38 research outputs found
Modelling global pyrogeography using data derived from satellite imagery
Doutoramento em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de Agronomia - ULVegetation burning has an important impact on the global atmosphere and vegetated land surface. Deforestation fires, peatland fires, and ecosystems with shortening fire return interval contribute substantially to the build-up of atmospheric greenhouse gases affecting environmental quality and the climate system at local and regional scales. Recognition of the role of fire in the Earth system led to its designation as an Essential Climate Variable (ECV), a physical, chemical, or biological variable that has a crucial contribution towards characterization of Earth’s climate. The central task of this thesis was the development of a new global classification and map of fire regimes, using multiple correspondence analysis and hierarchical clustering, and relying on active fire data from the Moderate Resolution Imaging Spectroradiometer (MODIS) MCD14ML product. That work was preceded by study dedicated to a thorough screening and exploratory spatial analysis of the dataset, and led to the development of an improved algorithm for identifying individual active fire clusters, and to global analysis of size inequality in their statistical distributions. In addition to this core research, other continental-global pyrogeography studies were developed, and are presented, dealing with: the time lag between the timing of optimal fire weather conditions and peak fire season dates as a diagnostic of anthropogenic vegetation burning; the spatial non-stationarity in the parameters of the relationship between population density and area burned; and the modulation of weekly cycles of vegetation burning in African croplands by regionally dominant religious affiliation. We hope that this set of studies may constitute a useful contribution to the burgeoning topic of global pyrogeograph
Detecção remota de áreas queimadas na Amazónia brasileira
The area burned in the brazilian Amazon during June-October 2000 was mapped using SPOT-VGT
images. The burned area estimate was calibrated with Landsat TM data. Pareto boundary analysis was used to
evaluate the best achievable classification accuracy, for 1.1km and 8km spatial resolution imagery. Finally, we
present preliminary results from an analysis of the performance of three active fire products for detecting
understory fires in the Acre rainforest during 2005
Wildfires in the Amazon region 2019
Analysis of wildfire trends in the Amazon regionJRC.E.1-Disaster Risk Managemen
Highlighting biome-specific sensitivity of fire size distributions to time-gap parameter using a new algorithm for fire event individuation
Detailed spatial-temporal characterization of individual fire dynamics using remote sensing data is important to understand fire-environment relationships, to support landscape-scale fire risk management, and to obtain improved statistics on fire size distributions over broad areas. Previously, individuation of events to quantify fire size distributions has been performed with the flood-fill algorithm. A key parameter of such algorithms is the time-gap used to cluster spatially adjacent fire-affected pixels and declare them as belonging to the same event. Choice of a time-gap to define a fire event entails several assumptions affecting the degree of clustering/fragmentation of the individual events. We evaluate the impact of different time-gaps on the number, size and spatial distribution of active fire clusters, using a new algorithm. The information produced by this algorithm includes number, size, and ignition date of active fire clusters. The algorithm was tested at a global scale using active fire observations from the Moderate Resolution Imaging Spectroradiometer (MODIS). Active fire cluster size distributions were characterized with the Gini coefficient, and the impact of changing time-gap values was analyzed on a 0.5° cell grid. As expected, the number of active fire clusters decreased and their mean size increased with the time-gap value. The largest sensitivity of fire size distributions to time-gap was observed in African tropical savannas and, to a lesser extent, in South America, Southeast Asia, and eastern Siberia. Sensitivity of fire individuation, and thus Gini coefficient values, to time-gap demonstrate the difficulty of individuating fire events in tropical savannas, where coalescence of flame fronts with distinct ignition locations and dates is very common, and fire size distributions strongly depend on algorithm parameterization. Thus, caution should be exercised when attempting to individualize fire events, characterizing their size distributions, and addressing their management implications, particularly in the African savannas
Burned area mapping in the brazilian savanna using a one-class support vector machine trained by active fires
We used the Visible Infrared Imaging Radiometer Suite (VIIRS) active fire data (375 m
spatial resolution) to automatically extract multispectral samples and train a One-Class Support Vector
Machine for burned area mapping, and applied the resulting classification algorithm to 300-m spatial
resolution imagery from the Project for On-Board Autonomy-Vegetation (PROBA-V). The active fire
data were screened to prevent extraction of unrepresentative burned area samples and combined with
surface reflectance bi-weekly composites to produce burned area maps. The procedure was applied
over the Brazilian Cerrado savanna, validated with reference maps obtained from Landsat images and
compared with the Collection 6 Moderate Resolution Imaging Spectrometer (MODIS) Burned Area
product (MCD64A1) Results show that the algorithm developed improved the detection of small-sized
scars and displayed results more similar to the reference data than MCD64A1. Unlike active fire-based
region growing algorithms, the proposed approach allows for the detection and mapping of burn
scars without active fires, thus eliminating a potential source of omission error. The burned area
mapping approach presented here should facilitate the development of operational-automated
burned area algorithms, and is very straightforward for implementation with other sensorsinfo:eu-repo/semantics/publishedVersio
Advance EFFIS report on forest fires in Europe, Middle East and North Africa 2019
This report contains an anticipated annual summary of the fire season of 2019 with an analysis of fire danger and
areas mapped in the European Forest Fire Information System (EFFIS). This report precedes that to be published
in August/September 2020, which will include detailed reports prepared by countries in the Expert Group on Forest
Fires.JRC.E.1-Disaster Risk Managemen
A new global burned area product for climate assessment of fire impacts
ABSTRACT Aim This paper presents a new global burned area (BA) product developed within the framework of the European Space Agency's Climate Change Initiative (CCI) programme, along with a first assessment of its potentials for atmospheric and carbon cycle modelling. Innovation Methods are presented for generating a new global BA product, along with a comparison with existing BA products, in terms of BA extension, fire size and shapes and emissions derived from biomass burnings. Main conclusions Three years of the global BA product were produced, accounting for a total BA of between 360 and 380 Mha year 21 . General omission and commission errors for BA were 0.76 and 0.64, but they decreased to 0.51 and 0.52, respectively, for sites with more than 10% BA. Intercomparison with other existing BA datasets found similar spatial and temporal trends, mainly with the BA included in the Global Fire Emissions Database (GFED4), although regional differences were found (particularly in the 2006 fires of eastern Europe). The simulated carbon emissions from biomass burning averaged 2.1 Pg C year 21
Religious affiliation modulates weekly cycles of cropland burning in Sub-Saharan Africa
Research ArticleVegetation burning is a common land management practice in Africa, where fire is used
for hunting, livestock husbandry, pest control, food gathering, cropland fertilization, and
wildfire prevention. Given such strong anthropogenic control of fire, we tested the hypotheses
that fire activity displays weekly cycles, and that the week day with the fewest fires
depends on regionally predominant religious affiliation.We also analyzed the effect of land
use (anthrome) on weekly fire cycle significance. Fire density (fire counts.km-2) observed
per week day in each region was modeled using a negative binomial regression model, with
fire counts as response variable, region area as offset and a structured random effect to
account for spatial dependence. Anthrome (settled, cropland, natural, rangeland), religion
(Christian, Muslim, mixed) week day, and their 2-way and 3-way interactions were used as
independent variables. Models were also built separately for each anthrome, relating
regional fire density with week day and religious affiliation. Analysis revealed a significant
interaction between religion and week day, i.e. regions with different religious affiliation
(Christian, Muslim) display distinct weekly cycles of burning. However, the religion vs. week
day interaction only is significant for croplands, i.e. fire activity in African croplands is significantly
lower on Sunday in Christian regions and on Friday in Muslim regions. Magnitude of
fire activity does not differ significantly among week days in rangelands and in natural
areas, where fire use is under less strict control than in croplands. These findings can contribute
towards improved specification of ignition patterns in regional/global vegetation fire
models, and may lead to more accurate meteorological and chemical weather forecastinginfo:eu-repo/semantics/publishedVersio