Study warns of poor ecological quality of rivers worldwide

A team of 29 experts from all continents, led by Maria João Feio of the Centre for Marine and Environmental Sciences (MARE) of the Faculty of Science and Technology of the University of Coimbra (FCTUC), has provided an update on the situation regarding the ecological quality of the world's rivers, and the news is not good.

The study, covering 88 countries, reveals poor river ecological quality and high biodiversity loss worldwide. In Europe and the United States, about half of the streams or rivers analysed are below acceptable levels, a third in Australia and a quarter in South Korea.

One of the consequences of the poor ecological quality of rivers "is a very high loss of biodiversity. In New Zealand, for example, 70% of freshwater fish species are threatened, while in Japan 40% are threatened. In other countries, physical-chemical monitoring shows a very high level of pollution that poses a threat to human health," points out Maria João Feio in the scientific paper "The Biological Assessment and Rehabilitation of the World's Rivers: An overview".

The scientists also assessed the state of implementation of river biomonitoring, i.e. the assessment of rivers based on aquatic communities - such as fish, benthic invertebrates, algae or other plants - and the measures taken to restore them, and concluded that "in most countries of the world, biological monitoring of rivers is not carried out on a regular basis. In most countries, there is at most a physical-chemical analysis of the water, which is not sufficient to translate the degradation of these systems caused by human activities (such as the artificialisation of the edges, the cutting of vegetation, the presence of non-native and invasive species, dams and reservoirs that alter the circulation of water, sediments and species along the hydrographic basins)", explains Maria João Feio.

The outlook for the implementation of river restoration measures is also not encouraging. According to the authors of the study, "although there are good examples, both in Europe (mainly in the North) and in the United States, Japan and South Korea, we conclude that very little has been done at this level worldwide".

"If they are restored, rivers can provide very important services to people, from the provision of water and food, to the improvement of air and soil quality, the mitigation of climatic extremes, and still provide recreational areas essential to human well-being," comments the FCTUC researcher.

With regard to Portuguese rivers, Maria João Feio says that we follow the European standard, "with about half of the water bodies analysed in good ecological status. And we have very critical situations in the case of large rivers, which are heavily affected by dams. Throughout the country, there are still cases of localised and diffuse pollution, as well as strong changes in the riparian vegetation, which is essential both for the functioning of the aquatic ecosystem and for improving the quality of the air and soil, and for filtering the run-off water that will have to go into the rivers".

With a view to improving the quality of rivers, the international team of experts also made a number of recommendations, highlighting for example "the need to define realistic and clear ecological objectives for rehabilitation/restoration plans; the obligation to draw up ecological rehabilitation/restoration plans based on data collected a priori in monitoring programmes and to follow up these plans with ecological monitoring".

The experts also defend the need to create interdisciplinary teams to draw up these plans - scientists with knowledge of ecosystems, engineers and even social scientists - in order to "allow the involvement of all types of water users (population, industry, decision-makers) towards a common goal". It is also essential to have adequate funding and to make river restoration a national and international political priority".

^{Translation by Diana Taborda}