Accelerated land use changes in the Brazilian Amazonian region over the last four decades have raised questions about potential consequences for local hydrology. Under the hypothesis of a lack of frontier governance, projections of future changes in the Amazon basin suggest that 20-30% or more of this basin could be deforested in the next 40 years. This could trigger a cascade of negative impacts on water resources. In this study, we examined how a future conversion of the forest into pasture would influence streamflow and water balance components by using a conceptual and semi-distributed hydrological model in a large (142,000 km 2) forested basin: specifically, the Iriri River basin in the Brazilian Amazon. The results showed that the land use change could substantially alter the water balance components of the originally forested basin. For example, an increase of over 57% in pasture areas increased a simulated annual streamflow by~6.5% and had a significant impact on evapotranspiration, surface runoff, and percolation. Our findings emphasize the importance of protected areas for conservation strategies in the Brazilian Amazonian region.

Question Tropical forests are subject to disturbances by logging, gathering of fuelwood, and fires. Can degradation trajectories (i.e. cumulative disturbances events over a period of timer) be identified using remote‐sensing Landsat time series? Location Paragominas (Pará, Brazil), a municipality covering 19,395 km² in the north‐eastern Amazon. Methods We used Landsat annual imagery from 2000 to 2015 and spectral mixture analysis to derive time series of the fraction of soil (S), active photosynthetic vegetation (PV), and non‐photosynthetic vegetation (senescent) (NPV) indicators. Results The NPV values over a 16‐year period revealed five different degradation trajectories (i.e., cumulative disturbances in space and over time): undisturbed forest, selectively logged forest (with a management plan), overlogged forest (no management plan), overlogged forest (charcoal production) and burned forest. The variance of NPV calculated per pixel over the same period is useful to map forest degradation over Paragominas municipality, highlighting the role of disturbance factors (logging, fuelwood gathering and fire). Conclusions The fractional cover of NPV obtained from spectral mixture analysis can be used to differentiate degradation trajectories and to map forest degradation.

International audienceThe Amazon has recently experienced a dramatic decline in deforestation coupled with economic development. However, this process is uneven. While large and medium-sized producers are intensifying and diversifying their production systems in the already cleared areas, thus apparently abandoning expansion strategies at the moment, family farming remains aloof from this decoupling between production and deforestation. In this article, the commitments of public authorities and sectors, their effects on deforestation and inequalities of adaptation are analyzed at the scale of the Legal Amazon and in a municipality considered as a model because involved in a Município Verde initiative: Paragominas, in the Eastern Amazon.L’Amazonie a amorcé depuis quelques années une baisse de la déforestation couplée à un développement économique. Le processus est cependant inégal. Si les grands et moyens producteurs font évoluer leurs systèmes de production vers l’intensification et la diversification dans les espaces déjà ouverts, délaissant en apparence les stratégies d’expansion, l’agriculture familiale reste à l’écart du découplage entre production et déforestation. Dans cet article, les engagements des pouvoirs publics et des filières, leurs effets en matière de déforestation et les inégalités d’adaptation sont analysés à l’échelle de l’Amazonie Légale et à celle d’une municipalité considérée comme un modèle car à l’initiative d’une démarche de Município Verde : Paragominas, en Amazonie orientale

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The phenology of tropical forests is tightly related to climate conditions. In the Amazon, the seasonal greening of forests is conditioned by solar radiation and rainfall. Yet, increasing anthropogenic pressures (e.g. logging and wildfires), raise concerns about the impacts of forest degradation on the functioning of forest ecosystems, especially in a climate change context. In this study, we relied on remote sensing data to assess the contribution of solar radiation and precipitation to forest greening in mature and fire degraded forests, with a focus on the 2015 drought event. Our results showed that forest greening is more dependent on water resources in degraded forests than in mature forests. As a consequence, the expected increase in drought episodes and associated fire occurrences under climate change could lead to a long-term drying of tropical forests.

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Os processos relacionados a arenização inicialmente conceituados para a região sudoeste do Rio Grande do Sul, também ocorrem em outras regiões do Brasil. Estudos demonstram que o ponto convergente entre essas áreas é o tipo de solo, os Neossolos Quartzarênicos Órticos (RQo). Este artigo analisa as propriedades das séries temporais de NDVI e EVI da cobertura vegetal em áreas de solos RQo no Rio Grande do Sul, Goiás, Tocantins e Piauí, no período entre 2000 e 2015. Para tanto a metodologia proposta utiliza as seguintes propriedades: média, tendência, variabilidade interanual (IAV) e sazonalidade das séries temporais MOD13Q1 sensor MODIS, de NDVI e EVI; mapa de solos e índices pluviométricos do satélite Tropical Rainfall Measuring Mission (TRMM). Os resultados mostram que o comportamento dos valores das propriedades sugere que a cobertura vegetal em áreas com solos RQo em Gilbués/PI e Mateiros/TO se apresentam mais estáveis na série temporal, sem dinâmicas naturais ou antrópicas que ocasionem grandes mudanças no comportamento temporal da vegetação para serem expressas pelas propriedades tendência e IAV. Maçambará e Serranópolis com dinâmicas de arenização nas áreas de RQo mais intensas, apresentaram resultados mais expressivos. Serranópolis por abranger extensas áreas de pastagens e atividades agrícolas e ainda conservar uma boa parte de remanescentes de Cerrado se destacou com valores mais elevados em relação a tendência e sazonalidade. A variação da sazonalidade nas quatro áreas é consequência principalmente da dinâmica climática sazonal. As séries temporais de NDVI e EVI MODIS se mostraram eficientes em mostrar as variações temporais da biomassa e possibilitaram analisar satisfatoriamente a variação espaço-temporal do verdor da cobertura vegetal em áreas de solos RQo associadas a arenização.