The Black River Lower Morass: a Threatened Wetland in Jamaica
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The Black River Lower Morass: a threatened wetland in Jamaica L. D. Garrick The Black River Lower Morass is Jamaica's 1983; Digerfeldt and Enell, 1984). A more largest wetland, and is a refuge for two en- immediate threat to the survival of the BRLM, dangered species—the American crocodile however, is a plan for large-scale drainage and and the West Indian manatee—as well as for a irrigation of the marsh for the cultivation of rice host of other plants and animals. It is inter- and soya beans. nationally important for many birds and a vital Wetlands cover only 2 per cent of Jamaica's economic resource for 20,000 people. Pro- surface area, and the Black River Lower Morass is posals for peat mining and drainage for agri- the most important. Its natural beauty and diver- culture now threaten this valuable area. The sity have been favourably compared with Ever- author has a long-standing interest in the glades National Park, USA (Wade, 1984). It is the wetland, having studied the American croco- purpose of this paper to demonstrate that its dile there since 1975. ecological significance is without parallel in A proposal to mine peat from the Black River Jamaica, and probably also in the Caribbean Lower Morass (BRLM) and the Negril Morass, Basin, and to urge that it be protected. Jamaica, has generated studies of the flora, fauna The Black River Morass and socioeconomics of these areas (NRCD, 1981; Coke etal., 1982; Bjork, 1983; Svensson, The Black River Morass dominates the arid Broad Water, the confluence of Broad River and Black River. Red mangroves line Black River as it nears the sea. The town of Black River is to the right (L.D. Garrick). Black River Lower Morass Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.22, on 23 Sep 2021 at 16:10:20, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300020007 Montego X Bay X Negr \ \/ ,^^1 ^^Black R. j R s ^ j tr , cri \C0^ \ -^ j Lacovia ,' "T> S w y'' \ . \ z V A3 / 1 i ' ^ 1 Figure 1. The Black River Upper Morass (UM) and Lower Morass (LM), St Elizabeth Parish, Jamaica. A2 is a highway. v \ 3r southern portion of St Elizabeth parish, and con- / \ 2 \ O sists of two separate wetlands, the Upper and Black ^% \ ^ River /r \ * Lower Morasses, each of approximately 7000 ha \ J in a basin of 67,000 ha (Figure 1). For the last 1 km _y y'' \ 1 decade, part of the Upper Morass has been V—<r — — managed for the cultivation of rice, peanuts and ) ^ sugar cane. The Lower Morass is a low-lying /i \ ( permanent herbaceous marsh, with patches of V swamp forest, mangrove forest, and limestone 1^ Parottee islands with agricultural plots. V Four rivers traverse the morass (Figure 2). The Black River, the largest in Jamaica, originates in the mountains north-east of the basin and Figure 2. Black River Lower Morass, Asterisks denote settle- meanders 44 miles before emptying into Black ments. Dashed lines are roads. A2 is a highway. River Bay at the town of Black River. The Black River leaves the Upper Morass through a gorge at months (NRCD, 1981). Some marine shrimps Lacovia and carries with it the waste from rum and many fish use the Morass as a nursery. Salt- production at the Appleton distillery, which water intrusion, which is determined by rainfall makes it the most turbid and nutrient-rich of the and tides, extends as far as 10 km along the Broad waterways within the marsh. Also within the River and 11 km up the Black River (Bjork, Lower Morass are two large north-south flowing 1983). Such saltwater dilution is important for rivers, the Middle Quarters and the YS, and one shrimp development (Hunte, 1978). The marsh large east-west flowing river, the Broad River, is also important in controlling flood waters from which is the most scenic. The combined outflow is the YS and Black Rivers and as a buffer against carried first to the Thalassia (turtle grass) beds and the sea. then to the patch reef system before being pushed westward along the coast. Flora Ecological significance The Lower Morass is an important genetic reserve, with 92 species of flowering plant, of The Lower Morass removes nutrients that the which 25 per cent are rare. Nine per cent are Black River carries from the Upper Morass, and endemic to Jamaica, 7 per cent endemic to the exports substantial organic carbon in the form of Greater Antilles, and 3 per cent endemic to the particulate detritus to the food web of estuarine West Indies. and coastal ecosystems. Primary productivity of the marshland is high; the biomass of the Most of the Lower Morass is composed of her- dominant sedge species can turnover in six baceous marshland of heterogeneous com- 156 Oiyx Vol 20 No 3. July 1986 Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.22, on 23 Sep 2021 at 16:10:20, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300020007 position. Several different associations have been Table 1. Herbaceous plant associations in the Black River described from four regions within the Morass Lower Morass (Coke et a/., 1982) (Table 1). Within the marsh, elevated limestone islands of various sizes permit Zone Associations human habitation, grazing of cattle and goats, Eastern zone Typha hummocky swamp and cultivation (Figure 2). The dominant natural Upper Broad River Cladium-Sagittaria plant form on the smaller islands, the econom- Basin association ically important Sabal jamaicensis (bull thatch), North-western zone Area bound by Middle C/adium-dominated has been replaced and/or complemented by Quarters. Holland and hummocky swamp Haematoxylum campechianum (logwood), Luana Thick Cladium association Mangifera indica (mango), and all too frequently Upper YS and Typhazone Cannabis sativa (ganja). Frenchman Rivers North-central zone Typha—Thalia geniculata Despite significant depletion of riparian forests, association good stands of Rhizophom mangle (red man- Crinum americanum—Sagit- grove) remain along the Black River and lower taria zone Broad River. This portion of the Broad River is Southern zone lined by these splendid tall trees. Southern mangrove complex Adjacent to Broad River Scirpus quaking bog. in which The Swamp Forest [Coke et al., (1982) prefer the humans and terrestrial vehicles term 'swamp' to 'marsh'] between the YS and cannot move Black Rivers and north of the Frenchman River is Fringing the non-riparian Cladium/Conocarpus mangrove forest, which (buttonwood) association the most distinctive floral assemblage in the entire extends finger-like from Morass. These small patches of forest, which were Broad River south to extensive 4500 years ago (Digerfeldt and Enell, Parottee Ponds, a 1984), are dominated by Grias cauliflora, the tall hypersaline lagoon anchovy pear tree, the only native member of the Brazil nut family in the West Indies, and Dominant plant species Roystonea princeps, the endemic swamp cab- Cladium jamaicense sawgrass bage palm. Also part of this community are Sagittaria lancifolia pond coco, or arrowhead Schoenoplectus a sedge various mahoes, Ficus, boar gum Symphonia americanus (syn. Scirpus globuhfera and long thatch Calyptronoma olneyi) occidentalis, bromeliads, vines such as Philo- Typha domingensis reedmace or cat-tail dendron, tall ferns, and herbs, for example Dieffenbachia and Ludwigia. Because of its relatively large size, the Lower Morass is truly the last refuge for the American crocodile in Jamaica. Our studies (L. D. Garrick, Fauna unpublished observations) in this habitat have The Lower Morass is habitat for hundreds of determined that both very large and hatchling vertebrates and invertebrates: 150 vertebrate crocodiles are found along the main rivers, an species are found in or are directly dependent on indication that nesting occurs on the limestone the marsh, of which 92 are protected under islands and on other higher ground. American Jamaican law and 20 have a range of less than 10 crocodiles prefer to nest in sand or soil (L. D. square miles. Two endangered species—the Garrick, unpublished observations; Garrick and American crocodile Crocodylus acutus and the Lang, 1977). Other reptiles include five species of West Indian manatee Trichechus manatus— Anolis lizard, the croaking lizard Aristelliger sp., inhabit the marsh or nearby Black River Bay. and an edible freshwater turtle, Chtysemys ter- According to fishermen at Black River, six rapen. Four amphibians, a native Hyla, an manatees spent a week in Black River Bay during Eleutherodactylus, and the introduced toad Bufo June 1983, and it is believed that the manatees marinus and bullfrog Rana catesbiana, axe swim upriver. present. Black River Lower Morass 157 Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.22, on 23 Sep 2021 at 16:10:20, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300020007 Swamp forest (foreground) at the confluence of Frenchman Broad River lined by mangroves, and adjacent marsh (L.D. River and Black River (L.D. Garrick). Garrick). As a habitat for birds the Lower Morass is out- are present, and 41 migratory species use the standing: 102 of the 227 species known from Morass. Common and abundant aquatic species Jamaica are found there. Internationally it is an include common and purple gallinules, jacana, important area for birds because of the variety American coot, pied-billed grebe, least bittern, and the high level of endemism. Seven species, yellow-breasted crake, great egret, and little blue, two subspecies and two genera are endemic to green and tri-coloured herons.