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.
In recent years we are facing a “declining population era” which means a continuously declining population. Along with population, agricultural activities are going into a decline especially in hilly and mountainous areas. Agricultural ecosystems have several ecosystem functions other than food production such as biodiversity conservation. Although traditional agricultural practices maintained biodiversity, recent agricultural situations may have negative consequences on biodiversity. In this paper, I reviewed the current agricultural situation in Japan, summarized studies on agricultural land use in a macro-scale, and discussed the future prospects for agricultural land use in Japan.
The project of re-introducing the Japanese crested ibis (Nipponia nippon) on Sado Island, Niigata, is a major environmental challenge promoted in Japan for the conservation of biodiversity. Since the habitat of this bird spreads across diverse agricultural landscapes, the success of this project depends on the active participation of local residents, which is becoming difficult due to serious human depopulation on the island. The author, in collaboration with other researchers and governmental workers, coordinated 43 participatory workshops between 2007 and 2010, and created opportunities to consider the impact of the project. In this paper, three examples of workshops are examined in order to elucidate how population issues were discussed by participants and how these discussions affected the consensus building processes for co-inhabitance with the ibis. One of the important criteria in designing consensus processes was to first encourage people to share any interests and then consider possible connections between their interests and co-inhabitance with the ibis. Even the issue of depopulation became a source of creative inspiration for generating ideas and actions for public empowerment. Based on the examination of the processes and outcomes of the workshops, I argue that consensus is generated organically from the sharing of various local concerns, and that the informal approach to consensus building fosters the possibility of local actions.
The report of Population census of Japan in 2015 shows that population of Japan has started to decline for the first time since the census started. Population decline are predicted to continue, and population in 2060 are predicted to reach to 2/3 of the current population. These changes may cause significant changes in ecosystem via land-use change. To discuss the solution, scenario approach will be one option to adapt to the uncertain future. We analyzed the effect of future land-use change under population ‘centralization’ and ‘decentralization’ on sika deer range expansion. Although total area of sika deer range was slightly larger at ‘centralization’ scenario, total area of agricultural land-use overlapping with sika deer range was larger at ‘decentralization’ scenario. Scenario approach will contribute to analyze trade-off between policies, and it will become tools to discuss future direction under declining population.
The food habits of the American mink (Neovison vison) were studied based on the analysis of 83 feces and the digestive tract contents of 22 individuals collected in the Gohyaku, Fujita, and Yata Rivers, tributaries of the middle basin of the Abukuma River, in Koriyama city, Fukushima prefecture, Japan from October 2009 to June 2011. The fecal and digestive tract samples contained 163 and 42 prey items, respectively. The prey items included crayfishes (Procambarus clarkii), insects, fishes, frogs, small mammals, birds, and shellfish. Generally, the main prey of mink in a river environment are fishes and small mammals, but the mink in the study area preyed mainly on red swamp crayfish and frogs, which are abundant in paddy fields. In the study area, many waterways connect the rivers and surrounding paddies. These environmental conditions may influence the food habits of the mink. The American minks preyed on many hibernating frogs, and it was concerned about negative impact on the local population of the frogs.