We propose a simple mathematical framework to define consistently the environmental quality of a given landscape based on the relative abundances of the constituting land cover classes. Unlike traditional diversity measures, the new method does not evaluate the simple dispersion of the relative abundances of land cover classes, but assigns a weight to each land cover class according to the rank along a gradient of environmental quality. To clarify the ideas discussed, the method is illustrated with data from a pilot study to assess landscape changes in an Italian periurban area over the last 50 years

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