• 1 Department of Life Sciences, MARE-Marine and Environmental Sciences Centre, University of Coimbra, 3000-456 Coimbra, Portugal
  • 2 Amnis Opes Institute, Corvallis, OR 97333, USA
  • 3 Laboratory of Ecology of Benthos, Department of Genetic, Ecology and Evolution, Institute of Biological Sciences, Federal University of Minas Gerais, Avenida Antônio Carlos 6627, CEP 31270-901 Belo Horizonte, MG, Brazil
  • 4 Centre for Applied Water Science, Institute for Applied Ecology, University of Canberra, 2601 Canberra, Australia
  • 5 Unilever Centre for Environmental Water Quality, Institute for Water Research, Rhodes University, P.O. Box 94, Grahamstown 6140, South Africa
  • 6 MARE-Marine and Environmental Sciences Centre, University of Évora, 7000-812 Évora, Portugal
  • 7 Department of Zoology, School of Natural Sciences, Trinity Centre for the Environment, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
  • 8 Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal
  • 9 Department of Biology and GeoBioTec-GeoBioSciences, GeoTechnologies and GeoEngineering Research Centre, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal
  • 10 Mexican Institute of Water Technology, Bioindicators Laboratory, Jiutepec Morelos 62550, Mexico
  • 11 Department of Animal and Environmental Biology (Applied Hydrobiology Unit), Federal University of Technology, P.M.B. 65 Minna, Nigeria
  • 12 School of Biologcal Sciences, University of Canterbury, 8140 Christchurch, New Zealand
  • 13 Department of Civil Engineering, Daejin University, Hoguk-ro, Pocheon-si 1007, Gyeonggi-do, Korea
  • 14 Department of Fisheries & Wildlife, Oregon State University, Corvallis, OR 97331, USA
  • 15 Korea Institute of Civil Engineering and Building Technology (KICT), 283 Goyangdaero, Ilsanseo-gu, Goyang-si 10223, Gyeonggi-do, Korea
  • 16 Key Laboratory of Yangtze River Water Environment, Ministry of Education of China, Tongji University, Shanghai 200092, China
  • 17 Department of Geography, Geomorphology and Water Resources Laboratory, Institute of Geosciences, Federal University of Minas Gerais, Avenida Antônio Carlos 6627, CEP 31270-901 Belo Horizonte, MG, Brazil
  • 18 MED-Instituto Mediterrâneo para a Agricultura, Ambiente e Desenvolvimento, LabOr-Laboratório de Ornitologia, Universidade de Évora, Polo da Mitra, 7002-774 Évora, Portugal
  • 19 Centro de Investigación en Biodiversidad y Conservacíon, Universidad Autónoma del Estado de Morelos, Cuernavaca, 62209 Morelos, Mexico
  • 20 Environment and Climate Change Canada and, Canadian Rivers Institute, Faculty of Forestry and Environmental Management, University of New Brunswick, Fredericton, NB E3B 5A3, Canada
  • 21 Water Environment Research Group, Public Works Research Institute, 1-6 Minamihara, Tsukuba 305-8516, Japan
  • 22 School of Natural Resources and Environmental Studies, Karatina University, P.O. Box 1957, 10101 Karatina, Kenya
  • 23 Environment, Planning and Sustainable Development Directorate, 2601 Canberra, Australia
  • 24 Wetlands, Policy and Northern Water Use Branch, Commonwealth Environmental Water Office, 2601 Canberra, Australia
  • 25 Acadia University, Canada Creek, Wolfville, NS B0P 1V0, Canada
  • 26 Grupo de Investigación en Biodiversidad, Medio Ambiente y Salud (BIOMAS), Facultad de Ingenierías y Ciencias Aplicadas, Ingeniería Ambiental, Universidad de Las Américas, Vía Nayón S/N, 170503 Quito, Ecuador
  • 27 Department of Animal Biology, Faculty of Sciences of the University of Lisbon, Campo Grande, 1749-016 Lisboa, Portugal
  • 28 Department of Geography, Western University and Canadian Rivers Institute, London, ON N6A 5C2, Canada
Water (Basel), 2021 Jan 31;13(3):371.
PMID: 33868721 DOI: 10.3390/w13030371


The biological assessment of rivers i.e., their assessment through use of aquatic assemblages, integrates the effects of multiple-stressors on these systems over time and is essential to evaluate ecosystem condition and establish recovery measures. It has been undertaken in many countries since the 1990s, but not globally. And where national or multi-national monitoring networks have gathered large amounts of data, the poor water body classifications have not necessarily resulted in the rehabilitation of rivers. Thus, here we aimed to identify major gaps in the biological assessment and rehabilitation of rivers worldwide by focusing on the best examples in Asia, Europe, Oceania, and North, Central, and South America. Our study showed that it is not possible so far to draw a world map of the ecological quality of rivers. Biological assessment of rivers and streams is only implemented officially nation-wide and regularly in the European Union, Japan, Republic of Korea, South Africa, and the USA. In Australia, Canada, China, New Zealand, and Singapore it has been implemented officially at the state/province level (in some cases using common protocols) or in major catchments or even only once at the national level to define reference conditions (Australia). In other cases, biological monitoring is driven by a specific problem, impact assessments, water licenses, or the need to rehabilitate a river or a river section (as in Brazil, South Korea, China, Canada, Japan, Australia). In some countries monitoring programs have only been explored by research teams mostly at the catchment or local level (e.g., Brazil, Mexico, Chile, China, India, Malaysia, Thailand, Vietnam) or implemented by citizen science groups (e.g., Southern Africa, Gambia, East Africa, Australia, Brazil, Canada). The existing large-extent assessments show a striking loss of biodiversity in the last 2-3 decades in Japanese and New Zealand rivers (e.g., 42% and 70% of fish species threatened or endangered, respectively). A poor condition (below Good condition) exists in 25% of South Korean rivers, half of the European water bodies, and 44% of USA rivers, while in Australia 30% of the reaches sampled were significantly impaired in 2006. Regarding river rehabilitation, the greatest implementation has occurred in North America, Australia, Northern Europe, Japan, Singapore, and the Republic of Korea. Most rehabilitation measures have been related to improving water quality and river connectivity for fish or the improvement of riparian vegetation. The limited extent of most rehabilitation measures (i.e., not considering the entire catchment) often constrains the improvement of biological condition. Yet, many rehabilitation projects also lack pre-and/or post-monitoring of ecological condition, which prevents assessing the success and shortcomings of the recovery measures. Economic constraints are the most cited limitation for implementing monitoring programs and rehabilitation actions, followed by technical limitations, limited knowledge of the fauna and flora and their life-history traits (especially in Africa, South America and Mexico), and poor awareness by decision-makers. On the other hand, citizen involvement is recognized as key to the success and sustainability of rehabilitation projects. Thus, establishing rehabilitation needs, defining clear goals, tracking progress towards achieving them, and involving local populations and stakeholders are key recommendations for rehabilitation projects (Table 1). Large-extent and long-term monitoring programs are also essential to provide a realistic overview of the condition of rivers worldwide. Soon, the use of DNA biological samples and eDNA to investigate aquatic diversity could contribute to reducing costs and thus increase monitoring efforts and a more complete assessment of biodiversity. Finally, we propose developing transcontinental teams to elaborate and improve technical guidelines for implementing biological monitoring programs and river rehabilitation and establishing common financial and technical frameworks for managing international catchments. We also recommend providing such expert teams through the United Nations Environment Program to aid the extension of biomonitoring, bioassessment, and river rehabilitation knowledge globally.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.