Human impact footprint as a predictor of invasive species risk

Species distribution modelling is a valuable tool for identifying areas most at risk of the spread of potentially harmful species. However, it usually relies on identifying key environmental variables that affect species spread such as (for aquatic species) water chemistry, and these data may not be comprehensive in some areas of interest as they are resource intensive to produce. Human activity is known to be an important risk factor for invasive species establishment and spread, alongside other environmental variables such as water chemistry, temperature etc. Here we examine whether a simple index of human impact levels (or “footprint”) can be used as an explanatory variable to successfully predict the presence of some important invasive aquatic species in Swedish lakes. Human footprint (HFP) performs well only when combined with mean annual temperature (an important limiting factor for most invasive species in Sweden), giving results close to those achieved with a set of relevant environmental variables and may be useful to identify lakes at most risk of the spread of invasive species. Where detailed environmental variables are also available, HFP can provide additional important information for modelling.