Alien species are animal and plant species introduced by humans into areas outside their original range. In many cases, the new species are unable to adapt to the new environment and disappear after a short time. In other cases, they not only adapt but spread very quickly, becoming invasive alien species.
The alien flora of coastal habitats
Despite the naturalistic value and the ecological functionality that characterizes them, dune ecosystems share a long history of exploitation and improper management. The resulting environmental problems include habitat loss, impoverishment of the natural landscape pattern, a reduction in the resilience of plant communities and the spread of alien species, which have become growing threats to native species.
Below we will describe two of the most invasive alien species present among the flora of the coastal dunes of the Northern Adriatic.
Oenothera stuchii is a hybrid originating in northern Italy from naturalized populations of Oenothera biennis L. and O. jamesii. The first indication of O. stucchii along the Veneto coast dates back to 1952 and, after a period of pause, seems to be currently in the expansion phase.
The high success in the diffusion demonstrated by the species of the genus Oenothera is linked to their ecology. Their two-year life cycle ensures their resilience and tolerance to the disturbance: in the first season the seedlings appear, and the growth of the vegetative organs begins, while the generative phase is reached only the following year with the production of the epigeal portion. This bi-phasic germination can stop even for years waiting for favorable vegetative conditions. The seeds have a strong affinity for light and can undergo a very long dormancy in the sand creating a “seed bank”, while human activities (trampling, collection of materials, removal of sand …) bring them back to the surface facilitating their germination. The strong tendency to grow in the light, the rapid growth and the high number of seeds (5,000 – 12,000 seeds per plant) determine the steady tendency to invasiveness Oenothera stucchii.
This plant also prefers habitats with large open spaces, very bright and sandy substrate, conditions that guarantee greater competitiveness in contexts disturbed by human action, unlike endemic species that do not survive trampling.
The Life Redune project contains the propagation of Oenothera stucchii with a manual eradication activity within 150,000 square meters. Extirpation occurs at the beginning of the growing season, around May, to prevent the production of new seeds and fruits.
Rosa rugosa (or dog-rose) is native to the Far East, where it is considered a wild plant. It has also spread to Europe and North America where it is cultivated in particular for ornamental and decorative purposes. It is a perennial, very robust plant that tolerates frost and heat, drought and sandy soil.
Rosa rugosa is a species with an upright bushy stem that can reach one meter in height. The reason why it is called “rugosa” must be found in its leaves, which have the characteristic veins, which during the autumn take on very suggestive colors. It blooms throughout Summer, the flowers are quite large and can be born alone or in groups and have a very delicate fragrance.
The individuals that colonize the beaches come from plants cultivated in gardens, but Rosa rugosa, due to its rusticity, is often used also in the traffic island and along the roads.
The Rosa rugosa has a strong negative impact on the richness of native species due to its shading effect that reduces the light to the ground. It also has a negative impact on the social and recreational beach activities as the invaded dunes become impenetrable due to the numerous thorns present on the plant stem and branches.
The Life Redune project constantly monitors the Rosa rugosa populations in the habitats of project interest to assess their expansion and colonization rate. To contain its spread, Life Redune together with voluntary environmental associations, organizes the bioblitzs for the eradication of Rosa rugosa plants.
Invasive alien species represent one of the main environmental emergencies and are considered by the international scientific community to be the second leading cause of biodiversity loss on a global scale. Their expansion in fact threatens biodiversity, but often also has great socioeconomic impacts, with direct damage to health or human activities.
Often the introduction of alien species is involuntary. However, many of the most widespread and dangerous invasive alien species have been imported into our country voluntarily. It is therefore important that everyone develops awareness of the problem, thus transforming itself from a potential vector of introduction to a sentinel against further spread of invasive alien species.
For further information, see the website of the Italian Higher Institute for Environmental Protection and Research: https://www.specieinvasive.it/index.php/it/
In addition to the classification of the problem linked to the introduction and spread of invasive alien species, the site contains the reference legislation, documents and technical guidelines useful for a correct law enforcement, and the information sheets of all the species included in the Union list of Relevance for which a series of obligations and prohibitions are in force.