Since 1965, 1,442 unique species have been detected outside of their native habitats across 49 global aquatic ecosystems - approximately one new detection every 8.4 days.
This synthesis highlights the magnitude of recent ANS detections, but the real numbers may well above those recorded by scientists. Many ANS go unreported due to limited search effort and diminishing taxonomic expertise.
The 1,442 unique species recorded in the study is more than ten-fold lower than the number of non-indigenous species observed in terrestrial ecosystems. This can be partly explained by the fact that land biodiversity is vastly higher than the combined diversity of marine and freshwater ecosystems, and thus more non-indigenous species would be proportionally expected in terrestrial systems. However, the truth remains that the documentation of the diversity of invasions in marine, estuarine and freshwater habitats has significantly lagged behind similar research on land.
"We suspect that we may be at the tip of an invasion iceberg in understanding the scale of introductions in coastal environments"
The introduction of species across biogeographic barriers by human activities is recognized as one of the major drivers of biodiversity change. Global warming has enabled non-indigenous species to expand into regions where previously they were not able to survive and reproduce, thus making it even more urgent for conservation policy and management to take urgent action to prevent new introductions and further spread of these species.
Studies such as this one, based on national and regional inventories of non-indigenous species, are only reliable if local experts can maintain and continually update lists of new records. It will be fundamental to continue and to expand research and survey efforts across aquatic ecosystems (marine, estuarine and large freshwater ecosystems), including by implementing standardized methods across regions and taxa to better inform both regional and global policy development and management activities.
