Port construction alters dune topography and coastal forest growth: A study on forest decline due to coastal erosion

• Published in: Ecological engineering 2022-07, Vol.180, p.106640, Article 106640
• Main Authors: Iwasaki, Kenta, Nanko, Kazuki, Nakata, Yasutaka, Masaka, Kazuhiko, Shinohara, Yoshinori, Nitta, Kyohei, Mizunaga, Hiromi
• Format: Article
• Language: English
• Subjects: Adhesion; Airborne lasers; Airborne remote sensing; Airborne salt; Airborne sensing; Beach erosion; Beaches; Canopies; Canopy; Coastal ecosystems; Coastal erosion; Construction; Decline; Digital surface model; Disaster prevention forest; Dune erosion; Dunes; Environmental stress; Estuaries; Estuarine dynamics; Forest ecosystems; Forest growth; Forests; Growth rate; Height; Lasers; Plant cover; Remote observing; Remote sensing; Salt spray; Salts; Sand; Soil erosion; Spatial variations; Spray; Surveying; Sustainability; Terrestrial ecosystems; Topography; Unmanned aerial vehicles; Vegetation
• ISSN: 0925-8574; 1872-6992
• DOI: 10.1016/j.ecoleng.2022.106640

Coastal forests are critical for protecting those living near the sea from wind, blown sand, salt spray, and tsunami. However, the sustainability of the coastal forest ecosystem is threatened by coastal erosion. To reveal the impact of erosion on coastal forest growth, we focused on the changes in coastal topography caused by port construction. The coastline has been advancing at the near side of a constructed port from the estuary (east) and retreating at the opposite (west) side since the 1980s in Ishikari, Japan. We conducted a transect survey, stem analysis, salt adhesion observation, and remote sensing analysis using airborne laser imaging detection and ranging data as well as an unmanned aerial vehicle. Results showed that the basal-area–weighted mean tree height in the east side was higher than that in the west side in 2019 and has increased by 2.82 m over the last 17 years. The tree height growth rate after the 2000s decreased in the west side, whereas the vigorous growth rate in the east side was maintained. The recent deposition of blown sand on the embryo dune was also detected on the east side. In contrast, the foredune was eroded, and the canopy height growth was inhibited toward several hundreds of meters inland from the seaward forest edge on the west side. The foredune erosion expanded from the point where the vegetation was destroyed, indicating the relevance of foredune vegetation in mitigating it. During winter, salt adhesion was higher in the eroded area, inhibiting canopy height growth. The most useful topographic variable to explain the spatial variability of the canopy height growth was the relative change in the cross-sectional area of the beach and dune upwind of the forest. These findings highlight the importance of monitoring vertical topographic changes in beach and foredune to evaluate the impact of coastal erosion on forest growth through airborne salt stress. [Display omitted] •Coastline advanced and blown sand deposited on a dune at the east side of the port.•Coastline retreated and foredune was eroded on the west side of the port.•Coastal erosion inhibited canopy height growth toward several hundred meters inland.•Airborne salt stress was high at the eroded area with inhibited canopy growth.•Change in cross-sectional area of beach and dune could explain canopy growth.