08.01.2026
Elo Rasmann, Rail Baltic Estonia environmental expert
The construction of the Rail Baltica route will inevitably affect those communities and species whose homes will be under the future infrastructure. One of them is a plant species of protection category II. swamp giant (Liparis loeselii) – one of the most modest, but ecologically fascinating, ungulates in Estonia. The relocation of the species in September 2025 was inevitable because the route passes through a giant swamp growth area and construction work would have destroyed it.
Last year's weather, the lack of previous water monitoring, and the technical nature of the work made the relocation difficult for both specialists and builders.
Who is the swamp giant?
The giant marsh marigold is small, low, with yellow-green flowers. The species is quite widespread globally, but is rare almost everywhere within its range and endangered in most countries. In Estonia, the species is also included in the II protection category – this means that the status of the giant marsh marigold is currently quite stable, but it can change quickly, because the individuals of the species are short-lived and the habitats are quite endangered.
The giant marsh plant is a modest-looking plant. It usually grows to a height of 5–15 centimeters and bears two broad leaves at the bottom of the stem. The inflorescence is also inconspicuous: several small greenish-yellow flowers open on the stem. The plant blooms in late June and early July and reproduces mainly by seeds.
The species grows in moist, predominantly calcareous and open habitats with fluctuating water levels. Suitable habitats include the edges of shallow bogs, temporarily flooded meadows, lake and pond shores, and the edges of quarry water bodies. The conditions of these sites are characterized by temporary changes in moisture, little competition, and suitable openness.
Several factors affect the survival of the giant marsh grass. Humidity and water regime are important: permanent standing water is not suitable for the species, but rather a changing water level. The openness of the growing site is equally important, because strong competition from dense grass, alder bushes or other tall vegetation does not allow the giant marsh grass to survive. The plant also depends on mycorrhizal fungi living in the soil, which are necessary for the development of the peduncles. The giant marsh grass is quite undemanding to these fungi, but without mycorrhiza, the seeds will not germinate or develop into young plants.
The species also requires occasional disturbance – such as animal trampling, mowing or other soil changes that create bare or thinly vegetated areas where seeds can germinate. As a result, populations of giant marsh hogweed easily disappear when the habitat becomes forested, the water regime changes or disturbances cease.
The situation of the growing area before resettlement – infrequent flooding and lack of knowledge about the previous water regime
In June 2024, specialists from the Environmental Board assessed the breeding site and found 300-400 individuals of the giant swamp frog there. In the summer of 2025, three compensation ponds were built near the route to improve the habitat of amphibians, and the relocation of the giant swamp frog was also planned in the same area. When digging the ponds, soil was piled up near the water bodies and the ditch leading west from the former quarry was closed. However, this changed the water regime of the entire area.
The year 2025 turned out to be exceptionally rainy, and by autumn the entire former quarry area was extensively flooded. The original growth area of the bog hogweed was under 10-50 cm of water.
The situation was problematic in several ways. There were no previous water level measurements, so it was not possible to objectively compare the water level with the past, and although the species can tolerate temporary flooding, it is not known how long and how deep the water cover it can actually withstand. However, the plants managed to flower in the summer, which gave hope that they were viable at the time of the relocation.
How did the resettlement take place?
The relocation of the bog giants took place during the period when the active growth period of the plants had ended. The plants were relocated with as large pieces of soil as possible, because this way the community that had grown around the relocated plant was also included. In this way, the viability of the plants in the new habitat is greater and the competition conditions between the plants are likely to change minimally. This is especially important for legume species, which require a symbiotic relationship with fungi for their survival, meaning they are particularly demanding of habitat conditions.
New growth areas were designed on the banks of the ponds so that the water surface would remain at a suitable height, an open area with little competition would be created, and periodic moisture and disturbance would be ensured.
In total, approximately 100 new ponds were built on the shores of the ponds. 1200 m² new growing area. The proportion of exposed soil in the new growth site is approximately 20%, which is beneficial in the context of the long-term survival of the bog giant, as it postpones the moment when the bog giant loses out to competition from other plants.
What happens next?
The resettlement does not end the work. From now on, the success of the resettlement must be assessed every year for the next six years. During the monitoring, the abundance of plants, the ratio of flowering and vegetative plants, the presence of young plants, the water regime, changes in the habitat and competition will be assessed. According to the monitoring results, it must be decided whether and how to make the habitat more suitable for the plants. The following decades will show whether the resettlement has been successful and whether a new viable giant fen growth area will develop along the Rail Baltica route.
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