27B razil has been unique worldwide in terms of land use. Although vast areas of forests and savannahs have been converted into farmland (Fig. 1) -placing the country as a leading global producer of agricultural commodities -it still safeguards the largest tracts of native tropical vegetation on Earth, with extremely high levels of biodiversity. Patterns of land use change, which until recently exhibited the highest worldwide absolute rates of tropical deforestation, largely resulted in low-productivity cattle pastures 2 . Moreover, climate change issues in Brazil are inextricably related to land use and land-use change (LUC) as approximately 80% of the country's total CO 2 -equivalent (CO 2 e) emissions in 2005 were sourced from agriculture and LUC 3 .Demand for farmland is the key immediate driver of LUC in Brazil, and there is little evidence that agricultural expansion is grinding to a halt 4-7 . In fact, Brazil holds the greatest potential for further agricultural expansion in the twenty-first century 8 . Understanding recent LUC patterns (Box 1) and visualizing a sustainable land-use pathway in Brazil have become highly strategic -not only for Brazilians, given that regional and global climate change, food and energy provision, and biodiversity conservation are all at stake. This Review presents an integrated analysis and provides new insights on recent trends in the Brazilian land-use system. In the first two sections we show how Brazil's agriculture is becoming both gradually decoupled from deforestation processes and increasingly intensified and oriented to large-scale farming of trade commodities throughout the country. Next we explain the economic and political factors driving those changes. The fourth section reveals the drawbacks of those changes in aggravating the long history of inequality in land ownership. We then explore repercussions for climate change, namely Agriculture, deforestation, greenhouse gas emissions and local/regional climate change have been closely intertwined in Brazil. Recent studies show that this relationship has been changing since the mid 2000s, with the burgeoning intensification and commoditization of Brazilian agriculture. On one hand, this accrues considerable environmental dividends including a pronounced reduction in deforestation (which is becoming decoupled from agricultural production), resulting in a decrease of ~40% in nationwide greenhouse gas emissions since 2005, and a potential cooling of the climate at the local scale. On the other hand, these changes in the land-use system further reinforce the long-established inequality in land ownership, contributing to rural-urban migration that ultimately fuels haphazard expansion of urban areas. We argue that strong enforcement of sector-oriented policies and solving long-standing land tenure problems, rather than simply waiting for market self-regulation, are key steps to buffer the detrimental effects of agricultural intensification at the forefront of a sustainable pathway for land use in Brazil.for the country's g...

[1] The evaluation of impacts of land use change is in general limited by the knowledge of past land use conditions. Most publications on the field present only a vague description of the earlier patterns of land use, which is usually insufficient for more comprehensive studies. Here we present the first spatially explicit reconstruction of historical land use patterns in Brazil, including both croplands and pasturelands, for the period between 1940 and 1995. This reconstruction was obtained by merging satellite imagery with census data, and provides a 5′ Â 5′ yearly data set of land use for three different categories (cropland, natural pastureland and planted pastureland) for Brazil. The results show that important land use changes occurred in Brazil. Natural pasture dominated in the 1950s and 1960s, but since the beginning of 1970s it has been gradually replaced by planted pasture, especially in southeast and center west of Brazil. The croplands began its expansion in the 1960s reaching extensive areas in almost all states in 1980. Carbon emissions from historical land use changes were calculated by superimposing a composite biomass map on grids of a weighted average of the fractions of the vegetation types and the replacement land uses. Net emissions from land use changes between 1940 and 1995 totaled 17.2 AE 9.0 Pg-C (90% confidence range), averaging 0.31 AE 0.16 Pg-C yr À1

Scientists predict that global agricultural lands will expand over the next few decades due to increasing demands for food production and an exponential increase in cropbased biofuel production. These changes in land use will greatly impact biogeochemical and biogeophysical cycles across the globe. It is therefore important to develop models that can accurately simulate the interactions between the atmosphere and important crops. In this study, we develop and validate a new process-based sugarcane model (included as a module within the Agro-IBIS dynamic agro-ecosystem model) which can be applied at multiple spatial scales. At site level, the model systematically under/ overestimated the daily sensible/latent heat flux (by À10.5% and 14.8%, H and kE, respectively) when compared against the micrometeorological observations from southeast Brazil. The model underestimated ET (relative bias between À10.1% and -12.5%) when compared against an agro-meteorological field experiment from northeast Australia. At the regional level, the model accurately simulated average yield for the four largest mesoregions (clusters of municipalities) in the state of São Paulo, Brazil, over a period of 16 years, with a yield relative bias of À0.68% to 1.08%. Finally, the simulated annual average sugarcane yield over 31 years for the state of Louisiana (US) had a low relative bias (À2.67%), but exhibited a lower interannual variability than the observed yields.

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