Conservation & Fisheries Department - Mangroves
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The Importance of Mangroves

MangroveMangroves are unique salt tolerant plants which occur along sheltered coastlines and in association with lagoons and salt ponds. With these plants it is the degree of salt tolerance which determines where a species of mangrove may grow. For example, the least salt-tolerant red mangroves will actually grow right in the sea water, whereas the more tolerant black and white mangroves will be found in the saline soil further inland. During the drier months of the year, evaporation of sea water in the black areas of mangrove stands results in increased salt concentrations which may in turn result in die- offs of the mangroves if levels become too high.

Mangroves serve many functions in the British Virgin Islands (BVI). The best known is their function as hurricane shelters for boats. This is most marked at Paraquita Bay where during Hurricane Hugo in 1989 over 200 boats sought shelter. Mangroves also protect the land and the sea from each other. The land is protected from wave action especially during high tides and storms. The marine environment is protected from soil run-off during heavy rainfall by the mangrove root structure. As time goes by, this process causes accretion as silt piles up among the mangrove roots. This is evidenced at Slaney Point, Tortola. Mangroves serve as nurseries for many young creatures such as fish, conch, sea eggs and lobsters which spend their young lives in mangroves. From here, these creatures migrate to sea grass beds and then to coral reefs. The spiny lobster and gray snapper actually go from the mangroves directly to the coral reefs. Mangroves also provide a habitat for many birds like the blue gaulin.

How to Help Mangroves

Because red mangrove saplings begin to grow on the parent plant, it is very easy to plant them. They plant themselves by becoming stuck in the substrate where they stop. We can therefore help by looking for and planting these saplings. Another important way that we can help mangroves and the environment is to avoid littering these areas. Because water circulation is restricted in bays and lagoons, live-aboard boats and motorboats are discouraged in these areas.

 Mangrove

Cutting or removal of mangroves for development should be avoided as should dredging and filling activities as these can have adverse effects on mangrove systems.

Red Mangrove (Rhizophora mangle)

MangroveRed mangroves grow directly in sea water. This trait is welcomed by many juvenile aquatic animals that use this root system as a nursery where they are well protected from predators. This prop root system may support a fifty-foot tree!

The red mangroves are unlike all the others in some interesting ways, for example their mode of propagation. They go from flower to seedling while they are actually on the parent tree. Once the seedling is large enough it will fall off the tree into the water where it may stick in the sand or be carried downstream by the water.

A unique feature of red mangroves is their land making ability. They act as giant filters to silt run-off from the hills during heavy rains. The root system traps the silt and gradually builds it up to land.

White Mangrove (Laguncularia racemosa)

MangroveThese mangroves have light-coloured bark as their name implies. They grow to a height of about 40 feet.

White mangroves are highly salt tolerant and may produce pneumatophores if growing in a swampy area. Pneumatophores are extensions of the root system that grow vertically to a height that will remain above settled water after rains or inundation by the sea. They allow the trees to have gaseous exchange despite their being surrounded by water.

Black Mangrove (Avicennia germinans)

MangrovesThe black mangrove is the most salt tolerant of all the species that occur in the BVI. They also grow to very impressive specimens of 40 feet.

This is probably the most utilized type of mangrove in the BVI. It is used for such things as fence posts and fish pots and it is burnt for charcoal; a good amount of the latter is done locally.

The black mangrove is one of the species that produces pneumatophores. These structures provide a hiding place for wading birds’ nests.

Gray Mangrove (Conocarpus erectus)

This type of mangrove is considered a peripheral species. It is not a true mangrove neither in association nor in size. It is often found on the coasts where no other types are present and it is relatively small. It is locally known as the Buttonwood.

In 1990 the Conservation & Fisheries Department with technical assistance from the OECS - Natural Resources Management Unit prepared an inventory and maps of all the major mangrove systems in the BVI. These mangrove systems were assessed on ecological and socioeconomic criteria and divided into three categories:

(1) Critical Importance
(2) Moderate Importance
(3) Not Very Important

The critically important sites are:

Tortola:
Paraquita, Witches Brew, Hodges Creek, Sea Cow’s Bay, Belmont Pond, Dubois Pt. Pond, Wickhams Cay, Pockwood Pond, Chapel Hill, Slaney.

Virgin Gorda: Deep Bay.

Anegada: East End, Flamingo Pond.

Beef Island: Beef Island Channel north and south, Hans Creek, Trellis Bay Pond.

Jost Van Dyke: East End.

  

BVI Critically Important Mangrove Sites

 
 

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