Vincent Hull

Feedback analysis in reserve management: studying local myths using qualitative models.

A qualitative modelling approach is used to highlight potential feedback mechanisms and secondary effects of management actions on a number of key species in a large Argentine wetland. The development of this qualitative model, in this case a loop model, was a first step in the creation of an overall management and monitoring programme for this important wetland. The use of loop models is a possible strategy in environmental management and monitoring programmes of large complex natural reserves, in which little quantitative data is available. Based upon observed ecological information, several loop trophic models were constructed and appropriate links made to reflect actual trophic relationships between trophic variables. The potential secondary effects of a hunting ban on caiman in a large shallow lagoon were examined. Indirect secondary effects were found to produce unforeseen negative impacts on other predator species (piscivorous birds, piranha) and species important to the abiotic environment (large bottom dwelling fish). As there are limited quantitative data, field investigations and the development of other types of models are necessary to examine in detail the quantitative variations on the populations in question. The results of this model were found useful to indicate where further study and quantitative data gathering might be best focused.

A trophodynamic model for the lagoon of Fogliano (Italy) with ecological dependent modifying parameters

A mathematical model for trophic and detrital dynamics of an Italian coastal lagoon is described, dominant importance is given to the ecological structure of the system. Three biotic components (phytoplankton producers, zooplankton consumers and bacterial pool decomposers) and three abiotic (nutrients, oxygen and organic matter) are considered. Temperature, solar radiation and wind are the environmental forcing functions acting on a seasonal and daily variation basis. Threshold functions are used to change parameter values of the model in the occurrence of notable ecological modifying processes in order to capture the effectiveness on the biotic variables. Simulations show the capability of the model to coherently describe qualitatively the ecological complexity and self-organizing evolution structure of the considered ecological system, but also show a convincing performance in relation to field observations and denoting the importance for considering dynamic parameters in ecological models.

Competition for spectral irradiance between epilimnetic optically active dissolved and suspended matter and phytoplankton in the metalimnion. Consequences for limnology and chemistry

In deep lakes, water column stratification isolates the surface water from the deeper bottom layers, creating a three dimensional differentiation of the chemical, physical, biological and optical characteristics of the waters. Chromophoric dissolved organic matter (CDOM) and total suspended solids (TSS) play an important role in the attenuation of ultraviolet and photosynthetically active radiation. In the present analysis of spectral irradiance, we show that the wavelength composition of the metalimnetic visible irradiance was influenced by epilimnetic spatial distribution of CDOM. We found a low occurrence of blue-green photons in the metalimnion where epilimnetic concentrations of CDOM are high. In this field study, the spatial variation of the spectral irradiance in the metalimnion correlates with the observed metalimnetic concentrations of chlorophyll a as well as chlorophyll a : chlorophyll b/c ratios. Dissolved oxygen, pH, and nutrients trends suggest that chlorophyll a concentrations were representative of the phytoplankton biomass and primary production. Thus, metalimnetic changes of spectral irradiance may have a direct impact on primary production and an indirect effect on the spatial trends of pH, dissolved oxygen, and inorganic nutrients in the metalimnion.

The Influence of Classic Sciences on Ecology and Evolution of Ecological Studies

Contemporary citizens of the Western world increasingly are found to flee city life as often as possible, in the supposition that it is desirable to escape from crowds and seek open space, return to nature, and escape pollution. Consider the amount of automobile traffic or the many airplane flights from any major airport as indicators of the demand to travel large distances. Beyond the extraordinary abilities current transport systems give to average citizens to cover large distances in short times, modern transportation also transforms the notion of place and space in modern societies. In turn, the evolution of Western societies contributes to the changes found in inhabitants and their desires. We cannot ignore the materialism of the eighties, but we also cannot deny that over the last 30 years we have witnessed an increased awareness of the environment and the development of environmental movements. Furthermore, many political ideologies that began with the industrial era have waned over time, and the large social changes of the last century have moved people into a new sensitivity toward the environment. Words like environment, ecology, and ecosystems are commonplace in today’s vocabulary, a simple sign of the widespread gain of environmentalism. Of course, often these words are used incorrectly: a classic example is the use of the term “ecological” to describe a commercial product and guarantee its quality or safety. Conflict abounds in Western societies where economic policies are based on a constant increase in consumption. Yet, there is an awareness that these policies beget degradation of the biosphere. Where is the unitary science to inform our understanding of society and nature? Of development? Of nonanthropocentric earth studies? It does not exist. The science closest to meeting these requirements is ecology, which has only belatedly and begrudgingly been recognized in the academic sphere. Ecology—or any science that attempts to bridge the complexity of nature, economics, and human society—must break the molds of standard science, which inevitably makes it a heretical science.

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.