Distribution of Mangroves
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Mangroves are found along the sea-coast and those riversides closer to the sea. In 2010 the Mangrove Forests in Guyana were an estimated 80,432 hectares . In 1990, FAO estimated 91,000 hectares.


Mangroves in Guyana have a unique distribution pattern- different from the norm known in other countries. Black Mangroves are known to colonize the coastal shorelines and Red Mangroves establish themselves further inland along the rivers. The pattern elsewhere is Red Mangroves, and then Black Mangroves followed by the White Mangroves further inland.



What affects its natural distribution?

The development of mangroves depends on the presence of a tropical climate, fine-grained alluvium, shores free of strong wave and tidal action, brackish water or saline conditions and a large tidal range. These factors influence the occurrence and size of mangroves, the species composition, species zonation, other structural characteristics, as well as the functions of the ecosystem.


Light, temperature, rainfall and wind all have a strong influence on the mangrove ecosystem. Apart from playing a significant role in the development of plants and animals, they also cause changes in physical factors such as soil and water. Light is vital for photosynthesis and growth processes of green plants. It also affects the respiration, transpiration, physiology and physical structure of plants. Mangrove plants are long-day plants and require high intensity full sunlight. This makes tropical coastal zones an ideal habitat. The optimum light requirement for mangroves ranges between 3000 - 3800 kcal / m 2 / day. The amount, duration and distribution of rainfall determine the development and distribution of plants and animals. Rainfall can influence the air and water temperature, the salinity of the surface and ground, which in turn affect the survival of mangrove species. Mangroves prefer an annual rainfall ranging between 1500 - 3000 mm. As with light, temperature is also important for physiological processes such as photosynthesis and respiration. The temperature requirement varies with species. In general, the temperature required for optimal growth of mangrove species varies between 18 and 26 0 C. Wind is required for pollination and seed dissemination. It can also increase evapo-transpiration of plants. Strong winds are capable of impeding plant growth and causing abnormal physiological characteristics.

Tidal and Wave action

In coastal areas, tidal and wave action have a strong influence on the zonation of plant and animal communities and on water salinity found within mangroves. Water salinity varies during spring and neap tides. During spring tides, highly saline water intrudes further into the mangrove areas than during neap tides. Tidal ranges between high and low tides, or intertidal zones can affect the root systems of mangroves. Mangroves prefer to have a large tidal range with little undercurrent wave action.


Mangrove vegetation grows in a coastal saline environment; nonetheless it is only capable of tolerating a certain degree of salinity. This tolerance of a saline environment varies with the species. Several mangrove species can withstand conditions of very high salinity. There is no clear evidence indicating the maximum interstitial water salinity that mangrove species can withstand, but the optimal range is 28-34 PPT (Aksornksae, 1993).







Mangroves develop under tidal regimes in salt and brackish water environments, such as estuaries, deltas and sediment-accreting open coasts. They may colonize sandy shores and corals, but the common soil substrates are clayey deposits (GFC 2001). Mangrove soils are formed by the accumulation of sediment derived from coastal or river bank erosion or eroded soils from higher areas transported down along rivers and canals.

Morphological Processes - Mud Banks, Sea Wall and Groynes

Guyana's intertidal zone is made up of long, sloping, ever-moving mud banks that originate at the mouth of the Amazon River. Huge deposits of fine silts and clays from the Amazon are carried north-west along the coast in slow moving 'slings'. As these mud banks, which extend out from the shore as far as three miles, progress along the coast, a pattern develops, where mud builds up in one region as the crest of the bank passes, followed by a period of depletion as a corresponding trough follows. The high banks provide ideal conditions for mangrove forest growth, whereas the troughs appear to lead to erosion and depletion. Local experience is that a severe erosion period lasts for about three years at any one place. This is the situation under which the mangrove forests of the north coast of South America have evolved, and with which it can be presumed to have been in some sort of dynamic equilibrium. However, in recent decades, as the mangrove belt has been progressively depleted, the dynamics of the system seem to be overriding the forest's ability to recover from an erosion cycle.

Man-made sea defence structures also probably play a role in the destabilization of the mangrove forest. They interrupt the normal wave-energy flow onto the land, and restrict the ability of mangrove stands to shift their boundaries as sea levels rise. Sea wall construction has also been responsible for damaging healthy stands during the construction process.

Further complications are possibly created when fresh water running off the land is intercepted by sea defence structures and channeled into drainage canals, thus altering the natural dispersion of fresh water into the mangrove forest. In local communities along the Guyana coast, there is a strong feeling that allowing the groynes originally constructed by the Dutch to deteriorate has accelerated the erosion of the mangroves. This is a subject of much discussion, as it is generally recognized by the engineering community that groynes - solid structures that run out into the sea perpendicular to the sea wall - are only effective in causing the deposition of heavy (sand) particles. They do not work with clays and silts. Nonetheless, their presence appears to have some protective effect on mangroves down-current from them. The specific impacts of these situations are poorly understood.

An alternative to groynes, in the form of low-crest, low-cost structures running parallel to the shore and acting as wave-force breakers, has been proposed. These can be constructed at relatively short notice, and could be the essential element in efforts to protect established and developing mangrove stands from erosion.

Our Vision

To augment Guyana's sea defence by protecting, restoring and managing the natural coastline barrier provided by our mangrove forests.

Contact Information

Guyana Mangrove Restoration Project
National Agricultural Research Institute
Agriculture Road, Mon Repos East Coast Demerara
Phone (592) 220-2843
Fax (592) 220-4481/220-2843
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