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1 前言最近,在北海道因河道治理还没有顾及到平原地区的小河道,所以在这些小河道上还残留着一部分茂密的天然护岸林。可以提供鱼类所需的饵料和栖息的场所,以及促使鲑科鱼类能够向上游回游,又可使以这些鱼类作食料的鸟类和兽类到这里生息。而且,像这样优越的河道环境,对其附近居民的生活也有很大的裨益。可是,目前,北海道为了开发耕地和防洪、水源利用,就是平原地区的小河道也进行了整治,这就迅速地推进了河道环境人工化的进程。因此,从明治时代以前就存在的树木,以及成群沿着河流向上回游的鱼类后代有可能从北海道的平原地区消失。
1 Introduction Recently, due to the fact that the river courses in Hokkaido have not taken into account the small river courses in the plains, some of the lush natural forest banks remain on these small river courses. Can provide the fishes and habitats required for the fish, and enables salmonids to migrate upstream, allowing birds and animals that feed on these fishes to feed. Moreover, such a superior river environment is also of great benefit to the lives of nearby residents. However, at present, in order to develop cultivated land and flood control, Hokkaido has also rehabilitated the use of waterways in small river courses in the plains. This has promptly accelerated the artificialization of the river environment. As a result, the descendants of trees that existed prior to the Meiji era, and fish that migrated upward along rivers, may disappear from the plains of Hokkaido.