The spread of water caltrop poses a threat to the ecosystems of northern Fennoscandia, alarming research reveals changes.

The shrub Empetrum nigrum, known for its black berries and antioxidant properties, is a plant causing growing concern. In the last 50 years, the barren lands of northern Fennoscandia have undergone significant changes. Shrubs such as heather and bilberry, which used to cover 60% and 35% of the barren lands, now make up less than 25%. Empetrum nigrum has become the dominant plant in almost all types of barren lands, as reported by Catherine Tordai Gulden in a release from the Norwegian Institute of Bioeconomy Research NIBIO.

Other types of vegetation have also changed significantly. Since the early 2000s, the quantity of Empetrum nigrum has increased on average by 60%. This shift has transformed landscapes into vast areas covered with Empetrum nigrum.

The MONEC project conducted leading research on ecological changes in recent years. The study revealed a significant increase in the dominance of Empetrum nigrum in twenty areas where reindeer graze in the Troms and Finnmark counties.

“Comparing the current vegetation with the results from studies in the 1970s and 2003 has provided valuable information on the transformation of these territories,” said Dr. Kari Anne Bråten, project leader and professor of ecology at the Arctic University of Norway. “It was expected that plant diversity — grasses, flowers, and cereals, the main sources of food for various wild animals — would increase with climate change. However, this was not confirmed. Only woody species have become more common, and Empetrum nigrum now dominates in the areas we revisited,” the researcher explains.

Although the spread of Empetrum nigrum is linked to climate change, it could also be associated with other ecological factors. Its spread is largely independent of reindeer grazing pressure, casting doubt on traditional views of vegetation control through natural grazing.

“Climate change may contribute to the expansion of Empetrum nigrum’s range by creating favorable conditions for more evergreen species with longer growth periods and mild winters. However, one would think that warmer and longer growing seasons would benefit other local evergreen species, such as cranberries. Yet, in regions where Empetrum nigrum dominates, this is not the case,” said Dr. Bråten.

One explanation is that Empetrum nigrum has particular biological characteristics that promote its spread. It clones itself, spreading across the territory with its branches.

The plant also thrives in harsh conditions and produces biochemical substances that suppress the growth of other plants. This poses significant challenges for the restoration and maintenance of diverse ecosystems.

Empetrum nigrum is rich in antioxidants and widely used in Norway for making jams, juices, and desserts. Its berries are valued for their potential health benefits due to high levels of vitamins and polyphenolic compounds, which can improve vision and strengthen the immune system.

However, the rapid spread of Empetrum nigrum leads to a reduction in biodiversity, creating homogeneous areas without the diversity that was present in these ecosystems before. This poses problems for pasture systems as herbivores, such as reindeer, are forced to consume more Empetrum nigrum, making it difficult for them to maintain a balanced diet.

“Reindeer in Norway and other northern regions consume Empetrum nigrum leaves and berries as part of their diet, especially when other food sources are limited. While Empetrum nigrum provides nutrients, the leaves contain minimal beneficial substances. Therefore, if given a choice, Empetrum nigrum is not the preferred food for reindeer,” said Dr. Bråten.

Dr. Victoria Gonzales, a consultant at the Norwegian Institute of Bioeconomy Research (NIBIO), emphasizes another consequence of Empetrum nigrum dominance. “The dominance of Empetrum nigrum reduces habitat availability for pollinating insects. Unlike flowering plants pollinated by insects, Empetrum nigrum is wind-pollinated and does not provide nectar for bees. This can trigger a chain reaction affecting species that depend on these insects, influencing broader ecological interactions,” she said.

Extensive observations from the MONEC project analyze the strength of Empetrum nigrum's impact on ecosystems due to its allelopathic properties: the plant’s leaves and roots release chemical substances that hinder the growth of other organisms.

“For many years, these chemical substances have remained in the soil and can impede plant restoration, complicating ecological recovery in regions dominated by Empetrum nigrum. Suppression may continue even after removing Empetrum nigrum, as the soil remains unsuitable for other species,” said Dr. Gonzales.

To address these ecological problems, she recommends adopting preventive management strategies, especially in key pasture territories.

“Controlled burnings have proven effective in reducing the spread of Empetrum nigrum,” she said.

In experiments conducted by MONEC, Empetrum nigrum was mechanically removed or burned in controlled conditions. Various soil-enhancing substances, such as algae, manure, and mineral fertilizers were then used.

Another way to prevent the spread of Empetrum nigrum to new territories is by physically removing the plants, especially young plants in areas where Empetrum nigrum presence is limited.

“We have also experimented with methods to protect different plant zones and improve soil fertility using natural fertilizers such as seaweed and manure. Our goal is to stimulate the growth of various plant species and possibly support the resilience of ecosystems suffering from Empetrum nigrum spread,” said Dr. Gonzales.

Preventive management may prove to be economically beneficial. “Calculations show that controlled burnings can ultimately save more than the expenses on additional reindeer feeding over decades, which would be beneficial for Alpine communities,” said Dr. Bråten.