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Fraction images derived from Terra Modis data for mapping burnt areas in Brazilian Amazonia

The objective of this paper is to present a method for mapping burnt areas in Brazilian Amazonia using Terra MODIS data. The proposed approach is based on image segmentation of the shade fraction images derived from MODIS, using a non‐supervised classification algorithm followed by an image editing procedure for minimizing misclassifications. Acre State, the focus of this study, is located in the western region of Brazilian Amazonia and undergoing tropical deforestation. The extended dry season in 2005 affected this region creating conditions for extensive forest fires in addition to fires associated with deforestation and land management. The high temporal resolution of MODIS provides information for studying the resulting burnt areas. Landsat 5 TM images and field observations were also used as ground data for supporting and validating the MODIS results. Multitemporal analysis with MODIS showed that about 6500 km2 of land surface were burnt in Acre State. Of this, 3700 km2 corresponded to the previously deforested areas and 2800 km2 corresponded to areas of standing forests. This type of information and its timely availability are critical for regional and global environmental studies. The results showed that daily MODIS sensor data are useful sources of information for mapping burnt areas, and the proposed method can be used in an operational project in Brazilian Amazonia.

Disentangling the contribution of multiple land covers to fire-mediated carbon emissions in Amazonia during the 2010 drought

Abstract In less than 15 years, the Amazon region experienced three major droughts. Links between droughts and fires have been demonstrated for the 1997/1998, 2005, and 2010 droughts. In 2010, emissions of 510 ± 120 Tg C were associated to fire alone in Amazonia. Existing approaches have, however, not yet disentangled the proportional contribution of multiple land cover sources to this total. We develop a novel integration of multisensor and multitemporal satellite‐derived data on land cover, active fires, and burned area and an empirical model of fire‐induced biomass loss to quantify the extent of burned areas and resulting biomass loss for multiple land covers in Mato Grosso (MT) state, southern Amazonia—the 2010 drought most impacted region. We show that 10.77% (96,855 km2) of MT burned. We estimated a gross carbon emission of 56.21 ± 22.5 Tg C from direct combustion of biomass, with an additional 29.4 ± 10 Tg C committed to be emitted in the following years due to dead wood decay. It is estimated that old‐growth forest fires in the whole Brazilian Legal Amazon (BLA) have contributed to 14.81 Tg of C (11.75 Tg C to 17.87 Tg C) emissions to the atmosphere during the 2010 fire season, with an affected area of 27,555 km2. Total C loss from the 2010 fires in MT state and old‐growth forest fires in the BLA represent, respectively, 77% (47% to 107%) and 86% (68.2% to 103%) of Brazils National Plan on Climate Change annual target for Amazonia C emission reductions from deforestation.

Monitoring land cover in Acre State, western Brazilian Amazonia, using multitemporal remote sensing data

This article presents the use of multitemporal remote sensing data for monitoring land cover changes in Acre State, western Brazilian Amazonia. For this study, the 2000 Landsat ETM+ (ETM+, Enhanced Thematic Mapper Plus), the 1990 Landsat TM (TM, Thematic Mapper) and 1980 Landsat MSS (MSS, Multispectral Scanner System) were used. The 2005 and 2007 Terra MODIS (MODIS, Moderate Resolution Imaging Spectroradiometer) images were also used to map deforestation that had occurred during the recent years and to map burned areas that occurred in the 2005 dry year. The ETM+, TM, MSS and MODIS images were converted to vegetation, soil and shade fraction images, using linear spectral mixing model, in order to reduce the data volume for digital processing. Then land cover maps were produced by digital classification of these fraction images. The results showed that deforestation increased by 7100 km2 from 1980 to 1990, by 5100 km2 from 1990 to 2000 and by 3300 km2 from 2000 to 2007. About 2100 km2 of vegetation regrowth areas were observed in the 2000 ETM+ images. The analysis of 2005 MODIS images showed that 3700 km2 of deforested areas and 2800 km2 of forested areas were burned in Acre State in 2005. This kind of information is important for regional and global environmental studies and for efforts to control such burning and deforestation activities in the future.

Mapeamento do uso e da cobertura atual da terra para indicação de áreas disponíveis para reservas legais: estudo em nove municípios da região Amazônica

RESUMO - O presente trabalho foi realizado com o objetivo de indicar as areas disponiveis para manutencao de reserva legal, com a finalidade de fornecer subsidios a discussao sobre a extensao das reservas legais na Amazonia brasileira. A metodologia empregada foi dividida em duas etapas: a primeira envolveu a delimitacao das areas originais de ocorrencia de formacoes florestais e de cerrado e a identificacao das areas sobre as quais recai a obrigatoriedade de manutencao de reserva legal; a segunda envolveu a identificacao dos remanescentes vegetais disponiveis para manutencao de reservas legais, bem como das areas que foram alteradas, realizada a partir do mapeamento do uso e da cobertura atual das terras, utilizando tecnicas de processamento digital de imagens e geoprocessamento. O estudo foi aplicado em nove municipios da Amazonia Oriental (quatro municipios no Para e cinco no Maranhao). Os resultados obtidos com base nas imagens TM Landsat do ano de 1999 mostram que todos os municipios estudados apresentaram valores inferiores a 80% de florestas remanescentes. Os municipios do Para apresentaram sua area de remanescentes florestais um pouco superior a 60%, enquanto os do Maranhao apresentaram valores mais baixos, inferiores a 50%, chegando a 6,46% em Itinga do Maranhao.

Mapping and monitoring deforestation areas in Amazon region using semi-automatic classification of Landsat Thematic Mapper images

The INPEs operational project (PRODES) to estimate annual gross deforestation in Amazon region based on manual analysis of 229 TM images faces several problems during the interpretation process (variable scales of different scenes, closing polygons in the interpretation maps due to complexity of deforestation pattern). Thus, the availability of results in a digital format has been restricted. This authors propose an approach to map and monitor deforested areas in the Amazon using digital analysis of TM/Landsat. This methodology will automate the PRODES manual interpretation tasks and will build a GIS database. This approach was developed and validated using TM image Path 231/067 (1997, 1998, and 1999) over Rondonia. The original TM bands were converted to vegetation, soil, and shade fraction images applying a linear mixing model. The selected fraction image was segmented using a region growing algorithm, classified using a per region clustering algorithm and the results were manually edited to generate the final map. Results showed 10,252 km/sup 2/ of deforestation up to 1997; increments in the deforested area for 1998 and 1999 were 695 and 388 km/sup 2/, respectively. A total of 1,149 km/sup 2/ was burned in 1998 (only 16% in recent clear cut areas). The proposed methodology is feasible and very useful for global studies using fine resolution satellite data such as Landsat TM.

Development of a Point-based Method for Map Validation and Confidence Interval Estimation: A Case Study of Burned Areas in Amazonia

Forest fires and their associated emissions are a key component for the efficient implementation of the Reducing Emissions from Deforestation and Forest Degradation (REDD+) policy. The most suitable method for quantifying large scale fire-associated impacts is by mapping burned areas using remote sensing data. However, to provide robust quantification of the impacts of fire and support coherent policy decisions, these thematic maps must have their accuracy quantitatively assessed. The aim of this research is to present a point-based validation method developed for quantifying the accuracy of burned area thematic maps and test this method in a study case in the Amazon. The method is general; it can be applied to any thematic map consisting of two land cover classes. A stratified random sampling scheme is used to ensure that each class is represented adequately. The confidence intervals for the user’s accuracies and for both overall accuracy and area error are calculated using the Wilson Score method and Jeffrey Perks interval, respectively. Such interval methods are novel in the context of map accuracy assessment. Despite the complexity of calculation of the confidence intervals, their use is recommended. A spreadsheet to calculate point and interval estimates is provided for users.

Mapping and monitoring land cover in Acre State, Brazilian Amazônia, using multitemporal remote sensing data

This paper presents the use of multitemporal remote sensing data for monitoring land cover changes in Acre State, Brazilian Amazonia. The 2000 Landsat ETM+, the 1990 Landsat TM, and 1980 Landsat MSS were used. The 2005 and 2007 MODIS images were also used to map deforestation occurred during the recent years and to map burned areas occurred in the 2005 dry year. The Landsat and MODIS images were converted to vegetation, soil, and shade fraction images. Then land cover maps were obtained by digital classification of these fraction images. The deforestation increased 7, 114 km2 from 1980 to 1990, 4, 900 km2 from 1990 to 2000, and 3, 258 km2 from 2000 to 2007. It also showed that about 2, 815 km2 of regrowth areas were observed in the 2000 ETM+ images. The analysis of MODIS images showed that 3, 700 km2 of deforested areas and 2, 800 km2 of forested areas were burned in Acre State in 2005. These information are critical for regional and global environmental studies and for efforts to control such burning and deforestation in the future.

Corrigendum: Size and frequency of natural forest disturbances and the Amazon forest carbon balance

Corrigendum: Size and frequency of natural forest disturbances and the Amazon forest carbon balance