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Sri Lanka Ecological Zones
The pattern of life in Sri Lanka depends directly on the
availability of rainwater. The mountains and the southwestern
part of the country, known as the "wet zone," receive ample
rainfall (an annual average of 250 centimeters). Most of the
southeast, east, and northern parts of the country comprise the
"dry zone, which receives between 120 and 190 centimeters of rain
annually. Much of the rain in these areas falls from October to
January; during the rest of the year there is very little
precipitation, and all living creatures must conserve precious
moisture. The arid northwest and southeast coasts receive the
least amount of rain--60 to 120 centimeters per year--
concentrated within the short period of the winter monsoon
(see
fig. 4).
The natural vegetation of the dry zone is adapted to the
annual change from flood to drought. The typical ground cover is
scrub forest, interspersed with tough bushes and cactuses in the
driest areas. Plants grow very fast from November to February
when rainfall is heavy, but stop growing during the hot season
from March to August. Various adaptations to the dry conditions
have developed. To conserve water, trees have thick bark; most
have tiny leaves, and some drop their leaves during this season.
Also, the topmost branches of the tallest trees often interlace,
forming a canopy against the hot sun and a barrier to the dry
wind. When water is absent, the plains of the dry zone are
dominated by browns and grays. When water becomes available,
either during the wet season or through proximity to rivers and
lakes, the vegetation explodes into shades of green with a wide
variety of beautiful flowers. Varieties of flowering acacias are
well adapted to the arid conditions and flourish on the Jaffna
Peninsula. Among the trees of the dry-land forests are some
valuable species, such as satinwood, ebony, ironwood, and
mahogany.
In the wet zone, the dominant vegetation of the lowlands is a
tropical evergreen forest, with tall trees, broad foliage, and a
dense undergrowth of vines and creepers. Subtropical evergreen
forests resembling those of temperate climates flourish in the
higher altitudes. Montane vegetation at the highest altitudes
tends to be stunted and windswept.
Forests at one time covered nearly the entire island, but by
the late twentieth century lands classified as forests and forest
reserves covered only one-fifth of the land. The southwestern
interior contains the only large remnants of the original forests
of the wet zone. The government has attempted to preserve
sanctuaries for natural vegetation and animal life, however.
Ruhunu National Park in the southeast protects herds of elephant,
deer, and peacocks, and Wilpattu National Park in the northwest
preserves the habitats of many water birds, such as storks,
pelicans, ibis, and spoonbills. During the Mahaweli Garga Program
of the 1970s and 1980s in northern Sri Lanka, the government set
aside four areas of land totalling 190,000 hectares as national
parks.
Data as of October 1988
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