Prosperous Bay Plain
Prosperous Bay Plain is an area on the eastern coast of Saint Helena, a British island territory in the South Atlantic Ocean. It is the site of the new Saint Helena Airport, and is notable for its high invertebrate biodiversity.
Prosperous Bay Plain forms part of the eastern arid area of Saint Helena, and covers about 2.25 km2, comprising one of the largest areas of relatively level ground on the island. It was formed 8.5 million years ago by lava flows from Saint Helena’s Southwest Volcano. The surface of the plain is covered by rocks, grit and dust, with what little soil there is containing high concentrations of mineral salts.
Within the plain there is a 60 hectare (0.6 km2) depression known as the Central Basin, with a level dusty base. This forms a miniature mature desert ecosystem.
It falls within the district of Longwood.
The climate of the plain is arid and plants are few, scattered and low-growing. Dusty areas and gullies are dominated by the native samphire Suaeda fruticosa. In rocky areas the more dominant plant is the introduced Hottentot fig (Carpobrotus edulis). On dry slopes, including those of the Central Basin, there are various chenopods, including the introduced saltbush Atriplex semibaccata. The plain holds a number of important populations of the island's endemic flora. The slopes of Dry Gut hosted the largest remaining group of barn fern (Ceterach haughtonii). Dry Gut was also home to the most abundant remaining population of the endemic boneseed, (Osteospermum sancta-helenae). Annual flushes of endemic babies'-toes (Hydrodea cryptantha), goosefoot (Chenopodium helenense) and neglected sedge (Bulbostylis neglecta) occur across the plain. There are a few scattered scrubwoods (Commidendrum rugosum), teaplants (Frankenia portulacifolia) and salad plant (Hypertelis acida), threatened endemics which may have grown more plentifully in the area in the past, before the introduction of exotic herbivores.
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