Yallahs IBA covers an elongated area along the south-east coast in the lee of the Blue Mountains, it forms part of two southeast watershed basins (16 & 17 Yallahs & Morant Rivers). The area is formed by a sedimentary basin through high-gradient streams depositing sediment and culminates in an alluvial fan delta. The Morant, Negro, and Yallahs Rivers have very small to small quantities of fresh water perennially available. However, there is a pipeline, located south of Llandewey on the Yallahs River, which transports about 26.7 million cubic meters per year (0.84 cubic meter per second) to the city of Kingston. About 13.3 million cubic meters per year (0.42 cubic meter per second) of water is also diverted from the Negro River to Kingston. These diversions may reduce these rivers to little more than intermittent streams in the dry season. Both the Morant and Yallahs Rivers have wide, rocky channels in their lower reaches with deep deposits of alluvium. These rivers may become intermittent in dry months, but then have torrential flows after moderate rains. The mid-to-upper reaches of these rivers have steep gradients, flow very quickly, and transport large amounts of sediments. Downstream, the river gradients flatten, flow decreases rapidly, and deposition of carried sediment. Artemia (brine shrimp) farming is considered for the ponds.
The highest point is Yallahs Hill at 730m. Vegetation is degraded xeric (dry/fairly dry limestone scrub on alluvium below 380m), with small patches in moister areas near to rivers or in higher elevations where there is remnant mesic forest on limestone and higher up, on shale.
Due to the position of Yallahs in the rain shadow foothills of the Blue Mountains, rainfall is generally low and the area is susceptible to stochastic events such as hurricanes, earthquakes and floods.
Yallahs supports a diversity of bird life – the suite of terrestrial species is not distinctive, but it is an important staging point for terrestrial migrants both arriving and departing, also for migrant sea and shore birds; and for nesting of some sea and shore birds. Notable migrants have been the Greater Flamingo and Roseate Spoonbill. The near threatened Plain Pigeon (Patagioenas inornata) has been observed here, and the invasive host parasite Shiny Cowbird (Molothrus bonariensis) was first recorded in the wild in scrub beside the ponds.
Non-bird biodiversity: Jamaican Kite Swallowtail Eurytides marcellinus (VU); Greater Fishing Bat Noctilio leporinus mastivus; Pallas’ Long-tongued Bay Glossophaga soricina antilarum; Jamican Fig-eating Bat Ariteus flavescens (IUCN Red List-VU); Jamaican Boa Epicrates subflavus (VU); A newly described crab species (Sesarma ayatum sp. n.,) is restricted to the eastern part of the island, it may occur here.
Habitat and land use
Vegetation is degraded xeric (dry/fairly dry limestone scrub on alluvium below 380m), with small patches in moister areas near to rivers or in higher elevations where there is remnant mesic forest on limestone and higher up, on shale.
Pressure/threats to key biodiversity
The major threat to the Yallahs IBA is human development and limestone and sand/gravel quarrying; there are also deposits of high-grade gypsum and marble. Other threats include clearing for agriculture and the encroachment of non-native plant species. All Forest Reserves are designated as Game Reserves but illegal shooting during the gamebird hunting season occurs along access roads and trails. None of the areas around the ponds is considered a game reserve and hunting occurs there regularly, although they are denoted as a Protected Area in the parish of St. Thomas. Some conservation and public awareness efforts are currently underway through NGOs (e.g. replanting of mangroves; tree-planting project, funded by EFJ, by the Yallahs Development Area Committee). These may be the genesis of Site Support Groups.
Conservation responses/actions for key biodiversity
Includes Forest Reserve “Lloyds” (Blocks A-E) approximately 60 ha. Total terrestrial area is approximately 8,139 ha. Two adjacent ponds: the big pond is the larger and covers 80 ha, with a maximum depth of 1.5 m. is 10 times saltier than the ocean. The smaller pond is less saline than the ocean on the surface, but of equal salinity three feet below. Ponds are denoted as a Protected Area in the parish of St. Thomas.