Ecological quality dynamics around marine reserves in the Bohai Sea coastal zone and their relationship with landscape artificialization
Numerous marine reserves worldwide are losing their ability to protect wild endemic species due to surrounding ecological deterioration caused by coastal landscape artificialization. Such risk of becoming invalid nature reserves is particularly high in China's Bohai Sea coastal zone, a region with rapid urbanization and industrialization. In this study, the ecological quality (EQ) status around Laizhou Bay Ostrea rivularis germplasm reserve (R1), Yellow River Estuary Meretrix meretrix germplasm reserve (R2), and Taoer Estuary Sinonovacula constricta germplasm reserve (R3) was dynamically diagnosed using seven indicators characterizing ecological support and threat from peripheral environments. A series of thresholds indicating EQ and corresponding landscape artificialization intensity (LAI) were determined based on multi-factor clustering analysis and relational regression simulation. The results show that the surroundings of these three reserves were favorable in 1984, insufficient in 2000, and unfavorable in 2015. With an average 7.5 times increase in LAI over the past three decades, the EQ levels around R1-R3 declined significantly and have deviated greatly from their optimal reference status by 2015, which stemmed mainly from intertidal landscape artificialization, such as establishing salt pans, industrial areas and ports after reclaiming wetlands. It was found that R3 > R1 > R2 in terms of overall peripheral ecological degradation, implying that the closer the marine reserve is to the land, the more likely it is to lose its effectiveness. The changes in EQ status and LAI were well indicated by the proportion of natural ecosystems, the distance between seawalls and protected boundaries, and the reserves' enclosed degree by artificial systems, which, as a quick and simple diagnostic approach, can facilitate spatial planning and management practices around marine reserves in the Bohai Sea coastal zone and elsewhere.