Ecological impacts of pond losses and abandonments on regional aquatic biodiversity: What will happen in the depopulating Japan?

Abstract

 Ponds are small waterbodies holding unique biota and relative-higher biodiversity than other freshwater ecosystems (i.e., rivers, lakes and streams). In Japan, irrigating farm ponds are typical lentic environments in Satoyama landscapes. Currently, however, there is growing concern for pond conservation because of declines and abandonments of ponds across the country. Japanese population number has started depopulating in 2011 and was estimated decreasing to about two-thirds in 2060. The social change in future Japan can affect agricultural landscapes, including farm ponds. In the paper, I reviewed and discussed ecological effects of pond abandonments on aquatic ecosystems, owing to the depopulation in future Japan. If farm ponds are abandoned, aquatic biodiversity drastically degrade and then most of aquatic species disappear, owing to vegetation succession. Although it needs maintaining operations (e.g., mowing and dredging) for conserving aquatic biota in farm ponds, it will be difficult in depopulated/abandoned settlements. I here suggested new systems and frameworks for conservation of pond ecosystems under the depopulating situation.