Heroes fight invasive plant species: On the old landfill site, lupins are kept away and species are valued

In southern Finland, the Vehkalanmäki area in Vantaa is subject to patient conservation work to control overgrowth and, in particular, extensive garden lupin growth. A local nature enthusiast and the city have played an important role in maintaining the area’s biodiversity.

Vehkalanmäki is a former landfill site owned by the City of Vantaa, where a diverse variety of plant and insect species, including several rare and endangered species, formed after the end of active use.

Without continuous conservation work, the area would be forested and filled with bushes and harmful invasive species, especially garden lupins. As a result, there would no longer be a suitable habitat for the valuable species in the area.

Garden lupins growing on the sunny hillside of Vehkalanmäki. Photo: Eeva-Liisa Korpela / WWF

There are also advocates for garden lupin due to its aesthetics and the food it provides for pollinators. However, the plant is associated with many adverse factors that threaten biodiversity. Garden lupin takes up habitat and also binds nitrogen to the soil, replacing original meadow plants. In addition, lupin pollen may also hinder the multiplication of pollinators (Link to study ).

The nature in Vehkalanmäki has been restored since spring 2020 by the local insect enthusiast Tomi Salin and the City of Vantaa. Salin has been mapping the species and created a management plan for the area while working at the Environment Centre of Vantaa. Voluntary work by the locals has helped to make progress on the tasks. 

In addition to garden lupin, work on warding off invasive plant species also began with warding off rugosa rose. In the early days, the sunny hillside, the richest in species and opening up to the southwest, in particular, was filled with garden lupins.

“The lupins have been destroyed by mowing, digging up the roots and, most importantly, by weeding. Most of the weeding has been done by cutting the plants at the root, as close to the ground as possible. The best time to cut and mow is when the plants are in their buds. During the blossom, before the seeds fall, mowing is the easiest and most effective way to proceed. Weeding is still also possible at that time,” says Salin.

In 2023–24, the voluntary event organised by WWF Finland will also bring activity to Vehkalanmäki. Volunteers and employees of cooperative companies who have registered through the environmental organisation will be able to continue the treatment from previous years. 

WWF Finland volunteers removing lupin. Photo: Vilja Tupola / WWF

In addition to demolishing garden lupins and other invasive plant species, the nature conservation work includes other activities to keep the area open, such as clearing trees and bushes and ring barking trees. In addition, the activities include drilling nesting holes for hymenoptera and sowing seeds for meadow plants. 

As a result of the repair and restoration, the habitat in Vehkalanmäki has become considerably more diverse. The amount of lupins has been reduced to about one tenth of the initial situation.

“Very moist and fresh points in the meadow have dried out and become more and more reminiscent of dry fields. Dry field patches are expanding and their plant species are changing towards more favourable flowering plants. The caterpillars of several butterflies have benefited particularly from the change, and above all the rarity of the area, Calamia tridens (viheryökkönen),” Salin describes.

Many other insects, such as Aculeata and Anthophila and several small butterflies, have also gained more habitat and breeding area on Vehkalanmäki.

Salin emphasises that the work cannot be left unfinished now, or everything would return to the initial condition within a few years. This valuable area requires the same long-term, continuous and expert care in the future as well.

Written by: Vilja Tupola (WWF)

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