Urs’arctos Research

Landscape ecology · Fragmentation

Neutral landscape lab

Make a simulated habitat map, remove habitat from it step by step, and find the point at which it breaks apart: its percolation threshold. Habitat is placed either at random (Gardner et al. 1987) or in fractal clumps (With & King 1997), with no terrain or land use behind it.

Landscape

Generator
0.50

Low values give small, scattered bits of habitat. High values give large, smooth clumps.

55.0%

The share of cells that are habitat.

Patch rule

Which cells count as touching. 4-cell: only cells that share an edge. 8-cell: cells that share a corner as well.

Grid size
Map

Metrics

Actual cover
55.0%
Patches (NP)
78
Largest patch (LPI)
51.6%
Mean patch size (AREA_MN)
115.5
Correlation length
42.5
Spans top to bottom
yes

Export

The .asc is a standard ESRI ASCII grid: terra::rast("fractal-128-4cell-seed2662176560.asc") in R, or drag it into QGIS. Cells are 1 for habitat and 0 for non-habitat.

Connected

  • Habitat
  • Spanning patch
  • Non-habitat

128 × 128 cells · fractal, H = 0.50 · 4-cell rule · seed 2662176560

Habitat-loss sweep

Generates 15 separate landscapes and removes habitat from each, from 100% cover down to 0%, measuring the patches at every step.

Run a sweep to see how connectivity responds to habitat loss.

Further reading

References

  • Gardner, Milne, Turner & O’Neill (1987) Neutral models for the analysis of broad-scale landscape pattern. Landscape Ecology 1:19–28. doi:10.1007/BF02275262
  • With & Crist (1995) Critical thresholds in species’ responses to landscape structure. Ecology 76:2446–2459. doi:10.2307/2265819
  • With & King (1997) The use and misuse of neutral landscape models in ecology. Oikos 79:219–229. doi:10.2307/3546007
  • McGarigal & Marks (1995) FRAGSTATS: spatial pattern analysis program for quantifying landscape structure. USDA Forest Service General Technical Report PNW-GTR-351. doi:10.2737/PNW-GTR-351