Turning the Tide

How Zurich fights back

In Switzerland it is forbidden by law to plant, tend to or distribute invasive neophytes. Populations and their locations must be reported to the authorities, who are compelled to remove them [6].

In order to deal with these troublesome neophytes, the Canton of Zurich has implemented two pieces of legislation to comply with the law and rid the area of Hog- and Ragweed. “Grün Stadt Zürich” (GSZ) is in charge of managing these species in the city since 2015 [7]. Their “Aktionsplan 2016-2020” identified neophytes that needed to be removed and specified methods for their removal. While some neophytes were removed successfully and some even exterminated entirely, many species managed to thrive, in spite of efforts against them. Reasons were changing climate, increased mobility of people and wares spreading seeds, as well as GSZ lacking the legal authority to fight neophyte populations on private property.

The new “Aktionsplan 2021-2030” aims to change that by introducing a model based on the pillars Eradication, Monitoring, Coordination and Information & Prevention to combat neophyte spread in the city. With this plan, GSZ aims to fulfill the overarching goal of preventing harm to native species, habitats, infrastructure and people. This is to be achieved by completing a plethora of different, smaller goals, like treating at least 80% of all registered neophyte locations at least once a year, or exterminating all populations of dangerous neophytes. 

Different actors in Zurich and their contributions to the four pillars, according to the Aktionsplan [Image 24].

 

To that end, they employ various removal methods for different neophytes. Giant Hogweed is best fought by cutting any plants to the ground early in the year as well as cutting the root at least 15cm below ground. It is recommended to wear protective clothing and avoid cutting the plants on sunny days. Common Ragweed is fought best by ripping out the plants before they can flower. Known colonies are revisited every year, since seeds can stay dormant in the soil for up to 10 years. Wearing gloves and a mask is recommended [8]. This information, as well as disposal methods, is distributed to the public, whose reports of sightings are fed into the GIS dataset we used for our analysis. Known and likely spots are also monitored in order to act as fast as possible when new plants emerge.

 

Volunteers remove Giant Hogweed along a river in France [Image 25].

Grün Stadt Zürich

Grün Stadt Zürich belongs to the Tiefbau- and Entsorgungsdepartement and is responsible for Zurichs urban nature. It looks after parks, forests, cemeteries, sports and swimming facilities, and also manages green spaces belonging to other municipal services. It is also committed to nature conservation, environmental education and operates special areas such as the succulent collection and the cities plant nursery [9].

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