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Most of the world's nations (around 130) have committed to reaching net‐zero carbon dioxide or greenhouse gas (GHG) emissions by 2050, yet robust policies rarely underpin these ambitions. To investigate whether existing and expected national policies will allow Brazil to meet its net‐zero GHG emissions pledge by 2050, we applied a detailed regional integrated assessment modelling approach. This included quantifying the role of nature‐based solutions, such as the protection and restoration of ecosystems, and engineered solutions, such as bioenergy with carbon capture and storage. Our results highlight ecosystem protection as the most critical cost‐effective climate mitigation measure for Brazil, whereas relying heavily on costly and not‐mature‐yet engineered solutions will jeopardise Brazil's chances of achieving its net‐zero pledge by mid‐century. We show that the full implementation of Brazil's Forest Code (FC), a key policy for emission reduction in Brazil, would be enough for the country to achieve its short‐term climate targets up to 2030. However, it would reduce the gap to net‐zero GHG emissions by 38% by 2050. The FC, combined with zero legal deforestation and additional large‐scale ecosystem restoration, would reduce this gap by 62% by mid‐century, keeping Brazil on a clear path towards net‐zero GHG emissions by around 2040. While some level of deployment of negative emissions technologies will be needed for Brazil to achieve and sustain its net‐zero pledge, we show that the more mitigation measures from the land‐use sector, the less costly engineered solutions from the energy sector will be required. Our analysis underlines the urgent need for Brazil to go beyond existing policies to help fight climate emergency, to align its short‐ and long‐term climate targets, and to build climate resilience while curbing biodiversity loss. [ABSTRACT FROM AUTHOR]

Countries have pledged to different national and international environmental agreements, most prominently the climate change mitigation targets of the Paris Agreement. Accounting for carbon stocks and flows (fluxes) is essential for countries that have recently adopted the United Nations System of Environmental-Economic Accounting - ecosystem accounting framework (UNSEEA) as a global statistical standard. In this paper, we analyze how spatial carbon fluxes can be used in support of the UNSEEA carbon accounts in five case countries with available in-situ data. Using global multi-date biomass map products and other remotely sensed data, we mapped the 2010–2018 carbon fluxes in Brazil, the Netherlands, the Philippines, Sweden and the USA using National Forest Inventory (NFI) and local biomass maps from airborne LiDAR as reference data. We identified areas that are unsupported by the reference data within environmental feature space (6–47% of vegetated country area); cross-validated an ensemble machine learning (RMSE=9–39 Mg C ha - 1 and R 2 =0.16–0.71) used to map carbon fluxes with prediction intervals; and assessed spatially correlated residuals (<5 km) before aggregating carbon fluxes from 1-ha pixels to UNSEEA forest classes. The resulting carbon accounting tables revealed the net carbon sequestration in natural broadleaved forests. Both in plantations and in other woody vegetation ecosystems, emissions exceeded sequestration. Overall, our estimates align with FAO-Forest Resource Assessment and national studies with the largest deviations in Brazil and USA. These two countries used highly clustered reference data, where clustering caused uncertainty given the need to extrapolate to under-sampled areas. We finally provide recommendations to mitigate the effect of under-sampling and to better account for the uncertainties once carbon stocks and flows need to be aggregated in relatively smaller countries. These actions are timely given the global initiatives that aim to upscale UNSEEA carbon accounting. [ABSTRACT FROM AUTHOR]

The potential of agroforestry systems (AFS) for atmospheric carbon sequestration in degraded tropical lands is of key interest for climate change and rural development policies. This study evaluated aboveground and soil (0–20 cm) carbon stocks of AFS, secondary forests (SF), conserved and logged mature forests, on 88 sites in the eastern Brazilian Amazon. Tree carbon stock was higher in young (< 10 years) and advanced (> 30 years) AFS (10.2 ± 2.0 and 47.2 ± 8.1 Mg ha−1, respectively) when compared to the same age SF (5.8 ± 2.5 and 26.5 ± 19.5 Mg ha−1). However, aboveground and total carbon stocks were statistically similar within the same age categories of AFS and SF, because shrub pool were higher in SF. Conserved mature forests had the highest carbon stocks (190.2 ± 11.0 Mg ha−1), and carbon stocks in logged mature forests (119.4 ± 5.1 Mg ha−1) were similar to the advanced stages of AFS (108.6 ± 7.5 Mg ha−1). Litter and soil organic carbon (SOC) did not differ significantly between land-use systems nor along succession. At 30 years, aboveground carbon recovery was 46% (± 16) in AFS and 35% (± 21) in SF. Vegetation structural diversity (measured by DBH and height variation) was a good predictor of aboveground carbon stocks. Our results show the potential of AFS for carbon recovery, especially in the tree pool at late stages of development. Structurally more complex AFS provide an alternative to recover degraded lands and to develop synergies between climate change mitigation, adaptation, and goods production in Amazon. [ABSTRACT FROM AUTHOR]

• Integrating the source to sink BECCS chain into an energy system optimization model. • CCS cost-storage curves are created to analyze cost-competitiveness of BECCS. • Assess the dynamic relation between negative emissions and land use change emissions. • Total system costs decrease when BECCS is modelled endogenously. • Source-sink matching shows higher CO 2 injection rates (250 Mt CO 2) can be reached than mentioned in scientific literature (up to 135 Mt CO 2). • Unrestricted modeling of BECCS increases demand for biomass. Even though this comes with a higher EF due to LUC emissions, still net GHG benefits are larger. Bioenergy with carbon capture and storage (BECCS) can lead to negative emissions, and is seen as an important option to decarbonize energy systems. Its potential decarbonization contribution depends on low-carbon resource availability, its ability to meet end-use demand and the geological storage potential to safely trap CO 2. Here an energy system model is used to assess the BECCS decarbonization potential in Brazil, considering uncertainty in low-carbon biomass resources, and storage potential, injection rates and costs of CO 2 storage, assessed in eight scenarios. A spatial explicit analysis is done to make improved estimates on the storage potential, injection rates, and costs for CO 2 storage in the Rio Bonito saline aquifer of the Paraná basin. Although there are large differences in storage potential (12–117 Gt CO 2) and costs (on average 5–15 $/t CO 2), the accumulated volume of CO 2 stored between 2010 and 2050 is 2.9 Gt CO 2 for all scenarios, with injection rates around 240 Mt CO 2 in 2050. This shows that BECCS is a cost-competitive option to decarbonize the Brazilian energy system, even under pessimistic estimates of CO 2 storage potential and costs, and low biomass availability. The cheapest sink locations are selected, in the high development scenario. When CCS development is low, injection rates are the limiting factor. Locations are selected with the highest injection rates, even though sometimes more expensive. When CO 2 storage is limited, total system costs increase, mainly because decarbonization of the industry and freight transport sector relies on more expensive decarbonization options such as green hydrogen. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon sequestration potential of the clay fraction. • Determination of the carbon saturation deficit of each mineral of the clay fraction. • Identification of the equation for the prediction of carbon sequestration potential. • Identification of land uses with the greatest carbon sequestration potential. The capacity of soil to sequester carbon (C) is a key process that promotes the reduction of CO 2 in the atmosphere. Soils can absorb as much as 20% of anthropogenic carbon emissions, which can contribute to mitigate climate change. This capacity relies on the organo-mineral association, which includes different minerals, Fe and Al oxides, which have a critical soil organic carbon (SOC) sorption surface. Based on an equation of the potential C saturation deficit of fine soil particles (<20 μm/silt and clay fractions) for tropical regions, this study investigated the SOC sequestration potential of the clay fraction for soils in Piracicaba region, São Paulo State, Brazil as influenced by the clay minerals. This potential was fitted to a spatial regression model for soil depths 0–20 cm and 80 to 100 cm. In the surface layer, the sequestration potential was mostly explained by the relative abundance of soil minerals (Kaolinite, Hematite, Goethite and Gibbsite) determined using vis-NIR-SWIR spectroscopy. A direct relationship was observed with Goethite and Gibbsite, indicating that low concentrations would reduce the sequestration potential. At 80 to 100 cm depth, Kaolinite and Hematite explained most variation in SOC sequestration potential. Additionally, the C associated with the mineral fraction and the C saturation potential as a function of minerals were modeled and a strong importance of hematite in the C sequestration and stabilization cycle was identified at both depths. The individual mineral contribution to SOC sequestration potential was also mapped, which identified high contributions of goethite and gibbsite for deep soil layers. The influence of land use on the carbon sequestration potential of minerals was observed, with the greatest potential being found in areas with pasture and cropping mosaics and grassland and forest mosaics, with a high presence of kaolinite and hematite. These minerals have a greater potential for carbon sequestration at greater depths and, therefore, could be critical in climate change mitigation strategies. [ABSTRACT FROM AUTHOR]

Bioenergy production from sugarcane can be one of the sustainable means of mitigating climate change. This was the central idea of the Conference, "Carbon Balance in the Sugar-Energy Sector," held in Brazil on September 14, 2021. The various panels showed that sugarcane stakeholders, including scientists, farmers, industrialists, and investors, are committed to making large-scale sugarcane production a key ingredient in the mitigation of climate change. Their strategies include sustainable land use and management practices to increase soil carbon sequestration; the large-scale production of biofuel, bioelectricity and bioproducts; negative emission industrial technologies; industrial waste recycling; and sector-specific policies rewarding farmers with carbon credits for avoided greenhouse gas emissions. Therefore, the sugarcane sector is not only key to promoting the social-economic development of Brazil, but also to promoting energy transition, curbing greenhouse gas emissions and consequently, reducing global warming and climate change. • Conference Report: 2021 Carbon balance in the sugar-energy sector. • Carbon Balance in the Sugar-Energy Sector 2021 Conference held by Luiz de Queiroz College of Agriculture (Esalq), University of São Paulo (USP), Piracicaba-SP, Brazil on September 14, 2021. • Sugarcane-derived bioenergy is a key ingredient in fighting climate change while simultaneously maintaining a balanced ecosystem (including enhanced soil health and increased capacity to sequester carbon) and promoting socio-economic development [ABSTRACT FROM AUTHOR]

Mangrove deforestation by land use conversions is the greatest threat to the conservation of coastal ecosystems, ranking Brazil as a country with high gross annual CO 2 emissions. Despite the recognized socio-ecological importance in providing essential ecosystem services (e.g., erosion prevention, protection against extreme weather events, provision of habitats for estuarine species, and blue carbon storage), mangroves have been converted from blue carbon sinks to sources. Here, we modelled and evaluated the spatial-temporal changes in blue carbon stocks and net sequestration potential in mangrove forests in Santos and São Vicente, Brazil, from 1988 to 2050. We used classified images obtained from MapBiomas and the InVEST Coastal Blue Carbon model, which quantifies the potential carbon sequestered in the study area based on changes in the land use and land cover over the determined study period. We found an increased trend in carbon stocks and net sequestration of mangroves in both municipalities. Over the analysis period, carbon stocks in the mangroves of the city of Santos increased 29% in total, while we found a smaller rise (14%) in São Vicente. We found that land use changed substantially during 1988 until 2018, with mangrove extent varying in the region from 3,375 ha in 1988 to 3,764 ha in 2018 within the entire study region. Overall, the net carbon sequestration was approximately 925,393 Mg CO 2 e and 287,130 Mg CO 2 e, in Santos and São Vicente, respectively, over a period from 1988 to 2050. To our knowledge, this study is the first to quantify soil carbon stock and accumulation in mangroves along an urban coastal landscape in Brazil and emphasizes the current and future role of mangroves in climate change mitigation. Our findings can support the development of public policies for mangrove conservation and restoration actions to mitigate climate impacts. • Land conversion is the main cause of mangrove deforestation in urban areas. • Net carbon sequestration has increased 29% and 14% in Santos and São Vicente. • Mangrove extent in the region varied from 3,375 ha in 1988 to 3,764 ha in 2018. • Net carbon sequestration may be as high as 925,393 Mg CO 2 e over 62 years. [ABSTRACT FROM AUTHOR]

During the past few decades, commercial silvopastoral systems (SPS) with exotic Eucalyptus (hybrid) trees have become popular in the Brazilian Cerrado (savanna). With the increasing awareness about the role of carbon (C) storage in soils as a climate-change mitigation strategy and the relationship between the nature of soil aggregates and the soil's carbon sequestration potential, it is important to understand the influence of such SPS systems on soil organic carbon (SOC) storage. We studied C content in three aggregate size classes in six land-use systems on Oxisols in Minas Gerais, Brazil. The systems were planted forest, native secondary forest, managed pasture, and three 8-year-old SPS, differing in their tree-planting configurations. Eucalyptus hybrid was the tree in SPS and planted forest treatments, and Urochloa decumbens was the grass in SPS and pasture treatments. From each treatment, replicated soil samples were collected from four depth-classes (0–10, 10–30, 30–60, and 60–100 cm), fractionated by wet sieving into the three aggregate-size classes, 2000 to 250 μm, 250 to 53 μm, and <53 μm size classes representing macroaggregates, microaggregates, and silt + clay, respectively, and their C contents determined. Down to 1 m, total SOC stock values ranged from 260 Mg ha−1 under pasture to 167 Mg ha−1 under native forest, with 174 Mg ha−1 for Eucalyptus plantation and about 195 Mg ha−1 for the three SPS. Compared to the degraded native forest, the pasture system had significantly higher SOC in the whole soil and the aggregate size fractions, especially in the lower soil-depth classes. The lower SOC stock of Eucalyptus hybrid SPS compared to open pasture differs from the general trend of SPS having higher stock. Given that the Cerrado biome is a biodiversity hotspot, the use of native nitrogen-fixing trees, of which there are several, is worth investigating. In addition, the conversion from Eucalyptus monocultures to SPS could be considered as a strategy to increase the SOC stock. • Soil C stock up to 1 m depth was significantly higher under pasture (260 Mg ha−1). • Pasture differed from other treatments in terms of soil C stock in deeper profiles. • Eucalyptus silvopastures had an intermediate level of soil C stock (∼195 Mg ha−1). • Macroaggregates stored most of the soil C stock, more so in the pasture treatment. [ABSTRACT FROM AUTHOR]

• The questionnaire assessed environmental awareness and knowledge about CCS technology. • The interviews were conducted using a face-to-face approach. • A structured research was employed using an ordinal qualitative scale. • Respondents were aware of the climate change. • Climate change mitigation actions are not a priority for respondents. Carbon Capture and Storage (CCS) is considered an important option to mitigate climate change. However, the success of the new technology does not only depend on engineering practices and techniques but also involves social, political, and economic factors, as well as public acceptance. The discussion about CCS in Brazil is recent and few papers addressing Brazilian public perception and engagement with CCS were found. In this sense, this paper aims to analyze the environmental awareness about climate change and the citizens' perception of CCS technology. A public perception survey was conducted with 800 people in two Brazilian cities. Descriptive statistical techniques combined with hypothesis tests were performed to depict the results and to verify associations between different demographic groups to climate change issues and support for the development of CCS technology in Brazil. The results show that the public is aware of climate change and its consequences. However, despite public support for governmental development and investments in CCS technology, investments to mitigate climate change are not a priority for the population. Only 2% and 5% of interviewed citizens in the cities of São Mateus and Vitória, respectively, considered investments in climate change mitigation as a priority. More than 70% of respondents considered that other social elements, as health, public safety, and job creation, should be prioritized by the Brazilian government. The results suggest that the population needs more information about CCS technology and its impacts. [Display omitted] [ABSTRACT FROM AUTHOR]