The Generalitat has already created one commission to analyze how the emptying of the Sau reservoir is managed. What is to be done with the invasive species that degrade the biodiversity? Its viable delete them as the reservoir loses water? The process will be monitored by the gaze of several experts and ecologists that match: you have to turn this crisis into an opportunity.
The first thing to be clear about is that a swamp is not a natural habitatis created by human action. It accumulates more sediment than normal and has a limited lifespan. But in Sau, the reservoir connects with some streams that have facilitated the arrival of fish such as the troutof amphibians like the webbed newt or mammals like the otter.
When these animals try to settle in this artificial ecosystemcollide with a tough rival: an army of invasive species who has taken control of the swamp. The militia is made up of catfish, walleye, bleak, carp and a crustacean with pincers: the american crayfish. Given this scenario, several biologists ask the Government to take advantage of the emptying of the reservoir to eliminate as many members of this aquatic battalion as possible.
“It’s what the law saysif they remove fauna they have no other option”, sentence Jaume Graufrom the conservation area of Ecologists in Action. It refers to the Spanish biodiversity law. He is aware that not all of them will be eliminated, but now that the Generalitat is considering it, he considers that it is necessary to try. Joan Maluquera biologist expert in amphibians and fish, considers it a difficult challenge: “It involves a lot of organization but the oxygen in the swamp will be reduced and the invasive species must be captured.”
Consulted by the Government
When the process is done, warns Grau, it would be necessary to put bars so that when the water goes down these species do not escape. “If they find native species, they have to be saved and moved upstream,” he details. In the latest State of Nature report, river systems appear to be the weakest. And what are the causes? Climate change and invasive species.
“Carp may not be slaughteredsports fishermen put pressure on them and they are considered a naturalized species,” laments marc ordeixdirector of Center d’Estudis dels Rius Mediterranis. Ordeix has received a message from the Agència Catalana de l’Aigua (ACA). They ask you to help advise the procedure. He has decided what he will tell them: “You have to do it with networks, in a big way, as if they fished in the sea. If not, it will be impossible for the work to have positive effects.”
piled up mud
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Another issue is the sediments that lie in heaps in the bottom of the reservoir. “They are a problem because they cause more algae to grow than it would touch -declares Ordeix-, then the water is more eutrophic, has less oxygen and loses quality”. With the acceleration of the emptying process launched by the Government, some experts propose the elimination of these remains of mud that have been accumulating for years.
“How do you get it out?” Maluquer wonders. “With heavy machinery it’s difficult because you can get stuck there and it would take months,” he answers to himself. One option would be to send it downstream to regenerate the fragile deltas. But first, it is important to check what state this sludge is in. The scientists consulted doubt that it can serve as adobe because it forms the most contaminated part of the swamp. After all, that is why the water is emptied towards Susqueda, so that do not catch this bad condition So classic of the lower marshes.