"The map is not the territory"
De Niro R. (1998)[1]
Nature is a complex matter. It is a complex system made up by complex subsystems, such as land, water bodies, inorganic and organic components (e.g. animals, plants, and other Kingdoms), where each part is at the same time a constituent and a factor both affecting and dependent. Consequently all the usual systems applied to investigate it have a very detailed and specific approach because no general methodology could apparently ever lead to a thorough analysis.
The IAO approach, on the other hand, intends to overcome these difficulties in order to obtain both a general and thorough approach. Due to the complexity of the structure of land, it cannot be considered as the mere sum of its components but an entangled mass of different factors affecting one another, therefore multidisciplinarity is at the basis of the methodology as well as a holistic view of the land.
A proper sustainable land management is considered a standing point in any human activity (e.g. in agriculture for food or non-food production, in landscape planning, in nature conservation, in erosion control). Sustainability can be briefly described as the way to exploit and preserve natural resources in a way by which future generations will inherit an environment at least as valuable as the one we inherited from the previous ones.
Any land management can only derive from a correct land evaluation that can be based on the analysis of the continuous variations of the land. The logic chain that leads from the analysis of the land to its evaluation and successive (and successful) management can be considered as follows (Ongaro, 1998):
The procedure will result as the contrary of any GIS methodology: while in the latter different layers of information are added in a unique component, in the former the same element (the land) is separated in its main constituents considering the relative inter-relationships.
The main components of the land (such as geology, geomorphology, soil, agriculture, and forests) are studied and taken into consideration not only as singular and independent factors but especially for their synergies and mutual relationships therefore leading to a synthetic ("holistic") result. This holistic approach can therefore constitute the reference framework for the traditional disciplines, also enhancing their mutual influences. The methodology can be considered very similar to the organic farming technique where the environment is thoroughly investigated in order to get the maximum help from the natural factors, considering the maximum possible number of their connections and dependencies.
The land classification, i.e. the grouping of similar land elements in a logical and hierarchical framework, in the IAO methodology, implies the detection of three different levels: the "site", the "facet", and the "land system". All these classification levels are referred to with the generic term "land unit", that is, a portion of the earth as it as been delineated on a map and described in the map legend. The term "landscape" instead of "land" depends on the different methodology or phases of the study. Before the field work the landscape units are identified from the remote sensing data. After the field work, when the landscape unit is described by sampling, this becomes a "land unit".
The site can be considered as the chosen station for the relevé (the characteristics of which represent it and can be extended to the whole site); it is the smallest land portion characterised by homogeneity of at least one of its attributes and its dimensions can vary according to the homogeneity of the context. The facet is a combination of sites, related both spatially and in terms of land attributes for at least one of them. Usually it is a mapping abstraction and its dimensions depend on the surveyor’s experience and his or her perception of the landscape. The representative site will have to be carefully chosen in the facet in order to get the right sampling. The land system can be considered as a combination of land facets that form a convenient mapping unit at the used scale; it is made up of geomorphologically and geographically associated land facets that form recurrent patterns, the boundaries of which, coincide with that of some discernible geological or geomorphological feature or process.
In the practice, the same environment is specifically investigated at the same time, by different specialists in mutual and constant co-operation and feedback, resulting in a comprehensive but not superficial analysis. As well as the fieldwork itself, the preliminary work is carried out by the whole team with different expertise in order to have a preliminary map that respect the various needs of analysis in the field.