Invasive
Species
IDRIJA UNESCO GLOBAL GEOPARK
Invasive non-native species are one of the biggest threats to biodiversity as their ability to spread rapidly threatens the existence of native species by displacing them or by introducing diseases and parasites to which native species are not resistant. They can also completely change inter-species relationships and nutrient cycling, as well as physical and chemical factors. As well as havng negative impact on nature, they can also pose a threat to human health: for example, the common ragweed is an allergenic species. They also affect the economy: invasive non-native fungi threaten tree species, and some species, such as the narrow-leaved ragwort, have a negative impact on grazing livestock.
Invasive non-native plants are typically extremely successful in colonising vacant, degraded land, where they spread rapidly and form monocultures. These problems are only increasing with the growth of international trade, transport and tourism and, ultimately, climate change.
So far, several stands of invasive non-native plants have been observed in the Upper Idrijca Landscape Park, especially at the entry point in Podroteja, at the Rake water channel, and in the vicinity of Lajšt. All sites have been entered in the Invasives web portal.
A 2023–2028 Action Plan for the control of invasive non-native species in the Upper Idrijca Landscape Park is also under preparation.
In the list below, you can learn about invasive non-native plant species in the Upper Idrijca Landscape Park.
Annual fleabane
Annual fleabane (Erigeron annuus) grows in unmown meadows, gravel pits and road verges, and is found in most of Slovenia. It is native to North America and arrived in Europe as a stowaway in the 19th century. In the Upper Idrijca LP, it is widespread along the Rake water channel, at the entry point in Podroteja, and in the vicinity of Lajšt.
Japanese knotweed
Japanese knotweed (Fallopia japonica) prefers to grow in moderately moist habitats along rivers and streams. It is ranked among the 100 most invasive plants in the world. It is native to East Asia and was introduced to Europe as an ornamental plant in the 19th century. It was also planted to harden banks and prevent erosion. In the Upper Idrijca LP, it can be found on the banks of the Idrijca River next to the Tuš shopping centre.
Himalayan balsam
Himalayan balsam (Impatiens glandulifera) is most common on river banks, se najbolj razširja ob bregovih rek, in shaded areas at the edge of meadows and in floodplains. The ripe fruits open explosively and drop many seeds, which is why it spreads so quickly. It is also listed as an invasive alien species of concern to the European Union. It is native to the Himalayas and was introduced to Europe as an ornamental plant and nectar source at the beginning of the 20th century. In the Upper Idrijca LP it is present along the Rake water channel, in Podroteja and in the vicinity of Lajšt.
Common ragweed
Common ragweed (Ambrosia artemisiifolia) grows mainly on ruderal sites, road verges, and field margins. As its seeds are also present in bird food mixes, it is often found at bird feeders. Owners of the land where it grows are legally obliged to remove it. Ragweed is a highly allergenic species. It is native to North America and was introduced to this area in the 20th century as an admixture to agricultural crops and bird seed mixes. In the Upper Idrijca LP, it can be found in Podroteja.
Tree of heaven
The tree of heaven (Ailanthus altissima) spreads along forest edges, roadsides, and rivers. It is also listed as an invasive alien species of concern to the European Union. It is native to East Asia and was introduced to Europe in the 19th century as an ornamental plant. In the Upper Idrijca LP, it can be found along the Rake water channel.
Black locust
Black locust (Robinia pseudoacacia) is native to North America and was introduced to Europe n the early 17th century as an ornamental tree. It is the most widespread alien species in our country. It is a light-loving species and thus thrives best on the forest edges. In the Upper Idrijca LP, it is widespread along the Rake walking path.
Canadian and giant goldenrod
Both goldenrod species (Solidago canadensis and Solidago gigantea) are herbaceous perennial plants that grow up to 2 m (Canadian goldenrod) or 2.5 m (giant goldenrod). They grow in abandoned meadows, forest edges, clearings, and along rivers. They are native to North America and were introduced to Europe as ornamental plants in the 19th century. In the Upper Idrijca LP, the goldenrod is widespread at the entry point in Podroteja.
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