Abstract

FERNANDES, Lucyanno dos Reis  and  AMARAL, Ricardo Farias do. Coastal landscape of Rio Grande do Norte (Brazil) eastern coast: temporal evolution and special patterns of the mobile dune fields. RGCI [online]. 2013, vol.13, n.1, pp.45-49. ISSN 1646-8872.  https://doi.org/10.5894/rgci340.

This study presents the results of a research carried out on the mobile dune fields in the littoral zone between the municipalities of Maxaranguape and Touros, state of the Rio Grande do Norte, northeastern Brazil. The littoral zones occupy a small area in relation to the whole earth surface; however they concentrate a large amount of world population. The study has as an objective, to map the emerged coastal zone on the eastern coast of Rio Grande do Norte, and mainly the space-time evolution of mobile dune fields, using geoprocessing techniques, including remote sensing, digital images processing, and geographic information services. In the study area, the coastal landscape of the mobile dune fields suggest a dynamic scene of spatial and temporal changes, with significant changes on the geometry of the surface sedimentary cover. The dunes act as natural barriers for the flow of sediments to the continent. The occurrence of mobile dune fields is a visible manifestation of a coastal ecosystem highly dynamic on space and time that hosts several endemic species. The methodology of our study consisted of the selection, acquisition, and processing of remote sensing imagery; update of the geological map; selection of pilot areas; supervised classification of pilot areas; and determination of dunes surfaces without vegetation and quantification of space-time changes. The results include a lithological map, map of mobile dune fields multitemporal evolution, and map of quantification of differences between mobile dune fields. The dynamic of transitions in the landscape were superior to the stability of dunes space standards, in such a way that the dune fields from the eastern coast of Rio Grande do Norte, and specially the mobile dunes of fields of Touros, Zumbi and Maracajaú, had a decrease in the sedimentary cover deprived of vegetation between 1988 and 2007. Episodes of El Niño that affect directly the atmospheric circulation, potentiating the sedimentary input for the sand dunes, may justify a relative increase of the non-vegetated area between 1993 and 2001. The results took in consideration that the comparison of images in different time and scales may show patterns, processes and properties of the dune system. Thus, it was possible to describe the dynamic of mobile dunes fields, interactions among features inside the landscape, and how those patterns and interactions changed over time. The use of multispectral images from Landsat 5TM and 7ETM+ family was efficient for mapping the dune fields at a 1:50.000 scale. The interpretation of images and the fieldwork confirms that the aeolian deposits are still active, and the class of surfaces without vegetation used to analyze the movement of dune fields showed to be an adequate indicator. The evolution scene indicates gradual reduction of surface without vegetation, but also, a slowdown on this process, not discarding a cyclic behavior of decennial magnitude. However, this behavior is not only associated with natural processes, such as those related to recovery of areas with vegetation, but also due to action of man, occupying and modifying spaces. This research emphasizes the need of management strategies to support the structure and operation of the foredunes and dune fields that are still actively migrating inland, where decision making about keeping a balance among environmental and sociocultural requirements allows the landscape maintenance. Finally, the techniques and data collected, eventually, may be applied to monitor the fields of mobile dunes for conservation and maintenance of dune ecosystems disposed along the whole coast of the state of Rio Grande do Norte.

Keywords : dune fields; remote sensing; time-space evolution; landscape patterns.

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