Small valley topology on terraced uplands is a unique groundwater-dependent ecosystem in East Asia. Traditionally, this characteristic valley topology has been used for rice paddies because of the sustained availability of spring water. It also provided a unique habitat for wildlife with moderate agricultural disturbance. Due to recent changes in the land use of terraced terrain, these semi-natural wetlands are disappearing rapidly without an accurate assessment of its conservation value. We examined the distribution of small valley habitats in the Shimousa Upland in northern Chiba Prefecture, Japan, and analyzed temporal changes in land cover from the 1970s to 2010s. We also compared the habitat affiliation of endangered wetland species in the small valley topology and the temporal change of their habitat suitability. We found that the relative percentage of urban area has increased rapidly in upland (from 18.6 to 37.9%) and valley (from 13.1 to 28.6%) areas. The abandonment of rice paddies in the valleys has also increased. Of the endangered wetland species, Geothelphusa dehaani, Lefua echigonia, and Lethenteron reissneri were more common in small valley wetland habitats. However, remained habitat for these species has been decreased due to the on-going urbanization in a terrace area.

中文翻译：

---

晚更新世中阶阶地发育的小河谷生境中的湿地物种的土地覆盖变化和分布

梯田高地上的小山谷拓扑是东亚独特的依赖地下水的生态系统。传统上，由于泉水的持续供应，这种典型的谷形拓扑已被用于稻田。它还为受到中度农业干扰的野生动植物提供了独特的栖息地。由于梯田土地用途的最新变化，这些半自然湿地在没有准确评估其保护价值的情况下迅速消失。我们研究了日本千叶县北部Shimousa山地小山谷生境的分布，并分析了1970年代至2010年代土地覆盖的时间变化。我们还比较了小河谷拓扑结构中濒危湿地物种的栖息地隶属关系及其栖息地适应性的时间变化。我们发现，高地（从18.6％增至37.9％）和山谷（从13.1增至28.6％）地区的城市面积相对百分比迅速增加。山谷中稻田的遗弃也有所增加。在濒危的湿地物种中，Geothelphusa dehaani，Lefua echigonia和Lethenteron reissneri在小山谷湿地生境中更常见。但是，由于梯田地区的持续城市化，这些物种的剩余栖息地已经减少。