fire weather types, each characterized by a combination of meteorological conditions. For each of the provinces, two significant fire weather types were identified—one dominated by high positive temperature anomalies and negative humidity anomalies, and the other by intense zonal wind anomalies with two distinct subtypes in the Iberian Peninsula., allowing for the identification of three distinct regions.

A Community Case Study on Geographic, Environmental, and Social Health Disparities in COVID-19 Disease: Yakima, Washington

Yakima County, Washington, a rural county with an urban core suffered disproportionately under the conditions presented by the COVID-19 pandemic and summer wildfires of 2020. With an infection rate of over 700 per 100,000 population at the height of the pandemic, the county concurrently experienced 14 consecutive days of an air quality index in the unhealthy to hazardous range in August 2020. This paper examines the contributing socioeconomic, geographic, and environmental vulnerabilities that make Yakima County particularly susceptible to the continuum of expected COVID-19 disease and related outcomes and suggests comprehensive areas of investigation to mitigate its impact on special populations, including Hispanic-Latino communities, agricultural, food production, and other essential workers.

Predicted ultrafine particulate matter source contribution across the continental United States during summertime air pollution events

Abstract. The regional concentrations of airborne ultrafine particulate matter mass (Dp<0.1 µm; PM0.1) were predicted in 39 cities across the United States (US) during summertime air pollution episodes. Calculations were performed using a regional source-oriented chemical transport model with 4 km spatial resolution operating on the National Emissions Inventory created by the U.S. Environmental Protection Agency (EPA). Measured source profiles for particle size and composition between 0.01 and 10 µm were used to translate PM total mass to PM0.1. Predicted PM0.1 concentrations exceeded 2 µg m−3 during summer pollution episodes in major urban regions across the US including Los Angeles, the San Francisco Bay Area, Houston, Miami, and New York. PM0.1 spatial gradients were sharper than PM2.5 spatial gradients due to the dominance of primary aerosol in PM0.1. Artificial source tags were used to track contributions to primary PM0.1 and PM2.5 from 15 source categories. On-road gasoline and diesel vehicles made significant contributions to regional PM0.1 in all 39 cities even though peak contributions within 0.3 km of the roadway were not resolved by the 4 km grid cells. Cooking also made significant contributions to PM0.1 in all cities but biomass combustion was only important in locations impacted by summer wildfires. Aviation was a significant source of PM0.1 in cities that had airports within their urban footprints. Industrial sources, including cement manufacturing, process heating, steel foundries, and paper and pulp processing, impacted their immediate vicinity but did not significantly contribute to PM0.1 concentrations in any of the target 39 cities. Natural gas combustion made significant contributions to PM0.1 concentrations due to the widespread use of this fuel for electricity generation, industrial applications, residential use, and commercial use. The major sources of primary PM0.1 and PM2.5 were notably different in many cities. Future epidemiological studies may be able to differentiate PM0.1 and PM2.5 health effects by contrasting cities with different ratios of PM0.1∕PM2.5. In the current study, cities with higher PM0.1∕PM2.5 ratios (ratio greater than 0.10) include Houston, TX, Los Angeles, CA, Bakersfield, CA, Salt Lake City, UT, and Cleveland, OH. Cities with lower PM0.1 to PM2.5 ratios (ratio lower than 0.05) include Lake Charles, LA, Baton Rouge, LA, St. Louis, MO, Baltimore, MD, and Washington, D.C.

Seasonal prediction of climate-driven fire risk for decision-making and operational applications in a Mediterranean region

In this paper, we assess and develop a climate service focused on the production of seasonal predictions for summer wildfires in a Mediterranean region through a participatory approach with end-users. We start by building a data-driven model that links a drought indicator (Standardised Precipitation Evapotranspiration Index; SPEI) with a series of burned areas in Catalonia (northeastern Spain). Afterwards, we feed this model with SPEI forecasts obtained through a combination of the antecedent observed conditions and climatology. Finally, we assess the forecasting skill of the system by using cross-validation to evaluate the predictions as if they had been made operationally. Our fire forecasting system reveals an untapped and useful burned area predictive ability. We argue that this source of predictability is mostly attributable to the effect of observed initial conditions on summer drought conditions. This system was conceived with the stakeholders, merging climate-driven predictions with information that is of interests to the users, including the identification of climate variables, thresholds and models. The co-production of this customized system allows fire-risk outlooks to be translated into usable information for fire management. This fire forecasting ability plays a crucial role in developing proactive fire management practices such as long-term fuel assessment and other fire-risk planning, thus minimising the impact of adverse climate conditions on summer burned area.

Formaldehyde and nitrogen dioxide in the atmosphere during summer weather extremes and wildfires in European Russia in 2010 and Western Siberia in 2012

ABSTRACTBased on the data from the Ozone Monitoring Instrument (OMI; Aura) satellite instrument, an analysis of changes in total formaldehyde (CH2O) column and tropospheric nitrogen dioxide (NO2) column, associated with the extreme summer weather regimes and wildfires in European Russia (ER) in 2010 and Western Siberia (WS) in 2012, was carried out. In both territories, over the clusters of intense fires, an approximately two-fold increase in CH2O content and a 20% increase in NO2 content were observed. Unlike NO2, the changes in the CH2O content over ER and WS also reveal positive correlation with the regional surface temperature.

Assessing the role of drought events on wildfires in the Iberian Peninsula

Southern European countries are particularly affected by summer wildfires and drought events. The occurrence of extreme meteorological conditions during preceding and contemporaneous months amplifies the risk of summer wildfires.The main scope of this study was to investigate the impact of drought periods on burned areas in the Iberian Peninsula. This will be achieved through the comparison of time series of two widely used multi-scalar drought indices (SPI and SPEI) calculated for each province and then associated with the time series of the standardized logarithm of normalized burned areas during the fire summer season. The SPI and SPEI were both calculated for the time scales spanning between 2 to 12 months and for each month from January to August, between 1980 and 2005. Based on the regression analysis between drought indicators and burned areas, the months that present lowest errors were identified for each province. From the obtained results two main conclusions were reached: (i) the association between drought and fires is a local scale process and should be analyzed at the province or sub-province level rather than at the country or continental level; (ii) the relation between wildfires and drought is better explained by the influence of the spring precipitation on the central sector and by the influence of temperature and precipitation during summer on most of the Portuguese provinces.

Frost Dynamics of Sagebrush Steppe Soils

Core Ideas Rangeland restoration seedings may sometimes fail due to frost damage. Seed coatings could delay seed germination until spring. Frost dynamics were characterized by soil temperatures on 14 sagebrush steppe sites. More than 60 frost periods occurred at 2‐cm depth from fall to spring. Freezing began in late October and ended in March. Sagebrush (Artemisia spp.) steppe rangelands in the western United States are converting to weedy landscapes after large‐scale wildfires. To restore ecosystem function, perennial grasses, shrubs, and forbs are sown in fall after summer wildfires or in association with mechanical fuel reduction projects. Recent research has indicated that seeds may germinate too soon after fall sowing and seedlings suffer high mortality from frost during the winter. To help determine the length of germination delay needed to avoid seedling frost mortality and to help guide frost‐tolerance experiments, we analyzed fall to spring soil temperatures from 2010 to 2014 on six sagebrush–bunchgrass sites and eight woodland sites where conifers had invaded sagebrush communities. Soil temperatures were measured using thermocouples attached to microloggers, with stations placed in untreated, prescribed burned, and mechanically treated plots. Soil freezing differed with site, year of measurement, and soil depth but was relatively unaffected by fire and mechanical fuel reduction treatments. The 2‐cm depth experienced much more freezing than lower depths (14–29 cm) and had >60 freeze–thaw cycles from late October into late March. Although maximum continuously frozen periods ranged from 11 to 45 d, most frost periods were <1 d long. Additional field and laboratory research is needed to determine the effects of different seed coatings on germination delay and frost dynamics on seedling mortality to best avoid frost mortality.

Does Shelter Site Selection Aid Persistence of a Threatened Alpine Lizard? Assessing Liopholis guthega Populations a Decade after Severe Fire in Southeastern Australia

Species' tolerance of and response to fire varies. Environments that experience frequent fires will contain fire-tolerant fauna, whereas fauna that occur in environments that burn infrequently may lack strategies to cope with fire. In 2003, intense summer wildfires in southeastern Australia's alpine region burned more than 1.3 million ha. The Guthega Skink, Liopholis guthega, is an endangered lizard that is restricted to two geographically isolated alpine locations affected by these fires: Kosciuszko National Park in New South Wales, and the Bogong High Plains in Victoria. We investigated the long-term effects of fire on L. guthega populations through surveys of burned and unburned habitat on the Bogong High Plains. We found L. guthega selected specific microhabitats that are restricted on the Bogong High Plains. Their selection of less-vegetated microhabitats suggests that they may favor an early successional environment. We found retreat site selection differed between sites; at burned sites L. guthega burrowed preferentially under rocks, and at unburned sites comparatively more burrows were positioned at the base of shrubs. Our results suggest that in this species' Victorian range they may be more tolerant to fire than previously thought, likely because of the protection afforded by their burrows. However, our surveys of L. guthega populations from past records also suggest potential local extinctions. To determine the immediate and longer-term effects of intense fires on threatened species, it is important to have prefire data on species and prompt postfire assessments to obtain results applicable to management.

Seasonal predictability of summer fires in a Mediterranean environment

In this study we explore the seasonal predictability of summer wildfires in a Mediterranean region (north-eastern Spain), developing a multiple linear regression model with antecedent and current-summer drought indices (Standardised Precipitation Index; and Standardised Precipitation Evapotranspiration Index). This model is based on the assumption that large summer fires in Mediterranean environments are favoured by current-summer drought (proxy for the climatic factors that affect fuel flammability) and by antecedent wet conditions (proxies for the climatic factors influencing fine fuel availability and connectivity). We test three forecast systems based on (i) seasonal European Centre for Medium-Range Weather Forecasts (ECMWF) System-4 forecasts; (ii) persistence and (iii) climatology. These approaches are evaluated through a leave-one-out cross-validation over the period 1983–2012. The climatology forecast, which considers only antecedent wet or dry conditions with a time lag of 2 years, shows some amount of skill in simulating above- or below-normal summer fire activity. ECMWF System-4 proves to be of limited added value with respect to the climatology forecast. Finally, the persistence forecast, which is driven by antecedent conditions and drought conditions just before the start of the fire season, allows more satisfactory results (correlation of 0.49). The results suggest that long-term forecasts of above-normal burned area are feasible in Catalonia (north-eastern Spain), information that could be potentially applied also to other Mediterranean-type regions.

An “Asymmetric Threat” That Should Have Been Anticipated: Political Discourse on 2007 Wildfires in Greece

This paper examines the pre-election interpretative repertoires employed by the two main political parties in Greece regarding the 2007 summer wildfires, which have been recorded as the worst natural disaster in contemporary Greek history. This involved a discourse analysis of press releases, interviews, and press conference statements. While the New Democracy governing party initially followed a “business-as-usual” scenario, comparing the situation with past wildfires under the administration of PASOK (the biggest opposition party), the increasing number of deaths over time rendered any such comparison invalid. In order to regain momentum, the government launched the interpretative repertoire of “asymmetric threat”, which proved instrumental in helping the government to get re-elected. This political discourse lacked any consideration of broad socioeconomic changes in rural areas in Greece which might have contributed substantially to the severity of the disaster. Implications for wildfire policy are discussed.

Satellite and ground-based monitoring of smoke in the atmosphere during the summer wildfires in European Russia in 2010 and Siberia in 2012

Using Moderate Resolution Imaging Spectroradiometer (MODIS) (Aqua and Terra satellites) and in situ observations, a comparative analysis of two large-scale smoke events caused by the summer wildfires in European Russia (ER) in 2010 and Western Siberia (WS) in 2012 was carried out. In the 5-day periods of the extreme smoke pollution (5–9 August 2010 in ER and 27–31 July 2012 in WS), the number of active fires in the equal territories, confined by the coordinates 47°–65° N, 25°–55° E and 51°–70° N, 71°–104° E, was found to be 4754 for ER and 3823 for WS. With this, the regional mean aerosol optical depths (AODs) were found to be (1.02 ± 0.02) and (1.00 ± 0.04), not much differing for both the events. The regional mean aerosol radiative forcing effects at the top (R1) and the bottom (R2) of the atmosphere over ER/WS according to MODIS observations were estimated to be (−61 ± 1) and (−54 ± 2) W m−2, and (−107 ± 2) and (−96 ± 3) W m−2, respectively. At the same time, the local values of AOD and the local absolute values of R1 and R2 over WS were considerably higher than those over ER. MODIS AOD (L3) data during the wildfires of 2010 were validated by AOD data obtained by the sun-sky photometer CIMEL, operating at the AERONET station Zvenigorod. The rates of radiative heating of the smoky atmosphere over ER and WS were also estimated and compared with the existed temperature anomalies, obtained using National Centers for Environmental Prediction National Center for Atmospheric Research reanalysis data. Optical and microphysical properties of smoke aerosols during the wildfires in ER and WS also revealed some similar characteristics. The aerosols were mostly found in the submicron-size fraction and characterized by very high single-scattering albedos (0.95–0.98). In the dense smoke conditions, the degree of linear polarization at the scattering angle 90° during both the events decreased to negative values ranging between −0.1 and −0.15. The optical properties of smoke aerosols were mainly conditioned by unusually narrow particle size distribution.

Climate change impacts on wildfires in a Mediterranean environment

We analyse the observed climate-driven changes in summer wildfires and their future evolution in a typical Mediterranean environment (NE Spain). By analysing observed climate and fire data from 1970 to 2007, we estimate the response of fire number (NF) and burned area (BA) to climate trends, disentangling the drivers responsible for long-term and interannual changes by means of a parsimonious Multi Linear Regression model (MLR). In the last forty years, the observed NF trend was negative. Here we show that, if improvements in fire management were not taken into account, the warming climate forcing alone would have led to a positive trend in NF. On the other hand, for BA, higher fuel flammability is counterbalanced by the indirect climate effects on fuel structure (i.e. less favourable conditions for fine-fuel availability and fuel connectivity), leading to a slightly negative trend. Driving the fire model with A1B climate change scenarios based on a set of Regional Climate Models from the ENSEMBLES project indicates that increasing temperatures promote a positive trend in NF if no further improvements in fire management are introduced.

Space-use and habitat associations of Black-backed Woodpeckers (Picoides arcticus) occupying recently disturbed forests in the Black Hills, South Dakota

Black-backed Woodpeckers (Picoides arcticus) are a disturbance-dependent species that occupy recently burned forest and mountain pine beetle (MPB) infestations. Forest management practices that reduce the amount of disturbed forest may lead to habitat loss for Black-backed Woodpeckers, which have recently been petitioned for listing under the Endangered Species Act. We studied home range size and resource selection of Black-backed Woodpeckers occupying habitat created by summer wildfire, fall prescribed fire, and MPB infestations in the Black Hills, South Dakota. We studied home range size and resource selection by attaching radio-transmitters to adult Black-backed Woodpeckers. We estimated home range size using fixed kernel density techniques (n=28 in habitat created by summer wildfire, n=19 in habitat created by fall prescribed fire, and n=27 in MPB infestations). We evaluated resource selection with a random-effects discrete choice model in a Bayesian framework (n=5 in habitat created by summer wildfire, n=16 in habitat created by fall prescribed fire, and n=8 in habitat created by MPB infestations). Home range size was smallest in 1–2year post summer wildfire habitat (mean home range size=79ha) and 2-year post fall prescribed fire habitat (mean home range size=143ha). Home range size was intermediate in MPB infestations (mean home range size=307ha) and was greatest in 3–4year post fire habitat (mean summer wildfire home range size=430 hectares, mean fall prescribed fire home range size=460ha). The relative probability that a Black-backed Woodpecker used a tree increased with increasing diameter at breast height (DBH) and basal area and was greatest on disturbance-killed trees. These results suggest 1–2year post summer wildfire habitat may have the greatest relative value to Black-backed Woodpeckers and that MPB infestations may be more important as post-fire habitats age. We recommend retaining patches of 1–2year post summer wildfire habitat that are at least 200ha by exempting portions of recently burned forest from salvage logging. This recommendation can be accomplished by exempting salvage logging in summer wildfires <200ha and retaining at least 50% of summer wildfires >400ha. Ideally, recently burned forest patches should be composed of ⩾27m2 basal area/ha of trees that burned at moderate or high severity, with at least 40% of the basal area composed of trees ⩾27cm DBH.

Are Early Summer Wildfires an Opportunity to Revegetate Exotic Annual Grass–Invaded Plant Communities?

Medusahead (Taeniatherum caput-medusae [L.] Nevski) is an exotic annual grass invading western rangelands. Successful revegetation of invaded-plant communities can be prohibitively expensive because it often requires iterative applications of integrated control and revegetation treatments. Prescribed burning has been used to control medusahead and prepare seedbeds for revegetation, but burning has been constrained by liability concerns and has produced widely varying results. Capitalizing on naturally occurring wildfires could reduce revegetation costs and alleviate liability concerns. Thus, our objective was to determine if early summer wildfires and fall drill seeding could be used as a treatment combination to decrease medusahead and increase perennial and native vegetation. Treatments were evaluated pretreatment and for 3yr postfire at six sites and included 1) an early summer wildfire combined with a seeding treatment (burn and seed) and 2) a nontreated (no burn, no seed) control. Perennial grass density was 4.6- to 10.0-fold greater in the burn-and-seed treatment compared to the control in the first 3yr posttreatment (P < 0.05). Exotic annual grass density and cover in the third year posttreatment were lower in the burn-and-seed treatment than in the control (P < 0.05). However, exotic annual grass density was still > 130 individuals · m‒2 in the burn-and-seed treatment. The density of exotic annual grass is of concern because over time medusahead may displace perennial grasses and annual forbs that increased with the burn-and-seed treatment. Though not directly tested in this study, we suggest that, based on other research, the burn-and-seed treatment may need to incorporate a preemergent herbicide application to further suppress medusahead and increase the establishment of seeded vegetation. However, it appears that early summer wildfires may provide an opportunity to reduce the cost of integrated programs to revegetate medusahead-invaded plant communities.

Regeneración de la vegetación y riesgos de erosion pos incendios forestales. Estudio de casos en paises mediterraneos

Se presentan tipos de efectos erosivos por fuegos vegetales, acaecidos en sectores de la zona mediterránea de Chile y Portugal. La zona mediterránea de Chile es donde anualmente se desarrolla la mayor parte de los incendios forestales de erano, en una región comprendida aproximadamente entre los 32° y 36° latitud sur. En Portugal, es la región Centro, ubicada entre los 39° y 41° latitud norte, la que detiene más superficie quemada por incendios forestales y la que suele registrar los incendios más grandes.

Pattern and process of prescribed fires influence effectiveness at reducing wildfire severity in dry coniferous forests

We examined the effects of three early season (spring) prescribed fires on burn severity patterns of summer wildfires that occurred 1–3years post-treatment in a mixed conifer forest in central Idaho. Wildfire and prescribed fire burn severities were estimated as the difference in normalized burn ratio (dNBR) using Landsat imagery. We used GIS derived vegetation, topography, and treatment variables to generate models predicting the wildfire burn severity of 1286–5500 30-m pixels within and around treated areas. We found that wildfire severity was significantly lower in treated areas than in untreated areas and significantly lower than the potential wildfire severity of the treated areas had treatments not been implemented. At the pixel level, wildfire severity was best predicted by an interaction between prescribed fire severity, topographic moisture, heat load, and pre-fire vegetation volume. Prescribed fire severity and vegetation volume were the most influential predictors. Prescribed fire severity, and its influence on wildfire severity, was highest in relatively warm and dry locations, which were able to burn under spring conditions. In contrast, wildfire severity peaked in cooler, more mesic locations that dried later in the summer and supported greater vegetation volume. We found considerable evidence that prescribed fires have landscape-level influences within treatment boundaries; most notable was an interaction between distance from the prescribed fire perimeter and distance from treated patch edges, which explained up to 66% of the variation in wildfire severity. Early season prescribed fires may not directly target the locations most at risk of high severity wildfire, but proximity of these areas to treated patches and the discontinuity of fuels following treatment may influence wildfire severity and explain how even low severity treatments can be effective management tools in fire-prone landscapes.

Climate change and the future occurrence of moorland wildfires in the Peak District of the UK

We investigated the impact of climate change on the number of wildfires in the Peak District uplands of northern England. Wildfires in peat can result in severe carbon loss and damage to water supplies, and fighting such fires is difficult and costly in such a remote location. The Peak District is expected to experience warmer, wetter winters and hotter, drier summers. Local weather simulations from a weather generator were used to predict the future incidence and timing of fires. Wildfire predictions were based on past fire occurrence and weather over 27.5 yr. A Probit model of wildfire incidence was applied to simulated weather data, which were generated by a Markov pro- cess and validated against actual baseline weather data using statistical criteria and success in repli- cating past fire patterns. The impact of climate change on the phenology and ecology of moorland and on visitor numbers was considered. Simulations suggest an overall increase in occurrence of summer wildfires. The likelihood of spring wildfires is not reduced by wetter winter conditions; how- ever, the chance of wildfires rises as rainfall decreases. Temperature rise has a non-linear impact, with the risk of wildfire occurrence rising disproportionately with temperature. Recreation use is a major source of ignition. Little change in wildfire incidence is projected in the near future, but as cli- mate change intensifies, the danger of summer wildfires is projected to increase from 2070; therefore, fire risk management will be necessary in future. In addition, moorlands may have to be managed to reduce the chance of summer wildfires becoming catastrophic, with consequent damage to eco- system services such as water supplies and peat carbon storage. Management measures may include controlled burning, grazing or mowing to remove fuel.

Fire and biofuel contributions to annual mean aerosol mass concentrations in the United States

We estimate the contributions from biomass burning (summer wildfires, other fires, residential biofuel, and industrial biofuel) to seasonal and annual aerosol concentrations in the United States. Our approach is to use total carbonaceous (TC) and non-soil potassium (ns-K) aerosol mass concentrations for 2001–2004 from the nationwide IMPROVE network of surface sites, together with satellite fire data. We find that summer wildfires largely drive the observed interannual variability of TC aerosol concentrations in the United States. TC/ns-K mass enhancement ratios from fires range from 10 for grassland and shrub fires in the south to 130 for forest fires in the north. The resulting summer wildfire contributions to annual TC aerosol concentrations for 2001–2004 are 0.26 μg C m −3 in the west and 0.14 μg C m −3 in the east; Canadian fires are a major contributor in the east. Non-summer wildfires and prescribed burns contribute on an annual mean basis 0.27 and 0.31 μg C m −3 in the west and the east, highest in the southeast because of prescribed burning. Residential biofuel is a large contributor in the northeast with annual mean concentration of up to 2.2 μg C m −3 in Maine. Industrial biofuel (mainly paper and pulp mills) contributes up to 0.3 μg C m −3 in the southeast. Total annual mean fine aerosol concentrations from biomass burning average 1.2 and 1.6 μg m −3 in the west and east, respectively, contributing about 50% of observed annual mean TC concentrations in both regions and accounting for 30% (west) and 20% (east) of total observed fine aerosol concentrations. Our analysis supports bottom-up source estimates for the contiguous United States of 0.7–0.9 Tg C yr −1 from open fires (climatological) and 0.4 Tg C yr −1 from biofuel use. Biomass burning is thus an important contributor to US air quality degradation, which is likely to grow in the future.

Mapping erosion‐sensitive areas after wildfires using fieldwork, remote sensing, and geographic information systems techniques on a regional scale

Alterations in the hydrological cycle following wildfire due to the loss of ground cover vegetation and changes in soil properties have been documented in many studies. Nevertheless, the rapid process of vegetation recovery reduces such negative effects. Vegetation cover before fire, fire severity, and geophysical properties are important factors that control spatial discontinuities involved in the vegetation‐covering process. The objective of this study was to estimate the probability of high erosion in order to map erosion‐sensitive areas after fire. The analysis was carried out in different plant communities burnt by summer wildfires in the pre‐Pyrenean area (Spain). Three‐year Landsat Thematic Mapper (TM) images have been used for mapping wildfire areas and severity levels. Conversion to spectral reflectance has been applied for radiometric correction by normalizing topographic and atmospheric effects. Likewise, other physical variables have also been incorporated into the geographic information system (GIS): vegetation types, parent material, illumination, slope, aspect, and precipitation. The dependent variable has been characterized by means of fieldwork and a photointerpretation process based on high‐resolution digital aerial orthophotographs taken 11–12 years after the fire. Different logistic regression models have been used for mapping the probability of erosion. Results indicate that prefire normalized difference vegetation index values and aspect are the most important variables for estimating erosion‐sensitive areas after fire (Nagelkerke r2 = 0.66; Kappa values = 0.65). Finally, the use of nonparametric models with environmental digital information based on GIS can facilitate the management of burnt areas.