Location and
physical attributes:
Saint Lucia is a small island developing state
located at latitude 13o59’ N and longitude 61o W, almost midway between
the island of Martinique to the north and St. Vincent to the south.
The island has an area of 616 km2 and a population of approximately
160,000. This volcanic island has a very rugged topography with a
central ridge of mountains, including Mount Gimie, the highest peak at
950m. The upper reaches of many of the island’s deeply incised
valleys lie within the high rainfall area associated with the central
ridge. The island’s young volcanic soils, steep topography
and its subjection to seasonal high rainfall under poor land management
practices, make it very susceptible to soil erosion.
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| Map of St. Lucia |
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Climate: Located within the Trade Wind belt, the
island experiences average temperatures of 27 degrees C (79OF) and a
relative humidity of 75%. Rainfall amounts show annual and spatial
variation. Mean annual rainfall varies from 1,450 mm at Hewanorra in
the South to 3,450 mm at Edmond Forest within the central ridge, with
the island experiencing two distinct wet (June to December) and dry
(January to May) seasons. Wet season rainfall is primarily cyclonic in
origin and is spatially distributed with the northern and southern tips
significantly drier, and the interior due to orographic effects,
significantly wetter.
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Climatic phenomena such as tropical cyclones and
extensive dry periods (drought) also contribute significantly to land
degradation, particularly with respect to the resultant accelerated
short-term erosion. In September 1994 when the island was ravaged by
Tropical Storm Debbie (TSD), antecedent rainfall conditions were such
that soils were already saturated when TSD brought with it an estimated
25 centimetres of rain over a ten-hour period. This event resulted in
widespread run-off, flooding, and massive landslides with soil, trees
and crops being washed away and tons of debris deposited in rivers, on
farmlands and on near shore coastal areas. It was estimated that as
much as ten percent (10%) of agricultural land was lost due to land
slippage, severe erosion and river relocation
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| Forest ecosystems and soils: The island’s natural
vegetation types have been classified into seven broad categories:
Elfin Woodland, Montane Thicket, Lower Montane Rainforest, Secondary
Forest, Savannah and Grazing Land and Dry Scrub Woodland. Soils have
been divided into three mineralogical groupings , allophanes,
kaolinites and montmorillonites. The allophone group is representative
of younger soils and occupies the highest rainfall areas particularly
in the south. Kaolinitic soils occupy the older land surfaces in high
rainfall areas in the north and finally, the montmorillonites are
located in the drier and some intermediate areas. The interior soils
tend to be inherently more stable to surface erosion (good aggregation
on account of extent of weathering), but are easily degraded once the
forest cover particularly on steep slopes are removed. The
montmorillonitic (expanding lattice) clays dominate the thin soils
around the coastal areas and are highly erodible once the vegetation is
disturbed.
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The natural environment is characterized by small and
fragile ecosystems, and by the high level of inter-connectivity among
these and their natural functions. Less than 10% of the total land
areaoccurs on slopes less than five (5) degrees (which translates to
the need for the application of some type of soil conservation measure
on more than 90% of the land area for any type of use). Activities
occurring in one area can very rapidly have negative environmental
impacts on surrounding ecosystems and in particular, changes taking
place in upper watershed areas very rapidly impact on lower watershed
and coastal areas.
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Land use trends: According to the last major land
use assessment carried out in 1992, rain-fed agriculture was the
dominant land use, accounting for just over 55% of the total land
area. Forest (all broad classes) accounted for just over 35%. The
bulk of agricultural production (dominated by bananas) takes place
within the flat alluvial plains of the major river valleys (such as the
Roseau, Cul de Sac and Mabouya watersheds), extending to the
mid-watershed reaches within the steep interior of the island. The
areas along the coastal corridor tend to less suited to rain-fed
cultivation on account of soil and water availability limitations.
Other land uses account for a relatively minor proportion of the total
land area (9.5%). The more heavily urbanized areas are clustered along
the coastline and some areas in the interior where the settlement
patterns tend to follow major roadways.
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Forest cover was in 1992 estimated at 21,741
hectares although in the period 1977 to 1989 the area under forest had
declined at a rate of 1.5% annually as lands were converted to
agriculture due to a then expanding banana industry. Table 1 presents
information on the land use categories for the island. Of the lands
under forest a total of 7,500 hectares are found in the Government
Forest Reserve, which is managed by the Department of Forestry.
Rainforests are located in the central mountainous ridge with
agriculture surrounding this central area. In spite
of the conversion of forests to agriculture, the 1996 agricultural
census indicates a gradual decline in land under cultivation in
particular in the productive land category. This is attributable to
the transition from large estate holdings (categorized as farm lands
under the census) with greater overall combined acreages to smaller,
more numerous, intensively cultivated holdings with less cumulative
land area.
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