Interpreting the geological record of Amazon biomass combustion requires comparing charcoal accumulation rates in various biomes at different time scales. Charcoal accumulation rates, a proxy for palaeofire records, were obtained in sediment cores from Amazon lakes surrounded by several vegetation types and from a reservoirs in an intense land use change region. The records presented in this study were obtained in the following areas i) a reservoirs in Alta Floresta region (northern Mato Grosso State); ii) Lago do Saci (southern Pará State), a lake close to Alta Floresta and located at the southern border of Pará State; iii) a bog in an ecotone area in the Humaitá region (southern Amazonas State); iv) lakes in lateritic iron crust of the Carajás Hills (southeastern Pará State); v) Lago Comprido, a floodplain lake close to the Amazon River and surrounded by tropical rain forest (Monte Alegre, Pará State; vi) Lagoa da Pata in the Morro dos Seis Lagos alkaline complex (São Gabriel da Cachoeira, Amazonas State) and vii) Lago Caracaranã, a secluded lake in the northern Amazon cerrado (Roraima State). The highest charcoal accumulation rates were observed for modern records related to an intense change in land use at Alta Floresta, which had no precedent during the Holocene history of the Amazon. High charcoal accumulation rates that were observed in the Carajás region during low lake level phases in the Amazon in the mid-Holocene were comparable to those at the onset of the human settlement in Alta Floresta region. An increase in charcoal accumulation rate was observed in the late Holocene when the lake level was high, suggesting an interaction between climates and human presence. Low charcoal accumulation rates are typical of modern high rainfall environments, as observed in Lagoa da Pata where the environment is not susceptible to occurrences of wildfires even during relatively drier climatic phases. Low charcoal accumulation rates also exist in the relatively dry cerrado (savanna type) biome even during relatively dry phases in the Caracaranã region where the savanna-type vegetation biomass is lower and thus generates less charcoal particles than forest ecosystems.

Genetically-modified soybean [Glycine max (L.) Merr.] resistant to glyphosate (N-phosphono-methyl-glycine) herbicide (GR) has turned out to be one of the most highly-used products of plant engineering. The impacts of the soybean, genetically transformed for glyphosate resistance, on the environment under Brazilian soil and climatic conditions are still unknown. For this purpose, two soybean genotypes, one genetically modified (GR BRS 244 RR) and a conventional isogenic genotype were grown under different weed-control methods: hand weeding and glyphosate or imazethapyr herbicide application. The study was performed in Rio Grande do Sul State with evaluations of soil microbial biomass and respiration, biological nitrogen fixation, isoflavone content in seed and glyphosate, and aminomethylphosphonic acid (AMPA) residues in seeds and soil. The use of GR did not affect soil microbial population, biological nitrogen fixation, or plant yield or isoflavone contents in seed. However, even though we used the recommended application doses, the glyphosate residues in the seeds were above levels permitted by Brazilian law. Also, AMPA residues were detected in the soil and the seeds.

We investigate the hypothesis that the conversion of forest and pasture land to cropland in Brazil decreases yields by 50%. Such hypothesis is being used by the California Air Resource Board to estimate the greenhouse gas emissions from indirect land use changes due to the expansion of biofuels production. We formulate several econometric models to test such hypothesis. The results from the majority of the models indicate that yields do not decrease under the expansion of cropland area in the country, or the decrease in yields is very small. Therefore, our results indicate the need for revising and correcting the parameters in the Californian low carbon emissions policy.

In an age of climate change, researchers need to form a deepened understanding of the determinants of environmental concern, particularly in countries of emerging economies. This paper provides a region-specific investigation of the impact of socio-economic status (SES) and objective environmental conditions on environmental concern in urban Brazil. We make use of data collected from personal interviews of individuals living in the metropolitan areas of Baixada Santista and Campinas, in the larger São Paulo area. Results from multilevel regression models indicate that wealthier households are more environmentally concerned, as suggested by affluence and post-materialist hypotheses. However, we also observe that increasing environmental concern correlates with a decline in objective environmental conditions. Interactions between objective environmental conditions and SES reveal some intriguing relationships: Among poorer individuals, a decline in environmental conditions increases environmental concern as suggested by the objective problems hypothesis, while for the wealthy, a decline in environmental conditions is associated with lower levels of environmental concern.

The purpose of this study was to determine the chemical and mineralogical composition of suspended sediments from the Acre River, located in the Purus Basin, upper Amazon basin, a region associated with the Fitzcarrald Arch. The elemental and mineralogical compositions of the sediments were assessed by using mass and atomic spectroscopy, and X-ray diffraction. A total of 46 samples were collected between 2008 and 2011 from four sites in the study area during wet and dry seasons. The suspended sediments contained feldspar, kaolinite, illite and quartz as well as the elements Hg, Zn, V, Ti, Si, Pb, Ni, Na, Mn, Mg, K, Fe, Cu, Cr, Cd, Ca, Al, S, and P in different proportions that were associated with the various weathering reactions linked to physical, chemical and biological processes in the region. The obtained results represent the first set of values and relationships regarding the mineralogy and chemical identification of the suspended sediments in the Acre River and can be used as a reference for the geochemical characteristics of the Purus Basin. Such regional studies will become increasingly necessary to observe the impacts of climate change and human activities on the suspended sediment load and composition of the Amazon River.

Knowledge of the seasonal variability of river discharge and the concentration of nutrients in the estuary waters of large rivers flowing into the tropical Atlantic contributes to a better understanding of the biogeochemical processes that occur in adjacent coastal and ocean systems. The monthly averaged variations of the physical and biogeochemical contributions of the Orinoco, Amazon, São Francisco, Paraíba do Sul (South America), Volta, Niger and Congo (Africa) Rivers are estimated from models or observations. The results indicate that these rivers deliver approximately 0.1 Pg C year−1 in its dissolved organic (DOC 0.046 Pg C year−1) and inorganic (DIC 0.053 Pg C year−1) forms combined. These values represent 27.3% of the global DOC and 13.2% of the global DIC delivered by rivers into the world’s oceans. Estimations of the air-sea CO2 fluxes indicate a slightly higher atmospheric liberation for the African systems compared with the South American estuaries (+10.6 ± 7 mmol m−2 day−1 and +5.4 ± 8 mmol m−2 day−1, respectively). During the high river discharge periods, the fluxes remained positive in all of the analyzed systems (average +12 ± 8 mmol m−2 day−1), except at the mouth of the Orinoco River, which continued to act as a sink for CO2. During the periods of low river discharges, the mean CO2 efflux decreased to +5.2 ± 9 mmol m−2 day−1. The updated and detailed review presented here contributes to the accurate quantification of CO2 input into the atmosphere and to ongoing studies on the oceanic modeling of biogeochemical cycles in the tropical Atlantic.

To provide long-term simulations of climate change at higher resolution, Regional Climate Models (RCMs) are nested in global climate models (GCMs). The objective of this work is to evaluate the Eta RCM simulations driven by three global models, the HadGEM2-ES, BESM, and MIROC5, for the present period, 1961-1990. The RCM domain covers South America, Central America, and Caribbean. These simulations will be used for assessment of climate change projections in the region. Maximum temperatures are generally underestimated in the domain, in particular by MIROC5 driven simulations, in summer and winter seasons. Larger spread among the simulations was found in the minimum temperatures, which showed mixed signs of errors. The spatial correlations of temperature simulations against the CRU observations show better agreement for the MIROC5 driven simulations. The nested simulations underestimate precipitation in large areas over the continent in austral summer, whereas in winter overestimate occurs in southern Amazonia, and underestimate in southern Brazil and eastern coast of Northeast Brazil. The annual cycle of the near-surface temperature is underestimated in all model simulations, in all regions in Brazil, and in most of the year. The temperature and precipitation frequency distributions reveal that the RCM and GCM simulations contain more extreme values than the CRU observations. Evaluations of the climatic extreme indicators show that in general hot days, warm nights, and heat waves are increasing in the period, in agreement with observations. The Eta simulations driven by HadGEM2-ES show wet trends in the period, whereas the Eta driven by BESM and by MIROC5 show trends for drier conditions.

A Climate Change Index (CCI) was designed to assess the degree of susceptibility to the climatic extremes projected for the future. Climate projections for the period 2041-2070 are extracted from the numerical integrations of INPE’s Eta-HadCM3 model, using the SRES A1B emissions scenario. Five indicators were chosen to represent the climatic extremes: Total annual precipitation, precipitation on the days of heavy rain, the maximum number of consecutive dry days in the year and the annual mean maximum and mean minimum temperatures. The methodology was applied to the state of Paraná. The results point to a very strong warming in 99% of the municipalities, with temperature increases between 6 and 8 times greater than the variance observed in the present climate. On the other hand, projections of precipitation do not indicate major changes in relation to present behavior.

The aim of this paper is to analyse the effects of climate change on irrigation adoption in Brazil. Temperature and precipitation projections for the 2010-2099 periods were employed under a number of different climate scenarios according the 4th Assessment Report of Intergovernmental Panel on Climate Change (IPCC). The results show that irrigation adoption will be affected by climate change. Given current conditions, irrigation has generally been adopted in Brazil to cope with reduced precipitation and temperature variations. The estimated irrigation probabilities in the future scenarios were quite different across Brazilian regions. The main explanation for this pattern is the distinct climatic conditions and production structures. Considering future climate change, over the next 30 years (2010 to 2039), the irrigation probability is expected to increase in all Brazilian regions. However, this trend is reversed in the long run.

This paper analyzes the potential effects of climate change on Brazilian agriculture by considering irrigation as an adaptive strategy. Investigations were performed to determine how climatic variability influences irrigation and whether this adaptive measure actually reduces producers’ vulnerability to climate change. We used a simultaneous equations model with endogenous switching to account for the heterogeneity in the decision of whether to use adaptive measures. We compared the expected land values under the actual and counterfactual cases of farm households that either adapt or do not adapt to climate change. Simulation results show that irrigation can be an effective tool for counteracting the harmful effects of climate change. The income of farmers tends to increase on lands where irrigation technologies are practiced. These conclusions confirm the need to invest in adaptation strategies to prepare Brazil for coping with the adverse effects of global climate change.

A key challenge for climate projection science is to serve the growing needs of impact assessments in an environment with substantial differences in the projections of climate models and an increasing number of relevant climate model results. In order to assist the assessment of water resources impacts under future climate change, this work provides a synthesis of the simulations of General Circulation Models (GCMs) for the region of Distrito Federal, Brazil. The work analyzes projections of mean surface air temperature and precipitation of 22 GCMs, as well as seven extreme indices of 10 GCMs. Trends of the multi-model ensemble median, as well as their significance, were calculated. The consistency in the sign of change was assessed through the percentage of agreement of simulations with the median. Finally, the probability density function of the multi-model ensemble provides valuable information about the uncertainties of projections. Investigations were performed for annual and seasonal temporal scales for the period 2011–2050. The main results here identified are: (a) a consensus of the multi-model ensemble and median to increasing temperature; (b) a slightly, but less consistent, decrease of precipitation in the dry season; and (c) increase of heat waves and droughts events, although changes in precipitation extremes are much less coherent than for temperature. The approach used gives a comprehensive assessment of the possible future climate until the middle of the twenty-first century, as well as the uncertainties involved in the multi-model ensemble projections.