The municipality of Nacka is experiencing urban development, with the construction of new housing and the exploitation of unspoiled land. New construction often involves the development of land in or near areas with high nature values. In this example, we have worked on conservation measures to protect frogs and other reptiles living in marshland. There are many ways to work to ensure sustainable development for biodiversity, even if the development is extensive.
Part of a swamp forest located south of Lake Sarvträsk in Nacka municipality is being cleared to make way for housing and a care facility. To ensure that protected species in the swamp forest are not adversely affected, several protective measures are taken. These protective measures are conditional in the judgment for water activities that we had to apply for to harvest and fill in for house construction. In addition to what is listed in the judgment, several measures are taken according to the action plan developed in the project.
The aim of the protection measures is to plan for the least possible impact on animals and nature during Nacka municipality's development, so that the species can remain even after the houses are completed. The protection measures implemented in the project include creating more standing and lying dead wood in the area and taking into account nesting periods for bird life.
- "When developing in Nacka municipality, we look at how we can plan for the least possible impact on animals and nature," says Petter Söderberg, environmental planner in Nacka municipality. "We are working on protective measures to compensate for the development as far as possible.
The valuable bat is also included in the protection measures, bat roosts have been set up and care has been taken when installing lighting to try to disturb the bat as little as possible.
In addition to previously constructed frog ponds, two frog hotels have been created near the lake. These are piles of stones mixed with branches and leaves, where frogs and reptiles crawl and hibernate during the cold season.
Inventories have shown that many amphibians, mainly toads, migrate down to the lake every year for the spawning season. To get to the lake, they have to cross a busy road where they risk being run over. That's why we've built tunnels under the road, so they can reach the lake and the swamp forest safely. To prevent the amphibians from getting onto the road, we have constructed guides along the road to lead the animals into the tunnels. By providing a safe passage for the frogs, we have minimized the number of frogs that die in traffic.
The stormwater dome wells in the area have been fitted with fine mesh netting to prevent amphibians from falling into the wells.
We have taken steps to create a new wetland in Klisätra, which is within the Nacka reserve. The new wetland is slightly larger than the area taken for exploitation from the swamp forest at Lake Sarvträsk. The area has been selected because it is an excellent environment for frogs and reptiles, which provides good opportunities for reproduction, spawning and safe frog migration without busy roads. Adjacent to the newly constructed wetland, stone cairns have been laid out to create good wintering sites.
As the newly constructed wetland is located within a nature reserve, it has strong legal protection under the Environmental Code. Work on the wetland in Klisätra was completed in April 2024.
When developing areas with high biodiversity, there is much that can be done to maintain and support it. The ideal situation would of course be to avoid building a busy road right over an area where amphibians have been migrating for many, many years. But sometimes interests collide and it is important to make the best of the situation. In the early stages of development, involve an ecologist. Ecologists see the area with their expert eyes and provide invaluable insights into compensation measures.
We've built tunnels under a busy road to enable the 'Little Frog Walk' - frogs should be able to get safely to a lake to spawn without having to cross the road.
Piles of soil, sticks and leaves have been built to provide a safe place for the amphibians to crawl and hibernate. We call them 'frog hotels'.
We have created a new wetland in a nature reserve, supporting biodiversity to compensate for development in and around a sensitive wetland area.
Petter Söderberg, environmental planner in Nacka municipality, petter.soderberg@nacka.se