This site is the largest remaining forest area on Montserrat, forming a single, almost continuous block of hill forest in the centre of the island. A series of small, steep streams (known locally as ghauts) radiate from central ridges. The boundary goes beyond the forest reserve to include areas where the Montserrat Oriole is found. There is a transitionfrom tropical deciduous forest in the drier lowlands (especially on the eastern and north-eastern sides), through semi-deciduous and evergreen tropical forest at higher altitudes to elfin forest on the summit of Katy Hill. The majority of the forest is secondary, having been cleared foragriculture during the plantation era. The frequent passage of hurricanes ensures that there is a range of successional stages. Most of the area is steep and pathless. Apart from small agricultural and banana plots around the periphery, the area is little used or visited by humans. It forms the main water catchment for the inhabited area of the island, and recently several trails have been cleared to allow tourists to explore the area.
The vast majority of the world population (thought to be 200 to 400 pairs) of the Critically Threatened Montserrat Oriole is resident in the Centre Hills. The Vulnerable Forest Thrush also occurs at relatively high densities throughout, and this site may well be the world stronghold for the species. The Near-threatened Bridled Quail-dove is also common. Seven other restricted-range species of the Lesser Antillean EBA are relatively common: the Purple-throated Carib, Greenthroated Carib, Antillean Crested Hummingbird, Brown Trembler, Scaly-breasted Thrasher, Pearly-eyed Thrasher and the Lesser Antillean Bullfinch. The Centre Hills is the major site on the island for most of these species. The main exceptions to this are the Green-throated Carib and the Lesser Antillean Bullfinch, which are more common in the surrounding lowlands. Pearly-eyed Thrashers and Antillean Crested Hummingbirds are abundant throughout Montserrat in all habitats. Brown Tremblers, Montserrat Orioles and Bridled Quail-doves are confined to the Centre Hills and Roche's Forest (MS003). Point count monitoring carried out between 1997 and 2003 indicates that populations of most species have increased in recent years. Exceptions to this are the Montserrat Oriole and Brown Trembler, both of which showed indications of a population decline during the monitoring period. Most of the key species are found in all forest types in the Centre Hills. The Purple-throated Carib reaches highest densities in dry forest, and the Pearly-eyed Thrasher is most abundant in lowland areas. The Montserrat Oriole occurs primarily in mesic and wet forest, and is scarce in dry forest. At around 19 birds ha-1, densities of the Pearlyeyed Thrasher are among the highest in its range (Arendt, in press).
Non-bird biodiversity: As by far the largest area under broadly natural vegetation cover in Montserrat, the Centre Hills is the stronghold for much native wildlife, including many of the island's endemic species and sub-species. The Montserrat galliwasp Diploglossus montisserrati (CR) has only ever been recorded from the Cassava Ghaut area of the Centre Hills. The mountain chicken Leptodactylus fallax occurs relatively abundantly and is absent elsewhere on the island (this, the second largest frog in the world, is found only in Dominica and Montserrat). The endemic Montserrat anole Anolis lividus (Iguanidae) is common in the Centre Hills, and through many parts of the island. The Montserrat ameiva Ameiva pluvianotata pluvianotata (Teiidae) and Southern Leeward dwarf gecko Sphaerodactylus fantasticus ligniservulus (Gekkonidae) are endemic sub-species. The former is found in the edges of the Centre Hills, but is more common in the lowlands. The latter is abundant in the Centre Hills and throughout Montserrat. The endemic subspecies Montserrat black snake Alsophis antillensis manselli (Colubridae) is relatively common in the Centre Hills, but rarer in inhabited areas of Montserrat. The endemic subspecies Montserrat blind worm snake Typhlops monastus monastus (Typhlopidae) occurs in the Centre Hills, and at some other sites in Montserrat, but its status is poorly known.As a generalisation, bat diversity on Montserrat is thought to be highest in the southern and western ghauts of the Centre Hills (Soldier Ghaut to Sappit Spring) (S Pedersen, personal communication). Tadarida brasiliensis (Nearthreatened) is probably present in this IBA, and is believed to be common and widespread throughout Montserrat, though under-recorded (ibid.). The endemic sub-species Ardops nichollsi montserrratensis is common on Montserrat, but specialises in smaller, native fruits, and although widespread, its population is likely to be concentrated in higher-altitude native forests. Hence, the Centre Hills are probably an important stronghold on the island. Similarly, the nectarivorous Monophyllus plethodon (Near-threatened) is probably most common in the Centre Hills, but widespread elsewhere in Montserrat.The insect fauna of Montserrat has been little studied, but was the subject of a major research project in 2000-2003, which focused on the Centre Hills. Extremely high levels of endemism are apparent. For example, several hundred to a thousand beetle species are thought to be present in the IBA, of which approximately 30% are previously undescribed, and 10% are endemic. The Centre Hills may be home to the world's smallest Cerambycid (longhorn beetle). An enormous scarab beetle larva found in dead logs in the Centre Hills awaits identification, but is likely to be a new genus; it is certainly endemic and may be the largest insect in the UK and its Territories. Among other taxa, the Centre Hills holds an undescribed endemic sawfly, an undescribed endemic long-horned grasshopper, and several undescribed flies that may be endemic. Although sampling has not been sufficiently widespread to determine the Montserratian range of these species, it is inevitable that the Centre Hills is the most important site on the island, since it is the largest area of natural vegetation and covers a large altitudinal range. It is important for the following globally threatened plant species: the red cedar Cedrela odorata (VU), lignum vitae Guaiacum officinale (EN), Brazilian mahogany Sweitenia macrophylla (VU) and American mahogany Swieteniamahagoni (EN).
Pressure/threats to key biodiversity
Introduced ship rats Rattus rattus are abundant in the Centre Hills, at least in some years, and appear to have increased during the period of volcanic activity; the causesof their population fluctuations are unknown. They are known to predate the nests of Montserrat Orioles and to predate mountain chicken; they probably have a profound effect on many other species and on the ecology of the forest. Feral pigs are spreading rapidly through the forest from the south-east, having escaped from abandoned farms in the volcanic exclusion zone. They have already destroyed large clumps of Heliconia caribea (the preferred nest plant of the Montserrat Oriole) along streams in the south of the Centre Hills. They may be significant predators of mountain chickens and other wildlife, and there is particular concern that they may predate the critically threatened Montserrat galliwasp, which appears to be extremely rare and to have a tiny range. Their effects on forest plant communities are unknown, but may be significant. Feral cats are present in the forest, and are known to predate Forest Thrushes. Their abundance and impact are difficult to assess at present.Much of the forest vegetation is secondary, and is also subject to the impacts of introduced rats, pigs and goats. There are known to be a number of non-native plants present, but their distribution, abundance and impact is unknown. It is therefore possible that the plant communities are far removed from the natural state, whichwould undoubtedly have consequences for animal communities. However, plant community ecology has not been studied.Although a native species, the exceptional density of Pearlyeyed Thrashers may also be a conservation problem. The abundance of planted fruit trees and the proximity ofagricultural plots may be a key factor permitting them to become so abundant; as a result, they are major nest predators of the nests of Montserrat Orioles and the Forest Thrush. Ash falls from the still-active volcano in the south of the island may continue to affect the ecology of the Centre Hills, particularly through the arthropod die-offs that result from heavy falls. Heavy falls also result in the physical destruction of the nests of Montserrat Orioles, and may have direct health impacts on bats and herptiles, though these impacts are poorly understood. Although most of the land is privately owned, there is relatively little pressure for forest clearance in the Centre Hills, and the importance of the forest cover for watershed protection is widely realised. However, small-scale encroachment around the fringes, both for housing and agricultural development, appears to be increasing.The boundary of the existing forest reserve does not take in all oriole sites. There are plans to extend it in the future, after consultation with landowners, to take in orioles thatare currently outside the boundary. Since the evacuation of the southern portion of the island, the Centre Hills now provides the water resources for the increasing human population of Montserrat. As a result, there has been an increase in spring-capping. The resulting reduction in stream flows may lead to increased dessication in valley bottoms. The ecological effects of this are unknown, but may be important for birds during the dry season, and also for herptiles. There is currently minimal bird hunting in the Centre Hills. However, applications have recently been made to begin hunting, and the law currently permits hunting of the Near-threatened Bridled Quail-dove, which is likely to be very vulnerable to hunting pressure, and for which Montserrat is probably a major stronghold.
Conservation responses/actions for key biodiversity
A Species Action Plan for the Montserrat Oriole is in preparation.
The Centre Hills area, although largely privately owned, is a forest reserve. Species protection is provided for by the Wild Birds Protection (Amendment) Ordinance (1987). A new proposal to declare the Centre Hills a National Park, and develop a site management plan is in the early stages of preparation.