The Decrease of Agricultural Areas and the Development of Urban Zones Analyzed with Spatial Statistics

Until a few decades ago it was very easy to distinguish between city and country: in most cases the edge was defined by defensive barriers. In recent times, the relationships between urban and rural areas completely changed, placing the country in a subordinate position. Consequently, many terms have been coined in order to describe the new phenomena taking place between city and country. The term adopted, “periurban area”, despite its large use, does not have a clear and unambiguous definition. Such various approaches are due to the complexity of the phenomenon to be analyzed and to the huge variety of territorial contexts in which it may reveal. The phenomenon is characterized by urban growth with soil consumption generating loss of competitiveness for agricultural activities. This paper defines more precise rules in order to describe the periurban phenomenon, using techniques of spatial statistic and point pattern analysis. This approach has been tested in the case of study of Potenza municipality. Interest in this area comes after the earthquake of 1980, when a large migration of inhabitants began towards the countryside around Potenza. DOI: 10.4018/jaeis.2011070102 International Journal of Agricultural and Environmental Information Systems, 2(2), 16-28, July-December 2011 17 Copyright © 2011, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. urban exodus, new conurbations, “rurbanization”, periurban countryside (Charrier, 1994). Therefore, it is not easy to define in a clear and unambiguous way which is the sharp boundary between urban and rural areas (Murgante & Las Casas, 2004; Murgante et al., 2008). Ahlqvist and Ban (2007) developed an ontology considering the degree of urbanization going from rural through exurban, from suburban to urban. In planning literature, the periurban phenomenon has been defined in different ways. Le Jeannic (1997) describes the population displacement as the need to escape from the dense city in order to have more space and a better environment. Also, growth of periurban belt is due to high costs of flats, the need of individual dwellings and land rents (Guerois & Pumain, 2001). Since 1980s it has been less and less possible to distinguish town from country, denying the concept of two separate entities which was for many years one of the cornerstones of spatial planning (Hidding et al., 2000; Van Den Berg & Wintjes, 2000). Rural areas are more urbanized and an uncontrolled growth of periurban belts has increased the number of inhabitants. At the same time, urban areas have lost resident population gaining population in transit (Alberti et al., 1994), because of the activities concentration in urban areas. All these situations produce a huge commuting phenomenon (Cavailhès et al., 2004). The main feature of this trend is a low density of urbanization which spreads in all directions (Camagni et al., 1998). Growth of these areas is strictly related to urban sprawl, generating negative repercussions on agricultural activities. A great amount of roads have been built to improve dwelling accessibility and car is the only means of transport (Camagni et al., 2002). This is an opposite trend compared to the period after the Second World War, when urban planners used statistical methods to give a dimension of the migratory flows towards towns. This tendency, strictly related to Urban Sprawl, is so complex to analyze, that classical statistics are not enough for a complete understanding of the phenomenon. Settlement location in zones surrounding urban areas takes into account environmental features, accessibility, agricultural losses of productivity. In order to achieve a more complete analysis it is important to analyze each phenomenon according to its spatial location, so that it is possible to consider the concentration of some events in some areas and their possible interactions. Geostatistics can be useful in order to study this problem with an innovative approach compared to the classic socio-economic techniques. This method allows an analysis which may determine the actual trend in one region. This technique has been applied in Potenza Municipality, where a migratory phenomenon began from urban to rural areas after a strong earthquake occurred in 1980. All the informative layers have been combined with a land suitability procedure in order to define a periurban fringe with a certain precision. 2. AN OVERVIEW OF SPATIAL STATISTICS TECHNIQUES The main aim of spatial analysis is a better understanding of spatial phenomena aggregations and their spatial relationship. Spatial statistical analyses are techniques which use statistical methods in order to determine if data show the same behaviour of the statistical model. Data are treated as random variables. The events are spatial occurrences of the considered phenomenon, while points are each other arbitrary locations. Each event has a set of attributes describing the nature of the event. Intensity and weight are the most important attributes; the first is a measure identifying the event strength, the second is defined by the analyst who assigns a parameter in order to define if an event is more or less important according to some criteria. Spatial statistics techniques can be grouped in three main categories: Point Pattern Analysis, Spatially Continuous Data Analysis and Area Data Analysis (Bailey & Gatrell, 1995). The first group, Point Pattern Analysis, considers the distribution of point data in the space. They can follow three different criteria: 11 more pages are available in the full version of this document, which may be purchased using the "Purchase" button on the product's webpage: www.igi-global.com/bookstore/article.aspx?titleid=55951