According to the thesis “Antropization effects on natural systems in Greater Granada: the rural-urban gradient”, carried out by Francisco Tarragona Gómez, directed by Professors José Luis Rosúa Campos and José Antonio Hódar Correa, from the Department of Botany of the University of Granada, progressive loss of biodiversity and transformation of complex habitats in simple ones is already an evidence in cities.
According to the author of the thesis, Francisco Tarragona, “landscape around cities is determined by human presence and the use they make of the territory, leading to a gradient which goes from a rural to an urban one”.
Humanized spaces as the fertil plain, poplar and olivar groves, next to river galleries, reach the maximum values of plant and bird denseness, richness and diversity and, according to the author of the thesis, “such indicators must be taken into account in the future to design the use of the territory and to keep the biological diversity in such area”.
This work suggests two possible tools to keep a comprehensive conservationist line: “the agricultural and forest park and the green corridor. The first one is applicable to fertil plain habitats and the second one to fluvial systems in Greater Granada. A systematic management of the protected territory would lead to the restoration of thenatural connectivity that rivers between Sierra Nevada and the fertil plains of Granada and Loja provide”.
According to Francisco Torres, “the management for urban habitats should hang on the expansion and improvement of green spaces to satisfy the leisure and recreation demand of the population and keep the biodiversity. Urban landscape improvement based in the use of ecological information as a comprehensive tool in habitat urban planning, would make territory management in line with sustainable development in cities and in Greater Granada feasible”.
A didactic unit of Urban Biodiversity could materialize from the results of this thesis for citizens to “learn to appreciate environmental problems and acquire a personal and collective commitment with the environment.”
According to Francisco Tarragona Gómez, “the rural-urban gradient has been studied in Greater Granada characterizing twenty-five habitats distributed in five strips of land, which represent the different influence degrees of the urbanization process. It has been quantified in these habitats the habitat structure and the plant and bird denseness, richness and diversity. The habitat structure shows that the percentage of territory covered with cement, very high in urban territorios, decreases in rural ones, whereas the presence of rocks and bare soils increases, as well as the vegetation. However, the maximum values of vegetation are in humanizad places like poplar and pine groves and gardens”.
On the other hand, studying the vegetation, you can appreciate a gradient, or variation, in the parameters of richness and diversity, which decrease from rural habitats to the urban ones, with fluvial habitats reaching the higher values in every strip of land. Some humanized habitats, like olivar groves, present higher values than natural ones, like holm-oak woods. The maximum values of the gradient appear in the fertil plain. The reason for the of diversity high values in humanizad habitats is the great amount of species, plenty of them exotic ones, used in gardens and crops.
“The abundance of bird life –the author of the thesis maintains—presents a progressive decrease from urban to rural habitats, eraching the maximum values in the fertil plain; instead, richness and diversity present an opposite pattern to abundance, with an increase from urban habitats to rural ones. The maximum richness values appear in the fertil plaina and in poplar and olivar groves again. There is also a direct relation between bird richness and diversity and tree-vegetation, as this is the one which increases the most the environment complexity”.
According to Francisco Tarragona, “the fact that a moderate level of development increases species diversity can lead to mistaken conclusions if too synthetic measures of diversity are taken, such as total richness or diversity rates. Moderate levels of development increase diversity, but this increase results from the adding of extensively distributed, generalists, invading or introducted species, at the expense of specialist species of Mediterranean ecosystems”.
Further information: Prof. Francisco Tarragona Gómez.
Dpt. of Botany. University of Granada
Phone numbers: 958-207885 y 639-197224.
E-mail: ftg09700@averroes.cica.es
