This paper examines the impact of changes in agricultural land use on deforestation at the local level in the Tapajós Basin in the Brazilian Amazon. It uses exogenous variation in crop-to-beef relative prices to investigate the effects of pasture-to-cropland conversion on deforestation. The findings indicate that increases in crop-to-beef relative prices increase the rate of pasture-to-cropland conversion and reduce the rate of deforestation. The magnitude of the effects implies that land conversion reduced deforestation at the local level by 5,300 square kilometers from 2002 to 2012. This reduction is the equivalent of almost 15 per cent of the total deforestation observed in the region during this period. These results are consistent with a land use model in which cattle ranching and crop cultivation have different input-intensities and there is imperfect mobility of productive factors between municipalities. This model highlights the fact that changes in relative prices affect deforestation through its effect on input prices.

Investigation of the determinants of metabolic outcomes associated with non-communicable diseases is increasingly important in developing countries, but such parameters have not been explored extensively during childhood. The present study assessed the impact of weight gain, measured as BMI-for-age Z-scores, on glucose and insulin concentrations, homeostasis model assessment index of insulin resistance (HOMA-IR) values, and systolic and diastolic blood pressure during school years among Amazonian children. A population-based prospective study of 696 children aged >4 to ≤ 10 years with complete anthropometric information at baseline (51 % females and 86 % of mixed race) was carried out; 411 children had data on metabolic parameters after a median follow-up period of 2·0 years (range 1·7–2·6 years). During follow-up, there was a significant increase in the proportion of overweight children (BMI-for-age Z-score >1) from 10·1 to 15·8 % (P= 0·003). In linear regression models adjusted for the child's sex, age, race/ethnicity, baseline household wealth, birth weight and pubertal development stage, for each unit of BMI-for-age Z-score variation during follow-up, an increase of 8·58 (95 % CI 7·68, 9·60) pmol/l in fasting plasma insulin concentrations and 1·47 (95 % CI 1·30, 1·66) in HOMA-IR values was observed. There was no significant impact of weight gain on glucose concentrations and systolic and diastolic blood pressure. In conclusion, we found evidence that an increase in BMI during a 2-year period affected insulin resistance during school years. Considering the significant increase in overweight in this age group, special attention should be paid to monitoring increases in BMI in children from the Brazilian Amazon.

There is burgeoning interest in predicting road development because of the wide ranging important socioeconomic and environmental issues that roads present, including the close links between road development, deforestation and biodiversity loss. This is especially the case in developing nations, which are high in natural resources, where road development is rapid and often not centrally managed. Characterization of large scale spatio-temporal patterns in road network development has been greatly overlooked to date. This paper examines the spatio-temporal dynamics of road density across the Brazilian Amazon and assesses the relative contributions of local versus neighbourhood effects for temporal changes in road density at regional scales. To achieve this, a combination of statistical analyses and model-data fusion techniques inspired by studies of spatio-temporal dynamics of populations in ecology and epidemiology were used. The emergent development may be approximated by local growth that is logistic through time and directional dispersal. The current rates and dominant direction of development may be inferred, by assuming that roads develop at a rate of 55 km per year. Large areas of the Amazon will be subject to extensive anthropogenic change should the observed patterns of road development continue.

Tropical deforestation is one of the most important components of global change. Rates of deforestation in Brazil, the nation with the single largest concentration of tropical forest on Earth, have fluctuated widely over the last twenty years. Based on local knowledge, such fluctuations have been variously attributed to a wide range of factors such as the expansion of cattle ranching and soybean farming, infrastructural expansion and the proliferation of paved and unpaved roads, macroeconomic shocks to the Brazilian economy and international exchange rates. Many, if not all, of these arguments are plausible explanations for temporal variation in deforestation rates, but have to date not been subjected to rigorous statistical testing; this study investigates the potential impact of these variables on Brazilian tropical deforestation over the period 1990–2005. When analysed at the basin-wide scale, nearly all variables were highly inter-correlated through time and were also closely correlated with deforestation rate, but appropriate time-series analysis found no statistical evidence that any of the variables have systematically caused variation in deforestation rates. Power analysis showed that the variables may exert small or medium influences on deforestation rates, but the impacts, if present, are not strong. Future analyses of time series data at finer spatial scales that exploit spatiotemporal variation in deforestation rates and in the hypothesized predictor variables may find significant causal processes that are overlooked when analysed at the basin-wide scale.

Over the past several decades, the Brazilian State of Rondônia has been the destination of many rural migrants drawn from Brazil's middle southern regions by massive government colonization projects. Factors such as explosive population growth, logging, mining, small-scale farming and ranching have synergistically fuelled deforestation in the state. The total area deforested in Rondônia in 1978 was 4200 km2. In 1988, the area increased to 30 000 km2, in 1998 to 53 300 km2 and by the year 2003, a total of 67 764 km2 of Rondônia was deforested. In response to the high rate of deforestation observed in Rondônia and other Amazonian states, state and federal agencies worked to create a network of conservation units (CUs) in Brazil during the 1990s that was signed into law(Law 9985/00) in 2000. The ability of these CUs to reduce the rate of deforestation was analysed. Remotely-sensed data from Landsat and thematic coverages were used to measure deforestation inside all CUs in Rondônia. A more detailed analysis of CUs with the highest levels of deforestation, including an analysis between soil types and deforestation and a forecast of potential future deforestation, was conducted. The creation of conservation units in Rondônia has been useful in curbing deforestation within their boundaries; however, many CUs face pressure from the combined activities of illegal loggers, cattle ranchers and small-scale farmers seeking new sources of timber and agricultural land. For example, an exponential increase in the amount of deforestation was observed in Rondônia's Bom Futuro National Forest between 1992 and 2000. A regression model indicated a total of 20 500 ha deforested by 2002, while measurements from 2002 imagery showed an actual total deforestation of 20 720 ha. Should this trend persist, Bom Futuro National Forest could be completely deforested by 2017. CUs in Rondônia must be developed and implemented jointly by all stakeholders through the creation of partnerships between local communities, non-governmental organizations and government agencies.

Phylogenetic relationships among Trypanosoma rangeli isolates from man, wild mammals and triatomine bugs from widespread geographical origin were inferred by comparison of the small subunit of ribosomal gene sequences. The phylogenetic trees indicated that the subgenus Herpetosoma is polyphyletic and strongly supported division of this group into two monophyletic lineages, one made up of T. rangeli, T. rangeli-like and allied species and other consisting of T. lewisi and related taxa. Based on phylogenetic analysis, morphology, behaviour in vertebrate and invertebrate hosts and epidemiology we propose: a) the validation of Herpetosoma as a taxon comprised only for species of group lewisi and the maintenance of T. lewisi as the type-species of this subgenus; b) the classification of T. rangeli, T. rangeli-like and allied species into a ‘T. rangeli-clade’ more closely related to Schizotrypanum than to T. lewisi or T. brucei. The phylogenetic tree disclosed at least 4 groups within the clade T. rangeli, all confirmed by polymorphism of the internal transcribed spacer, thus conferring for the first time phylogenetic support to groups of T. rangeli and corroborating the high complexity of this taxon. Grouping was independent of their mammalian host-species and geographical origin, indicating that other factors are determining this segregation.

We characterized 14 trypanosome isolates from sylvatic mammals (9 from primates, 1 from sloth, 2 from anteaters and 2 from opossum) plus 2 human isolates of Brazilian Amazon. These isolates were proven to be Trypanosoma rangeli by detection of metacyclic trypomastigotes in the salivary glands of triatomines and by a specific PCR assay. Polymorphism determined by randomly amplified polymorphic DNA (RAPD) revealed that most (12) of the Brazilian T. rangeli isolates from the Amazon differed from those of other geographical regions, thus constituting a new group of T. rangeli. Four Brazilian isolates clustered together with a previously described group (A) that was described as being composed of being isolates from Colombia and Venezuela. Isolates from Panama and El Salvador form another group. The isolate from Southern Brazil did not cluster to any of the above-mentioned groups. This is the first study that assesses the genetic relationship of a large number of isolates from wild mammals, especially from non-human primates. A randomly-amplified DNA fragment (Tra625) exclusive to T. rangeli was used to develop a PCR assay able to detect all T. rangeli groups.

Slash-and-burn is a widespread agricultural system practised by more than 250 million people in tropical regions. It is sustainable when fallow periods allow for the restoration of organic matter and nutrient losses that occur during the cropping phase. However, fallow periods have been reduced in most slash-and-burn systems as population density has increased. The consequent landscape structure modification occurring throughout this process can affect several ecological processes. As a first step in understanding these modifications, the present study aimed to test the effects of fallow period reduction on landscape structure by examining a total of 34 lots of 25–250 ha each in the north-east of the Brazilian Amazon. Sixteen lots with long fallow periods (about 10 years) were compared with 18 lots where fallow periods were reduced to c. four years. The reduction in fallow period created a more homogeneous landscape, largely dominated by agricultural and young secondary vegetation. The main mechanism leading to this homogenization was a more intensive use of initial secondary vegetation for agriculture. On average, the percentage of land used more intensively for agriculture was four times higher in short fallow period areas than in long-period areas. The increase in agricultural area is related to both an increase in the number of agricultural fields and also to an increase in the area of these fields. The proportions of forest and old secondary vegetation in the landscape were reduced as a consequence of a reduction in patch size, without significant fragmentation or patch losses. These structural changes appeared to be more usual in large properties belonging to several families. Further studies are needed to understand the consequences of these modifications for landscape functioning, but it is possible to speculate, based on previous studies, that these structural changes can lead to a reduction in the speed of regeneration processes.