Scale dependency and fractal dimension of rarity
The rarity of species in a country is usually determined by counting the number of grid cells occupied by those species on a geographical observation grid. In this paper, we present a measure of rarity that is less sensitive to the shape and size of a country. We demonstrate that the distribution of species on a national grid is not monofractal. Consequently, rarity figures cannot be scaled down to a finer grid merely using scale-area plots. We propose a downscaling method that takes into account the non-monofractal distribution of species. Rarity figures have often been published on a scale comprising a limited number of rarity classes. This article finally provides an insight into the degree of accuracy of such classes.
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Document Type: Research Article
Publication date: February 1, 2003