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One of the main factors that influences the fertility of cattle in grazing systems in hot tropical climates is heat stress. The objective of this study was to evaluate the effect of season, breed, hormonal and physiological condition on the quantity and quality of cumulus-oocyte complexes (COCs) and embryos produced in vitro, from Romosinuano (RM) and Tropical Milking (TM) donors. Three ovum pick-up and in vitro fertilization (OPU-IVF) were performed, one per season: hot dry (HD; 10, 10), hot humid (HH; 9, 9) and fresh dry (FD; 7, 10) in RM and LT donors. Serum levels of cortisol, insulin and glucose were measured, in addition to heart rate (HR), respiratory rate (RR) and rectal temperature (RT). Effect of season x genotype interaction (p ≤ 0.05) was observed in all COC variables and only in cleavage embryos (CLI) (p ≤ 0.05). Body weight (BW) affected all COC variables (p ≤ 0.01), except unviable (UNV) although affected degenerated embryos (DEG) (p ≤ 0.01) and total blastocysts (BLAST) (p ≤ 0.01). Cow age only affected viable COCs (VIAB) (p ≤ 0.05), code one blastocysts (BC1) and BLAST (p ≤ 0.01). Cortisol affected total COCs (COCsT), VIAB and total matured in vitro (TMIV) (p ≤ 0.01), as well as CLI, BC1 (p ≤ 0.01) and BLAST (p ≤ 0.05). Insulin affected COCsT (p ≤ 0.01), UNV (p ≤ 0.05), denuded oocytes (DE) (p ≤ 0.01), BC1 and code two blastocysts (BC2) (p ≤ 0.01). Glucose affected all COC variables (p ≤ 0.01), except UNV and all embryo variables except BC2. HR affected COCsT, DE, TMIV (p ≤ 0.01), CLI, BLAST and DEG (p ≤ 0.05). RR affected COCsT, UNV, VIAB, CLI (p ≤ 0.05), BC1, BLAST and DEG (p ≤ 0.01). RT only affected DE, VIAB (p ≤ 0.01) and BLAST (p ≤ 0.05). The seasonal climatic year variation of Veracruz and changes in physiological and hormonal variables have diverse effects on the cumulus-oocyte complexes and embryos produced by RM and TM donors.

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Introducción: El impacto del cambio climático en Cuba requiere acciones de adaptación. Para el sector de la salud, conocer e integrar los servicios ecosistémicos contribuye a la efectividad de la adaptación y seguridad a la salud humana. Objetivo: Abordar la contribución de los servicios ecosistémicos a la adaptación al cambio climático y la salud. Métodos: En la investigación se implementó un enfoque cuantitativo estructurado en dos etapas: diagnóstico del conocimiento de los recursos humanos del sector de la salud sobre los impactos del cambio climático en los municipios Ciénaga de Zapata y Martí, y la incorporación de criterios sobre la contribución de los servicios ecosistémicos a la adaptación al cambio climático y la salud. Se aplicaron métodos epidemiológicos mediante revisión documental, observación y trabajo en equipo. La clasificación de servicios ecosistémicos se realizó según la clasificación internacional establecida. Resultados: Se analiza la relación entre servicios ecosistémicos de las áreas, los impactos por las actividades socioeconómicas y los beneficios que ofrecen los mismos a la adaptación al cambio climático y la salud. Se identificó que los trabajadores del sector de la salud no perciben la variabilidad climática como riesgo y consideran sus conocimientos insuficientes. Conclusiones: Los servicios ecosistémicos contribuyen a la adaptación al cambio climático, ya que aportan recursos y son procesos que soportan actividades socioeconómicas. Las acciones de creación de capacidades se deben intencionar y reenfocar a las evidencias de basar la adaptación en mantener el flujo de estos servicios.

Introduction: The impact of climate change in Cuba requires adaptation actions. For the health sector, knowing and integrating ecosystem services contributes to the effectiveness of adaptation and security to human health. Objective: To address the contribution of ecosystem services to climate change adaptation and health. Methods: A quantitative approach structured in two stages was implemented in the research: diagnosis of the knowledge of human resources in the health sector on the impacts of climate change in the municipalities of Ciénaga de Zapata and Martí, and the incorporation of criteria on the contribution of ecosystem services to adaptation to climate change and health. Epidemiological methods were applied through documentary review, observation, and teamwork. The classification of ecosystem services was carried out according to the established international classification. Results: The relationship between ecosystem services of the areas, the impacts of socioeconomic activities and the benefits they offer to adaptation to climate change and health is analyzed. It was identified that health sector workers do not perceive climate variability as a risk and consider their knowledge insufficient. Conclusions: Ecosystem services contribute to adaptation to climate change, since they provide resources and are processes that support socioeconomic activities. Capacity-building actions must be intentional and refocused on evidence of basing adaptation on maintaining the flow of these services.

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We conducted a geochemical analysis on three sediment cores collected from soda and freshwater lakes in the Pantanal region, in Brazil. Our objective was to identify the primary sources of organic matter associated with the Pleistocene-Holocene transition, as previously documented in that area. The Nhecolandia region, located in the Pantanal, encompasses over 10,000 lakes, with approximately 10% of them exhibiting alkaline characteristics. Soda lakes became highly saline and alkaline after ~ 910 cal yr BP, which influences biogeochemistry and aquatic ecology. They have high electrical conductivity and pH can reach 10.5. In contrast to freshwater, soda lakes are absent of surrounding vegetation. Literature suggests a strong influence by the Last Glacial Maximum on the region. We hypothesized that periods of aridity and increased precipitation influenced the composition of organic matter present in sediments and preserved within these cores. Our analysis focused on examining the presence and distribution of fatty acids, organic carbon content, and total nitrogen. In general, the cores exhibited two distinct parts in terms of organic matter sources: the upper sections of the cores were primarily composed by terrestrial sources, identified by the presence of long-chain fatty acids, while the deeper sections were dominated by aquatic sources, therefore short-chain fatty acids. We did not find significant difference among fatty acid profile that could distinguish freshwater from soda lakes, the only remarkable difference was the occurrence of saturated fatty acids, which is lower in freshwater lake. These findings suggest the occurrence of humid and arid periods in the region. The C/N ratio displayed a similar trend to the fatty acid's profiles, exhibiting an abrupt change that was likely induced by climate variations. Although diagenesis can alter the composition of organic matter and, subsequently, the C/N values, it is noteworthy that the abrupt change observed in the Salina da Ponta (soda lake) core corresponds to 3,200 years BP. This coincides with documented climate changes that occurred during the Holocene. Our study revealed the influence of past climatic conditions on the sources and variations of organic matter in sediment cores from the Pantanal's soda and freshwater lakes. Consideration of diagenesis and climate variations is crucial for interpreting sedimentary records.

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While urbanization has great potential to facilitate poverty reduction, climate shocks represent a looming threat to such upward mobility. This paper empirically analyzes the effects of climatic risks on the function of urban agglomerations to support poor households' escape from poverty. Combining household surveys with climatic datasets, our analyses of Chile, Colombia, and Indonesia find that households in large metropolitan areas are more likely to escape from poverty, indicating better access to economic opportunities in those areas. However, climate shocks such as extreme rainfalls and high flood risks significantly reduce upward mobility, thus offsetting such benefits of urban agglomerations. The findings underscore the need to enhance resilience among the urban poor to allow them to fully utilize the benefits of urban agglomerations.

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Species loss in tropical regions is forecast to occur under environmental change scenarios of low precipitation. One of the main questions is how drought will affect invertebrates, a key group for ecosystem functioning. We use 1 year of data from a long-term rainwater exclusion experiment in primary Amazonian rainforest to test whether induced water stress and covarying changes in soil moisture, soil respiration, and tree species richness, diversity, size, and total biomass affected species richness and composition (relative abundance) of ground-dwelling ants. Data on ant abundance and environmental variables were collected at two sites (control and experimental) in the Eastern Amazon. Since 2002, drought has been induced in the experimental plot by excluding 50% of normal rainfall. Ant species richness in the experiment plot was reduced and some generalist species responded positively. Ant species richness also increased in the experimental plot with increasing diversity of the plant species of the leaf litter. The relative abundance of ants differed between plots. The experimental plot was characterized by a higher frequency of generalist and other species that appeared to be favored by the reduction in rainfall. Between-plot comparisons suggested loss and changes in ant species composition in tropical forests were affected by increasing dryness. These changes could ultimately lead to cascading effects on ecosystem processes and the services they mediate.

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Tropical ecosystems are under increasing pressure from land-use change and deforestation. Changes in tropical forest cover are expected to affect carbon and water cycling with important implications for climatic stability at global scales. A major roadblock for predicting how tropical deforestation affects climate is the lack of baseline conditions (i.e., prior to human disturbance) of forest-savanna dynamics. To address this limitation, we developed a long-term analysis of forest and savanna distribution across the Amazon-Cerrado transition of central Brazil. We used soil organic carbon isotope ratios as a proxy for changes in woody vegetation cover over time in response to fluctuations in precipitation inferred from speleothem oxygen and strontium stable isotope records. Based on stable isotope signatures and radiocarbon activity of organic matter in soil profiles, we quantified the magnitude and direction of changes in forest and savanna ecosystem cover. Using changes in tree cover measured in 83 different locations for forests and savannas, we developed interpolation maps to assess the coherence of regional changes in vegetation. Our analysis reveals a broad pattern of woody vegetation expansion into savannas and densification within forests and savannas for at least the past ~1,600 years. The rates of vegetation change varied significantly among sampling locations possibly due to variation in local environmental factors that constrain primary productivity. The few instances in which tree cover declined (7.7% of all sampled profiles) were associated with savannas under dry conditions. Our results suggest a regional increase in moisture and expansion of woody vegetation prior to modern deforestation, which could help inform conservation and management efforts for climate change mitigation. We discuss the possible mechanisms driving forest expansion and densification of savannas directly (i.e., increasing precipitation) and indirectly (e.g., decreasing disturbance) and suggest future research directions that have the potential to improve climate and ecosystem models.

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Hybridization can occur when two geographically isolated species are reproductively compatible and have come into sympatry due to range shifts. Yucca and yucca moths exhibit obligate pollination mutualism; yucca moths are responsible for the gene flow mediated by pollen among yucca populations. In the Baja California Peninsula, there are two yucca sister species, Y. capensis and Y. valida, that have coevolved with the same pollinator, Tegeticula baja. Both yucca species are endemic to the peninsula, and their current distributions are allopatric. Based on their morphological characteristics, it has been suggested that some plants growing in the southern part of the Magdalena flatland, a spatially disjunct part of Yucca valida's range, have hybrid origins. We conducted genomic and climatic analyses of the two yucca species as well as the putative hybrid populations. We genotyped 3,423 single nucleotide polymorphisms in 120 individuals sampled from 35 localities. We applied Bayesian tests and geographic cline analyses to the genomic data. Using climatic information from the occurrence sites, we projected species distribution models in different periods to assess changes in the distributional range, and we performed a statistical test to define the niche divergence between the paternal species and the putative hybrid populations. Structure analysis revealed mixed ancestry in the genome of hybrid populations, and the Bayesian models supported a scenario of post-divergence gene flow between the yucca species. Our species distribution models reveal that the geographical ranges of the parental species overlapped mainly during the Last Glacial Maximum, which could facilitate genetic admixture between those species. Finally, we found that most of the assessed environmental axes between the parents and hybrid populations are divergent, indicating that the climatic niche of the hybrid populations is shifting from that of the populations' progenitors. Our results show that the populations in the southern part of the Magdalena flatland are the result of combination of the genetic components of two species. Hybrid individuals with this novel genomic combination arose in a different habitat than their parental species, and they exhibit ecological divergence, which contributes to reproductive isolation through spatial and temporal barriers.

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On a global level, weed species have a large potential to threaten ecosystems under a changing climate. The determination of key monitoring areas is an effective approach to prevent and control the spread of such species. The 10 most important weeds have been listed on a global scale. It is therefore crucial to delineate the areas with high monitoring ranks for the 10 most important weed species under climate change. We coupled conservation prioritization analysis with habitat suitability modelling to determine key monitoring areas for these species, based on different types and vulnerability levels of biomes under current and future (i.e., 2040-2069 and 2070-2099) scenarios. We determined some specific biomes (i.e., tropical and subtropical biomes, flooded grasslands and savannas, Mediterranean forests, woodlands and scrub, and mangroves) as key monitoring areas for the 10 most important weed species under a changing climate. These biomes are distributed in most regions of Latin America, the United States, Europe, central and south Africa, south and southeast Asia, southeast Australia, and New Zealand, including large vulnerable ecoregions. Tropical and subtropical grasslands, savannas, and shrublands were particularly vulnerable, because these biomes had the largest area with a high monitoring rank, and this rank was predicted to further increase in the near future. Our study highlights the importance of effective management strategies for the prevention and control of these species across different biomes on a global scale.

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El Niño and La Niña climatic oscillations have dramatic effects on population dynamics and community structure of different animals. For marine birds, El Niño phenomenon drastically increases their mortality and reduces their reproductive success. In terrestrial ecosystems, the lack of long-term longitudinal data limits our understanding of the impact of El Niño and La Niña on bird populations and communities. We analyzed changes in abundance of frugivorous (large, medium, and small) and nectarivorous birds on three tropical forest types (lowland, premontane and montane) during El Niño, La Niña and neutral years using data from 16 Christmas' Bird Counts in Costa Rica. Abundance of large and medium size frugivores increased during La Niña events, and the abundance of nectarivores during El Niño in the lowland forest, but neither of these events affected the abundance of small frugivores. In the montane forest, abundance of all four bird groups increased during El Niño, but decreased during La Niña events. Abundance of large, and small frugivores increased in the premontane forest during La Niña events, but other bird groups were not affected by La Niña. The abundance of small frugivores also increased during El Niño. We hypothesize that changes in abundance of frugivores and nectarivores during La Niña and El Niño events is probably correlated with fluctuations in food resources as it has been reported for other terrestrial tropical ecosystems.

Las oscilaciones climáticas causadas por el fenómeno de El Niño y La Niña tienen efectos drásticos sobre la dinámica de las poblaciones y la estructura de las comunidades. Para aves marinas, el fenómeno de El Niño incrementa drásticamente su mortalidad y reduce su éxito reproductivo. En ecosistemas terrestres, la falta de datos a largo plazo limita nuestro entendimiento sobre el impacto de El Niño y La Niña sobre la dinámica de las poblaciones y comunidades de aves. Nosotros analizamos los cambios en la abundancia de aves frugívoras (grandes, medianos y pequeños) y nectarívoras en tres tipos de bosque tropical (lluvioso de tierras bajas, premontano y montano) durante los años de El Niño, La Niña, y años neutrales usando datos de al menos 16 conteos de navidad (Christmas' Bird Counts) en Costa Rica. La abundancia de frugívoros grandes y medianos incrementó durante los años de La Niña, y la abundancia de nectarívoros durante el Niño en el bosque lluvioso de tierras bajas, pero ninguno de estos eventos afectó la abundancia de frugívoros pequeños en este bosque. En el bosque montano, la abundancia de los cuatro grupos de aves incrementó durante los años de El Niño, pero disminuyó durante los años de La Niña. La abundancia de frugívoros grandes y pequeños aumentó en el bosque pre-montano durante los años de La Niña; sin embargo, la abundancia de los frugívoros medianos y los nectarívoros no fue afectada por los eventos por La Niña o El Niño. La abundancia de frugívoros pequeños también aumentó durante El Niño en este bosque. Proponemos la hipótesis de que los cambios en la abundancia de las aves frugívoras y nectarívoras reflejan fluctuaciones en el recurso alimentario, como ha sido reportado en otros ecosistemas terrestres tropicales.

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The impacts of the historical geologic and climatic events on the diversity and genetic structure of Neotropical taxa have recently become a subject of study. However, annual plants associated with tropical dry forests remain under-studied. The exploration of additional taxa in contrasting environments will improve the current understanding of responses of the Neotropical biota to these events. Here, we explore the species distribution and geographic structure of the annual herb Tithonia rotundifolia. We sampled 175 individuals from 19 populations of T. rotundifolia. Species distribution modelling and six microsatellite chloroplast loci were used to infer its population history. We identified areas of historical climate suitability and then tested if there is genetic structuring among these areas. Haplotypes showed strong phylogeographic structure. Historical climatic suitability areas were found along the Pacific coast; however, a gap was found at the Isthmus of Tehuantepec (IT). Although Bayesian analysis showed population structuring, amova revealed that the IT is not its main driver. Instead, a subdivision into a higher number of regions had higher FCT values. Also, populations to the east of the IT showed evidence of recent population expansion and migration in a south-north direction. Pleistocene climate fluctuations partially explain the geographic structure of T. rotundifolia. However, life-history characteristics such as limited seed dispersal and the patchy distribution of suitable habitats explain the high haplotype diversity and population sub-structuring and diversity. Lastly, the absence of geographic structure of some haplotypes may indicate long-distance dispersal, or hybridisation with the closely related T. tubaeformis.

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The Cerrado is the largest South American savanna and encompasses substantial species diversity and environmental variation. Nevertheless, little is known regarding the influence of the environment on population divergence of Cerrado species. Here, we searched for climatic drivers of genetic (nuclear microsatellites) and leaf trait divergence in Annona crassiflora, a widespread tree in the Cerrado. The sampling encompassed all phytogeographic provinces of the continuous area of the Cerrado and included 397 individuals belonging to 21 populations. Populations showed substantial genetic and leaf trait divergence across the species' range. Our data revealed three spatially defined genetic groups (eastern, western and southern) and two morphologically distinct groups (eastern and western only). The east-west split in both the morphological and genetic data closely mirrors previously described phylogeographic patterns of Cerrado species. Generalized linear mixed effects models and multiple regression analyses revealed several climatic factors associated with both genetic and leaf trait divergence among populations of A. crassiflora. Isolation by environment (IBE) was mainly due to temperature seasonality and precipitation of the warmest quarter. Populations that experienced lower precipitation summers and hotter winters had heavier leaves and lower specific leaf area. The southwestern area of the Cerrado had the highest genetic diversity of A. crassiflora, suggesting that this region may have been climatically stable. Overall, we demonstrate that a combination of current climate and past climatic changes have shaped the population divergence and spatial structure of A. crassiflora. However, the genetic structure of A. crassiflora reflects the biogeographic history of the species more strongly than leaf traits, which are more related to current climate.

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A lo largo de la historia la tierra ha experimentado cambios en los parámetros climáticos de temperatura, humedad, presión, vientos, precipitaciones, nubosidad, entre otros. Inicialmente, a esos cambios que dependen fundamentalmente de la naturaleza se les llamaba variabilidad natural del clima, pero desde hace varios años en estos ha incidido la acción del hombre, por lo que se ha usado también la expresión cambio climático antropogénico. Al respecto, los impactos del cambio climático en sistemas humanos y naturales se prevén graves, de largo alcance y capaces de afectar desproporcionadamente a los sectores de la población más vulnerables física y económicamente; por ello muchos países, entre ellos Cuba, han trabajado para minimizar las consecuencias de este. Los autores de este artículo consideraron importante describir los efectos actuales y futuros de la variabilidad y el cambio climáticos en la salud.

Along history the earth has experienced changes in the climatic parameters of temperature, humidity, pressure, winds, rains, nubosity, among others. Initially, those changes which depend fundamentally on nature were called natural variability of climate, but for several years the man's action has impacted on them, so that the expression anthropogenic climatic change has also been used. On this respect, the impacts of the climatic change on human and natural systems are considered severe, of long reach and able to affect disproportionately the physically and economically more vulnerable population's sectors; so that many countries, among them Cuba, have worked to minimize its consequences. The authors of this work considered important to describe the current and futures effects of the variability and the climatic change in health.

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Ambient particles may undergo modifications to their chemical composition as a consequence of climatic variability. The determination of whether these changes modify the toxicity of the particles is important for the understanding of the health effects associated with particle exposure. The objectives were to determine whether low levels of particles promote cardiopulmonary effects, and to assess if the observed alterations are influenced by season. Mice were exposed to 200 µg/m(3) concentrated ambient particles (CAPs) and filtered air (FA) in cold/dry and warm/humid periods. Lung hyperresponsiveness, heart rate, heart rate variability, and blood pressure were evaluated 30 min after each exposure. After 24 h, blood and tissue samples were collected. During both periods (warm/humid and cold/dry), CAPs induced alterations in red blood cells and lung inflammation. During the cold/dry period, CAPs reduced the mean corpuscular volume levels and increased erythrocytes, hemoglobin, mean corpuscular hemoglobin concentration, and red cell distribution width coefficient variation levels compared with the FA group. Similarly, CAPs during the warm/humid period decreased mean corpuscular volume levels and increased erythrocytes, hemoglobin, hematocrit, and red cell distribution width coefficient variation levels compared with the FA group. CAPs during the cold/dry period increased the influx of neutrophils in the alveolar parenchyma. Short-term exposure to low concentrations of CAPs elicited modest but significant pulmonary inflammation and, to a lesser extent, changes in blood parameters. In addition, our data support the concept that changes in climate conditions slightly modify particle toxicity because equivalent doses of CAPs in the cold/dry period produced a more exacerbated response.

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El cambio climático es un fenómeno global actual que posee diversas causas, tales como el incremento antropogénico en las emisiones de gases de efecto invernadero y su influencia en el planeta. El óxido nitroso (N2O) es un gas con un potencial de calentamiento 298 veces mayor que el CO2; es emitido por diversos sectores económicos, entre ellos la agricultura y la ganadería por el empleo de fertilizantes nitrogenados. Este uso no incrementa únicamente las emisiones de N2O, sino que afecta todos los eslabones del ciclo del nitrógeno, siendo importante reconocer las interacciones entre sus reacciones (amonificación, nitrificación, denitrificación, etc.) para comprender los efectos sobre la lixiviación de nitratos, volatilización de amoniaco y emisiones de N2O, tres compuestos naturales que afectan el medio ambiente. En Colombia, el IDEAM reportó que en 2004 el sector agropecuario nacional produjo 94,91 gigagramos (Gg) de N2O, pues los sistemas de producción agrícolas y bovinos utilizan altas cantidades de fertilizantes nitrogenados con bajos índices de asimilación. Por ello adquiere importancia implementar buenas prácticas que midan y mitiguen estas emisiones en campo, buscando mayor eficiencia en la transformación de componentes nitrogenados dentro del sistema. En este artículo se enfatiza un manejo adecuado del suelo y la utilización de inhibidores de nitrificación naturales (presentes en algunas plantas tropicales) o químicos, como la nitrapyrina, DCD y NBPT (este último como inhibidor de la amonificación), observando su forma de acción y medición, su efecto mitigador y los incrementos productivos. La presente es una revisión bibliográfica que aborda la problemática ambiental de la ganadería bovina.

Climate change is a global effect currently present with several causes, such as the increased of anthropogenic emissions of greenhouse gases and its influence on the planet. Nitrous oxide (N2O) is a gas with a global warming potential 298 times greater than CO, which comes of many sectors, one of them is the agriculture and livestock through the use of nitrogen fertilizers. This use not only increases N2O emissions, its affects all stages of the nitrogen cycle, being important to observe the interactions between their reactions (ammonification, nitrification, denitrification etc.) to understand the effects over nitrate leaching, ammonia volatilization and N2O emissions, three natural chemicals that affect the environment. In Colombia, IDEAM reports that for 2004, the national agricultural sector produced 94.91 Gg of N2O, knowing the agricultural and livestock productions use high quantities of nitrogen fertilizers, with low assimila2tion rates. Therefore, some adaptable practices and methodologies become important to measure and mitigate these emissions in the field, seeking greater efficiency in the transformation of nitrogen components in the system, being reviewed on this paper the appropriate land management or implementation of natural nitrification inhibitors (present in some tropical plants) or chemical inhibitors, such as nitrapyrina, DCD and NBPT (as an ammonification inhibitor). This is a literature review that approaches the environmental problems of livestock.

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Las enfermedades respiratorias como el asma y la rinitis, de origen predominantemente alérgico, constituyen un problema de salud pública para México, ya que son causas importantes de morbilidad hospitalaria y de ingresos a urgencias pediátricas. Los pólenes son transportados por el viento y se impactan en las vías aéreas causando enfermedad respiratoria alérgica en personas susceptibles. Estudios aerobiológicos en México muestran que en la temporada de secas se encuentra una mayor abundancia y diversidad de pólenes, siendo los árboles la fuente principal. Los tipos polínicos de árboles que sobresalen por su abundancia son Pinus, Fraxinus, Cupressaseae, Alnus, Liquidambar, Callistemon y Casuarina. Interesantemente, el polen de malezas y pastos alcanza su pico máximo de producción durante la temporada de lluvias. Los taxa de malezas y pastos que han sido encontrados de manera más numerosa son Compositae, Cheno-Am, Ambrosia y Gramineae, correspondiendo los primeros tres a malezas y el último a pastos. En la ciudad de México, la contaminación es un factor que exacerba la alergenicidad de los pólenes, ya que los contaminantes causan un efecto directo sobre el propio grano al liberar sus antígenos. En el mundo, el calentamiento global ha favorecido el desarrollo de alergias respiratorias debido a que las etapas de floración son más prolongadas. Todo esto en conjunto representa una amenaza para la salud de los pacientes alérgicos.

Allergic respiratory diseases such asthma and allergic rhinitis are a health problem throughout the world. In Mexico City, pollens are an important cause of allergic respiratory disease. Both, the geographic location- and the vegetation surrounding this City favor the distribution of pollens leading to respiratory disease in susceptible patients. Aerobiological studies have shown that during the mild dry winter there is a large amount of pollens in the environment with tree pollens being the most abundant of all. The most frequent tree pollens found in Mexico City include Fraxinus, Cupressaseae, Alnus, Liquidambar, Callistemon, Pinus, and Casuarina. In contrast, grass- and weed pollens predominate during the summer (rainy season) including Compositae, Cheno-Am, Ambrosia and Gramineae. An additional health problem in Mexico City is the air pollution that exerts a direct effect on individuals. This in turn increases pollen allergenicity by disrupting them leading to the release of their particles which then penetrate the human airways causing disease. Thus, the polluted environment along with global warming which is also known to increase pollen quantities by inducing longer pollen seasons may represent a health risk to Mexico City inhabitants.

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