An attempt to make environmental impact assessment of artificial beach and coastal revetment, using biodiversity as indicator, and consideration of new approach in creating an artificial beach

本研究在千叶市的一个人工海滩上，由数名植物和动物学分类学家对不同季节的植物和动物类群进行了调查。将结果与东京湾不同环境的结果进行了比较，并尝试对人工海滩进行环境影响评价。①陆地部分存在人工林、芦苇草、滨海草地等植物群落；在人工林中，由于缺乏地幔群落和套筒群落，过度干燥导致归化植物占主导地位，枯死树木明显。这种干燥也可能是昆虫和土壤动物多样性低的一个因素。即使在已开发的土地上，在有利的水条件下也出现了常见于河口潮滩的芦苇草地；芦苇草地的环境比人工林和生物潜水地湿润，多样性也较高，但栖息小动物的归化物种较多。(2)在涨潮漂线附近，与滨海草原的下邻部分，环境明显不同；漂线周围的漂藻被该地区的特色动物如昆虫、螨虫和沿岸寡毛纲利用。(3)在护岸石质潮间带，垂直混凝土堤防、四足动物和石质粘结体的多样性依次增加；特别是在大卵石和石缝内的漂浮物上，观察到以前只在河口潮滩发现的濒危物种，以及独特的沿海土壤动物。(4)潮间带砂质和泥质底引种贝壳数量增加，多样性较差。这可能与该区泥沙量小于河口带有关。基于这些结果，在建造新的人工海滩时，需要考虑的要点是：建造至少部分阻挡海风的植物群落；潮间带上游芦苇草地的生长；在建造海岸护岸时，最好使用石质粘结剂；在前海岸形成平缓的斜坡部分，提供更多的淤泥沉积。少

In the present study, wide variety of plant and animal groups were investigated by several taxonomists, both in botany and zoology, in an artificial beach in Chiba-shi through all seasons. The results were compared with those of various environments in Tokyo Bay and an attempt to make environmental impact assessment in the artificial beach was made.Rather diverse environments did exist in the artificial beach :(1)In land part, plant communities such as planted wood, reed grassland and littoral grassland are recognized. In planted wood, naturalized plants were dominant and dead planting trees were distinct because of excess drying which was derived from lacking of mantle communities and sleeve communities. This drying also might be a factor of low diversity of insects and soil animals. Even in developed lands, reed grasslands, usually seen in estuarine tidal flats, appeared under favorable water condition ; in such reed grasslands, environment was wetter than in planted wood and biodive … More rsity also higher but naturalized species were conspicuous in inhabiting small animals.(2)Around high tide drift line, lower adjacent part to littoral grasslands, distinct environments occurred ; drifted Ulva around drift line was utilized by characteristic animals at this zone such as insects, mites and littoral oligochaetes.(3)In rocky intertidal zone on coastal revetment, diversity increased in the order of vertical concrete embankment, tetrapod and stone bond ; in particular on the large pebbles and drifted materials within stone bond, threatened species previously only known in estuarine tidal flats were observed, as well as distinct littoral soil animals.(4)On sandy and/or muddy bottom in intertidal zone, introduced shells increased in number and diversity was fairly poor. This is supposed to be related to the fact that amount of mud in this zone was less than that of estuary zone.Based on these results, when creating new artificial beach, important points to be taken into consideration are as follows : making plant communities which blocks sea breeze at least partiallys ; growing reed grasslands in upper intertidal zone ; stone bonds are preferable in making coastal revetment ; creating gentle slope part in foreshore that provides more muddy sedimentation. Less