Assessment of the ecological effects of Vallisneria spiralis in the Netherlands
An assessment of the ecological risk that Vallisneria spiralis (Hydrocharitaceae) represents for the Netherlands has been performed following the Belgian Invasive Species Environmental Impact Assessment (ISEIA).
V. spiralis is a perennial, rhizomatous submerged aquatic plant originating from Asia, Southern Europe and Northern Africa. The species is known to colonize both tropical and subtropical areas and is increasing its potential range in the colder regions of Europe, although it does not tolerate temperatures below 5°C. In the EPPO region, V. spiralis is known to occur in Albania, Austria, Belgium, Bulgaria, Croatia, Czech Republic, France (including Corsica), Germany, Greece, Hungary (native), Italy (native), Israel (native), Luxembourg, the Former Yugoslav Republic of Macedonia, Moldova, Montenegro, the Netherlands, Poland, Romania, Russia, Serbia, Spain (including Baleares, Islas Canarias), the United Kingdom and Switzerland.
V. spiralis is traded in the Netherlands and in other EPPO countries as an aquarium plant. A survey revealed that 2% of 230 buyers of aquatic plants in the Netherlands had disposed of aquatic plants in open waters. V. spiralis reproduces vegetativelly through runners, sexually through seeds, and both runners and seeds spread via wind and water currents. Seeds can also be spread by waterfowl. The spread capacity of V. spiralis is considered as high.
Negative effects on native submerged macrophytes have been recorded in thermal waters in Poland, but in the Netherlands, there are no signs that aquatic plant species are replaced by V. spiralis. Furthermore, no adverse effects on ecosystem functioning had been observed. The plant is not regarded as invasive in all the European countries where it is present. However, the species forms dense monospecific stands that may decrease the drainage capacity of streams and negatively affect recreation sites. Social impacts are also expected to remain low.
It was concluded that there is therefore no basis to recommend restrictions on the sale of V. spiralis in the Netherlands. In addition, the early implementation of mechanical removal of the plant is not recommended due to the cost of the operation and of the potential for V. spiralis to spread even after a control action.
Sources
Collas FPL, Beringen R, Koopman KR, Matthews J, Odé B, Pot R, Sparrius LB, van Valkenburg JLCH, Verbrugge LNH ; Leuven RSEW (2012) Knowledge document for risk analysis of the non-native Tapegrass (Vallisneria spiralis) in the Netherlands. p 38.
Matthews J, Beringen R, Collas FPL, Koopman KR, Odé B, Pot R, Sparrius LB, van Valkenburg JLCH, Verbrugge LNH ; Leuven RSEW (2012) Risk analysis of the non-native Tapegrass (Vallisneria spiralis) in the Netherlands. p 32.
The Belgian Invasive Species Environmental Impact Assessment (ISEIA) protocol