A quantitative assessment of the contribution of small standing water bodies to the European waterscapes - case of Estonia and France

The abundance and properties of small standing water bodies (SSWB) is globally not well known for their ecological importance is undervalued and their detection suffers from technical limitations. In the current study, we used a combination of GIS-based methods (satellite, orthophoto, ground validation) to evaluate regional estimates of standing water body (SWB) inventories in two geographically different parts of Europe - France, and Estonia. In our study the SWBs surface area threshold limit was 0.00001 km², exceeding the limits of previous studies (>0.002 km²). The total number of SWBs in Estonia is 111 552 (2.5 per km²) and in France 598 371 (1.1 per km²). Our estimates show that the median size of SWBs in Estonia and France is 0.0003 km² and 0.0007 km² respectively, meaning that most of the SSWBs are not included in the global inventories, and their number is therefore underestimated. SSWBs (area below 0.01 km²) form a significant share of the total shoreline length of SWBs, 70.3% in Estonia and 58.8% in France. As nearshore areas are often very productive with diverse habitats, the SSWBs hold a crucial role in maintaining biodiversity. Our results provide quantitative evidence that SSWBs are vital and abundant landscape elements, freshwater resources, and habitats that should not be ignored in global inventories.