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1.
Nat Immunol ; 22(3): 347-357, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33432229

RESUMO

Activated Vγ9Vδ2 (γδ2) T lymphocytes that sense parasite-produced phosphoantigens are expanded in Plasmodium falciparum-infected patients. Although previous studies suggested that γδ2 T cells help control erythrocytic malaria, whether γδ2 T cells recognize infected red blood cells (iRBCs) was uncertain. Here we show that iRBCs stained for the phosphoantigen sensor butyrophilin 3A1 (BTN3A1). γδ2 T cells formed immune synapses and lysed iRBCs in a contact, phosphoantigen, BTN3A1 and degranulation-dependent manner, killing intracellular parasites. Granulysin released into the synapse lysed iRBCs and delivered death-inducing granzymes to the parasite. All intra-erythrocytic parasites were susceptible, but schizonts were most sensitive. A second protective γδ2 T cell mechanism was identified. In the presence of patient serum, γδ2 T cells phagocytosed and degraded opsonized iRBCs in a CD16-dependent manner, decreasing parasite multiplication. Thus, γδ2 T cells have two ways to control blood-stage malaria-γδ T cell antigen receptor (TCR)-mediated degranulation and phagocytosis of antibody-coated iRBCs.


Assuntos
Antígenos de Protozoários/imunologia , Citotoxicidade Imunológica , Eritrócitos/imunologia , Linfócitos Intraepiteliais/imunologia , Ativação Linfocitária , Malária Falciparum/imunologia , Fagocitose , Plasmodium falciparum/microbiologia , Antígenos CD/metabolismo , Antígenos de Diferenciação de Linfócitos T/metabolismo , Antígenos de Protozoários/sangue , Boston , Brasil , Butirofilinas/metabolismo , Células Cultivadas , Eritrócitos/metabolismo , Eritrócitos/parasitologia , Feminino , Granzimas/metabolismo , Interações Hospedeiro-Parasita , Humanos , Sinapses Imunológicas/metabolismo , Sinapses Imunológicas/parasitologia , Linfócitos Intraepiteliais/metabolismo , Linfócitos Intraepiteliais/parasitologia , Malária Falciparum/sangue , Malária Falciparum/parasitologia , Masculino , Plasmodium falciparum/crescimento & desenvolvimento
2.
Cell ; 172(6): 1160-1162, 2018 03 08.
Artigo em Inglês | MEDLINE | ID: mdl-29522736

RESUMO

The emergence and spread of Zika virus in the Americas continues to challenge our disease surveillance systems. Virus genome sequencing during the epidemic uncovered the timescale of Zika virus transmission and spread. Yet, we are only beginning to explore how genomics can enhance our responses to emerging viruses.


Assuntos
Genoma Viral/genética , Genômica/métodos , Infecção por Zika virus/transmissão , Zika virus/genética , América/epidemiologia , Brasil/epidemiologia , Doenças Transmissíveis Emergentes/epidemiologia , Doenças Transmissíveis Emergentes/transmissão , Doenças Transmissíveis Emergentes/virologia , Epidemias , Geografia , Humanos , Zika virus/patogenicidade , Infecção por Zika virus/virologia
3.
Cell ; 169(4): 597-609.e11, 2017 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-28475892

RESUMO

Antibodies to Zika virus (ZIKV) can be protective. To examine the antibody response in individuals who develop high titers of anti-ZIKV antibodies, we screened cohorts in Brazil and Mexico for ZIKV envelope domain III (ZEDIII) binding and neutralization. We find that serologic reactivity to dengue 1 virus (DENV1) EDIII before ZIKV exposure is associated with increased ZIKV neutralizing titers after exposure. Antibody cloning shows that donors with high ZIKV neutralizing antibody titers have expanded clones of memory B cells that express the same immunoglobulin VH3-23/VK1-5 genes. These recurring antibodies cross-react with DENV1, but not other flaviviruses, neutralize both DENV1 and ZIKV, and protect mice against ZIKV challenge. Structural analyses reveal the mechanism of recognition of the ZEDIII lateral ridge by VH3-23/VK1-5 antibodies. Serologic testing shows that antibodies to this region correlate with serum neutralizing activity to ZIKV. Thus, high neutralizing responses to ZIKV are associated with pre-existing reactivity to DENV1 in humans.


Assuntos
Anticorpos Neutralizantes/química , Anticorpos Antivirais/química , Infecção por Zika virus/imunologia , Animais , Anticorpos Neutralizantes/sangue , Anticorpos Neutralizantes/imunologia , Anticorpos Antivirais/sangue , Anticorpos Antivirais/imunologia , Linfócitos B/imunologia , Brasil , Feminino , Humanos , Memória Imunológica , Leucócitos Mononucleares/imunologia , Masculino , México , Camundongos , Infecção por Zika virus/sangue
4.
Cell ; 166(1): 2-4, 2016 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-27368092

RESUMO

The Zika virus (ZIKV) outbreak has stimulated collaborations between Brazilians, researchers from other South American countries, and scientists from around the world. The Brazilian response to the HIV/AIDS epidemic demonstrates capabilities that can be applied to the study of ZIKV and provides lessons for developing effective international infectious disease research collaborations.


Assuntos
Síndrome da Imunodeficiência Adquirida/virologia , Pesquisa Biomédica , Infecção por Zika virus/virologia , Síndrome da Imunodeficiência Adquirida/epidemiologia , Síndrome da Imunodeficiência Adquirida/fisiopatologia , Síndrome da Imunodeficiência Adquirida/terapia , Brasil/epidemiologia , Humanos , Cooperação Internacional , Infecção por Zika virus/epidemiologia , Infecção por Zika virus/fisiopatologia
5.
Nature ; 629(8010): 114-120, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38538797

RESUMO

Mountain ranges contain high concentrations of endemic species and are indispensable refugia for lowland species that are facing anthropogenic climate change1,2. Forecasting biodiversity redistribution hinges on assessing whether species can track shifting isotherms as the climate warms3,4. However, a global analysis of the velocities of isotherm shifts along elevation gradients is hindered by the scarcity of weather stations in mountainous regions5. Here we address this issue by mapping the lapse rate of temperature (LRT) across mountain regions globally, both by using satellite data (SLRT) and by using the laws of thermodynamics to account for water vapour6 (that is, the moist adiabatic lapse rate (MALRT)). By dividing the rate of surface warming from 1971 to 2020 by either the SLRT or the MALRT, we provide maps of vertical isotherm shift velocities. We identify 17 mountain regions with exceptionally high vertical isotherm shift velocities (greater than 11.67 m per year for the SLRT; greater than 8.25 m per year for the MALRT), predominantly in dry areas but also in wet regions with shallow lapse rates; for example, northern Sumatra, the Brazilian highlands and southern Africa. By linking these velocities to the velocities of species range shifts, we report instances of close tracking in mountains with lower climate velocities. However, many species lag behind, suggesting that range shift dynamics would persist even if we managed to curb climate-change trajectories. Our findings are key for devising global conservation strategies, particularly in the 17 high-velocity mountain regions that we have identified.


Assuntos
Altitude , Migração Animal , Biodiversidade , Mapeamento Geográfico , Aquecimento Global , Animais , África Austral , Brasil , Conservação dos Recursos Naturais , Aquecimento Global/estatística & dados numéricos , Umidade , Indonésia , Chuva , Refúgio de Vida Selvagem , Imagens de Satélites , Especificidade da Espécie , Temperatura , Fatores de Tempo
6.
Nature ; 627(8002): 182-188, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38267579

RESUMO

The origins of treponemal diseases have long remained unknown, especially considering the sudden onset of the first syphilis epidemic in the late 15th century in Europe and its hypothesized arrival from the Americas with Columbus' expeditions1,2. Recently, ancient DNA evidence has revealed various treponemal infections circulating in early modern Europe and colonial-era Mexico3-6. However, there has been to our knowledge no genomic evidence of treponematosis recovered from either the Americas or the Old World that can be reliably dated to the time before the first trans-Atlantic contacts. Here, we present treponemal genomes from nearly 2,000-year-old human remains from Brazil. We reconstruct four ancient genomes of a prehistoric treponemal pathogen, most closely related to the bejel-causing agent Treponema pallidum endemicum. Contradicting the modern day geographical niche of bejel in the arid regions of the world, the results call into question the previous palaeopathological characterization of treponeme subspecies and showcase their adaptive potential. A high-coverage genome is used to improve molecular clock date estimations, placing the divergence of modern T. pallidum subspecies firmly in pre-Columbian times. Overall, our study demonstrates the opportunities within archaeogenetics to uncover key events in pathogen evolution and emergence, paving the way to new hypotheses on the origin and spread of treponematoses.


Assuntos
Evolução Molecular , Genoma Bacteriano , Treponema pallidum , Infecções por Treponema , Humanos , Brasil/epidemiologia , Brasil/etnologia , Europa (Continente)/epidemiologia , Genoma Bacteriano/genética , História do Século XV , História Antiga , Sífilis/epidemiologia , Sífilis/história , Sífilis/microbiologia , Sífilis/transmissão , Treponema pallidum/classificação , Treponema pallidum/genética , Treponema pallidum/isolamento & purificação , Infecções por Treponema/epidemiologia , Infecções por Treponema/história , Infecções por Treponema/microbiologia , Infecções por Treponema/transmissão
7.
Nature ; 631(8019): 111-117, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38898277

RESUMO

Amazonia contains the most extensive tropical forests on Earth, but Amazon carbon sinks of atmospheric CO2 are declining, as deforestation and climate-change-associated droughts1-4 threaten to push these forests past a tipping point towards collapse5-8. Forests exhibit complex drought responses, indicating both resilience (photosynthetic greening) and vulnerability (browning and tree mortality), that are difficult to explain by climate variation alone9-17. Here we combine remotely sensed photosynthetic indices with ground-measured tree demography to identify mechanisms underlying drought resilience/vulnerability in different intact forest ecotopes18,19 (defined by water-table depth, soil fertility and texture, and vegetation characteristics). In higher-fertility southern Amazonia, drought response was structured by water-table depth, with resilient greening in shallow-water-table forests (where greater water availability heightened response to excess sunlight), contrasting with vulnerability (browning and excess tree mortality) over deeper water tables. Notably, the resilience of shallow-water-table forest weakened as drought lengthened. By contrast, lower-fertility northern Amazonia, with slower-growing but hardier trees (or, alternatively, tall forests, with deep-rooted water access), supported more-drought-resilient forests independent of water-table depth. This functional biogeography of drought response provides a framework for conservation decisions and improved predictions of heterogeneous forest responses to future climate changes, warning that Amazonia's most productive forests are also at greatest risk, and that longer/more frequent droughts are undermining multiple ecohydrological strategies and capacities for Amazon forest resilience.


Assuntos
Resistência à Seca , Secas , Florestas , Água Subterrânea , Fotossíntese , Solo , Luz Solar , Árvores , Brasil , Sequestro de Carbono , Secas/estatística & dados numéricos , Água Subterrânea/análise , Solo/química , Árvores/classificação , Árvores/metabolismo , Árvores/fisiologia , Clima Tropical , Resistência à Seca/fisiologia , Filogeografia , Conservação dos Recursos Naturais
8.
Nature ; 621(7977): 105-111, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37612501

RESUMO

The critical temperature beyond which photosynthetic machinery in tropical trees begins to fail averages approximately 46.7 °C (Tcrit)1. However, it remains unclear whether leaf temperatures experienced by tropical vegetation approach this threshold or soon will under climate change. Here we found that pantropical canopy temperatures independently triangulated from individual leaf thermocouples, pyrgeometers and remote sensing (ECOSTRESS) have midday peak temperatures of approximately 34 °C during dry periods, with a long high-temperature tail that can exceed 40 °C. Leaf thermocouple data from multiple sites across the tropics suggest that even within pixels of moderate temperatures, upper canopy leaves exceed Tcrit 0.01% of the time. Furthermore, upper canopy leaf warming experiments (+2, 3 and 4 °C in Brazil, Puerto Rico and Australia, respectively) increased leaf temperatures non-linearly, with peak leaf temperatures exceeding Tcrit 1.3% of the time (11% for more than 43.5 °C, and 0.3% for more than 49.9 °C). Using an empirical model incorporating these dynamics (validated with warming experiment data), we found that tropical forests can withstand up to a 3.9 ± 0.5 °C increase in air temperatures before a potential tipping point in metabolic function, but remaining uncertainty in the plasticity and range of Tcrit in tropical trees and the effect of leaf death on tree death could drastically change this prediction. The 4.0 °C estimate is within the 'worst-case scenario' (representative concentration pathway (RCP) 8.5) of climate change predictions2 for tropical forests and therefore it is still within our power to decide (for example, by not taking the RCP 6.0 or 8.5 route) the fate of these critical realms of carbon, water and biodiversity3,4.


Assuntos
Aclimatação , Calor Extremo , Florestas , Fotossíntese , Árvores , Clima Tropical , Aclimatação/fisiologia , Austrália , Brasil , Calor Extremo/efeitos adversos , Aquecimento Global , Fotossíntese/fisiologia , Porto Rico , Desenvolvimento Sustentável/legislação & jurisprudência , Desenvolvimento Sustentável/tendências , Árvores/fisiologia , Folhas de Planta/fisiologia , Incerteza
9.
Nature ; 621(7978): 318-323, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37612502

RESUMO

The Amazon forest carbon sink is declining, mainly as a result of land-use and climate change1-4. Here we investigate how changes in law enforcement of environmental protection policies may have affected the Amazonian carbon balance between 2010 and 2018 compared with 2019 and 2020, based on atmospheric CO2 vertical profiles5,6, deforestation7 and fire data8, as well as infraction notices related to illegal deforestation9. We estimate that Amazonia carbon emissions increased from a mean of 0.24 ± 0.08 PgC year-1 in 2010-2018 to 0.44 ± 0.10 PgC year-1 in 2019 and 0.52 ± 0.10 PgC year-1 in 2020 (± uncertainty). The observed increases in deforestation were 82% and 77% (94% accuracy) and burned area were 14% and 42% in 2019 and 2020 compared with the 2010-2018 mean, respectively. We find that the numbers of notifications of infractions against flora decreased by 30% and 54% and fines paid by 74% and 89% in 2019 and 2020, respectively. Carbon losses during 2019-2020 were comparable with those of the record warm El Niño (2015-2016) without an extreme drought event. Statistical tests show that the observed differences between the 2010-2018 mean and 2019-2020 are unlikely to have arisen by chance. The changes in the carbon budget of Amazonia during 2019-2020 were mainly because of western Amazonia becoming a carbon source. Our results indicate that a decline in law enforcement led to increases in deforestation, biomass burning and forest degradation, which increased carbon emissions and enhanced drying and warming of the Amazon forests.


Assuntos
Dióxido de Carbono , Sequestro de Carbono , Conservação dos Recursos Naturais , Política Ambiental , Aplicação da Lei , Floresta Úmida , Biomassa , Brasil , Dióxido de Carbono/análise , Dióxido de Carbono/metabolismo , Política Ambiental/legislação & jurisprudência , Atmosfera/química , Incêndios Florestais/estatística & dados numéricos , Conservação dos Recursos Naturais/estatística & dados numéricos , El Niño Oscilação Sul , Secas/estatística & dados numéricos
10.
Nature ; 615(7952): 436-442, 2023 03.
Artigo em Inglês | MEDLINE | ID: mdl-36922608

RESUMO

The globally important carbon sink of intact, old-growth tropical humid forests is declining because of climate change, deforestation and degradation from fire and logging1-3. Recovering tropical secondary and degraded forests now cover about 10% of the tropical forest area4, but how much carbon they accumulate remains uncertain. Here we quantify the aboveground carbon (AGC) sink of recovering forests across three main continuous tropical humid regions: the Amazon, Borneo and Central Africa5,6. On the basis of satellite data products4,7, our analysis encompasses the heterogeneous spatial and temporal patterns of growth in degraded and secondary forests, influenced by key environmental and anthropogenic drivers. In the first 20 years of recovery, regrowth rates in Borneo were up to 45% and 58% higher than in Central Africa and the Amazon, respectively. This is due to variables such as temperature, water deficit and disturbance regimes. We find that regrowing degraded and secondary forests accumulated 107 Tg C year-1 (90-130 Tg C year-1) between 1984 and 2018, counterbalancing 26% (21-34%) of carbon emissions from humid tropical forest loss during the same period. Protecting old-growth forests is therefore a priority. Furthermore, we estimate that conserving recovering degraded and secondary forests can have a feasible future carbon sink potential of 53 Tg C year-1 (44-62 Tg C year-1) across the main tropical regions studied.


Assuntos
Sequestro de Carbono , Carbono , Conservação dos Recursos Naturais , Florestas , Umidade , Árvores , Clima Tropical , Carbono/metabolismo , Conservação dos Recursos Naturais/métodos , Conservação dos Recursos Naturais/estatística & dados numéricos , Conservação dos Recursos Naturais/tendências , Árvores/metabolismo , Agricultura Florestal/estatística & dados numéricos , Imagens de Satélites , Temperatura , Floresta Úmida , Bornéu , África Central , Brasil
12.
N Engl J Med ; 390(5): 397-408, 2024 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-38294972

RESUMO

BACKGROUND: Butantan-Dengue Vaccine (Butantan-DV) is an investigational, single-dose, live, attenuated, tetravalent vaccine against dengue disease, but data on its overall efficacy are needed. METHODS: In an ongoing phase 3, double-blind trial in Brazil, we randomly assigned participants to receive Butantan-DV or placebo, with stratification according to age (2 to 6 years, 7 to 17 years, and 18 to 59 years); 5 years of follow-up is planned. The objectives of the trial were to evaluate overall vaccine efficacy against symptomatic, virologically confirmed dengue of any serotype occurring more than 28 days after vaccination (the primary efficacy end point), regardless of serostatus at baseline, and to describe safety up to day 21 (the primary safety end point). Here, vaccine efficacy was assessed on the basis of 2 years of follow-up for each participant, and safety as solicited vaccine-related adverse events reported up to day 21 after injection. Key secondary objectives were to assess vaccine efficacy among participants according to dengue serostatus at baseline and according to the dengue viral serotype; efficacy according to age was also assessed. RESULTS: Over a 3-year enrollment period, 16,235 participants received either Butantan-DV (10,259 participants) or placebo (5976 participants). The overall 2-year vaccine efficacy was 79.6% (95% confidence interval [CI], 70.0 to 86.3) - 73.6% (95% CI, 57.6 to 83.7) among participants with no evidence of previous dengue exposure and 89.2% (95% CI, 77.6 to 95.6) among those with a history of exposure. Vaccine efficacy was 80.1% (95% CI, 66.0 to 88.4) among participants 2 to 6 years of age, 77.8% (95% CI, 55.6 to 89.6) among those 7 to 17 years of age, and 90.0% (95% CI, 68.2 to 97.5) among those 18 to 59 years of age. Efficacy against DENV-1 was 89.5% (95% CI, 78.7 to 95.0) and against DENV-2 was 69.6% (95% CI, 50.8 to 81.5). DENV-3 and DENV-4 were not detected during the follow-up period. Solicited systemic vaccine- or placebo-related adverse events within 21 days after injection were more common with Butantan-DV than with placebo (58.3% of participants, vs. 45.6%). CONCLUSIONS: A single dose of Butantan-DV prevented symptomatic DENV-1 and DENV-2, regardless of dengue serostatus at baseline, through 2 years of follow-up. (Funded by Instituto Butantan and others; DEN-03-IB ClinicalTrials.gov number, NCT02406729, and WHO ICTRP number, U1111-1168-8679.).


Assuntos
Vacinas contra Dengue , Vírus da Dengue , Dengue , Vacinas Atenuadas , Adulto , Criança , Pré-Escolar , Humanos , Anticorpos Antivirais , Dengue/prevenção & controle , Vacinas contra Dengue/efeitos adversos , Vacinas contra Dengue/uso terapêutico , Vírus da Dengue/imunologia , Método Duplo-Cego , Vacinação , Vacinas , Vacinas Atenuadas/efeitos adversos , Vacinas Atenuadas/uso terapêutico , Brasil , Eficácia de Vacinas , Adolescente , Adulto Jovem , Pessoa de Meia-Idade , Seguimentos
13.
Nature ; 597(7877): 516-521, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34471291

RESUMO

Biodiversity contributes to the ecological and climatic stability of the Amazon Basin1,2, but is increasingly threatened by deforestation and fire3,4. Here we quantify these impacts over the past two decades using remote-sensing estimates of fire and deforestation and comprehensive range estimates of 11,514 plant species and 3,079 vertebrate species in the Amazon. Deforestation has led to large amounts of habitat loss, and fires further exacerbate this already substantial impact on Amazonian biodiversity. Since 2001, 103,079-189,755 km2 of Amazon rainforest has been impacted by fires, potentially impacting the ranges of 77.3-85.2% of species that are listed as threatened in this region5. The impacts of fire on the ranges of species in Amazonia could be as high as 64%, and greater impacts are typically associated with species that have restricted ranges. We find close associations between forest policy, fire-impacted forest area and their potential impacts on biodiversity. In Brazil, forest policies that were initiated in the mid-2000s corresponded to reduced rates of burning. However, relaxed enforcement of these policies in 2019 has seemingly begun to reverse this trend: approximately 4,253-10,343 km2 of forest has been impacted by fire, leading to some of the most severe potential impacts on biodiversity since 2009. These results highlight the critical role of policy enforcement in the preservation of biodiversity in the Amazon.


Assuntos
Biodiversidade , Conservação dos Recursos Naturais/legislação & jurisprudência , Secas , Agricultura Florestal/legislação & jurisprudência , Floresta Úmida , Incêndios Florestais/estatística & dados numéricos , Animais , Brasil , Mudança Climática/estatística & dados numéricos , Florestas , Mapeamento Geográfico , Plantas , Árvores/fisiologia , Vertebrados
14.
Proc Natl Acad Sci U S A ; 121(22): e2316924121, 2024 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-38768350

RESUMO

Dynamic ecosystems, such as the Amazon forest, are expected to show critical slowing down behavior, or slower recovery from recurrent small perturbations, as they approach an ecological threshold to a different ecosystem state. Drought occurrences are becoming more prevalent across the Amazon, with known negative effects on forest health and functioning, but their actual role in the critical slowing down patterns still remains elusive. In this study, we evaluate the effect of trends in extreme drought occurrences on temporal autocorrelation (TAC) patterns of satellite-derived indices of vegetation activity, an indicator of slowing down, between 2001 and 2019. Differentiating between extreme drought frequency, intensity, and duration, we investigate their respective effects on the slowing down response. Our results indicate that the intensity of extreme droughts is a more important driver of slowing down than their duration, although their impacts vary across the different Amazon regions. In addition, areas with more variable precipitation are already less ecologically stable and need fewer droughts to induce slowing down. We present findings indicating that most of the Amazon region does not show an increasing trend in TAC. However, the predicted increase in extreme drought intensity and frequency could potentially transition significant portions of this ecosystem into a state with altered functionality.


Assuntos
Secas , Florestas , Ecossistema , Brasil , Árvores/fisiologia , Árvores/crescimento & desenvolvimento , Mudança Climática
15.
Proc Natl Acad Sci U S A ; 121(22): e2316300121, 2024 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-38771876

RESUMO

The transition to remote learning in the context of COVID-19 led to dramatic setbacks in education. Is the return to in-person classes sufficient to eliminate these losses eventually? We study this question using data from the universe of secondary students in São Paulo State, Brazil. We estimate the causal medium-run impacts of the length of exposure to remote learning during the pandemic through a triple-differences strategy, which contrasts changes in educational outcomes across municipalities and grades that resumed in-person classes earlier (already by Q4/2020) or only in 2021. We find that relative learning losses from longer exposure to remote learning did not fade out over time-attesting that school reopening was at the same time key but not enough to mitigate accumulated learning losses in face of persistence. Using observational and experimental variation in local responses across 645 municipalities, we further document that remedial educational policies in the aftermath of the pandemic boosted learning recovery.


Assuntos
COVID-19 , Educação a Distância , Brasil/epidemiologia , COVID-19/epidemiologia , Humanos , Educação a Distância/métodos , Instituições Acadêmicas , SARS-CoV-2 , Pandemias , Estudantes , Aprendizagem , Adolescente
16.
Nature ; 579(7797): 80-87, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32132693

RESUMO

Structurally intact tropical forests sequestered about half of the global terrestrial carbon uptake over the 1990s and early 2000s, removing about 15 per cent of anthropogenic carbon dioxide emissions1-3. Climate-driven vegetation models typically predict that this tropical forest 'carbon sink' will continue for decades4,5. Here we assess trends in the carbon sink using 244 structurally intact African tropical forests spanning 11 countries, compare them with 321 published plots from Amazonia and investigate the underlying drivers of the trends. The carbon sink in live aboveground biomass in intact African tropical forests has been stable for the three decades to 2015, at 0.66 tonnes of carbon per hectare per year (95 per cent confidence interval 0.53-0.79), in contrast to the long-term decline in Amazonian forests6. Therefore the carbon sink responses of Earth's two largest expanses of tropical forest have diverged. The difference is largely driven by carbon losses from tree mortality, with no detectable multi-decadal trend in Africa and a long-term increase in Amazonia. Both continents show increasing tree growth, consistent with the expected net effect of rising atmospheric carbon dioxide and air temperature7-9. Despite the past stability of the African carbon sink, our most intensively monitored plots suggest a post-2010 increase in carbon losses, delayed compared to Amazonia, indicating asynchronous carbon sink saturation on the two continents. A statistical model including carbon dioxide, temperature, drought and forest dynamics accounts for the observed trends and indicates a long-term future decline in the African sink, whereas the Amazonian sink continues to weaken rapidly. Overall, the uptake of carbon into Earth's intact tropical forests peaked in the 1990s. Given that the global terrestrial carbon sink is increasing in size, independent observations indicating greater recent carbon uptake into the Northern Hemisphere landmass10 reinforce our conclusion that the intact tropical forest carbon sink has already peaked. This saturation and ongoing decline of the tropical forest carbon sink has consequences for policies intended to stabilize Earth's climate.


Assuntos
Dióxido de Carbono/metabolismo , Sequestro de Carbono , Florestas , Árvores/metabolismo , Clima Tropical , África , Atmosfera/química , Biomassa , Brasil , Secas , História do Século XX , História do Século XXI , Modelos Teóricos , Temperatura
17.
Nature ; 585(7824): 225-233, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32908268

RESUMO

Isoprene is the dominant non-methane organic compound emitted to the atmosphere1-3. It drives ozone and aerosol production, modulates atmospheric oxidation and interacts with the global nitrogen cycle4-8. Isoprene emissions are highly uncertain1,9, as is the nonlinear chemistry coupling isoprene and the hydroxyl radical, OH-its primary sink10-13. Here we present global isoprene measurements taken from space using the Cross-track Infrared Sounder. Together with observations of formaldehyde, an isoprene oxidation product, these measurements provide constraints on isoprene emissions and atmospheric oxidation. We find that the isoprene-formaldehyde relationships measured from space are broadly consistent with the current understanding of isoprene-OH chemistry, with no indication of missing OH recycling at low nitrogen oxide concentrations. We analyse these datasets over four global isoprene hotspots in relation to model predictions, and present a quantification of isoprene emissions based directly on satellite measurements of isoprene itself. A major discrepancy emerges over Amazonia, where current underestimates of natural nitrogen oxide emissions bias modelled OH and hence isoprene. Over southern Africa, we find that a prominent isoprene hotspot is missing from bottom-up predictions. A multi-year analysis sheds light on interannual isoprene variability, and suggests the influence of the El Niño/Southern Oscillation.


Assuntos
Atmosfera/química , Butadienos/análise , Butadienos/química , Mapeamento Geográfico , Hemiterpenos/análise , Hemiterpenos/química , Imagens de Satélites , África , Austrália , Brasil , Conjuntos de Dados como Assunto , El Niño Oscilação Sul , Formaldeído/química , Radical Hidroxila/análise , Radical Hidroxila/química , Ciclo do Nitrogênio , Óxidos de Nitrogênio/análise , Óxidos de Nitrogênio/química , Oxirredução , Estações do Ano , Sudeste dos Estados Unidos
18.
Nature ; 583(7815): 242-248, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32641817

RESUMO

Enhanced silicate rock weathering (ERW), deployable with croplands, has potential use for atmospheric carbon dioxide (CO2) removal (CDR), which is now necessary to mitigate anthropogenic climate change1. ERW also has possible co-benefits for improved food and soil security, and reduced ocean acidification2-4. Here we use an integrated performance modelling approach to make an initial techno-economic assessment for 2050, quantifying how CDR potential and costs vary among nations in relation to business-as-usual energy policies and policies consistent with limiting future warming to 2 degrees Celsius5. China, India, the USA and Brazil have great potential to help achieve average global CDR goals of 0.5 to 2 gigatonnes of carbon dioxide (CO2) per year with extraction costs of approximately US$80-180 per tonne of CO2. These goals and costs are robust, regardless of future energy policies. Deployment within existing croplands offers opportunities to align agriculture and climate policy. However, success will depend upon overcoming political and social inertia to develop regulatory and incentive frameworks. We discuss the challenges and opportunities of ERW deployment, including the potential for excess industrial silicate materials (basalt mine overburden, concrete, and iron and steel slag) to obviate the need for new mining, as well as uncertainties in soil weathering rates and land-ocean transfer of weathered products.


Assuntos
Agricultura , Dióxido de Carbono/isolamento & purificação , Produtos Agrícolas , Sedimentos Geológicos/química , Aquecimento Global/prevenção & controle , Objetivos , Silicatos/química , Atmosfera/química , Brasil , China , Política Ambiental/economia , Política Ambiental/legislação & jurisprudência , Aquecimento Global/economia , Índia , Ferro/isolamento & purificação , Mineração , Política , Probabilidade , Silicatos/isolamento & purificação , Aço/isolamento & purificação , Temperatura , Fatores de Tempo , Estados Unidos
19.
Proc Natl Acad Sci U S A ; 120(45): e2309123120, 2023 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-37903256

RESUMO

Tropical deforestation impacts the climate through complex land-atmosphere interactions causing local and regional warming. However, whilst the impacts of deforestation on local temperature are well understood, the regional (nonlocal) response is poorly quantified. Here, we used remote-sensed observations of forest loss and dry season land-surface temperature during the period 2001 to 2020 to demonstrate that deforestation of the Amazon caused strong warming at distances up to 100 km away from the forest loss. We apply a machine learning approach to show nonlocal warming due to forest loss at 2-100 km length scales increases the warming due to deforestation by more than a factor 4, from 0.16 K to 0.71 K for each 10-percentage points of forest loss. We estimate that rapid future deforestation under a strong inequality scenario could cause dry season warming of 0.96 K across Mato Grosso state in southern Brazil over the period 2020 to 2050. Reducing deforestation could reduce future warming caused by forest loss to 0.4 K. Our results demonstrate the contribution of tropical deforestation to regional climate warming and the potential for reduced deforestation to deliver regional climate adaptation and resilience with important implications for sustainable management of the Amazon.


Assuntos
Conservação dos Recursos Naturais , Árvores , Florestas , Clima , Estações do Ano , Brasil
20.
Proc Natl Acad Sci U S A ; 120(22): e2221346120, 2023 05 30.
Artigo em Inglês | MEDLINE | ID: mdl-37216556

RESUMO

Forests serve a crucial role in our fight against climate change. Secondary forests provide important potential for conservation of biodiversity and climate change mitigation. In this paper, we explore whether collective property rights in the form of indigenous territories (ITs) lead to higher rates of secondary forest growth in previously deforested areas. We exploit the timing of granting of property rights, the geographic boundaries of ITs and two different methods, regression discontinuity design and difference-in-difference, to recover causal estimates. We find strong evidence that indigenous territories with secure tenure not only reduce deforestation inside their lands but also lead to higher secondary forest growth on previously deforested areas. After receiving full property rights, land inside ITs displayed higher secondary forest growth than land outside ITs, with an estimated effect of 5% using our main RDD specification, and 2.21% using our difference-in-difference research design. Furthermore, we estimate that the average age of secondary forests was 2.2 y older inside ITs with secure tenure using our main RDD specification, and 2.8 y older when using our difference-in-difference research design. Together, these findings provide evidence for the role that collective property rights can play in the push to restore forest ecosystems.


Assuntos
Ecossistema , Propriedade , Brasil , Conservação dos Recursos Naturais , Florestas
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