Species distribution modelling (SDM) is a powerful tool used to estimate the invasion potential of alien species in adventive regions—areas where species have been introduced but are not yet fully established. Often based solely on macroclimatic variables, however, SDMs may overlook other conditions allowing alien species to overcome limitations imposed by broad-scale climate.
In this study, researchers explored the effect of human influence on niche conservatism and shifts by comparing native and alien distributions of 150 bird species using SDM predictions based on eight bioclimatic variables (e.g. temperature, precipitation, etc.) and/or two human impact variables: the Global Human Influence index, and, degree of urbanization.
The performance of SDMs improved significantly with the addition of human impact variables as opposed to bioclimatic variables alone. For most species, the native and alien niches were similar both in terms of climate and human impact, however, some alien expansions were registered—mostly involving colonization of colder climates and more disturbed environments.
In addition to highlighting the importance of human influence on modelling distributions of invasive species, the overall results showed that alien birds tend to invade areas with similar climatic and human impact conditions to their native range. When differences in niches are observed, these are typically related to species tolerance to human-modified habitats and time since introduction.