Factors driving the biogeochemical budget of the Amazon River and its statistical modelling Facteurs denext term contrôle du bilan biogéochimique previous termdenext term l'Amazone et modélisation statistique associée

International audienceThe seasonal and interannual fluctuations of the biogeochemical budget (solutes, suspended matter, isotopes) of the Amazon River basin were analyzed, with a special focus on 44 physicochemical parameters monitored over the period 1982-1984 during the Carbon in the AMazon River Experiment (CAMREX) project. The relevant factors driving this variability were identified and sorted through the implementation of a statistical-regressive model coupled to variance analysis. Basically, the compositional fluctuations in the Amazon River are related (1) to the variable contribution of major tributaries (variable regional source) to the river flow but also (2) to the variable contribution of hydrological sources, (3) to river processes, i.e. in-stream diagenesis and sediment dynamics and (4) to the hydrological budget of the floodplains. Their respective contributions to the variability of chemical signals observed in the stream waters depend on which parameter was investigated but their combination explains on average 85% of the observed variability. The variability related to regional sources was captured by the compared measures of flow discharge and biogeochemical fluxes at the outlet of the major tributaries. The variability of hydrological sources was described by the variable contribution of three runoffs of distinct but constant composition: forwarded direct runoff, delayed floodplain runoff and baseflow. Several methods were tested to depict the seasonal and interannual variations of their individual discharges. Biologically-mediated processes were related to a hydrobiological index IBIO = [O2]-[CO2] which allows tracking the nature of the dominant ecological regime (autotrophy vs. heterotrophy). The alteration of chemical signals related to the intermittent discharge of the floodplains (where specific processes occur such as: gas exchanges at the air-water interface, sorption of dissolved organic matter, chemical weathering, deposition vs. remobilization of sediments, etc.) was simulated by taking into account the default of hydrological balance between inflows and outflows, used as a marker of floodplains discharge. This analysis shows that the chemical baseline observed in the waters of the Amazon River is mostly acquired upstream from the junction of major tributaries with the Amazon main reach. Les fluctuations saisonnières et interannuelles du bilan biogéochimique (solutés, matière particulaire, isotopes) du fleuve Amazone ont été analysées, avec une attention particulière apportée à 44 paramètres physicochimiques mesurés entre 1982 et 1984 dans le cadre du programme CAMREX. Les facteurs exerçant une influence significative sur cette variabilité ont été identifiés et hiérarchisés par le biais d'un modèle statistique couplé à une analyse previous termdenext term variance. Les variations previous termdenext term composition des eaux previous termdenext term l'Amazone sont fondamentalement associées (1) à previous termlanext term contribution variable previous termdenext term ses affluents majeurs (source régionale variable) au débit total, mais aussi (2) à previous termlanext term contribution variable des pôles previous termdenext term mélange hydrologiques, (3) à des processus fluviaux correspondant au régime hydrobiologique et à previous termlanext term dynamique sédimentaire et (4) au bilan hydrologique des plaines d'inondation. Leurs contributions respectives à previous termlanext term variabilité des signaux chimiques observés dans les eaux du fleuve dépendent du paramètre considéré, mais leur combinaison explique en moyenne 85 % previous termde lanext term variabilité observée. previous termLanext term variabilité associée aux contributions régionales variables est appréhendée en procédant aux bilans entrées-sorties des débits et flux biogéochimiques. previous termLanext term variabilité previous termdenext term contribution des pôles previous termdenext term mélange est décrite par previous termlanext term contribution variable previous termdenext term trois écoulements previous termdenext term compositions distinctes mais constantes : l'écoulement direct à expression précoce, l'écoulement local previous termdenext term vidange alluviale à expression différée et l'écoulement previous termdenext term base. Douze méthodes ont été testées afin previous termdenext term décrire les variations saisonnières et interannuelles des débits individuels previous termdenext term chaque pôle previous termdenext term mélange. Les processus contrôlés par le vivant sont appréhendés à partir d'un indice hydrobiologique IBIO = [O2]-[CO2] qui permet previous termdenext term déterminer previous termlanext term nature du régime hydro-écologique dominant (autotrophe vs. hétérotrophe). L'altération des signaux chimiques générée par previous termlanext term vidange intermittente des plaines d'inondation (au niveau desquelles ont lieu des processus spécifiques : échanges gazeux, sorption previous termdenext term matière organique dissoute, érosion chimique, dépôt vs. remise en suspension previous termdenext term sédiments, etc.) est simulée en prenant en compte le défaut previous termdenext term bilan hydrologique entrées-sorties utilisé comme marqueur previous termdenext term débit des plaines d'inondation. Cette analyse montre que le bruit previous termdenext term fond chimique observé dans les eaux du fleuve Amazone est principalement acquis en amont des confluences entre le tronçon fluvial étudié et les principaux affluents qui l'alimentent

Simulation of the effects of land use changes in soil carbon dynamics in the Piracicaba river basin, São Paulo State, Brazil

Neste trabalho teve-se como objetivo testar o modelo CENTURY para simular os efeitos das mudanças de uso da terra nos teores de carbono no solo e na produção primária líquida na bacia do rio Piracicaba, SP. O modelo foi parametrizado e as simulações foram realizadas considerando-se áreas de florestas, pastagens e cana-de-açúcar, dada a sua importância econômica. Os resultados obtidos indicaram que a alteração do uso/cobertura do solo provoca a diminuição do estoque de carbono do solo. As simulações realizadas na transição de uma floresta para cana-de-açúcar indicaram um decréscimo de 28% no estoque de carbono nos primeiros 12 anos, e diminuição de 42% com 50 anos de cultivo do solo com essa gramínea. Na simulação da transição de uma floresta para pasto, seguida do cultivo da cana-de-açúcar, verificou-se que na primeira mudança (floresta-pastagem) a perda de carbono foi de 24%, enquanto na segunda alteração (pastagem-cana) a perda foi de 22%. Com relação à produção primária, os resultados obtidos de floresta (6,6 t ha-1 ano-1), cana-de-açúcar (77, 82, 80 t ha-1 ano-1) e pasto (6,5 t ha-1 ano-1), mostraram-se similares aos valores observados no campo por outros autores.The objective of this study was to test adequability of the CENTURY model to simulate the effects of land use changes on soil carbon content and net primary production to specific subtropical Brazilian environmental conditions. After parameterization, simulations were performed for forested areas, pasture and sugarcane cultures which have economical importance and representative areal extension in the Piracicaba River basin, São Paulo State, Brazil. The results obtained indicate that changes in use/cover from forest to agricultural practices resulted in lower soil carbon stocks. The simulations of the transition from forest to sugarcane indicated a decrease of 28% in soil carbon stocks for the first 12 years and 42% for 50 years of sugarcane cultivation. The simulation of the transition from forest to pasture and then to sugarcane resulted in a 24% loss of soil carbon stock for the first transition (forest-pasture) and of 22% for the second one (pasture-sugar-cane). The net primary production results obtained for forest (6.6 ton ha-1 yr-1), sugarcane (77, 82, 80 ton ha-1 yr-1) and pasture (6.5 ton ha-1 yr-1) were similar to those observed by other authors in field measurements

Hydroclimatology and biogeochemistry of the Amazon 1. Erosion

The Amazon is the largest stream in the world. Its basin covers at least 7. lo6 km2, which represents - 5% of the global continental area and almost 70% of the area of the continents localized in the equatorial zone, between 5"s and 5"N of latitude. The global tropical moist forest covers -9.35. lo6 km2, so that the Brazilian evergreen rain forest represents at least 50% of this area. At Obidos, the most accessible downstream station for collecting data, the area concerned is 4.619- lo6 km2. The purpose of these two extended abstracts is to show how changes and oscillations of climate can significantly affect erosion as well as carbon and nitrogen cycles, and may also mask the degradations of the environment due to deforestation

Contributions of C 3 and C 4 plants to higher trophic levels in an Amazonian savanna

Abstract We studied the energy¯ow from C 3 and C 4 plants to higher trophic levels in a central Amazonian savanna by comparing the carbon stable-isotope ratios of potential food plants to the isotope ratios of species of dierent consumer groups. All C 4 plants encountered in our study area were grasses and all C 3 plants were bushes, shrubs or vines. Dierences in d 13 C ratios among bushes (" x = A30.8, SD = 1.2), vines (" x = A30.7, SD = 0.46) and trees (" x = A29.7, SD = 1.5) were small. However the mean d 13 C ratio of dicotyledonous plants (" x = A30.4, SD = 1.3) was much more negative than that of the most common grasses (" x = A13.4, SD = 0.27). The insect primary consumers had d 13 C ratios which ranged from a mean of A29.5 (SD = 0.47) for the grasshopper Tropidacris collaris to a mean of A14.7 (SD = 0.56) for a termite (Nasutitermes sp.), a range similar to that of the vegetation

Main conclusions of the joint FAPESP programs BIOTA-BIOEN-climate change workshop: science and policy for a greener economy in the context of RIO+20

Este Ponto de Vista resume as conclusões de um Workshop conjunto, organizado pelos três Programas da FAPESP na Área Ambiental - BIOTA (O Instituto Virtual da Biodiversidade) - BIOEN (Pesquisa em Bioenergia) - Mudanças Climáticas, para discutir a contribuição da comunidade científica para a RIO+20, a Conferência das Nações Unidas para o Desenvolvimento Sustentável. O grupo de pesquisadores brasileiros reunidos pela FAPESP no início de março de 2012 levantou as seguintes preocupações: a) o número reduzido de oportunidades para a comunidade científica interagir com Conferências como a RIO+20; b) as graves deficiências do ZeroDraft, documento produzido pela Divisão das Nações Unidas para o Desenvolvimento Sustentável para a RIO +20; c) o fato do foco de pesquisa dos três Programas de Pesquisa Ambiental da FAPESP - biodiversidade, bioenergia e mudanças climáticas - não estarem na pauta das discussões da RIO+20; d) que pouca ênfase é dada aos oceanos na Agenda da Conferência; e) em relação aos mecanismos de mercado associados com a transição para uma economia mais verde, a necessidade de enfatizar a redução de subsídios perversos e a promoção de incentivos econômicos para atividades ou processos de mitigação e/ou seqüestro de carbono; f) a necessidade de estimular o desenvolvimento e a consolidação da pesquisa na área de avaliação e valoração de serviços ambientais, no Brasil. Os participantes do Workshop reconheceram a necessidade de aprofundar o conhecimento sobre as convenções, tratados e acordos internacionais assinados e ratificados pelo Brasil, bem como as instituições internacionais, programas e iniciativas que promovem a participação da comunidade científica no debate de políticas ambientais globais. Finalmente, do ponto de vista dos três programas da FAPESP dois pontos foram destacados: a) que é imperativo aprofundar o conhecimento científico em cada uma das três áreas focais - biodiversidade, bioenergia e mudanças climáticas - porque é necessário aumentar a massa crítica de pesquisadores e do conhecimento para participar das discussões internacionais nessas áreas estratégicas; b) também é imperativo apoiar e promover projetos de pesquisa que integrem as áreas focais dos três programas, estimulando a constituição de equipes inter e transdisciplinares. Esta é uma tendência mundial na área das mudanças ambientais globais, e os participantes dos três programas sentem que podem dar uma contribuição significativa para o avanço do conhecimento, para o debate internacional e para a efetiva solução dos problemas

Height and body-mass index trajectories of school-aged children and adolescents from 1985 to 2019 in 200 countries and territories: a pooled analysis of 2181 population-based studies with 65 million participants

Summary Background Comparable global data on health and nutrition of school-aged children and adolescents are scarce. We aimed to estimate age trajectories and time trends in mean height and mean body-mass index (BMI), which measures weight gain beyond what is expected from height gain, for school-aged children and adolescents. Methods For this pooled analysis, we used a database of cardiometabolic risk factors collated by the Non-Communicable Disease Risk Factor Collaboration. We applied a Bayesian hierarchical model to estimate trends from 1985 to 2019 in mean height and mean BMI in 1-year age groups for ages 5–19 years. The model allowed for non-linear changes over time in mean height and mean BMI and for non-linear changes with age of children and adolescents, including periods of rapid growth during adolescence. Findings We pooled data from 2181 population-based studies, with measurements of height and weight in 65 million participants in 200 countries and territories. In 2019, we estimated a difference of 20 cm or higher in mean height of 19-year-old adolescents between countries with the tallest populations (the Netherlands, Montenegro, Estonia, and Bosnia and Herzegovina for boys; and the Netherlands, Montenegro, Denmark, and Iceland for girls) and those with the shortest populations (Timor-Leste, Laos, Solomon Islands, and Papua New Guinea for boys; and Guatemala, Bangladesh, Nepal, and Timor-Leste for girls). In the same year, the difference between the highest mean BMI (in Pacific island countries, Kuwait, Bahrain, The Bahamas, Chile, the USA, and New Zealand for both boys and girls and in South Africa for girls) and lowest mean BMI (in India, Bangladesh, Timor-Leste, Ethiopia, and Chad for boys and girls; and in Japan and Romania for girls) was approximately 9–10 kg/m2. In some countries, children aged 5 years started with healthier height or BMI than the global median and, in some cases, as healthy as the best performing countries, but they became progressively less healthy compared with their comparators as they grew older by not growing as tall (eg, boys in Austria and Barbados, and girls in Belgium and Puerto Rico) or gaining too much weight for their height (eg, girls and boys in Kuwait, Bahrain, Fiji, Jamaica, and Mexico; and girls in South Africa and New Zealand). In other countries, growing children overtook the height of their comparators (eg, Latvia, Czech Republic, Morocco, and Iran) or curbed their weight gain (eg, Italy, France, and Croatia) in late childhood and adolescence. When changes in both height and BMI were considered, girls in South Korea, Vietnam, Saudi Arabia, Turkey, and some central Asian countries (eg, Armenia and Azerbaijan), and boys in central and western Europe (eg, Portugal, Denmark, Poland, and Montenegro) had the healthiest changes in anthropometric status over the past 3·5 decades because, compared with children and adolescents in other countries, they had a much larger gain in height than they did in BMI. The unhealthiest changes—gaining too little height, too much weight for their height compared with children in other countries, or both—occurred in many countries in sub-Saharan Africa, New Zealand, and the USA for boys and girls; in Malaysia and some Pacific island nations for boys; and in Mexico for girls. Interpretation The height and BMI trajectories over age and time of school-aged children and adolescents are highly variable across countries, which indicates heterogeneous nutritional quality and lifelong health advantages and risks

Worldwide trends in underweight and obesity from 1990 to 2022: a pooled analysis of 3663 population-representative studies with 222 million children, adolescents, and adults

Background Underweight and obesity are associated with adverse health outcomes throughout the life course. We estimated the individual and combined prevalence of underweight or thinness and obesity, and their changes, from 1990 to 2022 for adults and school-aged children and adolescents in 200 countries and territories. Methods We used data from 3663 population-based studies with 222 million participants that measured height and weight in representative samples of the general population. We used a Bayesian hierarchical model to estimate trends in the prevalence of different BMI categories, separately for adults (age ≥20 years) and school-aged children and adolescents (age 5–19 years), from 1990 to 2022 for 200 countries and territories. For adults, we report the individual and combined prevalence of underweight (BMI <18·5 kg/m2) and obesity (BMI ≥30 kg/m2). For schoolaged children and adolescents, we report thinness (BMI <2 SD below the median of the WHO growth reference) and obesity (BMI >2 SD above the median). Findings From 1990 to 2022, the combined prevalence of underweight and obesity in adults decreased in 11 countries (6%) for women and 17 (9%) for men with a posterior probability of at least 0·80 that the observed changes were true decreases. The combined prevalence increased in 162 countries (81%) for women and 140 countries (70%) for men with a posterior probability of at least 0·80. In 2022, the combined prevalence of underweight and obesity was highest in island nations in the Caribbean and Polynesia and Micronesia, and countries in the Middle East and north Africa. Obesity prevalence was higher than underweight with posterior probability of at least 0·80 in 177 countries (89%) for women and 145 (73%) for men in 2022, whereas the converse was true in 16 countries (8%) for women, and 39 (20%) for men. From 1990 to 2022, the combined prevalence of thinness and obesity decreased among girls in five countries (3%) and among boys in 15 countries (8%) with a posterior probability of at least 0·80, and increased among girls in 140 countries (70%) and boys in 137 countries (69%) with a posterior probability of at least 0·80. The countries with highest combined prevalence of thinness and obesity in school-aged children and adolescents in 2022 were in Polynesia and Micronesia and the Caribbean for both sexes, and Chile and Qatar for boys. Combined prevalence was also high in some countries in south Asia, such as India and Pakistan, where thinness remained prevalent despite having declined. In 2022, obesity in school-aged children and adolescents was more prevalent than thinness with a posterior probability of at least 0·80 among girls in 133 countries (67%) and boys in 125 countries (63%), whereas the converse was true in 35 countries (18%) and 42 countries (21%), respectively. In almost all countries for both adults and school-aged children and adolescents, the increases in double burden were driven by increases in obesity, and decreases in double burden by declining underweight or thinness. Interpretation The combined burden of underweight and obesity has increased in most countries, driven by an increase in obesity, while underweight and thinness remain prevalent in south Asia and parts of Africa. A healthy nutrition transition that enhances access to nutritious foods is needed to address the remaining burden of underweight while curbing and reversing the increase in obesit

Heterogeneous contributions of change in population distribution of body mass index to change in obesity and underweight NCD Risk Factor Collaboration (NCD-RisC)

From 1985 to 2016, the prevalence of underweight decreased, and that of obesity and severe obesity increased, in most regions, with significant variation in the magnitude of these changes across regions. We investigated how much change in mean body mass index (BMI) explains changes in the prevalence of underweight, obesity, and severe obesity in different regions using data from 2896 population-based studies with 187 million participants. Changes in the prevalence of underweight and total obesity, and to a lesser extent severe obesity, are largely driven by shifts in the distribution of BMI, with smaller contributions from changes in the shape of the distribution. In East and Southeast Asia and sub-Saharan Africa, the underweight tail of the BMI distribution was left behind as the distribution shifted. There is a need for policies that address all forms of malnutrition by making healthy foods accessible and affordable, while restricting unhealthy foods through fiscal and regulatory restrictions