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View from Space of a Spanish river flooding into the sea

Upstream, Downstream River, Episode 1

The Mediterranean Sea faces a critical challenge – a decline in its environmental condition. This acknowledged issue, often relegated to scientific reports, now demands urgent attention. Despite marine study projects in Spain revealing deficiencies in scientific data, the number of reports in decision-makers offices outweighs global solutions for the environmental challenges confronting this sea. 

In this context, comprehending the intricate workings of rivers and their vital connection to the Mediterranean becomes imperative. Esteemed experts, such as Jordi Camp, Mirna Petrovic, Jesus Mercado, and Patrizia Ziveri, contribute significantly to this inaugural podcast episode, shedding light on various critical aspects influencing the state of this emblematic sea. 

Jordi Camp, a researcher at the Institute of Marine Sciences of Barcelona, underscores the need to address nutrient accumulation and depletion in the Mediterranean Sea. Whether nutrients proliferate from Mediterranean rivers in estuarine zones or climate change prevents nutrients from the seafloor reaching the surface, Camp points to a shift towards oligotrophication – a decrease in nutrient availability. This reduction is attributed to decreased water and nutrients in rivers, bringing attention to the reservoir of deep waters, where annual thermocline phenomena act as a vital fertilizer, especially in locations like the Gulf of Leon - between northern Catalonia and southern France. 

This potent phenomenon triggers a rise in nutrients when summer concludes, and the first autumn storms arrive, accompanied by cooler temperatures, homogenizing the water column and causing a resurgence of nutrients. However, the effects of climate change hinder the thermocline from reaching its breaking point, preventing the release of nutrients retained below its spectrum. 

The effect mentioned by Jord Camp is closely tied to the quality of water flowing from rivers to the Mediterranean Sea. The mere excess of CO2 emissions in the atmosphere, stemming from human activity has consequences in the scenario of oligotrophication, as outlined by Camp in this podcast episode. Moreover, our processes are becoming increasingly intricate, and consequently, more demanding for our immediate environment to assimilate. 

Mirna Petrovic of the Catalan Institute for Water Research sheds light on the extensive use of organic compounds in our daily lives and industries, ranging from pesticides to pharmaceutical products. The diverse array of these organic pollutants can infiltrate water sources through various pathways. 

Petrovic also warns about the negative effects of climate change on rainfall, impacting the dilution of contaminants in rivers like the Llobregat. Water scarcity during droughts hinders dilution, exacerbating the concentration of contaminants in water bodies. 

In exploring eutrophication in the Mediterranean at eight points along the Spanish coast, Jesus Mercado, from the Spanish Institute of Oceanographic Research, highlights the persistent lack of precise data. Despite efforts to establish baseline studies and periodic research in places like the Bay of Algeciras, the mouth of the Guadiaro River, an area in the Bay of Malaga, the outer part of the Mar Menor, Cartagena, the surroundings of the city of Valencia, the Ebro Delta, and the Llobregat River, "there is no evolution; we find a situation very similar to what we found in 2010, unfortunately," Mercado emphasizes in the podcast. Moreover, integrating data from Autonomous Communities (local and public administration) has not been compatible with this organization's data. Therefore, a lack of detailed information persists on the amount of nutrients flowing from rivers to the sea. 

Mercado underscores the importance of accurately knowing the quantity of nutrients reaching the marine environment from various sources, especially the direct contribution from tributaries. However, the lack of characterization of this source and the absence of precise information on the volume flowing from rivers to the sea create uncertainty about nutrient pollution from Spanish rivers. 

In the final podcast segment, Patrizia Ziveri, a researcher and co-author of a key report named “Actions of cities and regions in the Mediterranean Sea area to fight sea pollution”, highlights the devastating impact of industrialization and agricultural practices in the region. Revelatory data from her research emphasizes that 80-90% of marine waste in the Mediterranean is plastic, with approximately 230,000 tons of plastic entering the sea annually from land-based sources. 

Ziveri points out that agricultural practices, the lack of adequate wastewater treatment facilities in urban areas, and the acceleration of climate change combine to exacerbate the problem. For instance, the Mediterranean tourism industry is responsible for 60% of beach waste.

Listen to the episode in English (translated using AI):

And the original version in Spanish: 


  • Listen to Episode 2 of this podcast series. 

This story was produced with support from Internews' Earth Journalism Network. It was first broadcast in Carijonas on 24 November 2023 in Spanish; this version has been adapted by EJN's Mediterranean Media Initiative.

Banner image: The Ebro River delta at the Mediterranean Sea, view from space / Credit: Michael Taylor and Joshua Stevens, using Landsat data from the U.S. Geological Survey.