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The mosquito Aedes aegypti , the principal vector of dengue and yellow fever viruses, is an anthropophilic species adapted to urban environments, particularly to housing. A decisive factor in the proliferation of this species is ambient temperature, which has a direct influence on the vital rates of the species. Here we present a structured matrix population model for analyzing the effect of temperature on the population dynamics of Aedes aegypti . The model is structured following the four natural stages of the species: egg, larva, pupa and adult. A set of population projection matrices (one for each temperature between 5 and 30 °C), was constructed and parameterized using published data on the biology of the species. The output of the models showed that pupation does not occur at temperatures below 8 °C. The population's growth rate was calculated for temperatures between 11 and 30 °C, resulting in an increasing function showing that temperatures above 12 °C are sufficient for population growth. For each matrix, a sensitivity and elasticity analysis of the parameters was performed. Together with the results from the population stable distribution analysis, they suggest that policies aimed at reducing the abundance of Aedes aegypti should seek to lower the survival probability in the egg and larval stages. The population dynamics was simulated under different seasonal scenarios. This seasonal analysis allows asserting that the egg stage dominates the population dynamics at all seasons.

Las lagunas pampeanas evidencian una dinámica muy cambiante (estacional, anual o cíclicamente) en diversos aspectos: profundidad, superficie libre, turbidez, concentración de nutrientes, de clorofila, de sólidos en suspensión, conductividad, etc. Trabajos previos señalan una relación inversa entre el volumen de agua y los valores de indicadores de estado trófico, vinculando precipitaciones y vientos con el grado de eutrofia de estas lagunas. La comprensión de las interrelaciones complejas entre procesos biológicos y geofísicos se dificulta porque éstos no son lineales y presentan retardos que aún no están cabalmente identificados ni cuantificados, con posibles retroalimentaciones entre dichos procesos. La comprensión de la dinámica de la interacción entre clima y ecosistemas lénticos es fundamental para poder conservarlos, utilizando sus recursos y garantizando sus servicios. Un primer paso esencial para relacionar la evolución de las lagunas con las precipitaciones consiste en contar con algoritmos confiables para el procesamiento de imágenes satelitales. Presentamos aquí un análisis comparativo de cinco métodos computacionales para determinar la superficie de agua libre de la laguna La Barrancosa a partir de la aplicación de los índices NDWI (Índice de Diferencia Normalizada de Agua) y MNDWI (Índice de Diferencia Normalizada de Agua Modificado) y métodos supervisados (Máxima Verosimilitud) y no supervisados (ISODATA y K-means) de clasificación en imágenes Landsat (4TM, 5TM y 7ETM+) a lo largo del período 1984-2004. Esto permitió evaluar la capacidad de cada uno para seguir la dinámica del área superficial e identificar el método que insume menos tiempo computacional y minimiza posibilidades de error en la implementación, Pampean shallow lakes exhibit very variable dynamics (seasonally, annually or cyclically) in various aspects: depth, free surface, turbidity, concentration of nutrients and Chl-a, suspended solids, conductivity, among others. Preliminary works indicate an inverse relationship between the volume of water and the values of trophic status indicators, linking rainfall and winds with the eutrophy degree of these lakes. The knowledge of the complex relationships between biological and geophysical processes is difficult because they are nonlinear and exhibit delays that are not yet fully identified nor quantified, with possible feedback between these processes. The understanding of the interaction dynamics between climate and lentic ecosystems is fundamental for their conservation, for resource utilization, and for services preserving. A first essential step to relate the evolution of the shallow lakes to precipitations is to achieve on reliable algorithms for the processing of satellite images. We introduce here a comparative analysis of five computational methods for estimating the area of free water surface of the La Barrancosa shallow lake in Landsat images (4TM, 5TM and 7ETM +) throughout the period 1984-2004, based on the application of NDWI (Normalized Water Difference Index) and MNDWI (Modified Normalized Water Difference Index) indices, as well as supervised (Maximum Likelihood) and unsupervised (ISODATA and K-means) classification methods. The performed analysis allowed us to evaluate the ability of each one to follow the dynamics of the surface area and to identify the method that requires less computational time and minimizes the possibility of error in the implementation., Instituto de Limnología "Dr. Raúl A. Ringuelet"

The use of common rhea, Rhea americana, as breeding bird requires knowledge of nutritional physiology. It is important the analysis jointly of feed intake, behavior and weight gain. Our objective was to determine and analyze differences in the feed intake, weight gained and behavior of captive subadults and adults male and female rheas during autumn and winter in the Humid Pampas, Argentina. Neither males nor females showed significant seasonal differences in the weights with which they initiated the trials. Daily feed consumption didn't show significant differences neither between seasons nor between sexes. However, we observed differences in weight gain by males between seasons and during the autumn trial, the weight gain was higher for males. Rhea behavior also varied seasonally. Males and females spent more time preening and resting than walking and feeding during autumn, the opposite occurred in winter. The males had a higher tendency towards walking than to feeding, the females showed the opposite in autumn. Analyzing the feed intake, weight gained and the time spent on feeding we hypothesized that males are more efficient for feeding. This analysis allowed us to observe there are nutritional issues that can be explained from a behavioral point of view.

An individual-based model for estimating the energetic costs in Rhea americana was developed considering their sexual and seasonal differences in the behavioral activities. The model includes as variables the individual's characteristics, as well as corporal weight, the time spent on different activities, and the cost associated with each activity. We estimated the daily energetic demand of an adult rhea based on the activities individuals normally develop during postreproductive, nonreproductive, and reproductive seasons, differentiating between sexes. The time spent in each activity for one given animal was calculated from field observations of individuals and the estimations of energetic costs for each activity were obtained from specialized literature. The model built varied between sexes because males and females have different reproductive costs. Both models have the same general formulation but they differ in the cost associated with reproduction. In Greater Rheas, while males assume all of the incubation, the females only lay eggs communally in a single nest. Also the possibility that the individual reproduces or not was considered. The model does not allow to determine whether the energetic costs associated with the breeding are the reason why few individuals try to reproduce but it indicates that there is a clear difference in the daily energetic costs of individuals which reproduce and those which do not reproduce. Other activities associated with parental care posthatching, not taken into account here, would increase these differences, and would explain the low number of breeding attempts observed at wild.

After the collective failure to achieve the Convention on Biological Diversity's (CBD's) 2010 target to substantially reduce biodiversity losses, the CBD adopted a plan composed of five strategic goals and 20 “SMART” (Specific, Measurable, Ambitious, Realistic, and Time-bound) targets, to be achieved by 2020. Here, an interdisciplinary group of scientists from DIVERSITAS – an international program that focuses on biodiversity science – evaluates these targets and considers the implications of an ecosystem-services-based approach for their implementation. We describe the functional differences between the targets corresponding to distinct strategic goals and identify the interdependency between targets. We then discuss the implications for supporting research and target indicators, and make several specific suggestions for target implementation.

Gastrointestinal parasitism is one of the diseases that has the highest economic impact on the Argentinian beef production system, rendering it inefficient. In the region of the Humid Pampas, it has been estimated that 22 million dollars are lost annually because of the death of calves and 170 million dollars are lost in sub-clinic costs. A mathematical model with fuzzy parameters was constructed for the analysis of the free-living stages of gastrointestinal parasites, with the purpose of estimating the pool of L3 larvae available for migration to pasture and the levels of infection in pasture at any time of the year under different climatic conditions. The model is formulated in terms of a system of three difference equations. These equations describe the abundance of parasites in each of the successive stages of the population development. The model was calibrated and tested with data gathered through fieldwork carried out in Tandil (37°19′S, 59°08′05″W), province of Buenos Aires (Argentina) and the corresponding weather data. A comparison between model simulations and fieldwork data obtained in other locations achieved satisfactory results.

Ostertagia ostertagi is a nematode, predominantly affecting cattle in the Pampean region of Argentina. A mathematical model parametrized using fuzzy rule-based systems of the Takagi-Sugeno-Kant type (FTSK) for estimating the development time from egg to infecting larval stage L3 of the gastrointestinal parasite O. ostertagi is here proposed. The estimation of development time of O. ostertagi is essential for the generation of appropriate control mechanisms, since this provides information about the time when parasites are ready to migrate to pastures. For the purpose of reflecting the natural environmental conditions, the mean daily temperature is taken as the main and only regulator of the development time. Humidity conditions are considered to be sufficient for the normal development of the larvae. Hence the individual's daily growth is a function of its length and the mean temperature recorded on the previous day. It is expressed in terms of a difference equation with fuzzy parameters, which are defined using laboratory data. Model outputs are tested against results of field experiments. Simulation results are very satisfactory, yielding a mean estimation error (MEE) of 0.64 weeks, with variance 0.34, and a determination coefficient R 2 = 0.74. The model clearly exhibits an inverse relationship between development time and temperature both in controlled and in field conditions. It also exhibits a very sensitive response both to the order in which the temperature sequence occurs, – reproducing the differences observed between spring and autumn – and to the amplitude of the temperature range.

The ˜ Nanduo rRhea americana is an au- tochthonous species perfectly adapted to the pampas environ- ment and only distributed in South America. The species exhibits an unusual breeding system combining polygyny, polyandry, communal nests and exclusive male parental care, which seems to contradict the idea of selfish genes. Our aim has been to construct a mathematical model based on the short term population dynamics of Rhea, living in the wild or in semi-captivity, and taking into account environmental factors that vary from year to year. Due to the characteristics of its life cycle, it was necessary to develop a model that al- lows us to differentiate between the survival and fertility rates of each age group and the distinct behavior during breeding and non-breeding seasons. Therefore, a quarterly differenti- ated stage-structured discrete model was needed. Time steps of different lengths are used for modeling chicks or "charos" on the one hand, and juveniles and adults on the other. En- vironmental variables have been incorporated into the model because they affect the reproductive success of the species. Different scenarios are given as illustrations of the model use. Finally, the possibility of harvesting has been introduced in the model. The model is intended as a first step towards more refined models and systematic data gathering with the purpose of leading the way to a computational tool for risk assessment and decision-making.

espanolFrecuentemente se manifiestan dificultades en la toma de decisiones debido a que no se cuenta con mecanismos robustos que permitan obtener indicadores predictivos utilizando como base los datos del pasado. Resulta entonces de vital importancia contar con herramientas y procedimientos que permitan aplicar metodos de pronosticos de indicadores para comprobar su factibilidad y uso dentro de la gestion del conocimiento organizacional. Esto ha motivado nuestra investigacion en pos de un marco metodologico que permita la ponderacion de la evolucion de los indicadores. El presente trabajo propone un aporte cientifico en el campo de la mejora de la gestion por indicadores, en organizaciones conscientes de la importancia de tomar decisiones estrategicas a partir de la evolucion de los indicadores que marcan el rumbo y el estado de salud de la organizacion. EnglishOften difficulties in decision-making arise because of the lack of robust mechanisms permitting to obtain predictive indicators based on past data. Hence, it is vitally important to have tools and procedures that allow us to apply forecasting methods by indicators to corroborate its feasibility and use within the management of organizational knowledge. This has motivated our research for a methodological framework that may allow weighting the indicators’ evolution. This work proposes a scientific approach in the field of improvement of management by indicators in organizations that are conscious about the importance of strategic decision-making based on the evolution of indicators that mark the direction and health status of the organization

Capybara (Hydrochaeris hydrochaeris ) is the largest living rodent, widely distributed in South America, with a considerable potential as an economic resource. There are large populations in the region of Esteros del Ibera that could be exploited in a sustainable manner and contribute positively to the development of the region. Such exploitation requires to be done responsibly and following a specially designed management plan. In the particular case of wildlife management, a sustainable exploitation of a given species requires knowledge of its dynamics, its density in the area, and its vital rates, as well as understanding how the natural environment will respond to the proposed manipulation. It is also important to determine which environmental variables lead the population dynamics in each region. A mathematical model is a very convenient tool for analyzing possible strategies. This work presents a matrix population model structured in five stages. Sensitivity and elasticity analyses of the model provide an understanding of the effects of differentiated class-dependent survival and growth probabilities on the life cycle. A harvest term has been included in the model with the purpose of evaluating the sustainability of a given exploitation scenario or comparing different harvest strategies. The different strategies depend on the exploitation pattern, the exploitation intensity, and the season in which the harvest takes place. The purpose is to formulate a simple tool that can be understood by a manager without specific training. Hence, the software interface was specially designed for a user with elementary knowledge of vital parameters of the species. © 2005 Elsevier B.V. All rights reserved.

The objective of this work is to analyze at a regional scale the hydrometeorological and hydrological characteristics of the Esteros del Ibera, a vast freshwater wetland located in NE Argentina. Since water is the main driving force in the inland wetlands and variations in water level impose conditions on the behavior of vegetation and animal populations, the knowledge of the main hydrometeorological variables that affect the hydrology is essential. Data correlation analysis makes it possible to evaluate the observed changes in the wetland and to infer its response to regional climatic change. As a first approach, the construction of a topo-bathymetric map provides a basic tool for developing a digital elevation model (DEM) using a geographic information system (GIS) and models that are based on a spatial scale.

There are several freshwater systems associated to large rivers in South America, being the inland wetlands one of substantial significance from an environmental and ecological point of view. Largely sub-valued and unknown, the permanent-temporary flooded ecosystems related to the Parana River in Argentina and Paraguay must be studied in view to their conservation. In the particular case of the Ibera wetlands, their extension (14,000 km2), their inaccessibility, and the scarcity of available data need to be taken into account when attempting to study water dynamics. As a tool to understand the hydrology, main driving force of the ecosystem, a water balance was performed for analyzing the state of the system. As a result, a good agreement between measured water levels and calculated balance was encountered and the possibility of a non-previously considered ground-water inflow tested.

We propose an individual-based energy budget model of the Greater Rhea (Rhea americana) with the purpose of analyzing the population's recruitment. One remarkable characteristic of this species is that female rheas lay eggs communally and males incubate the eggs and care for the chicks without the assistance of females. The model is based on a system of equations daily updating the weight of each bird as a function of its ingestion rate and the energetic cost of its activity pattern. Ingestion rate is calculated from field experiments. Daily energetic costs are estimated from activity patterns observed in the field, taking into account gender and factors that influence behavior (e.g., photoperiod, season). Concatenating daily model outputs, the weight dynamics of an individual can be calculated over any given period of time. The possible factors that affect the successful breeding of the Greater Rhea and therefore population growth are analyzed using the model. Different reproductive strategies for each gender are analyzed and the minimal body weight, and thus energy reserves, that an individual needs to achieve for ensuring reproductive success is determined. Model outputs show that the reproductive success of males depends strongly on their body weight while females exhibit low nutritional requirements for producing eggs. An analysis of model outputs allows inferring that males in wild populations might not be able to breed in consecutive years but could successfully breed every other year. They also allow estimating the incidence that food availability has on population growth. Management strategies that are easy to implement in extensive and semi-extensive farms may allow obtaining male individuals capable of breeding every year. Fil: Simoy, Maria Veronica. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Canziani, Graciela Ana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina Fil: Fernandez, Gustavo Javier. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Marinelli, Claudia Beatriz. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina

The management of the utilisation of natural resources from wetland ecosystems is a multiobjective and complex task. The creation of innovative decision making tools for sustainable wetland resource utilisation is an important challenge for the future. This is particularly crucial in the light of the growing shortages for high quality freshwater and the vanishing habitat for a large number of wetland fauna and flora species. Because wetlands combine attributes of both aquatic and terrestrial ecosystems, wetlands are often at the crossroads of a number of disciplines with no specific discipline of its own. Therefore, management programmes require a multidisciplinary approach founded on a systematic monitoring of key biological and physical parameters. A European Commission DG XII research project dedicated to the development of management tools for wetland resources in Latin America is being developed by a multidisciplinary team of researchers from eight universities, located in four EU member states, Argentina and Brazil. The study sites that will be utilised for this analysis are two shallow lakes in Northeast Argentina within the large (13 000 km2) wetland `Esteros del Ibera'. Continuous and periodic in-situ monitoring instrumentation has been installed in a long term monitoring programme of hydrological and meteorological factors, coupled with monthly biological and ecological data gathering. Potential future scenarios for wetland resource use are being discussed in a series of public meetings with key provincial and local actors (teachers, university professors, clergymen, local business persons and politicians). These meetings address both the small scale modifications of wetland use (water extraction for agriculture, tourism, controlled hunting) as well as regional projects related to the creation of large scale economic development (forestation, modification of nearby waterways for hydroelectric production and increased river transportation). Models are developed relating the chemical, physical, biological and ecological parameters monitored. These models will be dedicated to analysing the effects of development on wetland functions and resource quality. An economic model will be created to evaluate potential modifications in wetland functions in the local and regional socio-economic context. Evaluation instruments are developed and tested which include; qualitative models using loop analysis, goal functions based on the aquatic trophic web and the overall energy flux in the lagoon, and a geographical information system utilising satellite images. The purpose of these instruments is to examine the overall impacts of development alternatives on resource quality and ecosystem integrity, as well as demonstrating key parameters that should be more closely monitored. The final package will include an evaluation of the potential impacts of the development scenarios proposed by the key actors, recommendations to reduce specific impacts through alternative technologies, together with a monitoring programme and analysis tools for improved decision making in wetland resource management.

The model here presented describes the dynamics of adult Ostertagia ostertagi parasites in cattle in the field. The model also describes the population of infecting L3 larvae subject to the conditioning process while in the pasture as well as the inhibition–disinhibition process in ingested L4 larvae. The model has two modules: one for the conditioning process and the other for the parasitic stage. The first module determines the proportion of ingested L3 larvae that will go through an arrested stage of development, or hypobiosis, and for how long depending on the weather conditions and the length of the period of exposure in the pasture. The second one describes the adult population dynamics as disinhibiting larvae and recently ingested larvae accumulate in the animal. The model has a discrete daily step and is parameterized using fuzzy inference systems of the Mamdani type (FM). Given that the inhibition–disinhibition process is not yet fully understood, a series of perturbations on the different input variables were performed with the purpose of analysing the model's behavior. Simulations show that the adult population exhibits two maximal peaks of infection in the hosts in December–January (Summer) and April–May (Autumn). These high values are a consequence of hypobiotic larvae resuming their development at those times. Fil: Chaparro, Mauro Alejandro Eduardo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Canziani, Graciela Ana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina Fil: Fiel, Cesar Alberto. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Veterinarias. Departamento de Sanidad Animal y Medicina Preventiva; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

This study of a Daphnia population model suggests that sublethal effects of nonpolar narcotics on growth of individual organisms can result in ultimate extinction of the population at chronic chemical concentrations near the effect concentration that leads to a 50% reduction in individual growth (the 16-d EC50 for growth). A quantitative dose-response relationship (QDRR)—a population extinction threshold, relating the minimal chronic chemical concentration that yields population persistence and the octanol/water partition coefficient (Kow)—is generated from numerical simulation studies of a Daphnia population model. The transition from population persistence to extinction is examined in terms of density functions in the lipid, structure, and age variables associated with models of individual daphnids. The densities of populations undergoing transition from persistence to extinction due to increased toxicity suggest that critically stressed populations are age-bimodal with a component of old, large individuals and a component of small, nonreproductive individuals. The populations that persist near the threshold for extinction are unexpectedly diverse in age density and consist of relatively small individuals.

Suspended organic and inorganic particles, resulting from the interactions among biological, physical, and chemical variables, modify the optical properties of water bodies and condition the trophic chain. The analysis of their optic properties through the spectral signatures obtained from satellite images allows us to infer the trophic state of the shallow lakes and generate a real time tool for studying the dynamics of shallow lakes. Field data (chlorophyll-a, total solids, and Secchi disk depth) allow us to define levels of turbidity and to characterize the shallow lakes under study. Using bands 2 and 4 of LandSat 5 TM and LandSat 7 ETM+ images and constructing adequate artificial neural network models (ANN), a classification of shallow lakes according to their turbidity is obtained. ANN models are also used to determine chlorophyll-a and total suspended solids concentrations from satellite image data. The results are statistically significant. The integration of field and remote sensors data makes it possible to retrieve information on shallow lake systems at broad spatial and temporal scales. This is necessary to understanding the mechanisms that affect the trophic structure of these ecosystems.

The purpose of this work is to assess the impact on the Esteros del Ibera wetland ecosystem caused by the Yacyreta dam, a large hydroelectric power plant on the Parana River, Argentina, in comparison to other factors of environmental change. The project of the dam started around 1970. The power plant began operating in 1994. In 1989, the neighboring Ibera wetland ecosystem showed a substantial increase in the water level for which several different causes were conceivable, including climate change and the dam construction. We analyzed all existing hydrometeorological data and studied other changes that were observed in this ecosystem. A water balance model was used to analyze different scenarios. Increased groundwater inflow, generated since the construction of the dam, appears to be affecting the wetland more than any other factor. The study has implications for the assessment of global and regional consequences of building dams.

The vast majority of nations have fallen far short of the Convention on Biological Diversity's (CBD's) 2010 target: to reduce the rate of loss of biodiversity ( 1 , 2 ). This prompted the CBD to develop a new plan of action, supported by 20 “SMART” (specific, measurable, ambitious, realistic, and time-bound) targets for 2020 ( 3 , 4 ). As the 10th Conference of the Parties (COP) of the CBD meets in Nagoya, Japan, to negotiate both plan and targets, it is critical that targets also be grounded in the real interests that people have in benefits provided by biodiversity. To evaluate targets on this basis, we use the ecosystem services framework developed by the Millennium Ecosystem Assessment (MA) ( 5 ). This framework balances resource conservation and use according to how societies value consumptive (e.g., food and fuel) and nonconsumptive (e.g., health and aesthetics) services provided by ecosystems.

Faith argues that our approach to biodiversity conservation, which focuses on people's interest in the benefits of ecosystem services, may deprive us of future, unanticipated benefits. This claim is misplaced. In our Policy Forum, we argue that conservation goals should reflect the benefits we get