Large white bags have appeared on small islands near Suomenlinna Sea Fortress. The mysterious sacks puzzled local residents for weeks.
Suomenlinna resident Erja Tenhonen-Lightfoot first noticed the bags this autumn. She said they hadn't been there in previous years.
Environmental inspector Jere Salminen from Helsinki City Council explained the contents. The bags contain rugosa roses removed from the islands during autumn conservation work.
Rugosa rose is an invasive species difficult to eradicate. It forms dense thickets and regrows from remaining roots. Salminen called it the worst alien plant species on seashores.
The removal timing serves an important purpose. Conservation work happens in autumn to avoid disturbing bird nesting seasons.
Salminen noted autumn operations allow multiple visits without impacting wildlife. The islands serve as protected nature areas for seabirds.
The islands involved include Puolimatkansaari, Pormestarinhepo and Pormestarinluodot. All form part of Helsinki's protected coastal areas.
A 2018 management plan allows bringing gravel to these islands. The gravel could help improve nesting conditions for terns and waders if bird populations decline.
Local residents had speculated about the bags' purpose. Some wondered if they contained soil or materials for bird habitats.
The conservation effort highlights ongoing challenges with invasive species management in coastal ecosystems. Removing persistent plants like rugosa rose requires repeated interventions across seasons.