SUPERVISOR: Thomas HEIN

PROJECT ASSIGNED TO: Anthony BASOOMA

Introduction

Freshwater ecosystems are one of the highly over-exploited and degraded ecological realms globally (Dudgeon et al. 2006; Reid et al. 2019), despite their ecological and socioeconomic significance. For example, approximately 200 million people from Asia and Africa depend on freshwater fishes for animal protein (Hughes et al. 2021). Freshwater biodiversity is underfunded, undervalued, and overlooked (Cooke et al. 2016), which has coincided with high risk of extinction for a third of freshwater fishes (Hughes et al. 2021) and is more pronounced in migratory fishes (Deinet et al. 2020). Freshwater ecosystems are highly diverse inhabiting ~51% of the known fish species globally (Hughes et al. 2021) while occupying a diminutive surface area of less than 1% of the Earth’s planet (Strayer and Dudgeon 2010). Rivers and their associated floodplains are not only biodiversity hotspots (Reid et al. 2019), but heartbeat for most communities in providing a myriad of  indispensable ecosystem services (Vari et al. 2022). This incidentally creates over dependency on rivers for human survival and has concomitantly predisposed them to several ecological threats (Habel et al. 2020) and mutilation of their structural and functional connectivity. As the case, ecosystem connectivity is the backbone of the ecological functioning in river networks, and if altered, species migration for spawning will be drastically hindered. Noting of the Critically Endangered European eel (Anguilla anguilla) whose migratory population reduced to 1% of its historical numbers by 2010 (Hughes et al. 2021).

Humans, the direct beneficiary of the ecosystem services from rivers, have exacerbated the intensity and severity of anthropogenic stressors (Dudgeon et al. 2006; Reid et al. 2019). This hinders ecosystem resilience to persistent human-driven ecological stressors leading to collapse (Keith et al. 2023). Fragmentation of rivers and floodplains has received prominence from the scientific community as a major culprit for the loss of different facets of river connectivity (Nilsson et al. 2005; Zarfl et al. 2015; Winemiller et al. 2016; Hughes et al. 2021). The intensity and severity of river fragmentation is of global concern (Nilsson et al. 2005; Grill et al. 2019), with hotspots recorded in highly industrialized areas including Europe and North America (Nilsson et al. 2005; Zarfl et al. 2015; Belletti et al. 2020). For instance, an extensive survey of 147 rivers from 36 European countries recorded 1.2 million barriers (Belletti et al. 2020) and coincides with the highest decline of migratory fishes by 93% over the last 50 years in Europe (Deinet et al. 2020). This ecosystem tragedy requires a systematic and multifaceted attention to ensure that infrastructural developments coexist with biodiversity. The European Union strategy of achieving at least achieving 25,000km of free flowing rivers by 2030 and restoration of floodplains aims to address the threat (European Commission 2022).

The restoration of rivers and their associated floodplains requires a systematic evaluation to examine the cost effectiveness of the intervention by identifying barriers that yields higher ecological value if removed (Schwarz 2021), but also evaluate the level of connectivity (Zhao et al. 2021), and species distribution within the  ecosystem. Now that high resolution stream network (Amatulli et al. 2022), well documented stream barriers (Belletti et al. 2020), and species occurrences (https://www.gbif.org/) are available, the three aspects will be critically assessed to guide restoration efforts. Open-source data will be concretized by detailed assessment of the floodplains including evaluation of the local community participation at the restoration demonstration sites in Danube River Basin. The indicators of ecological connectivity such as changes in ichthyology composition mostly rheophilic and lagoon communities will guide on the restoration progress. To this end, I aim at assessing the diversity and species distribution from the major European rivers, examine the longitudinal and lateral connectivity, and evaluate the restoration efforts conducted on the major rivers in Europe. The study directly addresses two research clusters under HR21, namely connectivity and vulnerability (Hein et al. 2021). Since the infrastructural developments affects the ecosystem metabolism, there removal or restoration improves its ecological functioning. Also, the knowledge or research outputs will improve ecosystem governance. Therefore, the study fully contributes to novel aspect of Socio-Ecohydrological System (SEHS), which incorporates the ecological, hydrological, morphological and sociocultural transformation aspects in river ecosystem management (Hein et al. 2021).

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