Increased global trade and human movement have facilitated the spread of alien and invasive species worldwide. Since the Industrial Revolution, the world has experienced several waves of globalization that may have accelerated biological invasions, but the influence of these waves on invasion dynamics remains unclear.
In this study, Swiss researchers performed a global temporal analysis of rates of alien species first records between 1750 and 2000 using data of more than 10,000 insects and plants from the Alien Species First Records database. To account for variation in sampling effort, the authors extracted first records for more than 500,000 native species from GBIF.org for the same period.
The analysis revealed that increased alien first record rates were strongly correlated with sampling effort. For insects, an invasion wave was observed between 1820 and 1870 with first record rates 143 per cent higher than expected. Plant invasions started earlier, with first record rates 39 per cent higher than expected from 1750 to 1870.
Both groups experienced reduced invasion rates from around 1900 to 1960 with observed first records ~20 per cent fewer than model expectations, coinciding with major global events (World War I, the Great Depression and World War II).
To test the impact of large-scale variations in globalization on overall invasion dynamics, the authors used a global trade openness index, calculated based on the relationship between total import/export and gross domestic product (GDP). For both groups, they found strong correlations between trade opennesss and invasions, explaining both increases and decreases over the past centuries, making globalization a major socio-economic predictor of biological invasions.