Fluviodiversity and Climate Change in Circumpolar Regions

Biodiversity is of fundamental importance for ecosystem functioning as it provides goods and services essential to life on earth, serving human and societal needs (WHO). The positive relationship between ecosystem functioning and biodiversity shows how important biodiversity is to sustainably maintain key ecosystem functions and associated services (Benkwitt et al., 2020). One of the most important tools to protect diversity species is to preserve geodiversity, e.g., geodiversity or diversity of materials, landscape forms and processes, that supports the diversity of habitats (Beier et al., 2015). In particular, rivers are a source of geodiversity and key components of the hydrological cycle in circumpolar regions. They are considered dynamic hotspots that convey freshwater, heat, and terrigenous materials (sediment, nutrients, and carbon) that regulate the biological productivity of terrestrial and marine ecosystems (Feng et al., 2021).However, Arctic and Antarctic regions (circumpolar regions) are one of the most threatened ecosystems by climate warming. In land examples of climate change impacts in circumpolar regions are a reduction in snow cover (Dankers and Christensen, 2005), earlier snowmelt (Tan et al., 2011), increased water fluxes (Feng et al., 2021), or modifications in the frequency of extreme runoff events (Svetlana et al., 2017). These changes modify the hydrological cycle and have subsequent impacts on drainage networks, undoubtedly affecting the diversity of river processes and landforms.Thus, in this work we aim to explore river morphological diversity in a Sub-Arctic catchment, the Tana River, the biggest catchment in Fennoscandia draining to the Barents Sea. Tana is a transboundary river between Finland and Norway and of special importance to local socio-economic activities, biological diversity and, e.g., Atlantic salmon preservation. Therefore, a better understanding of the processes that shape river diversity in the present and in the past, to predict future consequences of climate warming is of crucial importance. In order to tackle this, we tested a bottom-up method to characterize fluviodiversity (the diversity of river landforms). This was performed by i) a systematic extraction of local characteristics of the river network (channel slope, width and confinement, morphological pattern, and geomorphic activity) at different scales, ii) an objective determination of river diversity by applying a K-means clustering algorithm and iii) a validation of results with field visits and aerial photo interpretation.This test showed promising results and indicated that machine learning algorithms such as K-means can successfully classify representative river types. Interestingly, the validation of the results also showed that assessing fluviodiversity of circumpolar regions requires additional understanding of the past landscape evolution to be able to identify present fluvial forms. This is mainly because these areas are usually affected by glacial retreat and land uplift combined with a fast change in runoff, and therefore geomorphic activity. Thus, future research needs to include additional parameters reflecting such post-glacial processes, to further understand past, present and future of fluviodiversity which can provide better insights to adapt to and mitigate the effects of climate change in circumpolar regions.