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Botany

Caribbean Islands: CPD Site CB10

BLUE AND JOHN CROW
MOUNTAINS
Jamaica
(Caribbean)

Geography 

The Blue and John Crow Mountains are located at the eastern end of Jamaica. In the broad sense, the Blue Mountains include the Port Royal and Mount Telegraph Ranges (Kerr et al. 1992), and these have been included in the new Blue and John Crow Mountains National Park. These lands, which are all Government-owned, lie within the parishes of St Andrew, St Thomas, Portland and south-east St Mary, and are within about 20 km of the capital, Kingston.

The National Park is located between latitudes 17°57'-18°12'N and longitudes 76°49'-76°16'W. The National Park area is 782 km², but much of this has been altered from its natural state and is now used for forestry, coffee production or subsistence farming.

The Blue Mountains have a complex geology reflecting volcanic and marine influences. The rocks are of igneous and sedimentary origin and the soils are mainly siliceous. There are some knolls of limestone. In contrast, the John Crow Mountains comprise white limestone overlain by marine sandstones and shale.

The Grand Ridge of the Blue Mountains stretches for 16 km across the eastern part of Jamaica, ending in the east with the Rio Grande valley, and in the west with the Wag Water River trough. Much of the range is over 1800 m, the major peaks being: Blue Mountain Peak, comprising Middle Peak (2256 m), the highest point of Jamaica, and East Peak (2246 m); Sugar Loaf Peak (c. 2150 m); High Peak (2082 m); Mossman's Peak (2028 m); and Sir John Peak (1927 m). Lesser peaks and ridges radiate from these and give way to slopes sometimes in excess of 70° and frequently over 50°. To the west of the Grand Ridge are the lower Port Royal Mountains and the Mount Telegraph Range. These include Mount Horeb (c. 1490 m) and Catherine's Peak (1539 m) in the vicinity of Hardwar Gap, and Mount Telegraph itself (1301 m) in a more northerly direction.

The John Crow Mountains run parallel to the eastern coast of the island, east of the Rio Grande valley. The range rises gently from the east to a maximum height of 1140 m, but ends abruptly along a steep escarpment to the west. The Rio Grande separates the John Crow Mountains from the Blue Mountains; the ranges join at Corn Puss Gap (640 m), the boundary of the parishes of Portland and St Thomas. Unlike the sharp peaks of the Blue Mountains, the summit of the John Crow Mountains is a slightly tilted plateau, with an unusual landscape of sinkholes and outcrops.

Average rainfall ranges between 1500 and 6000 mm per annum. The wettest parts of the park are the northern slopes of the Blue and John Crow Mountains, as a result of the prevailing moisture-laden winds (the trade winds) blowing from the Atlantic Ocean. On the northern slopes of the Blue Mountains, mist is present for about 70% of daylight hours for most of the year; the corresponding figure for the southern slopes is 30%. Average annual mean temperatures at 1500 m within the Blue Mountain forests are between 18.5° and 20.5°C (maximum: 24°C; minimum: 8.5°C).

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Vegetation 

Lower montane tropical forest
Wet limestone forest occurs in the John Crow Mountains at altitudes of less than 800-900 m. Dominant species are Calophyllum calaba, Calyptronoma occidentalis, Drypetes alba, Heliconia caribaea and Cyathea grevilleana.

Wet slope forest over sedimentary/igneous substrata occurs on (1) the steep western slopes of the John Crow Mountains and (2) on the northern slopes of the Blue Mountains below 1000 m. It is characterized by large trees (c. 26 m high, 70 cm dbh), including Calophyllum calaba, Symphonia globulifera, Pouteria multiflora, Ficus spp. and Hernandia catalpifolia, with smaller Calyptronoma occidentalis and species of Melastomataceae and Rubiaceae (see picture). Climbers are abundant.

Gully forest occurs in gullies in the Blue Mountains. The canopy height is 12-18 m. The most significant trees are Laplacea haematoxylon, Solanum punctulatum and Turpinia occidentalis. Melastomataceae and Rubiaceae are common smaller trees; Cyathea pubescens is frequent.

Upper montane tropical forest
Upper montane forest is the most extensive natural forest type of the Blue Mountains. Among the most abundant species are Clethra occidentalis, Podocarpus urbanii, Alchornea latifolia and Cyrilla racemiflora. In forests at very high altitudes, Clethra alexandri and Ilex obcordata are abundant. Mor Ridge Forest (see picture) is an uncommon variant which includes the tree ferns Blechnum underwoodianum and Cyathea gracilis.

Upper montane wet limestone forest occurs on limestone rocks capping the western slopes of the John Crow Mountains. Tall trees are absent from this vegetation type.

Montane scrub
Montane limestone thicket covers much of the high plateau area of the John Crow Mountains and is dominated by Clusia havetioides and C. portlandiana. A variant of this type occurs on John Crow Peak in the Blue Mountains and on other limestone outcrops in that region.

Montane grassland
Tall-grass montane savanna is confined to High Peak in the Blue Mountains and is dominated by Danthonia domingensis.

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Flora 

The flora of the Blue and John Crow Mountains contains more than 600 species of flowering plants and includes c. 275 vascular plant species and 14 varieties which are endemic to Jamaica (i.e. approximately 33% of the Jamaica's endemic vascular plant flora occurs in these mountains). About 87 vascular plant species are strictly endemic to the Blue and John Crow Mountains. Of these, 47 species are only known from the parish of Portland, 23 species only from St Andrew and 17 only from St Thomas.

Of Jamaica's seven endemic genera, representatives of at least one are found in the Blue and John Crow Mountains: Odontocline laciniata. Genera which are well represented by endemic species in the flora of the park are Pilea (12 spp.), Lepanthes (12 spp.), Psychotria (12 spp.) and Eugenia (11 spp.).

Due to differences in geology and topography, the Blue Mountains support a different flora to that of the John Crow Mountains. Thus, many of the endemic plants are confined to one or other of the two ranges. The National Park area, therefore, encompasses two centres of plant endemism.

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Useful plants 

Native forest plants have been used by local people as sources of timber, firewood, thatch, herbal medicine and food. Recently, the forests have also been used as a source of ornamental plants.

Timber trees include Sideroxylon spp., Calophyllum calaba, Nectandra spp., Guarea glabra, Hibiscus elatus and Cedrela odorata. Eugenia spp. (rodwood) are cut for firewood.

Hedyosmum spp. are used as a cure for headaches. Passiflora spp., Rubus spp. and Vaccinium meridionale provide edible fruits. Ornamental species include many orchids, bromeliads, Pilea and Peperomia.

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Social and environmental values 

The forests of the Blue Mountains protect the watershed of Jamaica's capital city, Kingston. Agricultural areas, including coffee plantations, on the lower slopes of both ranges depend upon the water supply assured by the forested slopes of the mountains.

Commercial forestry has occurred in these mountains in the past. Up to the 1970s, hardwoods such as Hibiscus elatus and Cedrela odorata were planted. In the 1970s and 1980s, Pinus caribaea was also planted on a very large scale. Commercial forest activities have been scaled down since Hurricane Gilbert destroyed many of the plantations in 1988.

A total of 36 restricted-range landbirds occur on Jamaica, of which 28 are endemic to the island (the highest total for any Caribbean island). Most of the birds occur in the mountain forests throughout the island, an exception being the recently split red-billed and black-billed streamertails, Trochilus polytmus and T. scitulus, which are confined to western/central and eastern Jamaica (including the John Crow Mountains) respectively.

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Threats 

The most immediate serious threat is deforestation as a result of large and small-scale cultivation, principally on the southern slopes of the Blue Mountains, but also in other areas. Deforestation causes massive soil erosion and the quality of the land deteriorates rapidly. Water courses leading from the mountains become heavily laden with sediment and water flows decrease and become more erratic. This results in water shortages alternating with floods at lower altitudes.

The deterioration in land quality renders it productive only for a few years, after which it is abandoned. The African grass Melinis minutiflora colonizes this land very successfully, to the exclusion of native species. Due to the susceptibility of this species to combustion, fires burn frequently on the mountainsides, eliminating any possibility of forest regeneration.

The gradual change of the floristic composition of the forests due to invasion by aggressive alien species is underway in some parts. Particularly troublesome in the Blue Mountains are Pittosporum undulatum and Hedychium gardnerianum.

A threat to some ornamental species is collecting for sale at local markets. Species of orchids and bromeliads are particularly at risk.

Some mineral prospecting licences extend within the park area and it is possible that there will be a conflict of interest if commercial deposits are discovered.

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Conservation 

Most of the natural forests of the Blue and John Crow mountains lie on Government-owned "Crown Lands". These lands have been the responsibility of the Government Forest Department, which has planted some of them with timber trees, leased parts to the Coffee Industries Board and left the more inaccessible parts in their natural state.

The entire area has now been declared a National Park under the jurisdiction of the Forest Department. Management plans are now being formulated. The plans include zoning for different land uses and creating a buffer zone where land uses will be controlled. The success of the park depends on the implementation of the management plan, along with the enforcement of regulations to prevent the removal of timber and other plants, and the inclusion of local people in decision-making and staffing arrangements.

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Map 34. Blue and John Crow Mountains, Jamaica (CPD Site CB10)

References

Adams, C.D. (1972). Flowering plants of Jamaica. University of the West Indies, Mona, Jamaica. 848 pp.

Grossman, D., Iremonger, S.F. and Muchoney, D.M.M. (1992). Jamaica: a rapid ecological assessment. The Nature Conservancy, Virginia, U.S.A.

Kelly, D.L. (1986). Native forests on wet limestone in north-eastern Jamaica. In Thompson, D.A., Bretting, P.K. and M. Humphries (eds), Forests of Jamaica: papers from the Caribbean Regional Seminar on Forests of Jamaica held in Kingston, Jamaica 1983. The Jamaican Society of Scientists and Technologists, Kingston, Jamaica. Pp. 31-42.

Kelly, D.L. (1988). The threatened flowering plants of Jamaica. Biological Conservation 46: 201-216.

Kerr, R., Lee, D., Walling, L., Green, G., Bellingham, P.J. and Iremonger, S.F. (1992). Management plan for the Blue Mountains/John Crow Mountains national park. Internal report, Forest Department, Government of Jamaica, Kingston, Jamaica.

Proctor, G.R. (1982). More additions to the flora of Jamaica. Journal of the Arnold Arboretum 63: 199-315.

Proctor, G.R. (1985). Ferns of Jamaica. British Museum (Natural History), London. 631 pp.

Tanner, E.V.J. (1986). Forests of the Blue Mountain and the Port Royal Mountains. In Thompson, D.A., Bretting, P.K. and Humphries, M.(eds), Forests of Jamaica: papers from the Caribbean Regional Seminar on Forests of Jamaica held in Kingston, Jamaica 1983. The Jamaican Society of Scientists and Technologists, Kingston, Jamaica. Pp. 15-30.

Authors

This Data Sheet was prepared by Dr Susan Iremonger (WCMC, 219 Huntingdon Road, Cambridge CB3 0DL, UK).

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