Fragmentation-Driven Divergent Trends in Burned Area in Amazonia and Cerrado

This is the final version. Available on open access from Frontiers Media via the DOI in this recordData Availability Statement: The original contributions presented in the study are included in the article/Supplementary Material; further inquiries can be directed to the corresponding author.The two major Brazilian biomes, the Amazonia and the Cerrado (savanna), are increasingly exposed to fires. The Amazonian Forest is a fire sensitive ecosystem where fires are a typically rare disturbance while the Cerrado is naturally fire-dependent. Human activities, such as landscape fragmentation and land-use management, have modified the fire regime of the Cerrado and introduced fire into the Amazonian Forest. There is limited understanding of the role of landscape fragmentation on fire occurrence in the Amazonia and Cerrado biomes. Due to differences in vegetation structure, composition, and land use characteristics in each biome, we hypothesize that the emerging burned area (BA) patterns will result from biome-specific fire responses to fragmentation. The aim of this study was to test the general relationship between BA, landscape fragmentation, and agricultural land in the Amazonia and the Cerrado biomes. To estimate the trends and status of landscape fragmentation a Forest Area Density (FAD) index was calculated based on the MapBiomas land cover dataset for both biomes between 2002 and 2018. BA fraction was analyzed within native vegetation against the FAD and agricultural land fraction. Our results showed an increase in landscape fragmentation across 16% of Amazonia and 15% of Cerrado. We identified an opposite relationship between BA fraction, and landscape fragmentation and agricultural fraction contrasting the two biomes. For Amazonia, both landscape fragmentation and agricultural fraction increased BA fraction due to an increase of human ignition activities. For the Cerrado, on the other hand, an increase in landscape fragmentation and agricultural fraction caused a decrease in BA fraction within the native vegetation. For both biomes, we found that during drought years BA increases whilst the divergent trends driven by fragmentation in the two contrasting global biomes is maintained. This understanding will be critical to informing the representation of fire dynamics in fire-enable Dynamic Global Vegetation Models and Earth System Models for climate projection and future ecosystem service provision.Newton FundESA Climate Change InitiativeEuropean Union Horizon 2020Natural Environment Research Council (NERC

Impacts of ground-level ozone on sugarcane production

This is the final version. Available on open access from Elsevier via the DOI in this recordData availability: Data will be made available on request.Sugarcane is a vital commodity crop often grown in (sub)tropical regions which have been experiencing a recent deterioration in air quality. Unlike for other commodity crops, the risk of air pollution, specifically ozone (O3), to this C4 crop has not yet been quantified. Yet, recent work has highlighted both the potential risks of O3 to C4 bioenergy crops, and the emergence of O3 exposure across the tropics as a vital factor determining global food security. Given the large extent, and planned expansion of sugarcane production in places like Brazil to meet global demand for biofuels, there is a pressing need to characterize the risk of O3 to the industry. In this study, we sought to a) derive sugarcane O3 dose-response functions across a range of realistic O3 exposure and b) model the implications of this across a globally important production area. We found a significant impact of O3 on biomass allocation (especially to leaves) and production across a range of sugarcane genotypes, including two commercially relevant varieties (e.g. CTC4, Q240). Using these data, we calculated dose-response functions for sugarcane and combined them with hourly O3 exposure across south-central Brazil derived from the UK Earth System Model (UKESM1) to simulate the current regional impact of O3 on sugarcane production using a dynamic global vegetation model (JULES vn 5.6). We found that between 5.6 % and 18.3 % of total crop productivity is likely lost across the region due to the direct impacts of current O3 exposure. However, impacts depended critically on the substantial differences in O3 susceptibility observed among sugarcane genotypes and how these were implemented in the model. Our work highlights not only the urgent need to fully elucidate the impacts of O3 in this important bioenergetic crop, but the potential implications air quality may have upon tropical food production more generally.Natural Environment Research Council (NERC)FAPESPCNRMet Office Hadley Centre Climate ProgrammeMet Offic

A multi-data assessment of land use and land cover emissions from Brazil during 2000–2019

This is the final version. Available on open access from IOP Publishing via the DOI in this recordData availability statement: The data that support the findings of this study are available upon reasonable request from the authors.Brazil is currently the largest contributor of land use and land cover change (LULCC) carbon dioxide net emissions worldwide, representing 17%-29% of the global total. There is, however, a lack of agreement among different methodologies on the magnitude and trends in LULCC emissions and their geographic distribution. Here we perform an evaluation of LULCC datasets for Brazil, including those used in the annual global carbon budget (GCB), and national Brazilian assessments over the period 2000-2018. Results show that the latest global HYDE 3.3 LULCC dataset, based on new FAO inventory estimates and multi-annual ESA CCI satellite-based land cover maps, can represent the observed spatial variation in LULCC over the last decades, representing an improvement on the HYDE 3.2 data previously used in GCB. However, the magnitude of LULCC assessed with HYDE 3.3 is lower than estimates based on MapBiomas. We use HYDE 3.3 and MapBiomas as input to a global bookkeeping model (bookkeeping of land use emission, BLUE) and a process-based Dynamic Global Vegetation Model (JULES-ES) to determine Brazil's LULCC emissions over the period 2000-2019. Results show mean annual LULCC emissions of 0.1-0.4 PgC yr-1, compared with 0.1-0.24 PgC yr-1 reported by the Greenhouse Gas Emissions Estimation System of land use changes and forest sector (SEEG/LULUCF) and by FAO in its latest assessment of deforestation emissions in Brazil. Both JULES-ES and BLUE now simulate a slowdown in emissions after 2004 (-0.006 and -0.004 PgC yr-2 with HYDE 3.3, -0.014 and -0.016 PgC yr-2 with MapBiomas, respectively), in agreement with the Brazilian INPE-EM, global Houghton and Nassikas book-keeping models, FAO and as reported in the 4th national greenhouse gas inventories. The inclusion of Earth observation data has improved spatial representation of LULCC in HYDE and thus model capability to simulate Brazil's LULCC emissions. This will likely contribute to reduce uncertainty in global LULCC emissions, and thus better constrains GCB assessments

Synthesis of the land carbon fluxes of the Amazon region between 2010 and 2020

The Amazon is the largest continuous tropical forest in the world and plays a key role in the global carbon cycle. Human-induced disturbances and climate change have impacted the Amazon carbon balance. Here we conduct a comprehensive synthesis of existing state-of-the-art estimates of the contemporary land carbon fluxes in the Amazon using a set of bottom-up methods (i.e., dynamic vegetation models and bookkeeping models) and a top-down inversion (atmospheric inversion model) over the Brazilian Amazon and the whole biogeographical Amazon domain. Over the whole biogeographical Amazon region bottom-up methodologies suggest a small average carbon sink over 2010-2020, in contrast to a small carbon source simulated by top8 down inversion (2010-2018). However, these estimates are not significantly different from one another when accounting for their large individual uncertainties, highlighting remaining knowledge gaps, and the urgent need to reduce such uncertainties. Nevertheless, both methodologies agreed that the Brazilian Amazon has been a net carbon source during recent climate extremes and that the south-eastern Amazon was a net land carbon source over the whole study period (2010-2020). Overall, our results point to increasing human-induced disturbances (deforestation and forest degradation by wildfires) and reduction in the old-growth forest sink during drought

Synthesis of the land carbon fluxes of the Amazon region between 2010 and 2020

This is the final version. Available on open access from Nature Research via the DOI in this recordData availability: The spatial dataset of the main figures are available in a raster format and can be found at https://doi.org/10.5281/zenodo.10423522. The annual carbon fluxes from each model used in this research (disturbances, old-growth sink and net flux) for the Brazilian Amazon and whole Biogeographical Amazon are available at https://doi.org/10.5281/zenodo.8348434.Code availability: The code and tables used to reproduce the main paper graphics of Figs. 2a, b, 3a, b, 4a and 5a are available in Zenodo https://doi.org/10.5281/zenodo.8348435. Further editions to combine the layout of graphics and maps were made in a design software (InkScape).The Amazon is the largest continuous tropical forest in the world and plays a key role in the global carbon cycle. Human-induced disturbances and climate change have impacted the Amazon carbon balance. Here we conduct a comprehensive synthesis of existing state-of-the-art estimates of the contemporary land carbon fluxes in the Amazon using a set of bottom-up methods (i.e., dynamic vegetation models and bookkeeping models) and a top-down inversion (atmospheric inversion model) over the Brazilian Amazon and the whole Biogeographical Amazon domain. Over the whole biogeographical Amazon region bottom-up methodologies suggest a small average carbon sink over 2010-2020, in contrast to a small carbon source simulated by top-down inversion (2010-2018). However, these estimates are not significantly different from one another when accounting for their large individual uncertainties, highlighting remaining knowledge gaps, and the urgent need to reduce such uncertainties. Nevertheless, both methodologies agreed that the Brazilian Amazon has been a net carbon source during recent climate extremes and that the south-eastern Amazon was a net land carbon source over the whole study period (2010-2020). Overall, our results point to increasing human-induced disturbances (deforestation and forest degradation by wildfires) and reduction in the old-growth forest sink during drought.Newton FundRECCAP2 projectEuropean Union Horizon 2020UK National Centre for Earth ObservationState of Sao Paulo Science Foundation (FAPESP

A comparative study of the contemporary carbon cycle and underlying human disturbance processes in the Brazilian ecosystems

Brazilian ecosystems are facing major threats to their conservation and functioning from human induced disturbances in combination with climate change. The two largest Brazilian ecosystems, the Amazon Forest and Cerrado, lost together approximately 15,690 km2 year-1 of their intact vegetation cover between 2010 and 2020 (equivalent to 12% year-1 of England area), with an intensification of vegetation loss from 2019. Brazil is responsible for the largest carbon dioxide emissions from land use and land cover changes (LULCC). Still, uncertainties arise in global carbon budget assessments on the magnitude and trends of these disturbance fluxes and its impacts on the carbon balance. In this thesis, I investigate the components of human disturbance and how they impact the contemporary carbon cycle of Brazilian ecosystems, such as LULCC, as well the relationship between fire occurrence and landscape fragmentation. The thesis ends with a synthesis of the contemporary net land carbon balance of the Amazon using a set of state-of-the-art estimates from different methodological approaches. In chapter 2 I attempt to reconcile estimates of LULCC emissions for Brazil. I first evaluated new global LULCC maps used in global bookkeeping and Dynamic Global Vegetation Models (DGVMs) from the Global Carbon Budget (GCB) assessments for Brazil. These new maps were based on Food Agriculture Organization (FAO) statistics combined with multi-year land cover data from the European Space Agency. I found good spatial agreement between the global LULCC maps with MapBiomas, the Brazilian remote sensing based LULCC maps. However, the global LULCC dataset still failed to capture the magnitude and recent increase in deforestation in Brazil. This is due to the method used to infer deforestation from agricultural area change reported to FAO in addition the use of a simple linear trend to extrapolate beyond the final census year. The findings of this study have been welcomed by the global land modelling community and led to the subsequent adoption of MapBiomas in the Global Carbon Budget assessment for 2022 (GCB2022). Conversion of intact vegetation cover to other land uses induce landscape fragmentation and fire spread. In chapter 3, I test the relationship between fire occurrence within intact vegetation fragments and the degree of landscape fragmentation in the two major and contrasting Brazilian ecosystems (Amazon and Cerrado). I found that there is an ecosystem-specific relationship between burned area fraction within intact vegetation fragments and landscape fragmentation induced by human activity. I find that fire occurrence within intact vegetation fragments associated to landscape fragmentation has an opposite relationship when comparing Amazon and Cerrado. These human-induced disturbances cause large losses of carbon to the atmosphere, thus impacting the carbon balance of tropical areas. Building on all the findings of chapters 2 and 3, in chapter 4, I use the latest data from a set of regional and global models to attribute and synthesise the contemporary net land carbon balance of Amazon. The different approaches agree that the south-eastern Amazonia is a net carbon source to the atmosphere. Bottom-up approaches suggest that Brazilian Amazonia was a net land carbon source in 2020 due to an increase in deforestation and fire emissions. Given the large uncertainties from the models and remaining knowledge gaps, there is insufficient data to reject the hypothesis that the Amazon was not neutral between 2010 and 2018. In conclusion, this thesis reconciles diverging estimates of land use and land cover emissions of Brazil in global carbon budget assessments. Moreover, this thesis brings together state-of-the art estimates of the Amazon carbon budget using bottom-up and top-down models and the knowledge gaps to reconcile them. Finally, I highlight the importance of the use of remote sensing data to constrain global estimates of land use and land cover change datasets and emissions. This thesis also demonstrates divergent fragmentation-fire relationships in the two major and contrasting Brazilian biomes. The results present in this thesis have important implications for the mitigation potential of Brazilian ecosystems within the goals of Paris Agreement

Extensive twenty-first century woody encroachment in South America’s Savanna

Woody encroachment is occurring in all tropical savannas of the world. However, in the Brazilian savanna (the Cerrado), the extent of this phenomenon is still poorly documented. Here, woody encroachment was quantified throughout the Cerrado biome and transitional ecotones using a trend analysis of the annual maximum of Enhanced Vegetation Index (EVI) obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS). The associations with potential local drivers, such as fire and land use regime, were assessed using satellite data of land cover and fire regime. We found that 19% of the remaining native vegetation showed significant evidence of woody encroachment in the last 15 years, and 7% exhibited degradation processes. The local factors that favored woody expansion in 19% of the biome were a decrease of fire (34%) and land use abandonment (26%). Our study highlights that local human‐associated drivers are playing a major role in woody encroachment and savanna degradation