Evaluating landscape quality with vegetation naturalness maps: an index and some inferences

Question: Can landscape quality be evaluated and compared by a single numerical value using vegetation maps? Location: Northern Apennines (Italy), at about 44° N and between 10° and 11° E. Methods: Seven phytosociological vegetation maps (1:25,000), which correspond to man’s different impact on mountain landscapes, were considered. Syntaxa were classified into five degrees of naturalness, ordered according to increasing naturalness criterion: urbanized, agricultural, semi-natural, sub-natural, and natural. Naturalness vegetation maps were derived in a vectorial GIS. The degrees of naturalness of vegetation were ordered according to increasing naturalness criterion. If ci is the cumulative relative value of every mapped area of the degrees of naturalness, the sum of these cumulative values is A = ∑ ci and is a measure of vegetation artificiality. Its maximum value is Amax = n-1. The Index of Vegetation Naturalness is IVN = 1 - A / Amax , ranging from 0 to 1. Our IVN is an extension of the ILC by Pizzolotto e Brandmayr (1996) due to the ordinal character of the vegetation classification into degrees of naturalness. The maps of vegetation naturalness were also analyzed by two known metrics for the evaluation of landscape quality: TECI (Total Edge Contrast Index) and MSI (Mean Shape Index). Results: The case studies show that the IVN has a linear correlation with the decreasing area of the urbanized and agricultural vegetation types as well as with the increasing area of the highest degree of naturalness. Conclusions: The IVN could be joined to the TECI for the evaluation of naturalness of landscapes. The TECI can supply additional information about the importance of landscape ecotones. Our case studies suggest that an urbanized landscape should correspond to IVN values lower than 0.20. A natural landscape should have IVN values higher than 0.80.