Managing multiple stressors in Iberian freshwater restoration
In recent years, scientists have increasingly shown how freshwater ecosystems are impacted by a range of human-caused stresses, which can significantly affect their health and biodiversity.
As a result, research into the interactions and impacts of so-called ‘multiple stressors’ has blossomed, both in Europe and globally. Now, a newly-published paper shows that the ecological degradation of Iberian freshwaters is largely caused by the impacts of two or more combined stressors.
The study authors reviewed 61 scientific articles exploring the effects of different stressor combinations on freshwater ecosystems and organisms from the Iberian Peninsula. The research team, led by Dr. Cayetano Gutiérrez-Cánovas (Doñana Biological Station-CSIC, Spain) and Dr. Susana Pallarés (University of Seville, Spain), collaborated with scientists from 11 Iberian and international institutions.
Writing in Limnetica, the authors found that the key stressors in Iberian Peninsula freshwaters are nutrient enrichment, toxic substances such as pesticides, salinity, ultraviolet radiation, flow reduction and warming.
The team also observed a high variability of stressor effects across different types of organisms, freshwater ecosystems and experimental approaches. For example, manipulative studies tended to find a higher prevalence of interactive effects for some organism groups, compared with observational studies. Such interactions arise from complex situations where the combined effect of different stressors is not equal to the sum of their individual effects.
“Our work highlights the need to consider the multiple impacts driving freshwater degradation in management and restoration actions,” says Cayetano Gutiérrez-Cánovas. “This work in the Iberian Peninsula demonstrates that the traditional single stressor perspective would be effective only in a minority of cases. And, more importantly, this situation could be applicable to other European areas, where 39% of EU water bodies are affected by two or more anthropogenic pressures,” continues Susana Pallarés.
The Iberian Peninsula is one of the most important global biodiversity hotspots, and supports a rich variety of climates and freshwater habitats. However, the ongoing climatic aridification in the area, combined with growing water demands for food production and urban areas, exerts increasing pressure on Iberian aquatic ecosystems.
To tackle this multiple stressor scenario, the study authors suggest the need to implement mitigation actions that consider climate change along with other impacts, including nutrient enrichment, hydromorphological alteration and invasive species.
The scientific team also identified research gaps to be addressed in future investigations. Among them, the authors suggest increasing research efforts on some aquatic ecosystems – such as lakes, lagoons and wetlands – and organisms that have not been studied in sufficient detail, such as algae and aquatic vegetation. They also propose more observational studies to address multiple stressor effects on natural freshwaters.
In addition, the authors suggest that the ongoing multiple stressor research agenda should include a more detailed investigation on the consequences of biodiversity loss for the ecosystem functioning and services provided by aquatic environments in a global change context, where several impacts often act simultaneously.
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