Esteros Del Research Articles

Qualitative models to predict impacts of human interventions in a wetland ecosystem

Abstract. The large shallow wetlands that dominate much of the South American continent are rich in biodiversity and complexity. Many of these undamaged ecosystems are presently being examined for their potential economic utility, putting pressure on local authorities and the conservation community to find ways of correctly utilising the available natural resources without compromising the ecosystem functioning and overall integrity. Contrary to many northern hemisphere ecosystems, there have been little long term ecological studies of these systems, leading to a lack of quantitative data on which to construct ecological or resource use models. As a result, decision makers, even well meaning ones, have difficulty in determining if particular economic activities can potentially cause significant damage to the ecosystem and how one should go about monitoring the impacts of such activities. While the direct impact of many activities is often known, the secondary indirect impacts are usually less clear and can depend on local ecological conditions. The use of qualitative models is a helpful tool to highlight potential feedback mechanisms and secondary effects of management action on ecosystem integrity. The harvesting of a single, apparently abundant, species can have indirect secondary effects on key trophic and abiotic compartments. In this paper, loop model analysis is used to qualitatively examine secondary effects of potential economic activities in a large wetland area in northeast Argentina, the Esteros del Ibera. Based on interaction with local actors together with observed ecological information, loop models were constructed to reflect relationships between biotic and abiotic compartments. A series of analyses were made to study the effect of different economic scenarios on key ecosystem compartments. Important impacts on key biotic compartments (phytoplankton, zooplankton, ichthyofauna, aquatic macrophytes) and on the abiotic environment (nutrients and sediment resuspension) were observed through model analysis. These models results do not indicate a definite relationship between activity and a possible impact, but a potential impact that can be further studied and modelled. Likewise, the model is not intended to be an end in itself, but as a tool to help focus further ecological study, monitoring and modelling. In the real world of wetland management, it is not always possible to conduct extensive (and expensive) analysis of all the principal ecological compartments. In the same manner, the construction of larger and more complex models for resource management usually needs to be focused to those areas most likely to effect resource quality or ecosystem functioning. In this light, the development of qualitative models was considered as a first step to help researchers and decision makers focus their efforts (and economic resources) in an intensive ecological sampling programme and the construction of predictive models.

Modelling energy fluxes in remote wetland ecosystems with the help of remote sensing

The study of the material and energy fluxes that characterise an ecosystem is fundamental to understanding the behaviour of that system and its resiliency in the face of changing local and global conditions. In the present research, an extended energy balance model was used to examine the fluxes that characterise the energy exchange between a large wetland area and its environment. For each flux term, a number of modelling approaches was compared. Modelling was complemented through the use of irradiance measurements from satellite data. The model output shows the daily and season variations in each energy term, as well as a comparison of the modelling approaches. The final output of the model is validated with the measured hourly variation in the enthalpy (water temperature) of the lagoon. A comparison is made of the relative importance of each energy term in the overall balance of the system. This physical based model is being used to examine possible modifications of local and global environments to the wetland energy balance. The model is also being combined with fauna models to examine the relation between climate and population characteristics (habitat). The present work is directed towards the study of a subtropical lagoon in the internationally important wetland, the Esteros del Ibera in Argentina.

Qualitative modelling tools for rural ecosystem management

SUMMARY Shallow lakes and wetlands are highly complex systems in which actions affecting a single compartment can have repercussions far away from the target parameter and those directly related species. In a large-scale study of the Esteros del Ibera wetland in Argentina, researchers have constructed a set of qualitative models with the objective of further understanding the interrelations between management actions and impacts on key abiotic and biotic ecosystem variables. The two qualitative models that have been developed relate to past and future modification of the wetland biotic and abiotic characteristics. The first model examines possible secondary effects of the recently successful ban on caiman hunting. The second model studies the potential impacts of growing regional economic development on water quality and biodiversity of the wetland. The results are qualitative, indicating where further analysis and modelling would be best concentrated. The output of the two models shows that particular populations (piscivorous waterfowl) and compartments (littoral aquatic macrophytes) are more likely to be sensitive to potential modifications in the ecosystem. This is the result of a number of feedback mechanisms that transfer the effects of management and resource-use practices to these compartments. Based on such observations, more attention has been given to creating monitoring instruments for these variables.

The use of systems analysis methods in the sustainable management of wetlands

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.