Spatial Downscaling of Alien Species Presences Using Machine Learning

Ioannis N. Daliakopoulos^1,2*, Stelios Katsanevakis³ and Aristides Moustakas⁴

¹TM Solutions, Specialized Health and Environmental Services, Crete, Greece
²School of Environmental Engineering, Technical University of Crete, Crete, Greece
³Department of Marine Sciences, University of the Aegean, Mytilene, Greece
⁴School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom

Spatially explicit assessments of alien species environmental and socio-economic impacts, and subsequent management interventions for their mitigation, require large scale, high-resolution data on species presence distribution. However, these data are often unavailable. This paper presents a method that relies on Random Forest (RF) models to distribute alien species presence counts at a finer resolution grid, thus achieving spatial downscaling. A bootstrapping scheme is designed to account for sub-setting uncertainty, and subsets are used to train a sufficiently large number of RF models. RF results are processed to estimate variable importance and model performance. The method is tested with an ~8 × 8 km² grid containing floral alien species presence and several potentially exploratory indices of climatic, habitat, land use, and soil property covariates for the Mediterranean island of Crete, Greece. Alien species presence is aggregated at 16 × 16 km² and used as a predictor of presence at the original resolution, thus simulating spatial downscaling. Uncertainty assessment of the spatial downscaling of alien species' occurrences was also performed and true/false presences and absences were quantified. The approach is promising for downscaling alien species datasets of larger spatial scale but coarse resolution, where the underlying environmental information is available at a finer resolution. Furthermore, the RF architecture allows for tuning toward operationally optimal sensitivity and specificity, thus providing a decision support tool for designing a resource efficient alien species census.

more at https://www.frontiersin.org/articles/10.3389/feart.2017.00060/full