Compressible primitive equation: formal derivation and stability of weak solutions

We present a formal derivation of a simplified version of Compressible Primitive Equations (CPEs) for atmosphere modeling. They are obtained from $3$-D compressible Navier-Stokes equations with an \emph{anisotropic viscous stress tensor} where viscosity depends on the density. We then study the stability of the weak solutions of this model by using an intermediate model, called model problem, which is more simple and practical, to achieve the main result

Land-use in Amazonia and the cerrado of Brazil.

The total area and annual rate of native vegetation clearing is greatest in the Cerrado region followed by the Brazilian states of Para, Mato Grosso, Maranhao and Rondonia. Amazonian forest clearing proceeds most quickly where abundant natural resources (wood or land) are accessible by roads and close to markets. These regions are concentrated along the eastern and southern flanks of Amazonia, particularly in eastern Para, Cuiaba and Rondonia. There are still large discrepancies in estimates of annual deforestation; Landsat (Thematic Mapper-based) mapping of deforestation in the closed-canopy forests of Amazonia has not include non-Brazilian countries and is incomplete for the cerrado biome. Amazonian deforestation was last mapped 1994. Current estimates of Amazonian forest clearing do not include most of the forests that are affected by logging each year, which is an area (about 7,000 km2 yr-1)more than half the size of the area of annual deforestation. Logging changes forest structure and increases forest flammability. The intensity of logging ranges from 1-to 100-species harvest, and averages 20m3 of wood harvested per hectare. Logging may increase dramatically in the coming years. Fire affects large, but difficult to measure, areas of pastureland, logged forests, secondary forests and primary forests. Forest ground fires are particularly difficult to map fom satellite data. Fire is more frequent where forest clearing is taking place, and where seasonal drought is most severe. The destiny of Amazonian forest land cleared for crops and cattle pasture is complex, and highly variables regionally. Areal estimates are needed for managed pasture, degraded pasture, cropland and secondadry forests, for these ecosystems are functionally distinct. Most forest clearing is for pasture establishment, followed by shifting cultivation. Cattle pasture is the logical land-use for both small-scale and large-scale rural Amazonians because cattle are easily sold or traded, and they maintain their value during inflation. Cattle patures help secure land claims and increase land value. In the Cerrado, there has been a shift from extensive cattle grazing of natural savannas to pasture planted with African forage grasses; mechanized soy bean production is the second most extensive land-use. Pastures are the most important land-cover for the LBA (Large-Scale Biosphere - Atmosphere experiment in Amazonia) science campaign. Brazilian Amazonia experiences reduced rainfall during ENSO events. ENSO-related drought is most severe in eastern Amazonia. A basin-wide reduction in rainfall would have its greatest affect on vegetation near the border between savanna and closed-canopy forest in Rondonia, Mato Grosso, Para and Tocantins. The LBA campaign should be conducted in variety of rural landscapes to capture the multiplicity of human effects on native ecosystems, as well as the range of cliamatic and edaphic conditions under which these ecosystems have evolved. It should address the current (ENSO) and predicted variations in climate, and should be designed to recommend those land-uses that best reconcile the maintenance of ecosystem processes with socially equitable economic growth

Agricultura e biodiversidade nas ciências sociais brasileiras: alimentando a comunicação entre ciência e políticas públicas.

O presente artigo decorre de uma reflexão sustentada em dois pressupostos: a) que as ciências e, em particular, as sociais, podem contribuir para informar as tomadas de decisão e a formulação de políticas públicas visando a melhoria da vida das pessoas no planeta e b) que o papel da agricultura na conservação da biodiversidade é uma questão atual de extrema relevância e que merece ser aprofundada. A relação entre a agricultura e a biodiversidade tem sido objeto de questionamentos recentes na sociedade e no campo das políticas públicas. Contudo, se os estudos relacionados à biodiversidade e à agricultura, separadamente, têm observado um considerável crescimento no Brasil, poucos são os investimentos de pesquisa sobre a relação entre esses dois grandes temas. A partir dessas considerações, seguimos dois objetivos principais: 1) investigar como o papel da agricultura familiar na preservação da biodiversidade tem sido abordado pelas Ciências Sociais no Brasil, particularmente nos artigos publicados em periódicos brasileiros nos últimos 20 anos; 2) testar uma metodologia de revisão bibliográfica, criteriosa, que possa ser útil aos tomadores de decisão em políticas públicas e demais interessados

Combining remote sensing and household level data for regional scale analysis of land cover change in the Brazilian Amazon

Land cover change in the Brazilian Amazon depends on the spatial variability of political, socioeconomic and biophysical factors, as well as on the land use history and its actors. A regional scale analysis was made in Rondônia State to identify possible differences in land cover change connected to spatial policies of land occupation, size and year of establishment of properties, accessibility measures and soil fertility. The analysis was made based on remote sensing data and household level data gathered with a questionnaire. Both types of analyses indicate that the highest level of total deforestation is found inside agrarian projects, especially in those established more than 20 years ago. Even though deforestation rates are similar inside and outside official settlements, inside agrarian projects forest depletion can exceed 50% at the property level within 10–14 years after establishment. The data indicate that both small-scale and medium to large-scale farmers contribute to deforestation processes in Rondônia State encouraged by spatial policies of land occupation, which provide better accessibility to forest fringes where soil fertility and forest resources are important determinants of location choic

Revisiting Theories of Frontier Expansion in the Brazilian Amazon: A Survey of the Colonist Farming Population in Rondônia's Post-Frontier, 1992-2002

Summary In the 1970s, extensive areas of Brazilian Amazon were settled by landless farmers. These internal migrations prompted theoretical scholarship on the nature and outcomes of frontier expansion from three general frameworks: the capitalist penetration thesis, the inter-sectoral articulation thesis, and the household life-cycle thesis. This paper reports selected findings of a 10-year (1992-2002) panel study of 240 farms in three settlement areas in Rondônia. The empirical findings of this longitudinal survey research do not unequivocally confirm any of these theses. Instead, elements of each emerge from the data analysis inviting a more locally nuanced, pluralistic approach to understanding the frontier colonization experience.