What Is a Fire? Identifying Individual Fire Events Using the MODIS Burned Area Product

Fire events, which delimit the extents of fires as well as fire start and end dates, provide important information for understanding fire regimes, including ignition points, spread rates, seasonality, and final size. Rates and patterns of spread associated with individual events are critical for modeling fire behavior across varied ecoregions and informing fire management. Fire events are not available from satellite-derived burned areas directly, and therefore a consistent process for aggregating burned pixels into fire events is needed. This study presents a flexible flood-fill algorithm that aggregates burned pixels into fire events based on varying spatial and temporal proximity. We tested our approach using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) Burned Area product (MCD64A Collection 5.1) for the western U.S. in the year 2007. We used a range of spatial (number of pixels) and temporal (number of days) distances to cluster Burned Area pixels into events. We then compared Burned Area perimeters to perimeters based on the Landsat-derived Monitoring Trends in Burn Severity (MTBS) product for the same events. Based on this comparison, we determined that for the western U.S., a distance of five pixels and nine days constituted the best spatial and temporal thresholds to define individual fire events with the MODIS Burned Area product. We present a fire event dataset for the continental U.S. based on MODIS burned area for 2001-2016. Our fire event maps include important metrics of the fire regime, such as ignition point, fire size, fire spread rate, and the start and end dates of each individual fire event. The comparison between the MODIS Burned Area derived fire events and the MTBS, as the ground truth data, showed that omission, commission errors, and final accuracy are 12%, 38% and 88% respectively. We expect that the five-pixel, nine-day criteria may vary by ecoregion or land use type, and have designed the code so that these aggregation criteria can be adjusted for different regions. Our aggregation method increases the utility of the MODIS Burned Area product for fire modeling and management by enabling the analysis of fire behavior for individual fire events

Cheatgrass (Bromus tectorum) distribution in the intermountain Western United States and its relationship to fire frequency, seasonality, and ignitions

Cheatgrass (Bromus tectorum) is an invasive grass pervasive across the Intermountain Western US and linked to major increases in fire frequency. Despite widespread ecological impacts associated with cheatgrass, we lack a spatially extensive model of cheatgrass invasion in the Intermountain West. Here, we leverage satellite phenology predictors and thousands of field surveys of cheatgrass abundance to create regional models of cheatgrass distribution and percent cover. We compare cheatgrass presence to fire probability, fire seasonality and ignition source. Regional models of percent cover had low predictive power (34% of variance explained), but distribution models based on a threshold of 15% cover to differentiate high abundance from low abundance had an overall accuracy of 74%. Cheatgrass achieves ≥ 15% cover over 210,000 km2 (31%) of the Intermountain West. These lands were twice as likely to burn as those with low abundance, and four times more likely to burn multiple times between 2000 and 2015. Fire probability increased rapidly at low cheatgrass cover (1–5%) but remained similar at higher cover, suggesting that even small amounts of cheatgrass in an ecosystem can increase fire risk. Abundant cheatgrass was also associated with a 10 days earlier fire seasonality and interacted strongly with anthropogenic ignitions. Fire in cheatgrass was particularly associated with human activity, suggesting that increased awareness of fire danger in invaded areas could reduce risk. This study suggests that cheatgrass is much more spatially extensive and abundant than previously documented and that invasion greatly increases fire frequency, even at low percent cover

The Possible Factors Correlated with The Higher Risk of Getting Infected by COVID-19 in Emergency Medical Technicians; A Case-Control Study

Objective: To assess the possible factors associated with increasing risk of COVID-19 among EMTs. Methods: This study was a case-control study conducted in Tehran, Iran. Case group was consisted of confirmed COVID-19 EMTs based on the results of reverse transcriptase polymerase chain reaction and/or lung computed tomography scan. Healthy EMTs were randomly selected as control group. Patients were asked to fill out a checklist including demographic data, data related to the work situation (such as number of missions and type of mask and cloth) and PPE precautions. Results: Sixty-eight patients and 148 healthy persons took part in this study as case and control group, respectively. Having two EMTs involved directly in taking care of patients (p <0.001) and working with a confirmed case teammate (p <0.001), considering the precautions such as seal check after wearing the mask (p=0.015), covering the hair with a medical hat (p <0.001), not using personal items despite protective clothing (p <0.001), and avoiding contact with the outer surface of clothing while removing (p <0.001) had significant difference in two groups. Conclusion: We found that the type and method of use of PPE were correlated with the increasing risk of COVID-19 in EMTs. Also, we found that when two EMTs were involved directly in taking care of the patients, and those who worked with a confirmed case teammate, more frequently affected

The Human Ecology and Geography of Burning in an Unstable Savanna Environment

According to new ecological theories, many savannas are inherently in disequilibrium and can flip from tree-dominated to grass-dominated landscapes depending upon the disturbance regime. In particular, a shift in a fire regime to a more frequent and intensive one can radically alter the tree-to-grass ratio in a given savanna. Drawing upon the ecological buffering model we argue that savanna persistence requires a relatively stable fire regime. We hypothesize that anthropogenic burning practices perform this function by producing a regular annual spatiotemporal pattern of fire that is linked to vegetation type. We test this hypothesis using a study of two areas, one in Mali and the other Burkina Faso. We use two sources of satellite data to produce an 11-year time series of the spatiotemporal pattern of fires and an example of the annual burned area pattern these fires produce. We combine the analysis of satellite imagery with interviews of rural inhabitants who set fires to understand the logic underlying the patterns of fire. Analysis of a time series of imagery reveals a strikingly regular annual spatiotemporal pattern of burning for both study areas, which cannot be explained by the regional climatic pattern alone. We conclude that the regularity of the annual fire regime in West Africa is a human-ecological phenomenon closely linked to vegetation type and controlled by people\u27s burning practices. We argue that the anthropogenic burning regime serves to buffer the savanna and maintain its ecological stability

Development and validation of the first iranian questionnaire to assess quality of life in patients with heart failure: IHF-QoL

Background: In its Constitution of 1948, WHO defined health as “a state of complete physical, mental, and social well-being, and not merely the absence of disease and infirmity” . In 1994, the Agency for Health Care Policy and Research published clinical practice guidelines recommending providers to routinely evaluate patients' HRQoL (Health Related Quality of Life) and use their assessment to modify and guide patient care. Objectives: to create a valid, sensitive, disease-specific Persian health status quality of life questionnaire for patients with chronic heart failure in Iran. Materials and Methods: Considering the existing relevant inventories and scientific literature, the authors designed the first draft of questionnaire which was modified and validated, using expert opinions and finalized in a session of expert panel. The questionnaire was processed among 130 patients with heart failure. Construct validity evaluated by principle component factor analysis, and promax method was used for factor rotation. MacNew quality of life questionnaire was selected to assess convergence validity, and the agreements were measured in 60 patients. Discriminant validity was also assessed. Thirty patients were followed for 3 months and responsiveness of questionnaire was measured. Cronbach's alpha, item analysis, and Intra-class correlation coefficients (ICCs) were used to investigate reliability of questionnaire. SPSS 15 for Windows was applied for statistical analysis. Results: Principle component factor analysis revealed 4 main components. Sub-group analysis suggested that IHF-QoL questionnaire demonstrated an acceptable discriminant validity. High conformity between this inventory and MacNew questionnaire revealed an appropriate convergence validity. Cronbach's alpha (α) for the overall questionnaire was equal to 0.922. Intra-class correlation coefficients (ICCs) for all components were significant (from. 708 to. 883; all P values < 0.001). Patients fallow-up revealed an acceptable responsiveness of our questionnaire. Conclusions: IHF-QoL questionnaire is a valid and reliable inventory. It can be applied in daily clinical practice and in the clinical research context