A sea–land gradient perspective on ecosystem services: unravelling spatiotemporal evolution and interaction mechanisms

Coastal ecosystem services (ESs) exhibit obvious sea–land gradient characteristics. However, their specific patterns and evolutionary mechanisms remain unclear. Therefore, we developed an analytical framework integrating this gradient perspective. In the case of the Yellow River Delta, we systematically revealed the sea–land gradient evolution pattern of ESs from multiple dimensions, including spatiotemporal trends, multi-scenario responses, interrelationships, and interaction mechanisms. Key findings include: (1) From 1980 to 2050, coastal areas exhibit higher ESs stability than inland zones. The water yield (WY) persistently increases by 20.10% of the study area, whereas habitat quality (HQ) degrades in 45.98% of inland regions. (2) ESs display distinct spatial patterns across the sea–land gradient. HQ declines with increasing distance from the coastline. Other ESs display fluctuating patterns, with poorer performance in nearshore areas (0–5 km). (3) Trade-offs dominate WY–HQ and WY–carbon storage (CS), while synergies prevail among other ESs. (4) Spatially, ESs interactions exhibit high heterogeneity and a clear sea–land gradient variation. (5) When the distance from the coastline is also considered, the influence of factors is significantly enhanced. This study provides a forward-looking research framework for coastal risk management by revealing the complex dynamics and underlying mechanisms of ESs under the influence of sea–land interactions.