Editing Geography of Sri Lanka (section)

==Ecological zones==
[[File:Sri Lanka Precipitation and Irrigation map.png|thumb|right|350px|Precipitation and irrigation map of Sri Lanka]]
The pattern of life in Sri Lanka depends directly on the availability of rainwater.<ref name=":1" /> The mountains and the southwestern part of the country, known as the "wet zone," receive ample rainfall (an annual average of 2500 millimeters).<ref name=":1" /> Most of the southeast, east, and northern parts of the country comprise the "dry zone,” which receives between 1200 and 1900&nbsp;mm of rain annually.<ref name=":1" /> 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.<ref name=":1" /> The arid northwest and southeast coasts receive the least amount of rain—600 to 1200&nbsp;mm per year—concentrated within the short period of the winter monsoon.<ref name=":1" />

The natural vegetation of the dry zone has adapted to the annual change from flood to drought.<ref name=":1" /> The typical ground cover is [[Shrubland|scrub forest]], interspersed with tough bushes and [[cactus]]es in the driest areas.<ref name=":1" /> Plants grow very fast from November to February when rainfall is heavy, but stop growing during the hot season from March to August.<ref name=":1" /> Various adaptations to the dry conditions have developed.<ref name=":1" /> To conserve water, trees have thick bark; most have tiny leaves, and some drop their leaves during this season.<ref name=":1" /> Also, the topmost branches of the tallest trees often interlace, forming a canopy against the hot sun and a barrier to the dry wind.<ref name=":1" /> When water is absent, the plains of the dry zone are dominated by browns and grays.<ref name=":1" /> 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.<ref name=":1" /> Varieties of flowering acacias are well adapted to the arid conditions and flourish on the [[Jaffna]] Peninsula.<ref name=":1" /> Among the trees of the dry-land forests are some valuable species, such as [[satinwood]], [[ebony]], [[ironwood]], and [[mahogany]].<ref name=":1" />

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.<ref name=":1" /> Subtropical evergreen forests resembling those of temperate climates flourish in the higher altitudes.<ref name=":1" /> [[Montane ecosystems|Montane]] vegetation at the highest altitudes tends to be stunted and windswept.<ref name=":1" />

Forests at one time covered nearly the entire island, but by the late 20th century lands classified as forests and forest reserves covered only one-fifth of the land.<ref name=":1" /> The southwestern interior contains the only large remnants of the original forests of the wet zone.<ref name=":1" /> The government has attempted to preserve sanctuaries for natural vegetation and animal life, however.<ref name=":1" /> [[Yala National Park|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.<ref name=":1" /> During the [[Mahaweli Ganga]] Program of the 1970s and 1980s in northern Sri Lanka, the government set aside four areas of land totalling 1,900&nbsp;km<sup>2</sup> as national parks.<ref name=":1" />