Non-indigenous species are species that have been spread as a result of human activities to areas where they do not belong naturally. The main concern are the invasive species, which are defined as causing a significant negative impact on biodiversity as well as serious economic and social consequences.

The dataset has been prepared first by individually mapping each aquatic invasive species that had a distinctive distribution area, which had been provided by several non-indigenous species online databases. The distribution of the species were then resampled into the EEA 10 km grid and summed together, showing the number of non-indigenous species per grid cell. The temporal reference of the dataset covers the last 30 years (1989 - 2018

This dataset has been prepared for the calculation of the combined effect index, produced for the ETC/ICM Report 4/2019 "Multiple pressures and their combined effects in Europe's seas" available on: https://www.eionet.europa.eu/etcs/etc-icm/etc-icm-report-4-2019-multiple-pressures-and-their-combined-effects-in-europes-seas-1.