Representing habitat

Mapping habitat

Habitat can be represented in many ways, ranging from complex species distribution models to relatively simple ecosystem mapping or site classification data.

In this tutorial, we use high resolution (1:5,000 scale) site classification mapping to map habitat for our target species. This versatile approach should be accessible to many communities, wherever land classification or terrestrial ecosystem mapping data are available. Otherwise, habitat can be mapped based on orthoimagery generated using a variety of methods (e.g., satellite, drone).

Filtering site classification mapping based on habitat types for target species

The site classification data we have at hand takes the shape of polygons circumscribing different ecosystem types or areas of land use. First, we select the site classifications representing suitable habitat for our targets: woodlands (WD), cliffs (CL), herbaceous (HB) habitat types.

# Polygons with feature attributes corresponding to land classifications describing the habitat of target species
landClass_Habitat <- landClass %>% dplyr::filter(CLASS == "CL" | CLASS == "HB" | CLASS == "WD") %>% dplyr::mutate(HPID = dplyr::row_number())

Converting polygons to gridded representation of habitat

Polygons representing habitat for target species are then represented as grid cells. For this methodology, a key consideration is to ensure that the grid scale corresponds with the precision of features representing search effort (see next section).

The map below shows green polygons representing habitat within Bellhouse Park, superimposed with a gridded representation of the same habitat (30x30 m^2 cells). Assuming Primula pauciflora as our target taxon, we delineate the extent of its historical habitat based on the best available information (in this case, based on a reasonably accurate GPS coordinate, knowledge of its habitat type (vernal pools), and first-hand knowledge shared by the collector, Harvey Janszen). The accuracy of this information allows us to select 9 cells from our habitat map to represent the historical habitat of Primula, shown in blue.

Expanding this grid to habitat features across the entire island, we produce the grid representing all potential habitat: