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Jamaican Wetlands

Sven Björk

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The project financed by the Swedish Agency for International Technical and Economic Co-operation
Berdningen för Internationellt Tekniskt-ekonomiskt Samarbete BITS

Welcome to Jamaica

 

Location of the Black River and Negril wetlands in Jamaica

Summary from Ambio 20, Björk & Digerfeldt, 1991: Development and degradation, redevelopment and preservation of Jamaican wetlands. - Ambio 20.

The wetlands

In Jamaica, coastal wetlands at Negril and Black River cover 23 and 61 km2, respectively, the latter is divided into the upper (18 km2) and the lower (43 km2) morass (Fig 1-3)

Because Jamaica in the early 1980s was dependent on imported oil for energy production by more than 90 %, an intensive search for domestic resources was conducted. As a result, local deposits of peat at Negril and Black River came into focus. It is estimated that the use of peat in a conventional steam-power plant could save about 30 % or more of Jamaica's domestic fuel consumption over a period of c. 30 years (Wade & Reeson 1985). The Jamaican government and authority responsible for energy production demonstrated an extraordinarily profound and serious interest in investigating and solving environmental problems before peat mining started (Wade 1985, Wade & Reeson 1985).

Studies on the environmental feasibility of peat mining and the optimum utilization of the Negril and Black River Morasses (Björk 1982, 1983, 1984, 1985) clearly indicated that there were great possibilities of combining the environmental aspects with multipurpose use - including peat mining - and management of the resources of these two wetlands, provided this was done in an ecologically realistic and sound way.

The origin and past development of the wetlands has been closely associated with the Holocene rise in sea level (Digerfeldt & Enell 1984, Digerfeldt & Enell 1985, Digerfeldt & Hendry 1987). When the rising water table reached the deepest areas of the wetland basins (at Negril 17 m and at Black River 12 m below present sea level) these areas successively changed to wetlands and peat began to accumulate. The wetland development until present times, including the progressive increase of the morass area, the environmental characteristics and vegetation, and the accumulation of peat, has been determined primarily by the rise in sea level. After Jamaica was conquered by the Spaniards, and especially as a result of subsequent British occupation, the wetlands became more and more influenced by man and degradation set in.

When dealing with the past, present and future wetland development, the morasses and their respective catchment areas should be treated as coupled units. This holistic view in time and space is a prerequisite for planning for what is now called sustainable development, which demands realistic and active management of the environment with man as an integrated component. The Jamaican wetlands and their drainage areas may serve as examples that only documentation of past changes and understanding of present functioning make it possible to predict future development. This is true at the local as well as at the regional and global level.

This summary concentrates on a discussion of the past, present and future development of the Black River Lower Morass, but some comments are given also on the Negril Morass.

The Negril Morass

The Negril Morass
The Negril Morass

In the late 1950s the Negril Morass was canalised and drained. Nowadays, saw grass (Cladium jamaicense) is the dominating vegetation species. Especially during periods with heavy precipitation, a plume of brown water (humic matter) emanating from the canalised South Negril River extends into the sea at the southern end of Long Beach, the main tourist attraction.

Starting from the eastern morass margin the peat land was exploited for extensive illegal cultivation of Cannabis sativa. Because of rapid mineralization and subsidence as a result of peat aeration, cultivation moved rapidly westwards, as previously cultivated plots were abandoned. Digging of canals and ditches, swamp-forest clearing and clear cutting accompanied by slash and burn methods characterized the preparation of the wetland for production of Cannabis.

From the environmental protection point of view, canalisation and drainage of the Negril Morass in the late 1950s can be considered the turning point in its current degradation as a wetland. Illicit cultivation activity has given rise to the creation of habitats for mosquitoes and sand flies, and devastation of the swamp forest.

The Black River Morasses

Black River Upper and Lower Morasses

Black River Upper and Lower Morasses

The Black River Upper Morass developed throughout as a freshwater wetland and has been the primary settling basin for matter transported by the Black River, the main watercourse connecting the Upper and Lower Morasses. At the same time as the Upper Morass acted as a settling basin, it also functioned as a sink for nutrients which were adsorbed on particles and assimilated by wetland plant.

The meandering Black River close to its outlet into the Caribian Sea

The meandering Black River close to its outlet into the Caribian Sea (S Björk)

The recently drained Upper Morass is now completely separated from the Black River by dikes and during the 1980s the former wetland was transformed, mainly for the production of rice. After drainage there is no reduction of nutrients when the water passes the Upper Morass. On the contrary, the area now acts as a source of nutrients. As a result of the mineralization following aeration of the top peat layer, nitrogen is released to the drainage water pumped to the Black River. The increased concentrations of nutrients in the water drained from the Upper Morass, including all ongoing aqua- and agricultural activities, cause increased growth, particularly of water hyacinth (Eichhornia crassipes) and generally fertilizes the Lower Morass.

Inflow of turbid water from the Black River into the Lower Morass through man-made openings in the levees (S Björk)

Inflow of turbid water from the Black River into the Lower Morass through man-made openings in the levees (S Björk)

In sharp contrast to the Negril Morass and Black River Upper Morass, the Black River Lower Morass is, superficially, still in good condition with certain areas and qualities well preserved. In the longer term there are, however, serious threats to the Lower Morass as a wetland.

Freshwater supplied to the Lower Morass originates from "blue holes" in the carstic Tertiary limestone. Among the four main streams of the Lower Morass, the Black and Y.S. Rivers have their springs outside the wetland, at the margin of the topographically rough Cockpit country. Their drainage areas are much larger than those of the Middle Quarters River, which is fed from springs at the north-western edge of the Lower Morass, and the Broad River which receives its water from magnificent blue springs in the eastern portion of the Lower Morass.

The Black River choked with water hyacinth in the Lower Morass (S Björk)

The Black River choked with water hyacinth in the Lower Morass (S Björk)

In Broad River, supplied with crystal-clear water welling up from the limestone bedrock in circular springs, the concentration of nutrients is very low. Both the strongly meandering river and the springs are from the bottom to the water surface delimited by vertical walls of Cladium peat.

Past development of the Black River Lower Morass

The reconstruction of past vegetation was carried out using microscopic peat identification. The chronology was based on 14C dating, usually at every 2 m throughout the peat cores. The availability of a large number of dating of basal peat, representing various depths below present sea level, enabled the construction of a curve showing the progressive Holocene rise in sea level. Since the Black River area has remained mainly tectonically stable throughout the Holocene (Hendry 1982, Digerfeldt & Hendry 1987), the curve correctly indicates the eustatic rise. The reconstruction of the morass area during selected periods is based on this curve and on a map of the peat thickness (Robinson 1983) showing the original basin morphology.

The progressive increase of the morass area and the recorded changes in vegetation and environment over the past 6500 years were made clear.

Generalized sea-level-rise curve for the Black River area.
6750-6500 BP (-7m) 6500-6250 BP (-6m) 6000-5750 BP (-4m)
 
47-4500 BP (-2m) 2250-2000 BP ()
Reconstructed past vegetation in the Black River Lower Morass during selected periods. The position of the sealevel according to the curve in fig 6 is given in the brackets . The identified peat types are formed in
a brachish-marine to brachish environments (i.e. Rhizophora, Rizophora - Conocarpus, Rizophora Acrosticum , and Rizophora - Cladium - Conocarpus peat)
b slightly brackish environments (i.e. Cladium - Rizophora , Cladium - Rhizophora - Concarpus, Concarpus - Cladium , and Acrosticum - Cladium - Concarpus - Rizophora peat) , and
c freshwater environments (i.e. Cladium and swamp forest peat)

Effects of climate change

At Black River, 1100 m upstream from the confluence in the Lower Morass with Frenchman River, 2 m of levee clay is underlain by 2.5 m. of swamp-forest peat. A 14C dating of the peat immediately below the clay yielded an age of 2580 BP (Before Present). The Black River levee close to the inflow of Frenchman River consists of 0.9 m of clay, under laid by 3.5 m of Cladium and Cladium-Rhizophora peat. Here 14C dating somewhat below the clay yielded the age of 2720 BP (Digerfeldt & Enell 1984).

The modern vegetation in the Black River Lower Morass

The cause of the incipient levee formation must be an increased soil erosion in the catchment area of Black River, and an intensified transport of clay and silt into the wetland. Since this change evidently took place about the same time as the recorded successive regression of Rhizophora and the seaward transgression of freshwater vegetation, it seems reasonable that the increase in soil erosion was caused by a climate change, which implied an increase in humidity. In addition to accelerated soil erosion, the increase in humidity must have resulted in an increased inflow of fresh water into the wetland which consequently reduced the influence of saline water and enabled the seaward transgression of the freshwater vegetation.

A similar change is also indicated along Y.S. River. Besides initiating or accelerating levee formation, the increased load of clay and silt of the inflowing water must also significantly have affected the environment and vegetation in the areas adjacent to the Black and Y.S. Rivers, which today are covered by a highly productive vegetation characterized by Typha domingensis and Thalia geniculata. The study of a peat core from the large Typha-dominated area west of Y.S. River reveals that the present character of the vegetation represents a late change in the wetland development. From the reconstruction of past vegetation it appears that the area west of Y.S. River, throughout most past development, has been occupied not by Typha but by Cladium. The immigration of Typha occurred some time after a recorded distinct decrease in peat humification and an equally distinct increase in ash content, which indicates increased flooding and increased supply of clay and silt. These changes can be estimated from available 14C dates to have occurred some time between 2500 and 2200 BP, i.e. at approximately the same time as the beginning of the levee formation along Black River upstream from Frenchman River. The replacement of Cladium by Typha was certainly an effect of the increased supply of suspended minerogenic matter and consequently improved tropic conditions. From reconnoitring studies of some short peat cores, the same changes have taken place in the vast Typha area east of Y.S. River and the Typha-Thalia area east of Black River and north of Frenchman River.

Cattle gazing along the levees in the Black River Lower Morass in the background vegtetation is being burned before cultivation (S Björk)

Cattle gazing along the levees in the Black River Lower Morass. In the background vegetation is being burned before cultivation (S Björk)

A distinct decrease in peat humification and a fairly common occurrence of layers of silty and clayey marl, indicating increased flooding, in the upper part of several of the studied peat cores are further evidence of the suggested increase in humidity. The available 14C dating of the change in peat humification vary between 2500 and 1500 BP, which might indicate fluctuations in the climate change.

The drained Black River upper wetland has been completely separated from the Black River by dikes

The drained Black River upper wetland has been completely separated from the Black River by dikes (P. Reeson)

Effects of human impact

Distinctly developed levees are also found downstream from the inflow of Frenchman River into Black River. The layer of clay is, however significantly thinner than upstream from the confluence. Downstream from the inflow of Middle Quaters River the levees gradually disappear. Levee transects were studied 750 and 1250 m downstream from Frenchman River, where the vegetation is dominated by Alpinia allughas (an introduced species, native to S. Asia) on both the western and eastern river banks and by Typha outside the levees.

Microscopic analyses of the peat immediately below the clay make it clear that Cladium covered the wetland right to the edge of the river until the levee formation started. Thus, the conditions were the same here as for the reaches further upstream where, as described, Typha and Typha-Thalia have invaded areas formerly dominated by Cladium. However, from 14C datings it appears that the beginning of the levee formation and the immigration of Typha to the wetland downstream from the inflow of Frenchman River represents a much later change, not associated with any climatic change but with recent human activities in the Black River catchment area.

The 14C dating of the Cladium peat immediately below the levee clay 350 m downstream from Frenchman River yielded the age 30±45 BP, and the dating 700 m downstream the age 120±50 BP. Because of the statistical uncertainty of the dating and the past variation in the atmospheric 14C concentration, it is not possible to obtain precise determination of age. However, if the dates are compared with the high-precision calibration curve presented by Stuiver (1982), it can be established that with 3 σ-confidence the peat was formed within the last 350 years. The possibility that penetrating roots have had significant age-reducing effects can be disregarded. During sampling it was observed that the roots of the present vegetation of Alpinia covering the levees are mainly confined to the clay layer. The few penetrating roots which were observed in the sampled peat were removed before the dating.

In view of the settlement history of the area, the incipient formation of levees downstream from Frenchman River, indicates increased supply and more long-distance transport than previously of clay and silt from the catchment area. This should certainly be connected with clearance of forests, sugar-cane plantations, and cultivation and logging of dyewoods. The latter clearance started during the British occupation in the 18th and 19th centuries (Wade 1985). These activities must have accelerated soil erosion and resulted in the intensified supply of clay and silt with river water. Both the extended levees downstream from Frenchman River and the luxuriant vegetation in this area are then the result of recent human impact of the watershed area.

The swamp-forest peat underlying the levee clay upstream from the confluence of Black River and Frenchman River proves that the forest vegetation west of the former rivers existed in this area throughout the entire past wetland development. It can be assumed that the increased supply of suspended minerogenic matter created more solid ground and generally imroved environmental conditions for the swamp forest.

Effects of recent drainage of the Upper Morass

Before the diking of the reach of Black River that passes the Upper Morass, this wetland functioned as an important hydrologically buffering basin and as a settling area for the load of clay and silt supplied by the river from the watershed upstream of the morass. The clay deposits in the Upper Morass are thickest along the river, from where they become thinner with increasing distance. Now the load of clay and silt is instead brought straight into the Lower Morass, resulting in a further acceleration and downstream transgression of the levee formation.

In the Black River Lower Morass shrimp (Macrobrachium acanthurus, M. carcinus, M. faustinum and Jonga serrei) fishery is still of economic importance for the local population. In order to enable the shrimp to move from the river into the wetland, the fishermen dig out and keep channels open through the levees. During flooding the levees are submerged, but turbid and nutrient-enriched river water is also forced through the openings, thereby causing the changes in the vegetation described above and accelerating the primary productivity and terrestrification ("Verlandung") over large areas. Along the levees the conditions for development of seedlings of opportunistic plant species are much better than in the wetland covered by Cladium and representing the original poor conditions of the morass. The settled minerogenic material is very firmly fixed by the root system of the riparian vegetation. In this way accumulation is favoured and erosion prevented.

The overall effect of human activities in the catchment area is an ageing of the wetland. The levees serve as human bridgeheads from which adjacent portions of the wetland are affected. Successively accessible new areas are utilized for cattle grazing and cultivation. Foreign plant species are being introduced at the same time as remaining small native swamp forests are cut down or devastated. The consequences of the loss of the upper basin have not yet been fully developed in the Lower Morass. The changes will, therefore, take place at a greater speed than before, but will follow the same lines indicated so far. It is not surprising that investigations on the possibilities of converting the Lower Morass or at least sections of it into arable land have already been carried out (Japan International Cooperation Agency. 1984.)

The drained Black River upper wetland has been completely separated from the Black River by dikes

Black River Lower Morass Broad River surrounded by mangrove (Rhizophora) (S Björk).

Plans for redevelopment and preservation

The Black River Lower Morass

 

The general design suggested for rejuvenation and preservation of the Black River Lower Morass is shown in the map below. The course of the rivers will be preserved with broad (at least 100 m) zones on both sides, including swamp forests, mangrove and riparian vegetation.

Areas suggested for peat mining in the Black river Lower Morass. The Proposal is based on consideration of the modern vegetation, peat - thickness, the nessessity to create sedimentation basins etc.

Areas suggested for peat mining in the Black river Lower Morass. The proposal is based on consideration of the modern vegetation, peat - thickness, the nessessity to create sedimentation basins etc.

The eastern section, i.e. the Broad River area, will basically be left in its present state. It is especially important not to affect the blue holes and the system for groundwater supply. The lowproductive sawgrass areas are very extensive and constitute an impressive counterpart to the areas around the Black and Y.S. Rivers with their highly productive vegetation of Alpinia allughas, Thalia geniculata, and Typha domingensis, which indicate a much richer environment than in the other parts of the wetland, especially those surrounding the nutrient-poor Broad River. It is suggested that fairly small-scale peat extraction should be allowed within two areas of the eastern section for production of horticultural peat. In these areas, the peat deposits are shallow and parts have rather high ash content. In the lower layers there are soil types which, when constituting the new bottom in constructed ponds, are suitable for development of submersed vegetation. The mining should, therefore, result in shallow freshwater lakes with islands and a rich submersed vegetation (rather clear water). This should imply the creation of highly attractive waterfowl biotopes.

It is recommended that swamp forests, mangrove and other types of wetland communities, are exempted from peat extraction. Extraction of fuel peat is suggested to result in a series of lakes surrounded by gently sloping, irregular littoral zones. Because freshwater peat dominates the upper parts of the morass and mangrove peat in the south, a gradient from fresh to brackish will characterize the water quality of the lakes after mining. Freshwater flow through some of the lakes can be arranged via intakes and outlets to the rivers. Lakes adjacent to the Black River will be of great importance as settling basins for the periodically highly turbid river water. All possible efforts should, of course, be made to minimize the sediment and increasing nutrient load on the Black River from the catchment area. An eco-redevelopment program for lakes and wetlands must always start with necessary regulatory measures in the catchment area. The water will, however, remain turbid and relatively rich in nutrients. The freshwater lakes/settling basins created through peat extraction will, therefore, be productive. Undoubtedly, it will be impossible to avoid infection by water hyacinth. Considerable growth of this plant must be expected in lakes supplied with river water. Lakes in the western part of the morass will become clearer. Instead of floating water hyacinths submerged vegetation will dominate the littoral zone. A vertical oxygen curve with total deficiency in the deepest layers, which is characteristic of high-temperature waters, can be predicted.

The shrimpery, which at present is economically the most important activity practised in the Lower Morass, will not be affected in those areas near the rivers. However, during flooding periods shrimp are also caught outside the rivers. Access to water in the flooded sections makes it possible for shrimp to move away from the rivers. Creation of lakes, permanently or temporarily connected with the rivers will offer possibilities for shrimp to spread to new, productive littoral zones. The new littoral zone accessible for shrimp and shrimpery after suggested mining will have a total area of 140 hectares. The minimum increase in shrimp production and yield has been estimated at four times the present (Karlsson & Leonardson 1984).

Mining also means creation of islands and other types of isolated biotopes which it may be possible to protect efficiently against man and the mongoose (introduced during British occupation). It is, therefore, anticipated that birdlife will improve considerably. From an ecological and environmental point of view the first goal must, of course, be to save the Lower Morass as a wetland. If plans to drain the wetland for agricultural purposes were realized, this action would constitute an ecological catastrophe and an economic disaster with long-term effects as demonstrated in other comparable projects.

The economically feasible way to save the Lower Morass as a wetland is by the mining of peat. In this manner, the multipurpose utilization of the area will be safeguarded. No single way or any combined forms for utilization of an unmined Lower Morass could compete economically with the combined peat mining/multipurpose use. Ecologically this combination is also without competition because it would be reliable in the long-term. The accomplishment of the eco-technical plans would also mean creation of new jobs and an improved standard of living in a region suffering from very high unemployment (Karlsson & Leonardson 1984).

The Negril Morass

In Negril Morass government efforts to stop production of Cannabis have resulted in the saving of the last remnants of a wet forest with the endemic swamp cabbage palm (Roystonea princeps). The southern part of the wetland, including the palm forest, is now a national park. Furthermore, a modern wetland research station has been built at the margin of the morass, close to those lakes, which were created through peat extraction at the start (1981-1982) of the Swedish-Jamaican environmental feasibility study of peat mining. In these lakes the local development of ecosystems (Cronberg 1983, Enell 1984) in waters with different depths, differently designed littoral zones, with and without islands, etc., have also been investigated. Among other things the importance of open water for the feeding and nesting of birds was demonstrated by the experimental lakes. In the drained Negril Morass, which proved to be generally poorer in birds than the Black River Lower Morass, water-birds were attracted to the experimental lakes with their islands and shallow shores and nesting occurred quickly after their construction (Björk 1983, Svensson 1983).

In Negril, a peat extraction project opens up unique possibilities for ecological-technical cooperation in the design and management of an ecologically diverse, sustainable wetland. The general appearance of the Negril Morass would change from its present degraded form to an environmental asset, with a mosaic of open water, islands and peninsulas. (Björk 1983, 1984, Karlsson & Leonardson 1984).

After redevelopment, the Negril and Black River Lower Morasses should be given the status of national parks in an ecologically modern sense, i.e. optimally utilized, managed and preserved. Parts of the Lower Morass should be granted this status immediately to ensure protection in the same way as the swamp-forest national park at Negril.

The necessity of a holistic view in time and space

In conservative types of environmental protection time factors are often forgotten and ecosystems seen as static. As in other similar systems, conditions in the Negril and Black River Morasses have changed considerably in the long-term and at high speed recently. The "don't touch" ideology should definitely not be applied here, but instead active design and management are needed, provided there is a serious desire to preserve the areas as sustainable, diverse, and useful wetlands. "In all cases of serious damage the need to establish scientifically sound practices to restore productive capacity calls for action: eco-redevelopment" (Brinck, Nilsson & Svedin 1988). Obviously, man affects nature not only negatively, but can also make improvements and, according to environmental and societal priorities, revitalize damaged ecosystems to produce sustainable units.

Certain landscapes, like the Scandinavian meadows with pollard trees, are highly esteemed and protected, though they were designed entirely by man. After lowering of water levels in shallow lakes, many of the lakes pass through a short, successional phase and are excellent biotopes for waterfowl during this period. Through application of limnological principles and experiences, methods to secure the prolongation of the favourable conditions in such ecosystems became available (Björk 1985, 1988, 1990). "Management of the environment involves both preventive measures as well as rehabilitative actions at reviving damaged ecosystems. Prevention involves long-term protection schemes where societal development and environmental goals are harmonized such as described in the work of the Brundtland Commission" (Rosemarin & Svedin 1988).

In the case of the Negril and Black River Lower Morasses there is an urgent need to revive the wetlands, and removal of peat is the only realistic way to accomplish this. The commonly expressed claim that large-scale mining of peat is impossible without destroying habitat and ecosystems is definitely not in agreement with modern, constructive environmental management; especially in the case of the damaged and endangered Jamaican Wetlands. A holistic view in time and space is inevitable for planning for what the Brundtland Commission terms "sustainable development". This commission provided the impulse for national aid organizations to include environmental protection as a prerequisite for assistance to developing countries.

Effects of predicted acceleration of sea-level rise (greenhouse effect)

The accelerated release of CO2 and other greenhouse gases into the atmosphere is calculated to increase the global mean temperature by 1.5-5.5 oC during the next century (Dickinson 1986). This global warming could be expected to cause a significant acceleration in sea-level rise because of volume increase in seawater and the melting of glaciers. Recently, it was concluded that the best estimate of future sea-level rise by AD 2050 is 24-38 cm, corresponding to a rise of 3-6 mm per year, which is 3-4 times greater than the global rates over the past 100 years (Tooley 1989).

Generally speaking, the presumed increase in the rate of sea-level rise will result in accelerated inundation of coastal lowland areas, and in erosion and landward migration of sandy shorelines. The ability of coastal wetlands, such as the Negril and Black River Lower Morasses, to sustain vertical growth and not to disappear due to flooding and drowning, will depend on the balance between organic production and peat formation and the rate of subsidence, combined with sea-level rise. In the Negril Morass, upward peat growth during the period of rapid sea-level rise in the early Holocene was able to keep pace with a rise of 3.8 mm per year (Digerfeldt and Hendry 1987). A sudden pulse of a probably still higher rate of sea-level rise, resulting from the greenhouse effect, will undoubtedly place stress on the wetland system.

In the Negril area, the narrow and low beach separating the coastal wetland from the sea is probably very sensitive to erosion. The sandy beach would migrate landwards and cover previously deposited peat. However, the risk for direct erosion of large peat quantities with effects on the offshore environment must also be great. So far the beaches have been protected by coral reefs.

In both areas, the seawater intrusion will increase and affect the wetland environment. The areas east of the present Negril Morass, which were drained for agricultural purposes in the late 1950s, but soon abandoned because of soil subsidence, will probably be transformed to wetland again. The area of the Black River Lower Morass will increase significantly as surrounding lowland will be transformed into wetland.

In the scenario including an accelerated sea-level rise, the wetlands will probably continue to develop as in the past, though in a more dynamic succession. Some of the serious degradation problems caused by man would then be solved automatically. However, also in the light of these prognoses, the plans for optimum utilization including mining of still available peat are the most realistic, both environmentally and socio economically.

The environmental feasibility study of peat mining in Jamaica, organization and cooperation

The investigations have been carried out as a joint Swedish-Jamaican project financed through Swedish and Jamaican governmental institutions, viz., the Swedish Agency for International Technical and Economical Co-operation (Swed: Beredningen för Internationellt Tekniskt Samarbete, BITS) and the Petroleum Corporation of Jamaica (PCJ). The Swedish team has been headed by Professor Sven Björk, Institute of Limnology, University of Lund, and the Jamaican team by Dr. Barry Wade, Director, Environment and Special Projects, PCJ.
The authors express their sincere thanks to the Swedish Agency and to Dr. Barry Wade and his co-workers at the PCJ for most stimulating, straightforward collaboration. The profound concern for the environment and for solving ecological problems demonstrated by PCJ is highly esteemed.

Further reading

Björk, S. 1982. Nutzung, Schutz und Pflege von tropischen Feuchtgebieten - Beispiele aus Jamaika. - Vjschr. naturf. Ges. Zürich 127.
Björk, S. 1983. Environmental feasibility study of peat mining in Jamaica. - Institute of Limnology, Lund, and Petroleum Corporation of Jamaica, Kingston.
Björk, S. 1984. Optimum utilization study of the Negril and Black River Lower Morasses, Jamaica. - Institute of Limnology, Lund, and Petroleum Corporation of Jamaica, Kingston.
Björk, S. 1985 a. Ecology of the Negril and Black River Lower Wetlands, Jamaica. - In: Proceedings of the international symposium on tropical peat resources - prospects and potential. - International Peat Society, Kingston, Jamaica.
Björk, S. 1985 b. Lake restoration techniques. - In: Proceedings of the international congress on lake pollution and recovery. - European water pollution control association, Rome.
Björk, S. 1988. Redevelopment of lake ecosystems - A case-study approach. - Ambio 17.
Björk, S. 1990. Governing ecosystems for sustainable function. - Verh. internat. Verein. Limnol. 24.
Björk, S. & Digerfeldt, G. 1991. Development and degradation, redevelopment and preservation of Jamaican wetlands. Ambio 20.
Brinck, P., Nilsson, L. & Svedin, U. 1988. Ecosystem redevelopment. - Ambio 17.
Coke, L.B., Bertrand, R. & Batchelor. S. 1982. Macrophyte vegetation of the Negril and Black River Morasses, Jamaica. - Botany department, Univ. of the West Indies, Kingston, and Petroleum Corporation of Jamaica, Kingston.
Cronberg, G. 1983. Plankton of the Negril and Black River Morasses, Jamaica. - Institute of Limnology, Lund, and Petroleum Corporation of Jamaica, Kingston.
Dickinson, R.E. 1986. How will climate change? The climate system and modelling of future climate. - In: The greenhouse effect, climatic change and ecosystems. - Bolin, B., Döös, B.R., Jäger, J. & Warrick, R.E. (e.d.s.) - John Wiley & Sons.
Digerfeldt, G. & Enell, M. 1984. Paleoecological studies of the past development of the Negril and Black River Morasses, Jamaica. - Department of Quaternary Geologi, Lund, and Petroleum Corporation of Jamaica, Kingston.
Digerfeldt, G. & Enell, M. 1985. Paleoecological studies of the past development of the Negril Morass, Jamaica. - In: Proceedings of the international symposium on tropical peat resources - prospects and potential. - International Peat Society, Kingston, Jamaica.
Digerfeldt, G. & Hendry, M.D. 1987. An 8000 year Holocene sea-level record from Jamaica: implications for interpretation of Caribbean reef and coastal history. - Coral Reefs 5.
Enell, M. 1984. Water chemistry of the Negril and Black River Morasses, Jamaica. - Institute of Limnology, Lund, and Petroleum Corporation of Jamaica, Kingston.
Fritzon, A. 1983. Periphyton of the Negril and Black River Morasses, Jamaica. - Institute of Limnology, Lund, and Petroleum Corporation of Jamaica, Kingston.
Hendry, M.D. 1982. Late-Holocene sea-level changes in Western Jamaica. - In: Holocene sea-level fluctuations: Magnitude and Causes. - Colquhuon, D.J. (ed.) Univ. S. Carolina, Columbia, SC.
Japan International Cooperation Agency. 1984. The agricultural development project on the Black River Lower Morass. - Report to the Government of Jamaica. Ministry of Agriculture.
Karlsson, S. & Leonardson, L. 1984. Extensive production and aquaculture in the Negril and Black River Lower Morasses, Jamaica. Present conditions and suggestions for improvements - marketing and economic assessment of wetland resources. - Institute of Limnology, Lund, and Petroleum Corporation of Jamaica, Kingston.
Larsson, G. 1984. Peat for horticulture from the Negril and Black River Lower Morasses, Jamaica. - Swedish Peat Scania Co, Swedish Peat Co., Sösdala, and Petroleum Corporation of Jamaica, Kingston.
Leonardson, L. 1984. Horticultural peat production in Jamaica. Design of excavation and processing units, economy, and implementation of operations. - Institute of Limnology, Lund, and Petroleum Corporation of Jamaica, Kingston.
Robinson, E. 1983. The peat resources of Jamaica and their potential for fuel supply. - Petroleum Corporation of Jamaica. Kingston.
Rosemarin, A. & Svedin, U. 1988. Ecosystem redevelopment. - Ambio 17.
Stuiver, M. 1982. A high-precision calibration of the AD radiocarbon time scale - Radiocarbon 24.
Svensson, S. 1983. Ornithological survey of the Negril and Black River Morasses, Jamaica. - Department of Animal Ecology, Lund, and Petroleum Corporation of Jamaica, Kingston.
Tooley, M.J. 1989. Floodwaters mark sudden rise. - Nature 342.
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