Towards strategic spatial planning of the peri-urban area of Santiago del Estero city, Argentina

Santiago del Estero is a city of about 300 k habitants in the NW of Argentina, at the right border of the Dulce river, in the ecoregion of Gran Chaco, under a semi-arid, hot climate. The southern peri-urban area of the city exhibits special environmental settings, because of an extensive irrigation infrastructure, providing water to an area of about 250 km2, contrasting with the semiarid surroundings. A couple of road projects, which will interconnect this area with the national road network, is actually triggering a fast, but somewhat uncontrolled transformation of the landscape by urbanisation and land-use change, which may threaten overall environmental quality. In order to provide criteria for a spatial strategic planning, the objective of this study was to assess the general grade of human modification and the provision of ecosystem services (SE) of the periurban-rural area. The methodology consisted in (i), an estimation of distance to naturalness of the landscape, by means of hemeroby grades, in a range from 1, natural, to 7, highly modified, based on visual inspection of high-resolution satellite imagery (Google Earth) (Paracchini and Capitani 2011, Sukopp (1976), Walz and Stein (2014)), and (ii), in assessing of different SE, by means of an expert based association matrix between land use / land cover (LULC) and the degree of provision of 11 individual SE, in the 4 classes of production-, regulation-, cultural and supporting services (Burkhard et al. 2009, Koschke et al. (2012), La Rosa and Privitera (2015)). The map of hemeroby reveals still near natural (grade 2) environments alongside the river, with typical riberian vegetation. Highly modified environments appeared at the southern fringe of the city area, reflecting the urban sprawl, whereas in the rest of the area, mean hemerobic grades (4/5) were observed along the main roads, indicating rural settlements and urbanisation cells, and large patches with low human impact (grades 2 to 3), representing wood and shrubland. The LULC map, based on Landsat Oli 8 image classification, confirmed the appreciation of hemeroby, showing a matrix dominated by wood- and shrubland (47 %) and mixed cultivation patterns. Respect to ecosystem services, a high provision for regulation-, cultural and supporting services (> 60 - 100) was observed, due to the high proportion of near natural vegetation and small-scale agriculture. Specifically, the potential of climate, water balance and soil erosion regulation capacities, combined with that of cultural services, provides very good conditions as a human habitat, on the backdrop of the climatic context and urbanisation progress. So, these aspects have to be cautiously administered during landscape transformation. The individualized spatial information, represented in maps, constitutes an important tool for planners and decision-makers, in defining guidelines for spatial planning integrating environmental quality.