Alien species are those that were not previously widespread in a certain area. Many of the species that reach an area where they were not previously spread fail to survive for long, and even if they do, they are not able to fully adapt and reproduce. However, if they begin to reproduce independently in nature and negatively affect native organisms, then we call them invasive alien species.

Invasiveness negatively affects the biodiversity and the benefits humans have from nature. Invasive species have negative impact on human health and/or cause economic damage in the area in which they are introduced. Invasive alien plant species are plants with a pronounced ability to reproduce widely at a great speed. They can be brought into a new area by intentional or unintentional human activity. An example of intentional planting is the planting because of the plant's decorative or economic benefit. An unintentional spreading is, for example, the spread of invasive species with seeds of other species such as ragweed seeds which spread from North America with cereal seeds.

Although some invasive alien species are widely known as harmful (e.g., ragweed or small Indian mongoose), the term invasive alien species is still unknown to the general public. These species have a significant impact on their environment, including humans, and the damage they cause to the world economy annually is estimated at up to US$1.4 trillion, i.e. 5% of its total value. The sectors most affected are the economy, health, agriculture, forestry and nature protection. Invasive alien species are considered the second biggest threat to biodiversity. They occur mainly in intensively used areas that have been significantly altered by man (e.g. urban areas, agricultural areas, parks, drained wetlands), so we can say that man has created conditions for the spread of invasive species because he disturbed natural balance in the environment and thus resistance to the arrival of alien species.

We hereby invite all interested parties to help us collect data on the spreading of invasive alien plant species through mobile applications Invazivke for Slovenia or Invasive Alien Species Europe for other countries.

Nowadays we can find numerous sources and databases useful for collecting data on the distribution of invasive alien species in the countries of Sava River Basin. The links below provide an overview of the most important ones:

Slovenia
1. Invazivke

Croatia
2. Invazivne vrste u Hrvatskoj (Invasive Species in Croatia)
3. FCD – Flora Croatica Database

International sources
4. EASIN – European Alien Species Information Network
5. DAISIE - Delivering Alien Invasive Species Inventories for Europe
6. ISSG - Invasive species specialist group -
7. GRIIS - Global Register of Introduced and Invasive Species

8. ESENIAS- East and South European  Network for Invasive Alien Species

9. NEOBIOTA