The share of present invasive species in the last decade shows an increasing trend. An increase in the share of invasive species is evident along the great rivers Sava, Mura and Drava, as well as along the Kolpa. In higher areas of Slovenia, particularly in the Alps and the Dinaric region, invasive species are very few or entirely absent. However, a notable increase in their share along the western border of the Dinaric region raises concerns.
From the perspective of nature protection, invasive species are generally those expanding spontaneously in their new natural or semi-natural environment and consequently causing serious disturbances/changes in the functioning of the ecosystem.
The indicator shows the comparison between periods by share of invasive species, based on the available data. For the calculation of shares, all available data from the period 1957–2006 were taken into account, while the comparison was made between the periods 1987–1996 (approximately 100,000 pieces of data) and 1997–2006 (approximately 130,000 pieces of data).
To draw up and adopt an operative programme of non-native invasive species management (Resolution on the National Programme of Environmental Protection, 2005):
· to stop or reverse the trend of the increasing share of invasive species in local flora by 2010;
· to prevent the introduction of new invasive species and take immediate action in cases of the beginnings of expansion of new invasive species in order to completely eliminate invasive species.
The share of invasive species recorded in the last decade is considerably higher than a decade earlier (red circles), while the number of quadrants where the share of invasive species decreased is considerably smaller (black circles). Each circle size is proportionate to the difference between the shares, meaning that quadrants with the same share of invasive species in both periods seem to have no invasive species, as the trend is 0 (zero). The increase in the share of invasive species over the last decade is notable.
Such a trend certainly raises concern. In addition, a decrease in the share of invasive species does not reflect the real situation due to various degrees to which flora was assessed in individual quadrants in the past decade.
In Slovenia, invasive species that expand spontaneously and, consequently, cause disturbances and changes in the functioning of ecosystems are not adequately covered by legislation. Measures (e.g. restriction of their introduction and expansion) in cases of massive occurrences of invasive species have also not been put in place.