Combining laser rangefinder and viewshed technologies to improve ground surveys of invasive tree distributions

Quantifying the spatial extent, location and habitat associations of invasive tree species is critical to predict their future spread prioritise areas for management. Species–environment relationship analyses are useful tools understanding predicting potential geographical distribution these species; however, such require rigorous extensive data about presence and, crucially, area surveyed. Here, we describe a method performing ground-based visual surveys trees from set viewpoints that utilises laser rangefinder global navigation satellite system (GNSS) technology detect locations. We then highlight novel use information (GIS) viewsheds as tool define Using conifer, Pinus radiata, our target, undertook ground-truthing exercise 50 established in wild assess accuracy determine suitable resolution GIS would be used subsequent species–environment analyses. For trees, error was positively related distance viewpoint. The calculated locations all within 600 m observer were 25 determined by GNSS unit, with median 4 m. These results indicate mapping can efficiently collected over large areas. also outline suggestions instructions computing surveyed area. This approach allows efficient collection accurate on occurrence non-native land underpin form basis risk maps prone invasion. Given speed which obtained using this method, standard easily accessible field equipment software, recommend other invasion ecologists.