In tropical countries soil erosion is often increased due to high erodibility of geologically old and weathered soils; intensive rainfall; inappropriate soil management; removal of forest vegetation cover; and mining activities. Stream ecosystems draining agricultural or mining areas are often severely impacted by the high loads of eroded material entering the stream channel; increasing turbidity; covering instream habitat and affecting the riparian zone; and thereby modifying habitat and food web structures. The biodiversity is severely threatened by these negative effects as the aquatic and riparian fauna and flora are not adapted to cope with excessive rates of erosion and sedimentation. Eroded material may also be polluted by pesticides or heavy metals that have an aggravating effect on functions and ecosystem services. Loss of superficial material and deepening of erosion gullies impoverish the nutrient and carbon contents of the soils; and lower the water tables; causing a “lose-lose” situation for agricultural productivity and environmental integrity. Several examples show how to interrupt this vicious cycle by integrated catchment management and by combining “green” and “hard” engineering for habitat restoration. In this review; we summarize current findings on this issue from tropical countries with a focus on case studies from Suriname and Brazil.

In many countries of the Global South, aquatic ecosystems such as streams, rivers, lakes, and wetlands are severely impacted by several simultaneous environmental stressors, associated with accelerated urban development, and extreme climate. However, this problem receives little attention. Applying a DPSIR approach (Drivers, Pressures, State, Impacts, Responses), we analyzed the environmental impacts and their effects on urban hydrosystems (including stagnant waters), and suggest possible solutions from a series of case studies worldwide. We find that rivers in the Global South, with their distinctive geographical and socio-political setting, display significant differences from the Urban Stream Syndrome described so far in temperate zones. We introduce the term of ‘Southern Urban Hydrosystem Syndrome’ for the biophysical problems as well as the social interactions, including the perception of water bodies by the urbanites, the interactions of actors (e.g., top-down, bottom-up), and the motivations that drive urban hydrosystem restoration projects of the Global South. Supported by a synthesis of case studies (with a focus on Brazilian restoration projects), this paper summarizes the state of the art, highlights the currently existing lacunae for research, and delivers examples of practical solutions that may inform UNESCO’s North–South–South dialogue to solve these urgent problems. Two elements appear to be specifically important for the success of restoration projects in the Global South, namely the broad acceptance and commitment of local populations beyond merely ‘ecological’ justifications, e.g., healthy living environments and ecosystems with cultural linkages (‘River Culture’). To make it possible implementable/practical solutions must be extended to (often poor) people having settled along river banks and wetlands.

Human welfare depends on the health of nature. Decades of ill-conceived management practices caused a decline in the quality of human life, as well as in biological and cultural diversity. Simultaneously, they increased social and ecological risks. For instance, mismanagement of urban rivers jeopardizes their ecological health and ability to provide ecosystem services. While demands for responsible urban riverscape design that fulfill both human and ecosystem needs are increasing, explicit recommendations to achieve these ambitious goals are still lacking. We present a first attempt of a conceptualization of Human–River Encounter Sites for urban rivers that targets reconciliation between humans and nature within urban river corridors. It builds upon the River Culture Concept with literature reviews and experiences from river restoration projects. We identify six tenets that are important to develop guidelines for Human–River Encounter Sites: health, safety, functionality, accessibility, collaboration, and awareness. This paper presents how these tenets can collectively help to harmonize the needs of citizens and biota, and to mitigate the current urban river crisis. This contribution feeds the debate on sustainable socio-ecological management of urban rivers and provides guidelines for the implementation of future urban river restorations and management efforts.

The European water governance took a decisive turn with the formulation of the Water Framework Directive (WFD), which demands the restoration of all water bodies that did not achieve sufficient ecological status. Urban rivers are particularly impaired by human activities and their restorations are motivated by multiple ecological and societal drivers, such as requirements of laws and legislation, and citizen needs for a better quality of life. In this study we investigated the relative influence of socio-political and socio-cultural drivers on urban river restorations by comparing projects of different policy contexts and cultural norms to cross-fertilize knowledge. A database of 75 projects in French and German major cities was compiled to apply (a) a comparative statistical analysis of main project features, i.e., motivation, goals, measures, morphological status, and project date; and (b) a qualitative textual analysis on project descriptions and titles. The results showed that despite a powerful European directive, urban river restoration projects still keep national specificities. The WFD drives with more intensity German, rather than French, urban river restoration. This study showed the limits of macro-level governance and the influence of microlevel governance driven by societal aspects such as nature perception and relationships between humans and rivers.