## 4 Discussion  
The developed analyses, focused on land use in the Vesuvius area over the last two centuries, have made it possible to recognize trends in LUCC using a qualitative-quantitative approach. The historical cartography available for the study area exhibited a high degree of reliability and the transformations they showed were connected to different anthropogenic and natural driving forces which intertwine and alternate. The graphic land representation/simulation and the process of interpreting the historical cartography effectively supported the comparative diachronic reading of the structure of the landscape in terms of its typological characteristics and invariants. A first aspect to consider concerns the level of detail on the maps: the resolution of the historical maps (between 1:25,000 and 1:50,000) made almost all of them substantially comparable. The only exception was the 1960 map, whose resolution (1:200,000) made it useful in comparison with other maps in terms of the qualitative definition of land use change trends and in the overall quantification of area amounts, but less significant in terms of landscape metrics, especially for issues related to land configuration. Accuracy is another interesting aspect to consider in relation to the use of historical maps. In the present work, a high level of accuracy was demonstrated by the low values of RMS error in ESRI ArcMAP and the MPE and SD indicators in the MapAnalyst software. When it comes observed transformations, overall, the reference period (1817-2009) records a reduction in forest and agricultural areas, to the benefit of urban and sparse vegetation ones:  
* the forests that used to make up 32% of the territory currently occupy 20% of it;
* agricultural areas and vineyards previously made up 43% and 21% of the territory, respectively, whereas now they make up 36% of it;
* sparse vegetation areas went from 1% to 20% in 2009;
* urban areas increased from 3% to 24%. The driving forces behind these changes are closely intertwined. Forest reduction, for example, must be read in the context of increases in both scattered vegetation areas and urban areas and the replacement of soils with agricultural areas. Almost 30% of the forests of 1817 are today covered by scattered vegetation areas. This ratio rises to 47% in 1907 compared to the 1817 map and stabilizes at 20% in the following two periods. In forestation terms, the last fifty years show a reversal of this trend when compared to the beginning of the century. The particular \"nature\" of the national park, with the presence of a volcano, explains the amount of variation (increases and decreases in scattered vegetation areas, which often replace forests) in areas close to the cone. It is possible that, due to the effect of the cessation of Vesuvius activity (the last eruption was in 1944), as well as the effect of the establishment of the natural protected area in 1991 (along with consequent policies of nature protection), in the recent decades, a re-forestation process has taken place near the crater. Analysis of the replacement of the original (1817) 400 ha of forests with anthropic areas (2009), in the different temporal phases, highlights a process which has unfolded over two centuries. The greatest impact on forests has occurred in the last fifty years, but, in the same period, this aggression has been balanced out by new reforestation in areas previously affected by vineyards and sparse vegetation. Instead, in the previous period (from 1960 to 1817), the process of urban growth had mainly affected agricultural areas and vineyards. The dynamic of the \"urban\" LU type, in terms of the overall area amount during the two centuries analysed, shows an increase trend. The comparison of this trend with that of the population (Figure 2) allows for the observation that the growth rate was quite different: urban areas in fact went from 590 ha to 4102 ha, with an increase of 700%, while the population went from 65,000 to 312,000 inhabitants, with a growth rate of 400%.