# The Biological Assessment and Rehabilitation of the World's Rivers: An Overview
## 4 Conclusions  
Existing ecological monitoring in the world is driven by different reasons: (1) the need to determine river condition; (2) environmental impact assessment projects; (3) assessing the effects of rehabilitation projects, and (4) citizen-science projects aimed at increasing awareness and educating. Independently of the reasons, ecological monitoring is widely and consistently implemented in Europe, North America, and Oceania. It is not widely implemented in South America, Africa, or Asia--despite occurring in some countries (e.g., Republic of Korea, Japan, South Africa). Thus, it is not currently possible to have an accurate overview of the ecological condition of rivers worldwide. From what was reported, rivers in all continents are impaired by excessive nutrient concentrations, migration barriers, altered flow, sedimentation, and alterations or removal of riparian forests. The biological condition of rivers is less than Good for more than half of the water bodies in Europe and the USA, and in Japan and New Zealand, a striking loss of biodiversity was observed in recent decades. However, to have a realistic overview of biodiversity and river condition and response to rehabilitation measures, long-term and large-extent regular monitoring programs are needed. Striking differences in ecological monitoring approaches among nations were detected especially in Africa, Asia, and South America, where national/regional bioassessment frameworks are not yet widely developed and implemented. Monitoring implementation is limited by (1) coordination across institutions and between stakeholders; (2) scientific knowledge gaps, and (3) insufficient resources. Countries, where rigorous ecological monitoring is not occurring, could benefit from the European Union's experience with the implementation of the WFD and USA's NRSA and be encouraged to develop biological monitoring. These measures would allow for a more complete overview of the ecological condition of rivers worldwide. This is particularly relevant for large transboundary rivers (e.g., Colorado, Grande, Yukon, Columbia, St. Lawrence, Rhine, Danube, Nile, Congo, Mekong, Amur). Yet, to be successful such international actions require better integration of nations ecologically, economically and politically, because some rivers drain across countries with very different conditions. Examples are the Amazon (draining parts of Bolivia, Peru, Ecuador, Colombia, and Brazil), Parana (draining parts of Argentina, Brazil, Paraguay, and Uruguay), and Africa's Niger, Nile, Congo, and Zambezi Rivers draining portions of 17 nations. Asia's Shatt al Arab, Indus, Brahmaputra, Mekong, and Amur rivers connect 13 countries. Benthic macroinvertebrates are the most commonly used assemblage in bioassessment and quality status is determined mostly through MMIs and predictive models. However, other assemblages (i.e., fish, macrophyte, and microalgae) are also regularly used in Europe,the USA, Australia, New Zealand, and Japan (e.g., [17; 58; 80; 83; 160; 400]). Other assemblages have had a restricted use such as waterbirds in the Murray-Darlin basin, Australia, or in the USA [401]. Nonetheless, given strong budget limitations, it is usually necessary to restrict the number of assemblages used. In most cases, macroinvertebrate and fish assemblages respond strongly to multiple types of disturbances (or rehabilitation), thus they should be used for large-extent and long-term programs. This would require defining appropriate river typologies, predictive models, and adapting or developing new indices based on the new reference conditions where they do not exist (for example for intermittent and saline rivers). A major shortcoming in existing bioassessments, especially those based on macroinvertebrates, is not considering the presence of non-native or invasive species or as a negative effect, and often they are simply included as one more taxon. On the other hand, some fish indices already negatively weight those taxa.