Escalating climatic and anthropogenic disturbances drive a fragmented and squeezed vegetation pattern: a case study in the yellow river Delta from 1990 to 2020

Abstract

Vegetation in saltmarsh wetlands provides critical ecosystem services, including carbon sequestration, coastal protection, and biodiversity maintenance. Both natural processes and human activities, however, have caused significant vegetation degradation. Despite growing concerns, the long-term dynamics of landscape patterns and the causal pathways underlying these changes remain poorly quantified. In this study, a framework is constructed that integrates eight landscape pattern indices. This framework is applied to investigate the spatiotemporal pattern of saltmarsh vegetation in the Yellow River Delta (YRD), China, and their causal mechanisms from 1990 to 2020. Results revealed that the vegetation degraded by 65.15 % over the past three decades (10.79 km² yr⁻¹), as characterized by decreasing distribution area, squeezing distribution range, and fragmented landscape patterns. Impact of climatic factors shifted from negative before 2000 to positive after 2005, while human activities consistently imposed the direct negative pressures on vegetation landscapes. Both climate and human activities indirectly altered soil properties such as soil organic matter and total phosphorus, exacerbating negative effects on saltmarsh vegetation, particularly after 2000. These impacts of natural and anthropogenic factors on saltmarsh vegetation showed strong spatial heterogeneity. Climate and human activities exerted widespread effects across the YRD, whereas soil properties impact saltmarsh vegetation locally. The findings highlight the complex interactions among various drivers and multiple causal pathways inducing alteration of vegetation landscape patterns. Targeted and localized management strategies are urgent for policymakers and environmental managers to achieve effective vegetation conservation and restoration in coastal wetlands.