Publicações

O bioma Caatinga representa cerca de 10% do território nacional e tem uma população estimada em 28 milhões de habitantes. Sua vegetação arbóreo-arbustiva, adaptada às condições de semiaridez, exerce um papel fundamental na manutenção do balanço hidrológico, na alimentação da matriz energética e na geração de receitas para o país. No entanto, o bioma ainda é um dos que recebe menor atenção da comunidade científica. Diante disso, o presente artigo de revisão visa apresentar elementos que contribuam para a atualização do estado da arte sobre o uso de dados ópticos de observação da Terra na conservação da vegetação da Caatinga, a partir da identificação das iniciativas de mapeamento em diferentes escalas que contemplam o bioma. Para tal, esse estudo fez uma revisão bibliográfica sistemática cujo enfoque principal foi a caracterização dos sensores orbitais imageadores, técnicas de classificação de imagem, legendas de uso e cobertura, estratégias de validação, e o intervalo temporal compreendido por cada iniciativa. Esse detalhamento permitiu avaliar o grau de usabilidade e confiabilidade dos produtos existentes. Assim, esse estudo espera abrir possibilidades para preencher lacunas científicas existentes e que carecem de investigação no que diz respeito ao papel dos dados ópticos de observação da Terra no mapeamento da vegetação da Caatinga e no subsídio de recursos para novas iniciativas, ações de restauração e, consequentemente, aprimoramento de políticas públicas em prol da conservação e uso sustentável dos recursos do bioma.

Increasing demand for water is one of the most challenging problems that human societies face today and has encouraged new studies to examine water security and water management. Seeking to discuss this important issue in the Brazilian context, we analyzed the impacts of urban expansion on water security in a basin located in the most populated region of Brazil. To quantify increased water demand, we combined urban sprawl and regional population increase projections. In this context, our study contributes to discussions on water security by addressing the importance of integration between water and urban planning. Simulations indicate good performance in reproducing actual water system conditions. The finding demonstrates that urban expansion in the region is mainly driven by road proximity. Urban occupation is projected to increase in 170% by 2050, increasing water demands for domestic use in 38%. Results indicate the feasibility of including landscape and socioeconomic constrains in order to obtain potential domestic water demand scenarios by using land use and land cover change modelling to assess urban expansion and population growth. For the study region, our findings suggest that although urban sprawl increases water demand, urban supply will not be compromised given the large volume of available water in the basin. However, the indirect consequences of urban sprawl, such as industrialization and agricultural intensification, may compromise the quality of this resource and require better water use management in the region.

Background: Tropical forests play a fundamental role in the provision of diverse ecosystem services, such as biodiversity, climate and air quality regulation, freshwater provision, carbon cycling, agricultural support and culture. To understand the role of forests in the carbon balance, aboveground biomass (AGB) estimates are needed. Given the importance of Brazilian tropical forests, there is an urgent need to improve AGB estimates to support the Brazilian commitments under the United Nations Framework Convention on Climate Change (UNFCCC). Many AGB maps and datasets exist, varying in availability, scale and coverage. Thus, stakeholders, policy makers and scientists must decide which AGB product, dataset or combination of data to use for their particular goals. In this study, we assessed the gaps in the spatial AGB data across the Brazilian Amazon forests not only to orient the decision makers about the data that are currently available but also to provide a guide for future initiatives. Results: We obtained a map of the gaps in the forest AGB spatial data for the Brazilian Amazon using statistics and differences between AGB maps and a spatial multicriteria evaluation that considered the current AGB datasets. The AGB spatial data gap map represents areas with good coverage of AGB data and, consequently, the main gaps or priority areas where further biomass assessments should focus, including the northeast of Amazon State, Amapá and northeast of Pará. Additionally, by quantifying the variability in both the AGB maps and field data on multiple environmental factors, we provide valuable elements for understanding the current AGB data as a function of climate, soil, vegetation and geomorphology. Conclusions: The map of AGB data gaps could become a useful tool for policy makers and different stakeholders working on National Communications, Reducing Emissions from Deforestation and Degradation (REDD+), or carbon emissions modeling to prioritize places to implement further AGB assessments. Only 0.2% of the Amazon biome forest is sampled, and extensive effort is necessary to improve what we know about the tropical forest.

Authors discuss school safety and disaster education in Brazil, Colombia, Cuba, the Dominican Republic, Jamaica and Puerto Rico. Case studies explore work to increase understanding of natural hazards and disaster preparedness. Puerto Rico offers innovative examples of reflection on memories of Hurricane Maria by primary students and university undergraduates. From Brazil comes description of work in schools to develop curriculum skills and research competencies at high-school level. The Brazilian scheme encourages schools to become producers of knowledge rather than reproducers of centrally disseminated information. Another case study focuses on efforts to protect university buildings in Colombia. The rich landscape of policy, practice and experience in South America and the Caribbean is informed by a model of the three pillars of Comprehensive School Safety: 1. Safe Learning Facilities, 2. School Disaster Management, and 3. Risk Reduction and Resilience Education.

The Sendai Framework for Disaster Risk Reduction 2015-2030 recommends several actions for early warning systems (EWSs). However, there is a lack of information about their means of implementation. This article used institutional ethnography to analyze the 2012-2018 implementation of a national warning system in Brazil. The challenges related to daily activities, and the interdisciplinary works in the four axes of EWSs towards multi-hazard and people-centered approaches are discussed. This national experience is then discussed in the light of the global challenges of EWSs considering two main issues: (1) experiences of implementation and barriers related to people-centered warning systems; and (2) types of national/regional warning systems and hazards/threats that are being monitored as an important input for multi-hazard approaches. There are few multi-hazard warning systems in place and EWSs are focused on hydrometeorological hazards, mainly related to floods. The Sendai Framework needs to improve access to data and information, identify views from the frontline, consider political threats and vulnerabilities, and find ways to talk about disaster risk creation processes at a larger scale.

Deforestation and drought are among the greatest environmental pressures on the Amazon rainforest, possibly destabilizing the forest-climate system. Deforestation in the Amazon reduces rainfall regionally, while this deforestation itself has been reported to be facilitated by droughts. Here we quantify the interactions between drought and deforestation spatially across the Amazon during the early 21st century. First, we relate observed fluctuations in deforestation rates to dry-season intensity; second, we determine the effect of conversion of forest to cropland on evapotranspiration; and third, we simulate the subsequent downwind reductions in rainfall due to decreased atmospheric water input. We find large variability in the response of deforestation to dry-season intensity, with a significant but small average increase in deforestation rates with a more intense dry season: with every mm of water deficit, deforestation tends to increase by 0.13% per year. Deforestation, in turn, has caused an estimated 4% of the recent observed drying, with the south-western part of the Amazon being most strongly affected. Combining both effects, we quantify a reinforcing drought-deforestation feedback that is currently small, but becomes gradually stronger with cumulative deforestation. Our results suggest that global climate change, not deforestation, is the main driver of recent drying in the Amazon. However, a feedback between drought and deforestation implies that increases in either of them will impede efforts to curb both.

Tropical forests regulate the global water and carbon cycles and also host most of the worlds biodiversity. Despite their importance, they are hard to survey due to their location, extent, and particularly, their cloud coverage. Clouds hinder the spatial and radiometric correction of satellite imagery and also diminishing the useful area on each image, making it difficult to monitor land change. For this reason, our purpose is to identify the cloud detection algorithm best suited for the Amazon rainforest on Sentinel2 images. To achieve this, we tested four cloud detection algorithms on Sentinel2 images spread in five areas of the Amazonia. Using more than eight thousand validation points, we compared four cloud detection methods: Fmask 4, MAJA, Sen2Cor, and s2cloudless. Our results point out that FMask 4 has the best overall accuracy on images of the Amazon region (90%), followed by Sen2Cors (79%), MAJA (69%), and S2cloudless (52%). We note the choice of method depends on the intended use. Since MAJA reduces the number of false positives by design, users that aim to improve the producers accuracy should consider its use.

Brazil hosts the largest expanse of tropical ecosystems within protected areas (PAs), which shelter biodiversity and support traditional human populations. We assessed the vulnerability to climate change of 993 terrestrial and coastal-marine Brazilian PAs by combining indicators of climatic-change hazard with indicators of PA resilience (size, native vegetation cover, and probability of climate-driven vegetation transition). This combination of indicators allows the identification of broad climate-change adaptation pathways. Seventeen PAs (20,611 km2) were highly vulnerable and located mainly in the Atlantic Forest (7 PAs), Cerrado (6), and the Amazon (4). Two hundred fifty-eight PAs (756,569 km2), located primarily in Amazonia, had a medium vulnerability. In the Amazon and western Cerrado, the projected severe climatic change and probability of climate-driven vegetation transition drove vulnerability up, despite the generally good conservation status of PAs. Over 80% of PAs of high or moderate vulnerability are managed by indigenous populations. Hence, besides the potential risks to biodiversity, the traditional knowledge and livelihoods of the people inhabiting these PAs may be threatened. In at least 870 PAs, primarily in the Atlantic Forest and Amazon, adaptation could happen with little or no intervention due to low climate-change hazard, high resilience status, or both. At least 20 PAs in the Atlantic Forest, Cerrado, and Amazonia should be targeted for stronger interventions (e.g., improvement of ecological connectivity), given their low resilience status. Despite being a first attempt to link vulnerability and adaptation in Brazilian PAs, we suggest that some of the PAs identified as highly or moderately vulnerable should be prioritized for testing potential adaptation strategies in the near future.

Deforestation and drought are among the greatest environmental pressures on the Amazon rainforest, possibly destabilizing the forest-climate system. Deforestation in the Amazon reduces rainfall regionally, while this deforestation itself has been reported to be facilitated by droughts. Here we quantify the interactions between drought and deforestation spatially across the Amazon during the early 21st century. First, we relate observed fluctuations in deforestation rates to dry-season intensity; second, we determine the effect of conversion of forest to cropland on evapotranspiration; and third, we simulate the subsequent downwind reductions in rainfall due to decreased atmospheric water input. We find large variability in the response of deforestation to dry-season intensity, with a significant but small average increase in deforestation rates with a more intense dry season: with every mm of water deficit, deforestation tends to increase by 0.13% per year. Deforestation, in turn, has caused an estimated 4% of the recent observed drying, with the south-western part of the Amazon being most strongly affected. Combining both effects, we quantify a reinforcing drought-deforestation feedback that is currently small, but becomes gradually stronger with cumulative deforestation. Our results suggest that global climate change, not deforestation, is the main driver of recent drying in the Amazon. However, a feedback between drought and deforestation implies that increases in either of them will impede efforts to curb both.

The Atlantic rainforest of Brazil is one of the global terrestrial hotspots of biodiversity. Despite having undergone large scale deforestation, forest cover has shown signs of increases in the last decades. Here, to understand the degradation and regeneration history of Atlantic rainforest remnants near São Paulo, we combine a unique dataset of very high resolution images from Worldview-2 and Worldview-3 (0.5 and 0.3m spatial resolution, respectively), georeferenced aerial photographs from 1962 and use a deep learning method called U-net to map (i) the forest cover and changes and (ii) two pioneer tree species, Cecropia hololeuca and Tibouchina pulchra. For Tibouchina pulchra, all the individuals were mapped in February, when the trees undergo mass-flowering with purple and pink blossoms. Additionally, elevation data at 30m spatial resolution from NASA Shuttle Radar Topography Mission (SRTM) and annual mean climate variables (Terraclimate datasets at ∼ 4km of spatial resolution) were used to analyse the forest and species distributions. We found that natural forests are currently more frequently found on south-facing slopes, likely because of geomorphology and past land use, and that Tibouchina is restricted to the wetter part of the region (southern part), which annually receives at least 1600 mm of precipitation. Tibouchina pulchra was found to clearly indicate forest regeneration as almost all individuals were found within or adjacent to forests regrown after 1962. By contrast, Cecropia hololeuca was found to indicate older disturbed forests, with all individuals almost exclusively found in forest fragments already present in 1962. At the regional scale, using the dominance maps of both species, we show that at least 4.3% of the current region’s natural forests have regrown after 1962 (Tibouchina dominated, ∼ 4757 ha) and that ∼ 9% of the old natural forests have experienced significant disturbance (Cecropia dominated).

The South American Monsoon System (SAMS) is a major climatic feature of South America, and its domain extends from Amazon to La Plata basin. The SAMS region is vulnerable to variations of climate and precipitation patterns, which could impact economic activities and lead to potential societal consequences. In the face of a warming future scenario, the importance of the study of the past climate with numerical simulations is to evaluate the climate models and to assure the reliability of future projections. Here we investigate the Mid-Holocene SAMS, evaluating changes in strength, life cycle and associated dynamical mechanisms in ten Earth System Models simulations. Our results show that the SAMS was weaker in the Mid-Holocene than in the pre-industrial climate in December-January-February (DJF), but stronger in September-October-November (SON). This is probably a consequence of insolation variations in the Mid-Holocene, which contributed to changes in the moisture flux from the Atlantic Ocean to the continent, the strength of the upper-level atmospheric circulation, and the amount of precipitation over the SAMS region. Moreover, we suggest that the life cycle of the SAMS was altered during the Mid-Holocene, with an earlier onset and demise. Our results also indicate that Mid-Holocene SAMS changes are connected to precipitation variations near Northeast Brazil, in a dipole configuration of precipitation between western Amazon and Northeast Brazil, due to the influence of the Walker cell. Finally, this study highlights a need for improvement of the numerical models to better simulate the amount of precipitation over South America and the upper-level circulation over western Amazon in SON, which are crucial factors for a more realistic representation of the SAMS.