Development of a Sentinel-2 burned area algorithm: Generation of a small fire database for sub-Saharan Africa

A locally-adapted multitemporal two-phase burned area (BA) algorithm has been developed using as inputs Sentinel-2 MSI reflectance measurements in the short and near infrared wavebands plus the active fires detected by Terra and Aqua MODIS sensors. An initial burned area map is created in the first step, from which tile dependent statistics are extracted for the second step. The whole Sub-Saharan Africa (around 25 M km(2)) was processed with this algorithm at a spatial resolution of 20 m, from January to December 2016. This period covers two half fire seasons on the Northern Hemisphere and an entire fire season in the South. The area was selected as existing BA products account it to include around 70% of global BA. Validation of this product was based on a two-stage stratified random sampling of Landsat multitemporal images. Higher accuracy values than existing global BA products were observed, with Dice coefficient of 77% and omission and commission errors of 26.5% and 19.3% respectively. The standard NASA BA product (MCD64A1 c6) showed a similar commission error (20.4%), but much higher omission errors (59.6%), with a lower Dice coefficient (53.6%). The BA algorithm was processed over > 11,000 Sentinel-2 images to create a database that would also include small fires (< 100 ha). This is the first time a continental BA product is generated from medium resolution sensors (spatial resolution = 20 m), showing their operational potential for improving our current understanding of global fire impacts. Total BA estimated from our product was 4.9 M km(2), around 80% larger area than what the NASA BA product (MCD64A1 c6) detected in the same period (2.7 M km(2)). The main differences between the two products were found in regions where small fires (< 100 ha) account for a significant proportion of total BA, as global products based on coarse pixel sizes (500 m for MCD64A1) unlikely detect them. On the negative side, Sentinel-2 based products have lower temporal resolution and consequently are more affected by cloud/cloud shadows and have less temporal reporting accuracy than global BA products. The product derived from S2 imagery would greatly contribute to better understanding the impacts of small fires in global fire regimes, particularly in tropical regions, where such fires are frequent. This product is named FireCCISFD11 and it is publicly available at: https://www.esa-fire-cci.org/node/262, last accessed on November 2018.This research was carried out within the Fire_cci project (https://www.esa-fire-cci.org/, last accessed on November 2018), contract no. 4000115006/15/I-NB, which has been funded by the European Space Agency (ESA) under the Climate Change Initiative Programme. The FireCCISFD11 product can be downloaded at https://www.esa-fire-cci.org/node/262 (last accessed on November 2018)

Landsat and Sentinel-2 Based Burned Area Mapping Tools in Google Earth Engine

Four burned area tools were implemented in Google Earth Engine (GEE), to obtain regular processes related to burned area (BA) mapping, using medium spatial resolution sensors (Landsat and Sentinel-2). The four tools are (i) the BA Cartography tool for supervised burned area over the user-selected extent and period, (ii) two tools implementing a BA stratified random sampling to select the scenes and dates for validation, and (iii) the BA Reference Perimeter tool to obtain highly accurate BA maps that focus on validating coarser BA products. Burned Area Mapping Tools (BAMTs) go beyond the previously implemented Burned Area Mapping Software (BAMS) because of GEE parallel processing capabilities and preloaded geospatial datasets. BAMT also allows temporal image composites to be exploited in order to obtain BA maps over a larger extent and longer temporal periods. The tools consist of four scripts executable from the GEE Code Editor. The tools’ performance was discussed in two case studies: in the 2019/2020 fire season in Southeast Australia, where the BA cartography detected more than 50,000 km2, using Landsat data with commission and omission errors below 12% when compared to Sentinel-2 imagery; and in the 2018 summer wildfires in Canada, where it was found that around 16,000 km2 had burned.This research was funded by the Vice-Rectorate for Research of the University of the Basque Country (UPV/EHU) through a doctoral fellowship (contract no. PIF17/96)

Towards operational validation of annual global land cover maps

Annual global land cover maps (GLC) are being provided by several operational monitoring efforts. However, map validation is lagging, in the sense that the annual land cover maps are often not validated. Concurrently, users such as the climate and land management community require information on the temporal consistency of multi-date GLC maps and stability in their accuracy. In this study, we propose a framework for operational validation of annual global land cover maps using efficient means for updating validation datasets that allow timely map validation according to recommendations in the CEOS Stage-4 validation guidelines. The framework includes a regular update of a validation dataset and continuous map validation. For the regular update of a validation dataset, a partial revision of the validation dataset based on random and targeted rechecking (areas with a high probability of change) is proposed followed by additional validation data collection. For continuous map validation, an accuracy assessment of each map release is proposed including an assessment of stability in map accuracy addressing the user needs on the temporal consistency information of GLC map and map quality. This validation approach was applied to the validation of the Copernicus Global Land Service GLC product (CGLS-LC100). The CGLS-LC100 global validation dataset was updated from 2015 to 2019. The update was done through a partial revision of the validation dataset and an additional collection of sample validation sites. From the global validation dataset, a total of 40% (10% for each update year) was revisited, supplemented by a targeted revision focusing on validation sample locations that were identified as possibly changed using the BFAST time series algorithm. Additionally, 6720 sample sites were collected to represent possible land cover change areas within 2015 and 2019. Through this updating mechanism, we increased the sampling intensity of validation sample sites in possible land cover change areas within the period. Next, the dataset was used to validate the annual GLC maps of the CGLS-LC100 product for 2015–2019. The results showed that the CGLS-LC100 annual GLC maps have about 80% overall accuracy showing high temporal consistency in general. In terms of stability in class accuracy, herbaceous wetland class showed to be the least stable over the period. As more operational land cover monitoring efforts are upcoming, we emphasize the importance of updated map validation and recommend improving the current validation practices and guidelines towards operational map validation so that long-term land cover maps and their uncertainty information are well understood and properly used

Biomass burning fuel consumption dynamics in the (sub)tropics assessed from satellite

Landscape fires occur on a large scale in (sub)tropical savannas and grasslands, affecting ecosystem dynamics, regional air quality and concentrations of atmospheric trace gasses. Fuel consumption per unit of area burned is an important but poorly constrained parameter in fire emission modelling. We combined satellite-derived burned area with fire radiative power (FRP) data to derive fuel consumption estimates for land cover types with low tree cover in South America, Sub-Saharan Africa, and Australia. We developed a new approach to estimate fuel consumption, based on FRP data from the polar-orbiting Moderate Resolution Imaging Spectroradiometer (MODIS) and the geostationary Spinning Enhanced Visible and Infrared Imager (SEVIRI) in combination with MODIS burned-area estimates. The fuel consumption estimates based on the geostationary and polar-orbiting instruments showed good agreement in terms of spatial patterns. We used field measurements of fuel consumption to constrain our results, but the large variation in fuel consumption in both space and time complicated this comparison and absolute fuel consumption estimates remained more uncertain. Spatial patterns in fuel consumption could be partly explained by vegetation productivity and fire return periods. In South America, most fires occurred in savannas with relatively long fire return periods, resulting in comparatively high fuel consumption as opposed to the more frequently burning savannas in Sub-Saharan Africa. Strikingly, we found the infrequently burning interior of Australia to have higher fuel consumption than the more productive but frequently burning savannas in northern Australia. Vegetation type also played an important role in explaining the distribution of fuel consumption, by affecting both fuel build-up rates and fire return periods. Hummock grasslands, which were responsible for a large share of Australian biomass burning, showed larger fuel build-up rates than equally productive grasslands in Africa, although this effect might have been partially driven by the presence of grazers in Africa or differences in landscape management. Finally, land management in the form of deforestation and agriculture also considerably affected fuel consumption regionally. We conclude that combining FRP and burned-area estimates, calibrated against field measurements, is a promising approach in deriving quantitative estimates of fuel consumption. Satellite-derived fuel consumption estimates may both challenge our current understanding of spatiotemporal fuel consumption dynamics and serve as reference datasets to improve biogeochemical modelling approaches. Future field studies especially designed to validate satellite-based products, or airborne remote sensing, may further improve confidence in the absolute fuel consumption estimates which are quickly becoming the weakest link in fire emission estimates

Dinâmica de incêndios florestais e alterações biofísicas na Amazônia e Cerrado brasileiros a partir de séries temporais de sensoriamento remoto

Tese (doutorado)—Universidade de Brasília, Instituto de Ciências Humanas, Departamento de Geografia, Programa de Pós-Graduação em Geografia, 2019.Os biomas brasileiros se adaptaram a diferentes padrões de presença ou ausência do fogo. Dados derivados de sensoriamento remoto têm sido uma das principais bases para a detecção de incêndios florestais e os danos na estrutura da vegetação, especialmente com o desenvolvimento de sensores com alta resolução temporal e espectral, e o estabelecimento de longas séries contínuas. Nesse sentido, esta tese buscou aprofundamento em três pontos: (1) Qual a potencialidade de produtos de sensoriamento remoto para a descrição da dinâmica do fogo no Brasil? (2) Como detectar cicatrizes de queimadas a partir de séries temporais em ambientes amazônicos?; e por fim (3) Quais os danos na vegetação resultantes da alteração do regime histórico do fogo e como podem ser quantificados por sensoriamento remoto? Para ampliar o conhecimento sobre essas questões foram utilizados diversos produtos derivados dos sensores Moderate Resolution Imaging Spectroradiometer (MODIS), Thematic Mapper (TM), Enhanced Thematic Mapper Plus (ETM+) e Operational Land Imager (OLI), além de diversos dados espaciais, em três escalas: uma para todo o território nacional, uma área específica do Cerrado e duas áreas específicas da Amazônia. A metodologia básica consistiu na análise de séries temporais MODIS para detecção e quantificação dos efeitos do fogo. Os resultados permitiram concluir que: (1) Os produtos globais MODIS de detecção de cicatrizes de queimadas apresentaram altas taxas de erros de omissão no Brasil, superiores a 78% em média no território nacional, sendo seu uso recomendado apenas para análises regionais ou globais. Os produtos de queimadas apresentaram as menores acurácias nos biomas dos Pampas, Amazônia e Mata Atlântica e as maiores acurácias nos biomas do Cerrado e da Caatinga. Apesar desta limitação, o produto MCD64 permitiu descrever o regime do fogo no país, as principais regiões de ocorrência e a influência da umidade e classe de vegetação neste padrão. Foram estabelecidas como limite para a ação do fogo, as zonas sem estiagem, como o Oeste da Amazônia e litoral leste do Brasil, assim como as áreas do semiárido nordestino. (2) Dentre os métodos analisados de diferença sazonal e normalização temporal, a normalização pela média da banda espectral do Infravermelho Próximo foi responsável pela maior acurácia na detecção de cicatrizes de queimadas na Amazônia, retificando a utilização de alguns índices especializados originalmente para vegetações temperadas, como o Normalized Burn Ratio (NBR). Outros métodos analisados, como a diferença sazonal e normalização por z-score, apresentaram melhor acurácia que imagens originais, mas inferior em comparação com a normalização pela média. (3) A alteração da recorrência do fogo teve influência direta no padrão biofísico e fenológico da vegetação nas áreas de estudo na Amazônia e no Cerrado. As variáveis de produtividade primária bruta e albedo apresentaram baixa representatividade espacial. As mudanças com maior inclinação da tendência, do Enhanced Vegetation Index (EVI) e temperatura superficial, foram tanto relacionadas com a recorrência do fogo, quanto com a classe de uso da vegetação, como nas terras indígenas. A inclinação da tendência, no EVI e temperatura superficial, foi maior na área do Cerrado, reforçando a necessidade urgente de conservação deste bioma. A pesquisa atestou a importância de dados de sensoriamento remoto para avaliação da dinâmica do fogo e dos seus efeitos na vegetação. A utilização de séries temporais do sensor MODIS permitiu tanto identificar as áreas queimadas com maior acurácia que outros produtos disponíveis, quanto quantificar as fragilidades da vegetação relacionadas ao padrão de fogo atual.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).Brazilian biomes have adapted to different patterns of presence or absence of fire. Data derived from remote sensing have been one of the main techniques for the detection of forest fires and damage to vegetation structure, especially with the development of high temporal and spectral resolution sensors and the establishment of long continuous series. Thus, we intend to focus on three points in this thesis: (1) What is the potential of remote sensing products for the description of fire dynamics in Brazil? (2) How to detect burn scars from remote sensing time series in Amazonian environments? And finally (3) What damages in the vegetation resulting from the alteration of the historical fire regime and how can they be quantified by remote sensing? In order to increase the knowledge about these issues, several products derived from the Moderate Resolution Imaging Spectroradiometer (MODIS), Thematic Mapper (TM), Enhanced Thematic Mapper Plus (ETM+) and Operational Land Imager (OLI) sensors were used, in addition to diverse spatial data, in three scales: one for the whole national territory, one specific area of the Cerrado and two specific areas of the Amazon. The basic methodology consisted of the analysis of MODIS time series for the detection and quantification of fire effects. The results allowed to conclude that: (1) MODIS global burned area products presented high omission errors rates in Brazil, higher than 78% on average in the national territory, and their use is recommended only for regional or global analyzes. The burned area products showed the lowest value in the biomes of the Pampas, Amazon Forest and Atlantic Forest, and the highest values in the biomes of the Cerrado and Caatinga. In spite of this limitation, the product MCD64 allowed to describe the fire regime in the country, the main regions of occurrence and the influence of moisture and vegetation class in this pattern. Were established as a limit for the action of the fire the areas without drought, such as the Western Amazon and the east coast of Brazil, as well as areas with low availability of rainfall and fuel, such as the semi-arid in the Northeast. (2) Among the analyzed methods of seasonal difference and temporal normalization, the normalization of the Near Infrared spectral band by the zero-mean, was responsible for the greater accuracy in the detection of burn scars in the Amazon region, rectifying the use of some indices originally specialized for temperate vegetation, such as the Normalized Burn Ratio (NBR). Other methods analyzed, such as the seasonal difference and z-score normalization, showed better accuracy than original images, but lower than normalization by the zero-mean. (3) The alteration of fire recurrence had a direct influence on the biophysical and phenological pattern of vegetation the study areas of Amazon and Cerrado. The variables of gross primary productivity and albedo showed low spatial representativeness. The changes with higher trend slope, of Enhanced Vegetation Index (EVI) and surface temperature, were related both to fire recurrence and to the vegetation use class, as in indigenous lands. The slope of the trend in EVI and surface temperature was higher in the Cerrado area, reinforcing the urgent need for conservation of this biome. The research attested the importance of remote sensing data for the evaluation of fire dynamics and its effects on vegetation. The use of MODIS time series allowed both identifying the burned areas with greater accuracy than other available products, and quantifying the fragilities of the vegetation related to the current fire pattern

Identificação e datação de áreas queimadas em Portugal com base em informação dos canais NIR e MIR dos satélites Terra e Aqua

Portugal é considerado o país mais propenso (por unidade de área) à ocorrência de queimadas, que são responsáveis por uma série de prejuízos, tais como a emissão de gases de efeito estufa e poluentes, contribuição para as mudanças climáticas, perda de vegetação e de vidas, erosão do solo, facilitação de enchentes no período posterior ao fogo, impacto econômico, entre outros. Além disso, este país tem experimentado, nas últimas décadas, um aumento na ocorrência de incêndios, cuja causa pode ser atribuída a modificações no uso do solo e às mudanças climáticas. Todo ano, o Instituto da Conservação da Natureza e das Florestas (ICNF) de Portugal confecciona mapas anuais do perímetro do fogo, os quais utilizam imagens do satélite Landsat TM/ETM (Land Remote Sensing Satellite Thematic Mapper/Enhanced Thematic Mapper) de fim de estação para mapear as áreas queimadas maiores que 5 hectares. No entanto, estes mapas fornecem apenas a localização da cicatriz, não oferecendo qualquer estimativa da data dos incêndios. Tal informação é, contudo, de fundamental importância para se compreender o regime e a sazonalidade dos incêndios, bem como as complexas interações entre fogo, cobertura vegetal e meteorologia. O objetivo deste trabalho foi aplicar o Índice de Queimadas (V,W) para a identificação e datação de áreas queimadas em Portugal recorrendo à informação de reflectâncias no infravermelho próximo (NIR) e no infravermelho médio (MIR), proveniente do instrumento Moderate Resolution Imaging Spectroradiometer (MODIS) a bordo dos satélites Aqua e Terra, além das informações dos focos de calor do mesmo sensor. Utilizando apenas imagens de julho, agosto e setembro de 2005, foram gerados compostos mensais do índice de queimadas, aos quais foram aplicados limiares fixos e contextuais de acordo com a vizinhança do píxel. O algoritmo foi desenvolvido para detectar mudanças persistentes nas séries temporais de W e considerar o dia em que se identifica a mudança mais intensa como o dia da queima. A comparação entre o mapa de áreas queimadas gerado pelo algoritmo e o gerado pelo ICNF com base em imagens Landsat de fim de estação resultou em um Acerto Global de 95,6%. A probabilidade de detecção foi de 62,9%, ou seja, o algoritmo identificou corretamente quase dois terços das cicatrizes de queimadas ocorridas em todo o ano de 2005. O método de datação também se mostrou eficiente, sendo capaz de datar corretamente 63,5% dos píxeis, isto é, em quase dois terços dos píxeis a diferença entre a datação e as datas de ocorrência dos focos de calor é igual ou inferior a dois dias, para mais ou para menos. Se considerarmos como acertos de datação diferenças de cinco dias ou menos, a porcentagem de píxeis corretamente datados sobe para 75,0%

Assessing the Temporal Stability of the Accuracy of a Time Series of Burned Area Products

Temporal stability, defined as the change of accuracy through time, is one of the validation aspects required by the Committee on Earth Observation Satellites’ Land Product Validation Subgroup. Temporal stability was evaluated for three burned area products: MCD64, Globcarbon, and fire_cci. Traditional accuracy measures, such as overall accuracy and omission and commission error ratios, were computed from reference data for seven years (2001–2007) in seven study sites, located in Angola, Australia, Brazil, Canada, Colombia, Portugal, and South Africa. These accuracy measures served as the basis for the evaluation of temporal stability of each product. Nonparametric tests were constructed to assess different departures from temporal stability, specifically a monotonic trend in accuracy over time (Wilcoxon test for trend), and differences in median accuracy among years (Friedman test). When applied to the three burned area products, these tests did not detect a statistically significant temporal trend or significant differences among years, thus, based on the small sample size of seven sites, there was insufficient evidence to claim these products had temporal instability. Pairwise Wilcoxon tests comparing yearly accuracies provided a measure of the proportion of year-pairs with significant differences and these proportions of significant pairwise differences were in turn used to compare temporal stability between BA products. The proportion of year-pairs with different accuracy (at the 0.05 significance level) ranged from 0% (MCD64) to 14% (fire_cci), computed from the 21 year-pairs available. In addition to the analysis of the three real burned area products, the analyses were applied to the accuracy measures computed for four hypothetical burned area products to illustrate the properties of the temporal stability analysis for different hypothetical scenarios of change in accuracy over time. The nonparametric tests were generally successful at detecting the different types of temporal instability designed into the hypothetical scenarios. The current work presents for the first time methods to quantify the temporal stability of BA product accuracies and to alert product end-users that statistically significant temporal instabilities exist. These methods represent diagnostic tools that allow product users to recognize the potential confounding effect of temporal instability on analysis of fire trends and allow map producers to identify anomalies in accuracy over time that may lead to insights for improving fire products. Additionally, we suggest temporal instabilities that could hypothetically appear, caused by for example by failures or changes in sensor data or classification algorithms

Dinâmica dos incêndios florestais no estado do Acre

Over the last 40 years, forest fires in Amazonia have occurred at intervals of 4 to 5 years, causing economic, environmental and social damage. To understand the spatial and temporal dynamics of forest fires in Brazil’s state of Acre over a period of 33 years (1984 to 2016), we used images from Landsat 5, 7 and 8, applying the burn scar index (BSI) derived from the fractions of photosynthetic material, non-photosynthetic material and soil generated by CLASlite© software. Based on this mapping, we used the weights of evidence method in Dinamica-EGO software to analyze the factors resulting from human action and from natural features of the landscape that have the strongest influence on the occurrence of forest fires. To understand the changes in the forest, we selected four areas based on mapping the 2005 and 2010 fires and their areas of overlap. In this forest inventory we measured the diameter at breast height of all living and dead individuals larger than 10 cm in diameter in three 100 m × 50 m plots and all bamboo culms independent of diameter in 5 m × 5 m sub-plots. Information was collected on the total height of trees, whether the trees were broken or pressured by bamboo and whether termites were present. The total area of forest impacted by the fire in the period of 33 years in the entire State of Acre was 5,251 km 2 . However, of this total there were forests that were affected by fire only once (3,883 km 2 ), twice (598 km 2 ) and three times (57 km 2 ). In 2005, the municipalities (counties) of Acrelândia, Plácido de Castro and Senador Guiomard had more than 50% of their remaining forest impacted by fire. The main factors favoring fire occurrence were fragmentation and the proximity of cattle pastures and roads. Forest types most susceptible to fire were open forest with bamboo, open forest with palms and alluvial forest. Degradation caused by fire caused a strong impact in the reduction of density trees, species richness and decreases in dry above-ground biomass. An additional effect of the impact of the fire was an expansion of bamboo to densities 7 to 9 times that in unburned forest. The expansion of the bamboo had a linear relationship with decrease in the number of trees, in addition to increasing the number of trees damaged and broken, affecting up to 24% of all trees. For the open forests of southwestern Amazonia it is important to consider the contribution of bamboo (Guadua) in estimates of the total above-ground biomass of the forest. Bamboo increases the total biomass by 3 Mg ha -1 in intact forest, 26 Mg ha -1 in forest burned in 2005, 23 Mg ha -1 in forest burned in 2010 and 26 Mg ha -1 in forest burned in both 2005 and 2010, raising the biomass by percentages ranging from 1% to 38% with respect to the tree component. Up to 2016, the reduction of forest biomass caused a committed emission of 38 Tg of CO 2 for the state of Acre in an area of 3800 km 2 of remaining forest that had been affected by fire. This Xcommitted emission reduces by 17% the net climatic benefit of Acre’s goal for reducing the state’s greenhouse-gas emissions by 2020. This study made it possible to understand the scale of forest fires and their impacts in the forests of the state of Acre in drought years, which points to a future full of challenges for reducing the process of forest degradation.Nos últimos 40 anos, os incêndios florestais têm ocorrido em intervalo de 4 a 5 anos em diferentes regiões da Amazônia brasileira, causando danos econômicos, ambientais e sociais. Para compreender a dinâmica espaço-temporal dos incêndios florestais no Estado do Acre, foi analisado um período de 33 anos (1984 a 2016) de imagens Landsat (5, 7 e 8) através da aplicação do Índice de Cicatriz de Fogo (Burn Scar Index – BSI) derivado das frações de Material Fotossintético, Não-Fotossintético e Solo, geradas pelo software CLASlite©. Com base neste mapeamento, analisamos os fatores fruto da ação antrópicas e características naturais da paisagem que mais influenciam a ocorrência dos incêndios florestais pelo software Dinamica EGO através do método de pesos de evidência. Para compreender as mudanças na floresta, selecionamos quatro áreas com base no mapeamento dos incêndios de 2005 e 2010 e sua reincidência. Neste inventário florestal medimos o diâmetro a altura do peito de todos os indivíduos vivos e mortos maiores que 10 cm em três parcelas de 100 m × 50 m e todos os colmos vivos de bambu independentes do diâmetro em sub-parcelas de 5 m × 5 m em floresta intacta (testemunha), floresta queimada em 2005, floresta queimada em 2010 e floresta queimada em 2005 e 2010. Foram coletadas informações sobre a altura total, árvores quebradas ou danificadas pelo bambu, presença de cupim e infestação de cipós na copa das árvores. A área total de floresta impactada pelo fogo no período de 33 anos em todo o Estado do Acre foi de 5.251 km 2 . No entanto, deste total houve florestas que foram afetadas pelo fogo somente uma vez (3.883 km 2 ), duas vezes (598 km 2 ) e três vezes (57 km 2 ). Em 2005, os municípios de Acrelândia, Plácido de Castro e Senador Guiomard tiveram mais de 50% do remanescente florestal impactado pelo fogo. Os principais fatores que favoreceram à ocorrência de incêndios florestais foram: a fragmentação, proximidade de florestas às áreas de pastagens e estradas. A maior ocorrência dos incêndios foi atribuída às florestas abertas com bambu e palmeira e florestas aluviais. A degradação florestal ocasionada pelo fogo causou a redução na densidade de árvores, na redução da riqueza de espécies e redução na biomassa seca acima do solo. Entretanto, houve aumento no número de espécies pioneiras. Observou-se um efeito adicional ao impacto do fogo, uma expansão da densidade de colmos de bambu na proporção de 7 a 9 vezes com relação a floresta intacta. A expansão do bambu teve relação linear com a redução do número de árvores, além de aumentar o número de árvores danificadas e quebradas, afetando até 24% do total de árvores. Para as florestas abertas da Amazônia Sul Ocidental é importante considerar a contribuição da biomassa do bambu (gênero Guadua) para estimativa da biomassa total da floresta acima do solo. O bambu aumentou a biomassa total em 3 Mg ha -1 na floresta intacta, 26 Mg ha -1 na floresta queimada em 2005, 23 Mg ha -1 na floresta queimada em 2010 e 26 Mg ha -1 na floresta queimada reincidente, elevando a biomassa em termos percentual de 1% a 38% com relação ao componente arbóreo. Até 2016, a redução da biomassa florestal causou uma emissão comprometida de 38 Tg de CO 2 para o Estado do Acre em uma área de floresta remanescente afetada pelo fogo de 3.800 km 2 . Esta emissão significa um comprometimento de 17% da meta de redução de gases de efeito estufa do Acre até 2020. Este estudo possibilitou compreender a dimensão dos incêndios florestais e os seus impactos nas florestas do Estado do Acre em anos de secas extremas, possibilitando visualizar um futuro cheio de desafios para redução do processo de degradação florestal

Avaliação de diferentes sensores para caracterização de áreas queimadas no estado do Tocantins, Brasil

Orientador: Prof. Dr. Antonio Carlos BatistaCoorientadores: Prof. Dr. Marcos Giongo, Profa. Dra. Daniela Biondi BatistaTese (doutorado) - Universidade Federal do Paraná, Setor de Ciências Agrárias, Programa de Pós-Graduação em Engenharia Florestal. Defesa : Curitiba, 27/10/2020Inclui referências: p. 93-108Área de concentração: Conservação da naturezaResumo: O fogo é um distúrbio natural nas savanas e auxilia na formação da fisionomia e estrutura da vegetação, muitas vezes influenciando a diversidade de espécies. A obtenção de informações sobre áreas queimadas vem sendo estudada e aprimorada nas últimas décadas, mas ainda há carência de informações acerca da confiabilidade dos dados globais de áreas queimadas a serem empregados numa região específica como em áreas de Cerrado para auxiliar na prevenção. O estado do Tocantins possui 91% do seu território inserido no bioma Cerrado e, desta forma, apresenta uma rica biodiversidade, que está ameaçada pelo processo de ocupação antrópica sobre seu território, principalmente por figurar entre os estados mais atingidos pelas queimadas e/ou incêndios florestais. O sensoriamento remoto, associado aos sistemas de informações geográficas, se apresenta como uma ferramenta de elevado interesse, pois possibilita obter informações de extensas áreas de forma rápida, sendo possível a identificação de áreas queimadas e a intercomparação de diversos produtos oriundos das técnicas de geoprocessamento automatizados, semiautomatizados e manuais. O presente estudo teve como objetivo analisar a dinâmica espacial e temporal dos incêndios florestais e das queimadas ocorridos no estado do Tocantins de 2014 a 2017 e avaliar a precisão dos dados globais de áreas queimadas MODIS MCD64A1, ESA Fire_CCI e PROBA, por serem as mais representativas globalmente, utilizando dados de áreas queimadas obtidas das imagens do sensor OLI do Landsat- 8 como referência, e as respectivas capacidades de cada método por uso e cobertura do solo. Foi realizado o processamento e interpretação visual das imagens Landsat- 8, a vetorização das áreas queimadas e sua caracterização. Os dados vetoriais dos mapas anuais de áreas queimadas foram inter-relacionados com dados globais de identificação de áreas queimadas e com variáveis temporais e espaciais relacionadas ao uso e cobertura do solo. Constatou-se que o procedimento de interpretação visual das imagens L8 foi o que obteve maior inter-relação em relação aos demais produtos. Os produtos globais de áreas queimadas ESA Fire_CCI, MODIS MCD64A1 e PROBA fornecem dados com resolução temporal maior, mas para a área de estudo subestimaram a quantidade de áreas queimadas em relação a referência. O produto ESA Fire_CCI foi o que obteve melhor inter-relação espacial com os dados de referência. No período de 2014 a 2017, referência, ESA Fire_CCI, MODIS MCD64A1 e PROBA obtiveram, respectivamente, 14.936.226,81, 13.865.884,31, 14.013.351,37 e 5.479.362,34 hectares de áreas queimadas. As duas classes de uso e cobertura do solo com maiores áreas queimadas paratodos os métodos testados foram as áreas de formação campestre e formação savânica. Em média, referência, ESA Fire_CCI, MODIS MCD64A1 e PROBA obtiveram, respectivamente para a classe de formação campestre, 1.972.699,16, 1.769.713,18, 1.898.423,54 e 821.282,92 hectares, e na de formação savânica 932.874,59, 881.644,98, 793.235,16 e 274.524,38 hectares. Palavras-chave: Cerrado. LandSat. Fire_CCI. MODIS. PROBA.Abstract: Fire is a natural disturbance in savannas and assists in the formation of the physiognomy and structure of vegetation, often influencing the diversity of species. Obtaining information on burnt areas has been studied and improved in recent decades, but there is still a lack of information about the reliability of global data on burnt areas to be used in a specific region as in Cerrado areas to assist in prevention. The state of Tocantins has 91% of its territory inserted in the Cerrado biome and, therefore, presents a rich biodiversity, which is threatened by the process of anthropic occupation on its territory, mainly for being among the states most affected by burnings and/or forest fires. Remote sensing, associated with geographic information systems, presents itself as a tool of high interest, as it allows obtaining information from extensive areas quickly, being possible the identification of burnt areas and the intercomparison of several products from automated, semi-automated and manual geoprocessing techniques. This study aimed to analyze the spatial and temporal dynamics of forest fires and fires that occurred in the state of Tocantins from 2014 to 2017 and evaluate the accuracy of global data of burnt areas MODIS MCD64A1, ESA Fire_CCI e PROBA, for being the most representative globally, using data from burnt areas obtained from images of the sensor OLI of the Landsat-8 as a reference, and the respective capacities of each method by use and land cover. Visual processing and interpretation of the Landsat-8 images, the vectorization of the burned areas and their characterization were performed. The vector data from the annual maps of burnt areas were interrelated with global data for the identification of burnt areas and with temporal and spatial variables related to land use and cover. It was found that the procedure of visual interpretation of the L8 images was the one that obtained the greatest interrelation in relation to the other products. The global products of burnt areas ESA Fire_CCI, MODIS MCD64A1 and PROBA provide data with higher temporal resolution, but for the study area, they underestimated the amount of burnt areas in relation to the reference. In the period from 2014 to 2017, reference, ESA Fire_CCI, MODIS MCD64A1 and PROBA obtained, respectively, 14,936,226.81, 13,865,884.31, 14,013,351.37 and 5,479,362.34 hectares of burnt areas. The two classes of land use and land cover with the largest burnt areas for all the tested methods were the areas of field formation and savanna formation. On average, reference, ESA Fire_CCI, MODIS MCD64A1 and PROBA obtained 1,972,699.16, 1,769,713.18, 1,898,423.54 and 821,282.92 hectares, respectively, for the field formation class, and the savanna formation class, respectively. 932,874.59, 881,644,98, 793,235.16 and 274,524.38 hectares. Keywords: Savanna. LandSat. Fire_CCI. MODIS. PROB