6,200 square meters of giant balsam was controlled in Riihimäki using a mobile game

The summer 2025 alien species control campaign has been completed in Riihimäki. Crowdsorsa players removed a total of 6,200 square meters of harmful giant balsam during the summer. The most effective alien species remover earned over 300 euros.

The city of Riihimäki is activating residents to participate in prevention efforts with a mobile game that combines nature conservation and rewards. Using the Crowdsorsa application, 20 participants marked, prevented and documented giant clam occurrences around the city map and also received a monetary reward for their work.

– It was positive to see that young adults actively participated in the fight against invasive species. In Riihimäki, the proportion of 17–22-year-olds was the largest of all participants, says Saila Nummela, the city's park manager.

A total of 970 euros were awarded to players. From this pot, the most active participant in Riihimäki earned over 300 euros during the summer.

– We plan to continue combating giant balsam with the mobile application again next summer, Nummela says.

This was the first time the city has crowdsourced the control of giant balsam using a mobile game. Giant balsam is a harmful invasive species that threatens biodiversity by displacing native plant species.

The City of Riihimäki will next start collecting observations about accessibility problems using the Crowdsorsa mobile game. Accessibility problems can be reported and earned starting Monday, October 13, 2025.

This is how the foreign-species defense works in the game.

To complete the giant embalmer task, the player filmed a video of the giant embalmer's appearance before and after the fight. The videos were then uploaded to the app for quality control approval.

Each approved instance appeared in real time on the app's local game map. The same targets could be re-targeted after at least two weeks had passed since the previous attack, ensuring that the elimination of the instances would be as effective and long-lasting as possible.