Algae blooms on the surface of the Mar Menor this winter

The Mar Menor: Action at last to save a dying sea

Image credit: Photograph: Pacto por el Mar Menor

After decades of ignoring warnings from scientists and campaigners, the authorities in Spain are finally acting to save the Mar Menor lagoon, but some solutions on the table, including the installation of giant woodchip bioreactors, are proving controversial.

The largest permanent saltwater lagoon in Europe is very sick, says 71-year-old campaigner Isabel Rubio, and what is so sad is that the devastation has been caused by human greed.

For the people living and working near the Mar Menor, “it is as if we have suddenly found ourselves living next to a garbage dump,” she says, fighting back tears. The devastation of the lagoon is one of the greatest ecological collapses in Europe, in what was once one of the most beautiful areas of Spain.

Rubio has lost hope that the protected body of water that juts out into the Mediterranean in the south-east of Spain will be restored in her lifetime, but says she will fight “to her last breath” in the hope that one day it may be healed.

As a child, Rubio would spend her summers swimming in the crystal-clear waters of lagoon, once home to vulnerable species such as seahorses and European eels, but now when the weather gets warmer, the 135km2 body of water becomes a green soup, and death casts its grim shadow.

In 2016, 85 per cent of the seabed vegetation died as a result of extreme eutrophication, where an excess of nutrients boosts growth of algae and plants, removing oxygen from the water and blocking light. In 2019 thousands of dead fish and crustaceans were washed up on shore and the gruesome images were beamed across the world. The grim spectacle repeated itself again in 2021.

Dead fish

Eutrophication has led to the death of thousands of fish in the Mar Menor. Photograph: Ecologistas en acción

Image credit: Eutrophication has lead to the death of thousands of fish. Photograph: Pacto por el Mar Menor

Local campaigners hope this summer will be different, but the signs are ominous. Rubio says this winter she has seen something she has never before witnessed: thick plumes of algae bobbing on the surface at the eastern edge of the lagoon. Algae in this part of the lagoon is a bad sign, say biologists, and it is likely to mean more mass fish deaths this summer.

A legacy of mining and a huge expansion in tourism since the 1960s have contributed to the destruction, but it was a switch from traditional agriculture to intensive farming methods in the surrounding catchment area that has caused the most damage.

What is so frustrating, according to biologist Julia Martínez-Fernández, who has been studying the Mar Menor for 20 years, is that the first report that warned of the risk of eutrophication caused by intensive farming was published in 1998. “Each year the risk of eutrophication increased but nobody in the public administrations took it seriously,” she says.

The birth of intensive agriculture in the region stems back to the Franco years when work started on a huge engineering project to transfer water from the Tagus River almost 300km to the north. It was completed in 1979 after the dictator’s death, enabling the Cartagena countryside - one of the least rainy regions in Europe - to abandon traditional rainfed crops and become "the garden of Europe", providing inhabitants of countries like the UK with fresh salad all year round.

But this came at a huge price. For decades, run-off from the farming land rich in nitrates has entered the lagoon, causing a huge increase in phytoplankton. This stops sunlight penetrating the surface of the water, killing plants on the seabed, reducing the oxygen levels in the water and snuffing out life.

Some of the intensive farming practices are illegal. A theoretical buffer zone exists close to the edge of the lagoon where the intensive use of inorganic fertilisers is prohibited, but this is routinely ignored.

And because the water from the Tagus River is not enough alone to irrigate the whole area, farmers built wells and installed hundreds of desalination plants to turn the brackish groundwater of the aquifer into water suitable for irrigation. The brine this produces is full of nitrates and has been reaching the Mar Menor for decades. When this practice was outlawed, some farmers illegally tipped the brine into the aquifer.

According to the Spanish government, around 8,000 hectares of farming land surrounding the Mar Menor is irrigated without the correct legal permissions in place.

The Court of Instruction of Murcia is investigating the illegal practices. This year it called for prison sentence for two former regional politicians, who it says were responsible for a failure by their departments to carry out inspections on the illegal network of wells and desalination plants.

It accuses the former regional environment minister between 1999 and 2015, Antonio Cerdá, of a failure to control the nitrates pollution, suggesting that it “could have been deliberate, on the understanding that he was apparently not concerned about the possible impact of nitrates of agricultural origin on the state of the Mar Menor”.

It also describes a “permissive attitude” at the regional regulator the Segura Hydrographic Confederation, which "facilitated and motivated a multiplicity of farmers and agricultural companies…to use desalination machines lacking any type of authorisation or control for the discharge of brine.”

In addition, 39 farming companies are being investigated for illegal practices, including Gs España, a British company that provides UK supermarkets with fresh salad during the winter. The magistrates say Gs was responsible for €2.5m worth of environmental damage – the most out of all the companies being investigated.

“The problem was neglected by the farmers and the regional government, who did not want to apply measures that might introduce some limitations on intensive irrigation. The public administration has allowed the big farming companies to proceed how they wanted for years and years,” says Martínez-Fernández.

As well as the environmental, the economic consequences have been colossal too. The price of housing, according to the Banco de España, has decreased by 45 per cent, equating to a €4.5m loss. Tourists now choose other regions of the Mediterranean, forcing local businesses to shut and livelihoods to be lost.

Finally, the public authorities in Spain have been forced to take action.

This month, the central government pledged an extra €100m in funding to saving the lagoon. In total it will invest almost €0.5bn by 2026. Some €20m of the newly announced funding will be used to help farmers in the region reduce nitrate pollution at source and help them adapt to climate change with nature-based solutions.

In addition, the funding is aimed at substantially increasing measures to restore ecosystems in the perimeter strip of the Mar Menor, while another €20m will be spent on supporting local councils to improve sanitation networks and systems that prevent discharges into the lagoon.

Campaigners have welcomed this focus. The ‘SOS Mar Menor Platform’, which comprises several environmental campaign groups including Pact for the Mar Menor, ANSE (Asociación de Naturalistas del Sureste) and Ecologists in Action, as well as WWF, praised the government’s “clear commitment to measures at source and based on nature”.

But the group was critical of the Spanish government’s plans to expand and restore an old pumping station at the mouth of the Rambla del Albujón, the region’s principal natural waterway, which carries the run-off water from the surrounding farms. The measure would see the contaminated water pumped to a treatment plant and then reused for agricultural purposes.

Campaigners say the move is little more than a conciliatory gesture towards the farmers and an unnecessary expense if measures are implemented to stop the pollution at its source.

“It will not solve anything but gives water at a very good price to the farmers,” said Martínez-Fernández, who is equally dismissive of another idea proposed – to treat the contaminated run-off and release it into the Mediterranean.

“This would be a waste of money and also a high environmental risk, because any incident or breakdown would result in polluting a section of the Mediterranean Sea that contains endangered seagrass meadows, which are protected under EU law,” she said.

Intensive agriculture

Intensive and illegal farming practices have led to an excess of nitrates in the Mar Menor. Photograph: Ecologistas en acción

Image credit: Photograph: Ecologistas en acción

The regional government of Murcia has committed to investing €85m to saving the Mar Menor. Part of these plans will involve the construction of 15 denitrification bioreactors which will span 48,500 square metres in a plot of land alongside of the Rambla del Albujón.

Contaminated water will be pumped to the land where 15 bioreactor ponds will be located, each 100m long, 14m wide and filled with wood chips.

The system will be able to denitrify 200 litres per second and could eliminate about 70 or 80 per cent of nitrates in the waters, depending on different times of the year, according to the team from University Polytechnic of Cartagena, which is leading the project.

Professor José Álvarez Rogel, from the department of agricultural engineering at the University of Cartagena says “the effectiveness of bioreactors in denitrifying water is scientifically proven. There is no doubt about it”.

However, campaigners, as well as scientists and engineers say the problem needs to be tackled at source and moreover that the technology has not been adequately tested at such a scale.

Ramón Pagán, a chemical engineer and campaigner, is concerned that no Environmental Impact Assessment (EIA), had been carried out, “which we think is essential”.

“We also have doubt about the harm the big amount of biomass could cause the environment and the polluting substances that it could generate,” he adds.

Martínez-Fernández argues that the restoration of natural wetlands would have been better option than the large-scale deployment of bioreactors.

She is proposing an ecological restoration of the mouth of the Rambla del Albujón so that the water can enter this new area of natural wetlands, allowing them to do their work of “purifying the water for free”.

She argues that the advantage of this is that when floods occur, which wash out huge amounts of nitrogen and phosphorus accumulated in the basin over many months, “the natural wetlands will receive the water, store it and over the next ten or twenty years, will purify the water and release it slowly into the lagoon”.

“There is not any type of big public infrastructure that can cope with the big rainfall events,” she argues.

While bioreactors can treat small-scale at-point pollution, they cannot treat diffuse pollution caused by intensive agriculture, adds Martínez-Fernández. Pagán agrees that it would be more effective to install smaller bioreactors in the farms, paid by the owners.

Professor José Álvarez argues that “bioreactors are undoubtedly much more effective than wetlands in removing nitrates from water,” but he acknowledges that “wetlands can remove other potential pollutants such as phosphate, organic matter, pathogenic micro-organisms”.

His team has therefore proposed the construction of an auxiliary pond which will act as a manmade wetland that filters out any pollutants from the denitrification process. 

For Álvarez, bioreactors and wetlands are complementary systems, “each with advantages and disadvantages”.

“The question is not only about choosing the most efficient system. It is also about assessing how and where to install both systems and how to manage them,” he argues.

The subject of who should pay for remediation efforts is a particularly sensitive one. The projected cost of the bioreactors project has doubled from €2.5m to €5m in recent weeks, leading to further criticism from some campaigners who feel the polluting farming companies should foot the bill, not the public.

Pedro Luengo, a spokesperson for Ecologists in Action, says the remediation should be paid for by the agricultural companies, “since they have been obtaining extra benefits while polluting the Mar they should assume part of the costs of recovery, attending to the principle of ‘polluter pays’. It would not be fair or ethical for all the costs to be assumed with public money”.

Isabel Rubio

Isabel Rubio is fighting for future generations. Photograph: Pacto por el Mar Menor/E.Peris

Image credit: Photograph: Pacto por el Mar Menor

Ecologists in Action argues that these end-of-pipe measures also divert money from where it could be spent on “other really effective measures, such as the purchase and renaturalisation of agricultural areas, soil and nutrient retention measures at different scales of the catchment area”.

Rubio is fighting for future generations. She hopes that one day her grandchildren will enjoy the calm and clear waters of a restored Mar Menor like she once did, but it is going to take more than throwing money at the symptoms of intensive agriculture.

There is a consensus that it is only when the root cause of the problem is halted that the destruction can begin to be reversed in a meaningful way.

Álvarez agrees that his bioreactor project and the construction of wetlands “can contribute to mitigating the impacts of anthropogenic activities”, but that it is “essential” that these activities are modified in the first place.

The biologist Martínez-Fernández says that at from the time polluted agricultural run-off is stopped from entering the Mar Menor, it may take another ten years before any first signs of progress may be seen. Therefore, supermarkets in Europe need to ensure they are responsibly sourcing produce, she argues.

“For us it is important that the Mar Menor ecological collapse is acknowledged in the rest of the world, in England, in the rest of Europe, because most of these agricultural products are sold and consumed in Europe and UK. An important part of the solution needs to come from the market saying no to the destruction of the Mar Menor.

“This is one of the biggest hopes.”

Sign up to the E&T News e-mail to get great stories like this delivered to your inbox every day.

Recent articles