La influencia humana, clave para entender la biogeografía de especies invasoras en el Antropoceno

Abstract

Biological invasions have challenged the traditional concept of biogeography in the Anthropocene. This is because the geographical distribution of invasive species is no longer dependent on its movement ability and the presence of biogeographical barriers, rather on the human activities that promote the expansion of invasive species, intentionally or accidentally. Consequently, modelling techniques must take into account the idiosyncrasies of invasive species in order to effectively anticipate their potential distribution. In this study we use as reference a list of 57 of the worst invasive species in Europe (18 plants, 15 vertebrates, 12 invertebrates and 12 aquatic organisms) to compare the influence of climate and human activities on the large-scale distribution of invaders. We identified nine major vectors of distribution, highlighting transport, ornamental use and trade. We also located seven human variables that we could use as surrogates of those vectors in Ecological Niche Models (ENM): accessibility, population density, GDP, human influence index, urban and agriculture cover, distance to roads and commercial ports. Minimum annual temperature was the most important predictor in models integrating climatic and human variables, followed by distance to ports, GDP and accessibility. Surprisingly, integrated models were not statistically better than models based on climate variables only, yet they anticipated an average increase of 8% in the European surface susceptible to invasion. Such increment is especially notorious in areas under a high human influence where we can presume a higher propagule pressure. In the Iberian Peninsula, the integrated model suggests a higher risk of invasion than the climate model in the eastern coast, Ebro valley and surroundings of major cities. We conclude that climate is important, but not enough to effectively anticipate the spread of invasive species and thus information directly related with the vectors of species introduction must be included routinely in ENM to optimize resources invested in the prevention, rapid response and long-term control of invasive species.