Effects of breakwater on vegetation in open-coast beaches along the Pacific Coast of Chiba Prefecture

Abstract

While it is proven that breakwaters are effective in protecting and rehabilitating coastal vegetation, most cases are observed in enclosed beaches. The impact of breakwaters on vegetation in open-coast beaches, which are exposed to stronger wave disturbances, has not been extensively investigated. In this study, we examined the effects of breakwaters on the species composition and structure of vegetation along the Pacific coast of Chiba Prefecture. We compared areas with and without breakwaters, conducting vegetation surveys and soil analyses. The results showed that coastal areas with breakwaters had higher coverage of inland species and coastal species preferring stable dunes, while species typical of the annual plant zone were less frequent. These findings suggest that breakwaters reduce wave energy and alter topography, which leads to vegetation in open-coast beaches resembling that of stable zones, promoting the invasion of inland species and causing a reduction in the annual plant zone.