The HQI map: inspired by the American Habitat Suitability Index, the habitat quality index (HQI) is a mathematical model that includes several variables considered important for the species. Firstly, a relative value is assigned to each of these variables (plant or physical characteristics). Secondly, an average value for all the variables is calculated (often from a geometric average or a weighted sum) in order to generate an overall index, with a value between 0 (zero quality) and 10 (highest quality).