A tide of water hyacinths (Eichhornia crassipes), the largest recorded in Galicia of this invasive species included among the 100 most dangerous in the world by the International Union for Conservation of Nature (IUCN), flooded several beaches a few weeks ago in a strip of more than one hundred kilometers.
This dense floating mass, weighing hundreds of tons, was dragged by the currents coming from Portugal. It began to make landfall at the end of October, infiltrating sandbanks in the province of Pontevedra and A Coruna, which has alerted biologists and naturalists who warn of the “catastrophic consequences” if any fragment of the plant that could germinate reached rivers. and protected wetlands. Xunta experts rule out that the hyacinths are a danger to the sandbanks.
The first floating clusters of this freshwater aquatic plant, also known as a camalote and similar to a water lily, were sighted in the Cies Islands archipelago -in the Atlantic Islands National Park- and on the beaches of Vigo, Cangas, O Grove and part of Sanxenxo. But the intensity of the tides favored the dispersion of this wave. It advanced from the Rias Baixas towards the north and cumulus clouds appeared, although in smaller proportions, on the coast of Ribeira, A Pobra, Boiro and Porto do Son, in the province of A Coruna.
A smaller tide was recorded in the fall of 2011, although experts estimated the tons of water hyacinth that then washed ashore in the tens. The growth of this invasive variety is very fast and the cumulus doubles in just 12 days, blocking the sunlight and reducing the concentration of oxygen. “This event is worrying because we are talking about a very dangerous species and a real environmental threat, which requires specific control to prevent its expansion before it is too late,” explains naturalist Cosme Damian Romay, from the Association for the Ecological Defense of Galicia (Adega), which is monitoring these migrations.
The origin of this unusual tide of hyacinths is in the Cavado River, in Portugal. The plants traveled for a week towards Galicia at the mercy of the currents. In Europe this species has only been detected so far in Italy, Portugal and Spain. It was discovered for the first time in the latter country in 1974, when it began to proliferate in wetlands and watercourses in areas with a warm climate in the provinces of Alicante, Caceres, Castellón, Valencia and Tarragona. In 2004 its presence was confirmed in the Guadiana river basin, where the hydrographic confederation has spent years trying to eradicate the species. It has only been possible to contain its expansion with expensive investments.
Romay believes that state and regional measures to stop the water hyacinth have not been effective and ensures that protected areas in Galicia such as the Cachadas lagoons, in Sanxenxo (Pontevedra), or the Rego de Trabe, in Culleredo (A Coruna), They are already in danger. “The tons of this plant that are reaching the Galician sandbanks are becoming more frequent and intense due to the high temperatures of recent summers, so that its possible leaks are potentially more dangerous,” explains the Adega biologist.
The General Directorate of Natural Heritage of the Ministry of the Environment of the Xunta downplays the consequences of this latest tide of hyacinths on the beaches, although it adds that it has activated surveillance so that it does not enter the Mino river or its tributaries from his lower zone. This autonomous department affirms that what happened a few days ago “is the result of the dragging of non-viable specimens, a consequence of the swelling of the rivers and the dynamics of the winds and the coast.” The council experts consulted have indicated that these cumulus “do not have the capacity to survive or reproduce in salt water, so their deposit in the sand does not entail any risk for the conservation of biodiversity, and it is advisable to leave them to dry in the sand to avoid that, due to improper handling or transport, they are taken to a favorable habitat”. And he stressed that, in any case, “the cleaning of the affected beaches is entirely municipal responsibility.”
The greatest threat is in the hydrographic basins, Romay emphasizes, since these plants can cover the entire sheet of water, preventing photosynthesis in the deepest layers, affecting the food chain, the development of aquatic ecosystems and the survival of fish. In addition, these high concentrations of specimens prevent the circulation of water and can dry up rivers and streams. “It is essential that the Xunta act forcefully with measures to eliminate the populations detected and a bimonthly review of all the black spots affected by this pest, in addition to a control of companies that sell plants and individuals,” Romay stresses.
The Environment Department admits that it is following up to prevent the species from entering the Mino basin. This surveillance, adds the Xunta, is part of the “risk analysis” system that is used to act against invasive alien species.
The indiscriminate entry of these plants for gardening from the 1990s forced the central government to prohibit their commercialization and prepare a catalog of invasive species regulated by a royal decree that came into force in August 2013. Expressly, The regulations oblige the State and the autonomous communities to monitor these potentially invasive species and take urgent measures “in the event of verifying the existence of a serious threat to the environment”, as well as for their “monitoring, control and possible eradication”.
For Adega, there are few current controls to deal with the water hyacinth. In June 2019, Seprona seized 200 plants that a resident of Gondomar (Pontevedra) grew in his home and sold over the internet. The intervention was possible due to the surveillance that the Civil Guard carries out on the network. The agents verified that the seller had a pond in the garden that served as a nursery for plants, most of them of this invasive species.
Water hyacinth removal methods are few and far between. Manual removal with shovels and excavators is the only remedy used for the most serious cases of expansion, as occurs in the Guadiana basin, where the battle against the invader has lasted 15 years. The use of herbicides is ruled out in hydrographic basins, streams and wetlands, since other essential species of the ecosystem would be eliminated.
At the beginning, this plant usually presents a very aggressive invasive character, since it quickly colonizes all the environment that is favorable to it. However, populations can fluctuate significantly from one year to the next, depending on the water level (especially in temporary wetlands) or winter temperatures. Its demographic trend is very erratic, with sometimes locally massive appearances and also sudden disappearances.
