Habitat Quality Index Calculator

This calculator produces a Habitat Quality Index (HQI) modeled on the structure of the U.S. Fish & Wildlife Service's Habitat Evaluation Procedures (HEP) — the agency's standard framework, documented in its Ecological Services Manual (102 ESM) and Service policy 870 FW 1, for scoring habitat quality and expressing it as "Habitat Units" (see the reference below). This tool borrows that structure and vocabulary — a 0-100 quality index, a Habitat Suitability Index, and Habitat Units as index × area — but substitutes generalized, fixed percentage weights for the species-specific Habitat Suitability Index curves that a real HEP assessment builds for the species being evaluated. Seven site conditions are normalized to a 0-1 scale and then combined using the fixed percentage weights below to produce the 0-100 HQI score. Vegetation cover and food abundance each carry the heaviest weight (20%), followed by water availability and structural diversity (15% each), inverted human disturbance (15%, so a pristine site scores highest), a log-scaled patch-size score (10%, since larger patches disproportionately support more species per the log10 curve used here), and an edge-penalty term (5%) that discounts quality as the edge-to-interior ratio grows.

A separate, simpler Habitat Suitability Index takes the geometric mean of vegetation, water, and food scores — useful as a quick cross-check when those three core resources dominate suitability for a species. The resulting HQI score sorts into five bands from Unsuitable to Optimal, and a management-priority recommendation (protect, enhance, restore, maintain, or low-priority) is generated by cross-referencing the score against disturbance level and patch size. The calculator also flags whichever input scored lowest as the "limiting factor" — the single variable most worth improving first. Two caveats: species capacity and habitat units are rough multipliers of the HQI score and patch size, not calibrated wildlife-population estimates, and the weighting scheme is a generalized approximation — a rigorous HEP assessment for a specific species uses species-specific suitability index curves rather than these fixed percentages.