The Livestock Frontier in the Paraguayan Chaco: A Local Agent-based Perspective.

Deforestation is one of the most relevant transformations characterizing global environmental change in the tropics at present. There is wide consensus in pointing the context-dependent nature of tropical deforestation. In this sense, a better characterization of the phenomenon considering the social context could provide a more accurate picture of tropical deforestation. With this aim, a Q-methodology discourse analysis was conducted to characterise the different discourses that coexist in the particular region of the Paraguayan Chaco concerning the development of cattle ranching and derived deforestation. Four different discourses were identified as making sense the wide range of interests and values coexisting and clashing in the Paraguayan Chaco, namely: the Environmentalist discourse, the Business discourse, the Resigned discourse, and the Possibilist discourse. The results point that the fundamental differences between the discourses are largely explained by the different positions on three specific domains: (i) the socio-economic benefits the expansion of cattle ranching brings about; (ii) the environmental impacts the expansion of cattle ranching and the derived deforestation brings on; and, finally (iii) the degree to which an active intervention from the side of policy making to regulate the expansion of cattle ranching and to minimize possible detrimental effects is seen as necessary. The position of the different discourses in relation to these domains could help policy makers to make measures and regulations more widely accepted and followed.

Assessing soil erosion in a semiarid ecosystem in Central Argentina using 137Cs and 7Be measurements.

Argentina is a Latin American country which encounters soil degradation problems. The most productive regions have implemented conservative land practices (no-till). However, agricultural frontier has been displaced to marginal lands with arid and semiarid climates, with the consequent disappearance in many areas of native forest and land degradation. In this work, the fallout of gamma-emitting radionuclides, 137Cs and 7Be, was jointly used to assess changes in soil erosion in a recently converted semiarid ecosystem into agricultural land. 137Cs was utilized to estimate the erosion over the past 60 years, whereas 7Be was employed to estimate the erosion after the conversion of the area to cultivated land and soil tillage. For 137Cs the Proportional Model (PM), the Mass Balance Model II (MBMII) and the MODERN model were used, for 7Be the Profile Distribution Model (PDM) and the MODERN model were used. 137Cs indicates mean erosional rates of 8.2, 10.5 and 6.5 Mg ha-1 a-1, using MBMII, PM and MODERN, respectively, and that a soil layer between 0.5 and 0.8 mm was annually lost by erosion. By applying a 7Be tracer, we measured erosion rates of 2.4 and 3.3 Mg ha-1 (with PDM and Modern, respectively), indicating the loss of the upper 0.2 mm of soil. This erosion can be attributed to a few heavy rainfalls that occurred within the past 90 days. The results suggest that current land management practices have led to an increase in soil erosion. This could be attributed to the fact that the soil remains bare after crop harvest, which may compromise its conservation and future productivity.

Effects of intensive agriculture and urbanization on water quality and pesticide risks in freshwater ecosystems of the Ecuadorian Amazon.

The Ecuadorian Amazon has experienced a significant land use change due to the demographic increase and the expansion of the agricultural frontier. Such changes in land use have been associated to water pollution problems, including the emission of untreated urban wastewater and pesticides. Here we provide the first report on the influence of urbanization and intensive agriculture expansion on water quality parameters, pesticide contamination and the ecological status of Amazonian freshwater ecosystems of Ecuador. We monitored 19 water quality parameters, 27 pesticides, and the macroinvertebrate community in 40 sampling locations of the Napo River basin (northern Ecuador), including a nature conservation reserve and sites in areas influenced by African palm oil production, corn production and urbanization. The ecological risks of pesticides were assessed using a probabilistic approach based on species sensitivity distributions. The results of our study show that urban areas and areas dominated by African palm oil production have a significant influence on water quality parameters, affecting macroinvertebrate communities and biomonitoring indices. Pesticide residues were detected in all sampling sites, with carbendazim, azoxystrobin, diazinon, propiconazole and imidacloprid showing the largest prevalence (>80% of the samples). We found a significant effect of land use on water pesticide contamination, with residues of organophosphate insecticides correlating with African palm oil production and some fungicides with urban areas. The pesticide risk assessment indicated organophosphate insecticides (ethion, chlorpyrifos, azinphos-methyl, profenofos and prothiophos) and imidacloprid as the compounds posing the largest ecotoxicological hazard, with pesticide mixtures potentially affecting up to 26-29% of aquatic species. Ecological risks of organophosphate insecticides were more likely to occur in rivers surrounded by African palm oil plantations, while imidacloprid risks were identified in corn crop areas as well as in natural areas. Future investigations are needed to clarify the sources of imidacloprid contamination and to assess its effects for Amazonian freshwater ecosystems.

Estratégias reprodutivas e evolução da fronteira agrícola na Amazônia brasileira: um estudo qualitativo em Machadinho d'Oeste / Reproductive strategies and development of the Brazilian Amazon agricultural frontier: a qualitative study in Machadinho d'Oeste / Estrategias reproductivas y evolución de la frontera agrícola en la Amazonía brasileña: un estudio cualitativo en Machadinho d'Oeste

Analisam-se as estratégias reprodutivas de duas coortes de mulheres que viveram seu período reprodutivo em diferentes estágios de evolução de uma região de fronteira agrícola na Amazônia brasileira. Entende-se por estratégia reprodutiva a adoção de determinado comportamento reprodutivo e contraceptivo segundo as possibilidades e adversidades oferecidas no contexto da fronteira. O objetivo é avaliar as mudanças nessa estratégia ao longo do processo de desenvolvimento desse tipo de fronteira. As distintas condições socioeconômicas que os estágios de desenvolvimento da fronteira oferecem tornariam as estratégias reprodutivas diferenciadas, influenciando as decisões das mulheres que viveram seu período reprodutivo nas fases iniciais ou nas mais avançadas da fronteira. Foram realizadas entrevistas semiestruturadas em Machadinho d'Oeste, Rondônia, com 60 mulheres. Os resultados apontam que, contrariamente ao referido na literatura, não haveria uma relação direta entre uso da terra e o número de filhos. O comportamento reprodutivo de cada coorte se relaciona mais à infraestrutura de serviços de saúde sexual e reprodutiva e às condições socioeconômicas individuais e da fronteira. Para ambos os grupos, porém, a união e a maternidade são precoces e existem elevada falha contraceptiva e alta proporção de laqueadura.

We analyze the reproductive strategies of two cohorts of women whose reproductive period was experienced in different stages of the agricultural frontier evolution in the Brazilian Amazon. Reproductive strategy consists of certain reproductive and contraceptive behaviors adjusted to the possibilities and adversities offered in the context of the frontier. We evaluate changes in reproductive and contraceptive strategies throughout the development process of the agricultural frontier. The different conditions throughout the development stages offered by the frontier would trigger different reproductive strategies, thus decisions would be different for women that lived their reproductive period during initial or more advanced stages of the frontier. We carried out semi-structured interviews with 60 women in Machadinho d'Oeste, Rondônia. Despite what the literature claims, the results indicate that there is no direct relationship between land use and number of children. Rather, the reproductive behavior of each cohort is related to the infrastructure of sexual and reproductive health services and to individual and frontier socioeconomic conditions. Despite the differences, union and childbearing occur at young ages in either stage, with a reasonable proportion of pregnancy due to contraceptive failure as well as a high rate of female surgical sterilization.

Se analizan las estrategias reproductivas de dos cohortes de mujeres que vivieron en diferentes etapas de evolución de una región de frontera agrícola en la Amazonia brasileña. Se entiende por estrategia reproductiva la adopción de ciertos comportamientos reproductivos y anticonceptivos de acuerdo a las posibilidades y adversidades del contexto de la frontera. Se busca evaluar los cambios en las mencionadas estrategias en la medida en que evoluciona una región de este tipo. Las diferentes condiciones socioeconómicas por las que pasa la frontera agrícola durante este proceso diferenciarían a las estrategias reproductivas al influir en las decisiones tomadas por las mujeres que vivieron su período reproductivo en las primeras o en las fases más avanzadas de la frontera. Se realizaron entrevistas semiestructuradas en Machadinho d'Oeste, Rondônia, a sesenta mujeres, cuyos resultados muestran —a diferencia de lo que señala la literatura— que no habría relación directa entre el uso de la tierra y el número de hijos. El comportamiento reproductivo de cada cohorte está más relacionado con la infraestructura de los servicios de salud sexual y reproductiva y con las condiciones socioeconómicas individuales y fronterizas. No obstante, para ambos grupos, la unión y la maternidad son precoces, se observan alta falla anticonceptiva y alta proporción de esterilización.

Impacts of land-use and land-cover change on stream hydrochemistry in the Cerrado and Amazon biomes.

Studies on the impacts of land-use and land-cover change on stream hydrochemistry in active deforestation zones of the Amazon agricultural frontier are limited and have often used low-temporal-resolution datasets. Moreover, these impacts are not concurrently assessed in well-established agricultural areas and new deforestations hotspots. We aimed to identify these impacts using an experimental setup to collect high-temporal-resolution hydrological and hydrochemical data in two pairs of low-order streams in catchments under contrasting land use and land cover (native vegetation vs. pasture) in the Amazon and Cerrado biomes. Our results indicate that the conversion of natural landscapes to pastures increases carbon and nutrient fluxes via streamflow in both biomes. These changes were the greatest in total inorganic carbon in the Amazon and in potassium in the Cerrado, representing a 5.0- and 5.5-fold increase in the fluxes of each biome, respectively. We found that stormflow, which is often neglected in studies on stream hydrochemistry in the tropics, plays a substantial role in the carbon and nutrient fluxes, especially in the Amazon biome, as its contributions to hydrochemical fluxes are mostly greater than the volumetric contribution to the total streamflow. These findings demonstrate that assessments of the impacts of deforestation in the Amazon and Cerrado biomes should also take into account rapid hydrological pathways; however, this can only be achieved through collection of high-temporal-resolution data.

Composição demográfica domiciliar e dinâmica do uso do solo em Machadinho d'Oeste, Rondônia: evidências baseadas nos estágios iniciais da fronteira / Household demographic composition and land use dynamics in Machadinho d'Oeste, Rondônia: evidence from the frontier onset / Composición demográfica domiciliaria y dinámica del uso del suelo en Machadinho d'Oeste, Rondônia: evidencias basadas en las etapas iniciales de la frontera

Vários estudos sugerem a importância da mudança na composição demográfica domiciliar sobre a demanda e o uso da terra em fronteiras agrícolas. A maioria desses estudos, no entanto, analisa essa relação em estágios mais avançados do desenvolvimento das fronteiras, produzindo evidências conflitantes sobre o papel dos determinantes populacionais. Este artigo examina os efeitos da composição demográfica domiciliar (ciclo de vida domiciliar) e do tempo na propriedade (ciclo no lote) sobre a dinâmica de uso do solo em pequenas propriedades rurais em Machadinho d'Oeste, Rondônia. Foram utilizados dados de uma pesquisa censitária sobre os colonos do projeto de assentamento original, para 1987 e 1995. A relação entre os ciclos e as classes de uso do solo foi analisada por meio de modelos de regressão Beta e de Dirichlet. Observou-se uma relação consistente entre oferta de trabalho familiar e estoque desmatado no nível da propriedade rural. O tempo na propriedade também se mostrou associado ao desmatamento, embora seu efeito não linear sugira a experimentação com o ambiente biofísico local. Sugere-se que os efeitos do ciclo de vida e no lote se autodeterminam nos estágios iniciais da fronteira, indicando a importância dos efeitos da composição demográfica sobre a dinâmica de uso da terra.

Previous studies have found evidence of the importance of changes in household composition to explain land use choices in agricultural frontiers. Most of these studies, however, analyze these dynamics at later stages of the frontier development, rendering mixed evidence on the role of population drivers. This study examines the effects of household demographic composition (household life cycle) and time on property (property life cycle) on land use dynamics in small farms at Machadinho d'Oeste, Rondônia. Based on a unique dataset covering the agricultural frontier since its onset, the study analyzes these effects when their association with land cover dynamics is most likely. Data collected in 1987 and 1995 for a census survey regarding settlers on the original settlement area was used for the study. The relationship between cycles and types of land use was analyzed and modelled by means of Beta and Dirichlet regression models. A consistent relation between family labor supply and deforested stock was observed with regards to rural property. Time on the property was also associated with deforestation, although its non-linear effect suggests experimentation with the local biophysical environment. The effect of the life cycle and of the lot are self-determined in the initial stages of frontier development, indicating the relevance of the demographic dynamics of households for land use choices in agricultural frontiers.

Varios estudios sugieren la importancia de los cambios en la composición demográfica domiciliaria sobre la demanda y el uso de la tierra en fronteras agrícolas. La mayoría de esos estudios analiza sin embargo esa relación en etapas más avanzadas del desarrollo de las fronteras, y han producido evidencias conflictivas sobre el papel de los determinantes poblacionales. Este artículo examina los efectos de la composición demográfica del hogar (ciclo de vida domiciliaria) y del tiempo en la propiedad (ciclo en el lote) sobre la dinámica del uso del suelo en pequeñas propiedades rurales en Machadinho d'Oeste, Rondônia. Para ello fueron utilizados datos censales sobre los colonos del proyecto de asentamiento original para los años 1987 y 1995. La relación entre los ciclos y los tipos de uso del suelo fue analizada por medio de modelos de regresión Beta y de Dirichlet. Se observó una relación consistente entre la oferta de trabajo familiar y el stock deforestado en el nivel de la propiedad rural. El tiempo en la propiedad también aparece asociado a la deforestación, aunque su efecto no linear sugiera la experimentación con el ambiente biofísico local. Se sugiere que el efecto del ciclo de vida y en el lote se determina en las etapas iniciales de la frontera, indicando la importancia de los efectos de la composición demográfica sobre la dinámica del uso de la tierra.