Characterization and mapping of illegal landfill potential occurrence in the Canary Islands

The proliferation of illegal landfills (IL) has a negative impact, especially for ecologically sensitive areas or those attractive for tourists. This research focuses on the drivers of the IL spatial distribution in archipelagic environments for mapping the IL potential occurrence. 286 and 153 illegal landfills localizations were identified through fieldwork in the islands of Gran Canaria (GC) and La Palma (LP), respectively. The characterization of IL was carried out from a set of features (177) such as: waste type, control and surveillance, socioeconomic, accessibility, distance to elements of interest, visibility and physiographic. Feature selection was performed using the Discriminant Analysis technique (DA). The DA model selected 10 and 9 features for GC and LP, respectively. The GC IL potential occurrence was mainly related to the greenhouse density, type of cadastral plot and distance to the coast. For the case of LP, the following features were selected: population density, distance to natural protected areas, distance to urban areas, slope and Normalised Difference Vegetation Index (NDVI). Different potential illegal landfill occurrence maps were obtained: (i) likelihood of occurrence of IL; and (ii) areas potentially affected by IL, based on the application of ROC (Receiver Operating Characteristics) curves and success rate. ROC was equal to 0.973 and 0.979 in LP and GC, respectively. Success rate was equal to 81.58% considering an affected area of 21.95% in LP, whereas success rate was equal to 87.32% in GC considering 20.10% affected area.