Foreign invasive plant poses ecological threat to Hungary’s waterways
An aggressively spreading aquatic plant native to North and Central America is causing serious problems in Hungary’s freshwater ecosystems.
Invasive plant species spreading across Hungary
Over the past decades, the encroachment of non-native plant species on Hungary’s natural habitats has become increasingly common. These invasive species reproduce rapidly, outcompeting native flora and fauna and causing significant ecological and economic damage. In some cases, newly introduced species have overwhelmed lakes and rivers almost overnight, proving nearly impossible to eradicate.
In recent days, biologist and ecologist Dr. Gusztáv Jakab sounded the alarm on his Facebook page about a recently spreading invasive plant, the large-flowered water primrose.
Ecological disaster along the Körös rivers
The water primrose is native to parts of South and Central America—such as Costa Rica and Cuba—as well as the southeastern United States. Originally imported into Europe as a decorative pond plant, the species has since begun spreading rapidly in Hungary’s natural waters. It forms dense green mats on the water’s surface, posing a severe threat to indigenous aquatic vegetation and the entire freshwater ecosystem.
“Its spread is so extensive that we can now speak without exaggeration of an ecological catastrophe,” warned Dr. Gusztáv Jakab.
An area along the Körös rivers near the town of Békés had been known for its rich and diverse aquatic vegetation for decades. Dense beds of aquatic and shoreline plants characterized the landscape, preserving remnants of ancient habitats. But in recent years, the ecosystem has undergone dramatic changes. Invasive non-native species—chief among them the large-flowered water primrose—have fundamentally altered the region’s natural balance.
“I’ve known the area for over 25 years and have spent considerable time photographing it. It was once covered by a species-rich, fairy veil-and-water chestnut plant community, echoing memories of the old Kis-Sárrét wetlands. But this rich ecosystem has been entirely destroyed in just a few years. The fairy veil, water chestnut, and bladderwort have vanished—at least I haven’t seen any trace of them, even though they used to be abundant. The environmental damage, if quantified monetarily, would amount to billions. It’s heartbreaking to think how stunning this region was twenty years ago,” the biologist said of the changes.
He also shared photos of the current conditions, taken on the Körös Plains near Békés.
The threat posed by the fast-spreading water primrose
The Hungarian Invasive Species Knowledge Base has also raised concerns: when the plant grows in dense populations, it can block waterways, hindering transportation and impairing infrastructure such as dams. It can also alter the composition of organic matter in the water, causing severe degradation to aquatic habitats.
The water primrose’s thick surface mats block sunlight and hinder gas exchange, resulting in oxygen-deprived conditions that can kill fish and other aquatic life. It also slows down water flow, promotes silt buildup, and disrupts the nutrient cycle, endangering entire ecosystems over the long term.
“Eradicating the large-flowered water primrose is extremely difficult and expensive. Who’s going to deal with this? All signs point to the species continuing to spread, which could have devastating consequences for the entire Körös river system and other domestic waterways. (…) Authorities must act urgently!” Dr. Jakab warned.
The biologist also emphasised that beyond its environmental impact, the spread of the large-flowered water primrose could affect agriculture as well. The plant can clog irrigation channels, making it difficult—or even impossible—to deliver water to farmlands. This can lead to substantial financial losses for growers, as the plant’s rapid spread continues to exacerbate the problem. For these reasons, the large-flowered water primrose also presents a serious economic threat to Hungary’s wetlands and surrounding infrastructure.
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