Alien plant introductions from a historic pathway of entry (raw wool)
It is well documented that the international movement of raw wool has been a pathway of entry for invasive plants. In Europe, there are several industrial areas used as wool processing facilities which have a unique alien flora. After the mid-20th century these wool processing facilities largely closed. One such area is the Vesdre River valley (province of Liège, Belgium) which received raw wool from Australia, South Africa, and South America. After cleaning the wool, the wastewater was discharged into the river, where contaminant seed spread and germinated downstream of the mills. In July 2021, the valley faced unprecedented floods which resulted in previously colonised banks being exposed of vegetation and in 2022 and 2023, seeds from the long-buried sediment, which had been introduced many decades ago, germinated. During field work in 2022 and 2023, 178 alien taxa were identified, most of them from Australia and South Africa. Five families accounted for more than 87% of the taxa (Malvaceae, Fabaceae, Juncaceae, Geraniaceae and Convolvulaceae). Malvaceae showed a high level of diversity with 71 taxa; 11 species of Abutilon and 15 of Sida. Plant families such as Asteraceae and Poaceae which may also be wool contaminants were not found in the surveys, likely because their seed did not survive wool processing or did not have a long viability. Although the processing of raw wool is historic in the EPPO region, wool waste is now used as a natural fertilizer. This pathway should be closely monitored to ensure invasive plant seeds are not moved as a contaminant.
Sources
Verloove F, Gonggrijp S, Valentini S, Barker R, Gwynne-Evans D, Planchuelo AM, Vandelook F, Leliaert F, Dana ED (2026) Raw wool as an important vector for plant introductions: insights from the 2021 floods in the Vesdre River valley (Belgium). Management of Biological Invasions 17(2), 343–362.