Diógenes Salas Alves

Mapping deforestation and land use in amazon rainforest by using SIR-C imagery☆

Abstract In this paper, the potential use of spaceborne polarimetric synthetic aperture radar (SAR) data in mapping landcover types and monitoring deforestation in tropics is studied. Here, the emphasis is placed on several clearing practices and forest regeneration that can be characterized by using the sensitivity of SAR channels to vegetation biomass and canopy structure. A supervised Bayesian classifier designed for SAR signal statistics is employed to separate five classes: primary forest, secondary forest, pasture-crops, quebradao, and disturbed forest. The L- and C-band polarimetric SAR data acquired during the shuttle imaging radar-C (SIR-C)/X-SAR space-shuttle mission in 1994 are used as input data to the classifier. The results are verified by field observation and comparison with the Landsat data acquired in August of 1994. The SAR data can delineate these five classes with approximately 72% accuracy. The confusion arises when separating old secondary forests from primary forest and the young ones from pasture-crops. It is shown that Landsat and SAR data carry complementary information about the vegetation structure that, when used in synergism, may increase the classification accuracy over secondary forest regrowth. When the number of land-cover types was reduced to three classes including primary forest, pasture-crops, and regrowth-disturbed forest, the accuracy of classification increased to 87%. A dimensionality analysis of the classifier showed that the accuracy can be further improved to 92% by reducing the feature space to L-band HH and HV channels. Comparison of SIR-C data acquired in April (wet period) and October (dry period) indicates that multi-temporal data can be used for monitoring deforestation; however, the data acquired during the wet season are not suitable for accurate land-cover classification.

Global land-Cover Change: Recent Progress, Remaining Challenges.

Since time immemorial, humankind has changed landscapes in attempts to improve the amount, quality, and security of natural resources critical to its well being, such as food, freshwater, fiber, and medicinal products. Through the increased use of innovation, human populations have, slowly at first, and at increasingly rapid pace later on, increased its ability to derive resources from the environment, and expand its territory. Several authors have identified three different phases - the control of fire, domestication of biota, and fossil-fuel use - as being pivotal in enabling increased appropriation of natural resources (Goudsblom and De Vries 2004; Turner II and McCandless 2004).

Causes and Trajectories of Land-Use/Cover Change

One of the key activities of the Land-Use/Cover Change (LUCC) project has been to stimulate the syntheses of knowledge of land-use/cover change processes, and in particular to advance understanding of the causes of land change (see Chap. 1). Such efforts have generally followed one of two approaches: broad scale cross-sectional analyses (cross-national statistical comparisons, mainly); and detailed case studies at the local scale. The LUCC project applied a middle path that combines the richness of indepth case studies with the power of generalization gained from larger samples, thus drawing upon the strengths of both approaches. In particular, systematic comparative analyses of published case studies on landuse dynamics have helped to improve our knowledge about causes of land-use change. Principally, two methods exist for comparative analyses of case studies. These methods are sufficiently broad geographically to support generalization, but at a scale fine enough to capture complexity and variability across space and time.

Characterizing landscape changes in central Rondonia using Landsat TM imagery

An analysis of landscape changes in a region of pioneer settlements in central Rondonia, western Brazilian Amazon, was derived from Landsat TM data. Total deforested area increased from 206 x 103 ha in 1977, to 565 x 103 ha in 1985 and to 1210 x 103 ha, or 35.5% of the region, in 1995. Eighty-one per cent of the total 1995 deforestation had occurred in regions within 12.5km from areas of pioneer colonization deforested by 1977. Deforested area exceeded 79% in regions within 12.5km from the regions first road.

The changing rates and patterns of deforestation and land use in Brazilian Amazonia.

Investigating the rates and patterns of land cover and land use change (LCLUC) in Amazonia is a central issue for Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) research. LCLUC, along with climatic changes affects the biological, chemical, and physical functions of Amazonia, thereby linking environmental chance at the local, regional, and global scales. Considerable research has focused on estimating rates of forest conversion in Amazonia, mainly through the use of satellite remote sensing and evaluating factors that influence these rates, Beyond the rates of forest loss, LCLUC research in Amazonia has also considered the variety of agricultural uses that reokace firest civer, forest degradation from logging and fire, and secondary vegetation on previously cleared lands.

Fractional forest cover mapping in the Brazilian Amazon with a combination of MODIS and TM images

High deforestation rates in Amazonia have motivated considerable efforts to monitor forest changes with satellite images, but mapping forest distribution and monitoring change at a regional scale remain a challenge. This article proposes a new approach based on the integrated use of Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat Thematic Mapper (TM) images to rapidly map forest distribution in Rondônia, Brazil. The TM images are used to differentiate forest and non-forest areas and the MODIS images are used to extract three fraction images (vegetation, shade and soil) with linear spectral mixture analysis (LSMA). A regression model is built to calibrate the MODIS-derived forest results. This approach is applied to the MODIS image in 2004 and is then transferred to other MODIS images. Compared to INPE PRODES (Brazils Instituto Nacional de Pesquisas Espaciais – Programme for the Estimation of Deforestation in the Brazilian Amazon) data, the errors for total forest area estimates in 2000, 2004 and 2006 are −0.97%, 0.81% and −1.92%, respectively. This research provides a promising approach for mapping fractional forest (proportion of forest cover area in a pixel) distribution at a regional scale. The major advantage is that this procedure can rapidly provide the spatial and temporal patterns of fractional forest cover distribution at a regional scale by the integrated use of MODIS images and a limited number of Landsat images.

Land-use and land-cover change processes in the Upper Uruguay Basin: linking environmental and socioeconomic variables

Land-use and land-cover change affects both ecological and socioeconomic processes, motivating the integration of environmental and socioeconomic data to help understand this change. In this study, we propose a method for the characterisation and spatial analysis of land use and cover change in the Upper Uruguay River Basin (Brazil) based on (i) the characterisation of six LUCC processes—degradation, regeneration, intensification, extensification, silviculture expansion and urbanisation—by the combination of 2002 and 2008 land-use and land-cover classifications of Landsat/TM imagery and on (ii) the investigation of the relationships between the LUCC processes and environmental and socioeconomic variables via the combination of canonical correspondence analysis, linear and local spatial regression models (OLS and GWR) and spatial clustering procedures (SKATER), using environmental data, including geomorphometric data, landscape metrics and census socioeconomic statistics. The LUCC processes could be explained in terms of the associations between the selected physical, ecological and social variables that allowed the terrain, landscape fragmentation and socioeconomic characteristics to be related to various LUCC processes.

Science and technology and sustainable development in Brazilian Amazon

Deforestation in the Brazilian Amazon increased from 10 million hectares in the 1970s to more than 60 million hectares at the turn of the century, resulting in growing awareness about deforestation impacts like greenhouse-gas emissions, loss of biodiversity, and motivating a number of initiatives involving the science and technology (S&T) field to address the issues of deforestation and sustainable development in the Amazon. The present work summarizes part of the large-scale land cover-use changes that occurred in the region and then analyses the organization of four S&T programs carried out in the Amazon in the context of alarming deforestation rates and rapidly changing land use in the Amazonian frontier. The four programs include two major research programs - the Large-Scale Biosphere-Atmosphere Experiment in the Amazon (LBA) and the Science & Technology Subprogram (S&T) of the Pilot Program to Conserve the Brazilian Rain Forest (PPG7) - and two examples of environmental monitoring and management - the Ecological-Economic Zoning (ZEE) and deforestation monitoring programs. In the context of high rates of forest loss and generally very weak institutions, the initiatives organized with the concourse of the S&T field may have significantly contributed to advance the discussions of sustainable development and sustainable land use in the frontier, and to mature some ideas about the participation of civil society, national environmental policy and, also, international cooperation. These exercises also suggest that the tasks of reducing and mitigating deforestation impacts and fostering sustainable land use are not to be engineered but, rather, negotiated, and that understanding how to contribute to such negotiations seems to be a major challenge for the science and technology field in Brazil.

Secondary vegetation dynamics in the Brazilian Amazon based on thematic mapper imagery

Secondary vegetation (SV) is an important element of the landscape after forest is cleared in Brazilian Amazon. Deforestation maps derived from thematic mapper (TM) imagery were used to sample random areas of old and recent settlement, and small and large farms. TM data were then used to classify SV in the selected areas. Results showed that SV represented higher fractions of the landscape in areas of more recent and small-farm settlement than in areas of old and large-farm settlement. These findings emphasize the importance of considering the long-term evolution of land use systems if the relationship between secondary succession, land rotation and abandonment is to be better understood.

People and Environment in Amazonia: the LBA Experience and Other Perspectives

Amazonia and Global Change synthesizes results of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) for scientists and students of Earth system science and global environmental change. LBA, led by Brazil, asks how Amazonia currently functions in the global climate and biogeochemical systems and how the functioning of Amazonia will respond to the combined pressures of climate and land use change, such as: wet season and dry season aerosol concentrations, and their effects on diffuse radiation and photosynthesis; increasing greenhouse gas concentration, deforestation, widespread biomass burning and changes in the Amazonian water cycle; drought effects and simulated drought through rainfall exclusion experiments; the net flux of carbon between Amazonia and the atmosphere; floodplains as an important regulator of the basin carbon balance including serving as a major source of methane to the troposphere; and the impact of the likely increased profitability of cattle ranching. This book will serve a broad community of scientists and policy makers interested in global change and environmental issues with high-quality scientific syntheses accessible to nonspecialists in a wide community of social scientists, ecologists, atmospheric chemists, climatologists, and hydrologists. [Book Synopsis]