Characteristics and models of anthropogenic disturbances on islands from perspective of coastline: Extensive cases from Indian Ocean and mediterranean sea

The negative impacts of anthropogenic disturbances on the ecology of small island states or regions are important topics mentioned by United Nations' Sustainable Development Goals. This study used the coastline as an indicator to analyze four parameters (the annual variation rate of the artificial coastline length, the index of coastline utilization degree, the index of coastline type diversity, and the standard deviation ellipse of the latter two indicators) to study the changing characteristics of coastal development and utilization of over 13,000 islands, revealing the spatiotemporal evolution characteristics and patterns of human disturbance in island coastal zones. The results indicated that:(1) The spatial–temporal patterns of coastline length and structure undergone significant changes. The length of artificial coastline increased, while natural coastline decreased. The most pronounced change in the artificial coastline was the proliferation of aquaculture embankments, and the most drastic changes occurred in the coastal areas of Southeast Asia.(2) The intensity of coastal development and utilization, as well as the diversity of coastline types, showed an upward trend on the islands. (3) The centroid of coastline utilization degree and type diversity both shifted southeastward by 59.53 km and 931.05 km, respectively. (4) The anthropogenic disturbance patterns on the islands primarily included land reclamation and occupation of original wetland systems. Our study revealed the spatiotemporal characteristics and multiple scenario patterns of anthropogenic disturbance on islands at a large spatial scale from 1990 to 2020, and we quantitatively analyzed the relationship between anthropogenic disturbance factors and changes in the coastline of islands. Islands are currently facing significant pressures from development and conservation. This work is of great significance for the study of sustainable development and management of islands experiencing high-intensity human activities.