Fragmentation impact metrics

Map metrics:

(1) Edge Influence [0 – 100]: assesses the configuration of landscapes and is calculated as a continuous, bounded spatial metric that quantifies local variations in percentage of tree cover. Local is defined by specifying a window of analysis (e.g. 1 km).

0 (no edges within a 1-km radius), i.e. forest core or matrix core habitat; 100 (a pixel is surrounded by a different habitat for 1 km in all directions), i.e. habitat strongly affteced by the edge

We developed this metric to specifically account for the cumulative effects of multiple
edges (including edge shape and patch size) that exacerbate the realized impact of habitat edges on species. By computing the metric from continuous gradients in percentage tree cover (measured at the levels of pixels and ranging from 0 to 100%), as opposed to computing it from a binary classification of forest or non-forest habitat, we also account for variation in edge contrast and breadth and therefore quantify the controlling influence of matrix habitat on the fragmented forest.

Biodiversity impact metrics:

(1) Fragmentation Impact [0 – 1]: Proportion of individuals lost to the landscape due to fragmentation. Computed for each species. Useful for comparing species within a landscape.

(2) Edge Sensitivity [0 – 1]: Proportion of the edge influence spectrum that is not occupied by the species. Computed for each species. Derived from comparing the abundance surface of a species on the Point tree cover − Edge Influence graph with the abundance surface the species would have if it was insensitive to edge effects. Useful for comparing species between landscapes.

0 (no change in local abundance due to edge effects) ; 1 (restricted to small parts of the edge infleunce spectrum and thus highly sensitive to changes in habitats)

That means for example, that a forest core species with high edge sensitivity (close to 1), would only be abundant in forest core areas with little edge effects within the window used for analysis (e.g. 1 km) and a forest edge species with high edge sensitivity (close to 1) would only be abundant in forest edge areas of specific edge influence values. Both of these species have edge sensitivity and as such would be sensitive to changes in their preferred edge influence characterised habitat.


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