Alien Species First Records Database

The Alien Species First Records data set contains years (first records) when an established alien species was first recorded in a region (mostly countries, but also sub-national units).
The first records were gathered in a collaborative effort involving >50 researchers worldwide from various sources consisting of online databases, scientific publications, reports and personal collections. A full list of data sources is provided in the data set and the data are described in more detail in the  (compilation of data, list of data sources, delineation of continents, analyses etc.) in the following publication, which can be downloaded with free access:
Seebens, H., Blackburn, T. M., Dyer, E. E., Genovesi, P., Hulme, P. E., Jeschke, J. M., … Essl, F. (2017). No saturation in the accumulation of alien species worldwide. Nature Communications, 8(1), 14435. https://doi.org/10.1038/ncomms14435
The data set was revised and further extended in version 1.2, which was introduced by:
Seebens, H., Blackburn, T. M., Dyer, E. E., Genovesi, P., Hulme, P. E., Jeschke, J. M., … Essl, F. (2018). Global rise in emerging alien species results from increased accessibility of new source pools. Proceedings of the National Academy of Sciences, 115(10), E2264–E2273. https://doi.org/10.1073/pnas.1719429115
One of the above references needs to be cited in case of using the data set.
Note that single years of first records were generated from original records in cases latest years (e.g., '<1920', 'pre-1920') or ranges (e.g., '1920s', 1920-1930') were provided in the original document following these rules:

If latest years were provided (e.g., '<1920'), this year was taken (e.g., '1920')
If ranges of years larger 20 years were provided in the original source, these records were removed.
If ranges of years equal or less than 20 years were provided in the original document, a random year was selected from this time period. This was done to avoid artificial peaks at e.g. the mean value or the first year of that period.
Consequently, some records represent years randomly drawn from the original time period, which makes the column 'FirstRecord' different from the original data source. The original first record as provided in the source is provided in the column 'FirstRecord_orig' of the data set.