Islands in the Pacific: Settings, Distribution and Classification

Abstract

Oceanic islands have a history of being misunderstood by outsiders, commonly marginalized in global synthesis and planning, their considerable diversity often understated. To capture and explain the diversity of islands in the Pacific, a classification is developing using elevation and lithology (rock type) as the highest level criteria. For each of the 1779 islands, defined as ocean-bounded landmasses ≥1 ha (0.01 km2) in area, data were collected on locations and shapes, areas, names, elevations and lithologies. Eight island types were identified—volcanic high islands (≥30 amsl, ≥80% igneous); volcanic low islands (<30 amsl, ≥80% igneous); limestone high islands (≥30 amsl, ≥80% calcareous); limestone low islands (<30 amsl, ≥80% calcareous); reef islands (≥80% unconsolidated sediments); composite high islands (≥30 amsl, <80% igneous, <80% calcareous); composite low islands (<30 amsl, <80% igneous, <80% calcareous); continental (≥80% continental rocks). The broad distribution of each island type in the Pacific can be explained by its geological history. In addition, this classification could be used as an objective basis for assessing island vulnerability to external stressors like climate change or pollution as well as a tool for national/regional planning.