Socio-economic drivers of biological invasions. A worldwide, bio-geographical analysis of trade flows and local environmental quality.

The introduction of harmful non-indigenous species has long been acknowledged to depend both on the propagule pressure imposed by the openness to international trade, and on the health of the receiving ecosystem, largely determined by the level of anthropogenic disturbance due to local economic activities. We estimate the relative weight of the socio-economic drivers of biological invasions, for 115 countries in all continents and for invasive species of all taxa. Our results confirm the theoretical prior of trade, agricultural imports in primis, as an important driver of biological invasions, but also shed more light on the factors of disturbance to local ecosystems that emerge as playing an even more important role. We then develop an analytical model linking introductions of invasive species to import volumes disaggregated by country of origin, and weighted by bioclimatic similarity between source and destination country of the trade flow. The results allow us to identify the relative risk of biological invasions entailed by different directions of trade among 134 countries aggregated in geographic regions.