The recovery of biodiversity in European rivers that was seen from the improvement of channels and pollution control between the 1990s and 2000s has slowed sharply since 2010. This stagnation in the increase in life wild is noted in a recently published study in ‘Nature’ magazine in which the researcher from the University of Murcia (UMU) David Sánchez Fernández and the professor Andrés Millán Sánchez have participated and which uses the presence of invertebrates as an indicator to evaluate the health of river ecosystems.
“European rivers have stopped recovering in recent years and we do not know what is going to happen,” explains biologist David Sánchez (Cehegín, 1977) to LA VERDAD, who works in the Department of Ecology and Hydrology of the UMU with a Ramón y Cajal postdoctoral contract.
What has happened so that the advances in water purification and the renaturalization of the banks promoted by the environmental regulations of the European Union have ceased to be effective thirty years later? «The problems are very well diagnosed: on the one hand there is pollution, sometimes associated with changes in land use such as irrigation, which arrives through direct or diffuse discharges; and on the other hand, water extraction for agriculture and livestock,” details this scientist, who has worked at the Museum of Natural Sciences (Madrid), the Institute of Evolutionary Biology of Barcelona, the Doñana Biological Station and also at universities. Paulista State (Brazil), Plymouth (United Kingdom), CUNY of New York and Lisbon.
Diptera, worms and mollusks
«Climate change and lack of rain are added to these pressures, so rivers carry less and less water. And it also happens that, due to the reduction in flow, the pollutants are more concentrated », he adds. As infallible witnesses of this slowdown in the advancement of aquatic life, the richness, abundance and functional diversity of insects such as beetles, bed bugs and diptera, along with worms, mollusks and crustaceans, were analyzed.
The research includes data on macroinvertebrates – larger than a millimeter in size – collected in more than 1,800 river stretches in twenty-two European countries with samples taken for more than fifty years, the vast majority after 1990.
«It is surprising how the improvement of the ecological quality of rivers has slowed down for twenty years, with little or no change despite the many recovery measures developed in the last decade,” he insists.
Among the rivers monitored, Rhine, Rhône and Loire, and in Spain channels such as the Ebro, Sella, Cares and Deva. Segura was not included in the study because the required follow-up time series, at least a decade in each location, was not met by just one year. In any case, the situation of the basin between the source of the river in Santiago-Pontones (Jaén) and the mouth in Guardamar (Alicante) conforms to the trend reflected in this scientific work.
David Sánchez: “We are concerned about the Northwest, where the channels with the greatest biodiversity in the Region are located”
An extreme case is the Turrilla River, in Lorca, allegedly drained due to the irregular capture of its flow by a pig cattle company that has motivated a judicial investigation in which the businessman, the CHS Water Commissioner and one of their service chiefs.
Luckily, this situation can be reversed with measures that David Sánchez lists: «Respect a minimum flow and the natural regime of the rivers, that is, that they carry water when it hits and not when it is released from the dams; limit extractions and monitor illegal drilling; control urban and industrial discharges; stop agricultural and livestock pollution; and prevent and eliminate the entry of exotic species.
El Segura, “neither better nor worse”
“The Segura has not improved in the last fifteen years, but it has not gotten worse either,” says David Sánchez after reviewing for this newspaper the data of biological indices collected by the Hydrographic Confederation in five points of the river from the headwater area (Huelga Utrera) to the city of Murcia (Fica bridge).
“In the Region of Murcia we are concerned about the Northwest, where the rivers with the greatest biodiversity in the Community are located,” warns Sánchez. “In Quípar, Argos, Alhárabe and Mula we have seen some stability in recent years, but this situation is not good at all because they should be much better.”
The recent evolution of rivers is influenced, he illustrates, by “two opposing forces. On the one hand, the effort to improve water quality with purification and discharge control; and on the other, the changes in territorial planning that are increasingly noticeable, for example in the Northwest, where intensive crops are now advancing.
The “spectacular” state of the Mula River
While there is cause for concern, a reason for hope shines in the background: «Mediterranean systems have the capacity to recover very quickly because they are historically exposed to natural disturbances and the communities that live in these changing environments react very well to droughts, floods or pollution processes,” says David Sánchez. An example is the Mula River, “which has recovered very well and is spectacular right now,” after the extraction of a well for irrigation ceased, according to a court ruling, and the water resurfaced at its source. A state that should be consolidated “if land uses are maintained and are not abused with water extraction.” Otherwise, recalls the UMU researcher, “if the impacts are not punctual and become chronic, those qualities that facilitate recovery are lost.”
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