Natural forests in Sri Lanka | |
---|---|
Ecology | |
Realm | Indomalayan |
Biome | Tropical forest |
Borders | Indian Ocean |
Geography | |
Area | 10,825 km2 (4,180 sq mi) |
Country | Sri Lanka |
Climate type | Tropical climate |
Sri Lanka exhibits a remarkable biological diversity [1] and is considered to be the richest country in Asia in terms of species concentration. [1]
In 2019 a total area of 16.5% [2] of Sri Lanka was forested. In 2010, it was 28.8% [3] (and 32.2% in 1995. [4] )
9.0% [5] of Sri Lanka's forests are classified as primary forest (the most biodiverse form of forest and the biggest carbon sinks on Earth).
Sri Lanka's forests contain 61 million metric tons of carbon in living forest biomass (in 2010 [5] ).
Between 1990 and 2005 alone, Sri Lanka lost 17.7% of its forest cover. [2]
Sri Lanka continental separated from the south eastern tip of peninsular India by the more than 20 m deep Palk Strait. There had been repeated land connections with India across this strait during successive glacial periods, the last being between 10,000 and 20,000 years ago when the sea level was about 120m below the present level creating a 140 km wide land bridge. Notwithstanding these intermittent land connections with India, when exchange of species undoubtedly would have taken place between the island and mainland, Sri Lanka fauna and flora, especially those in the south western quarter, show remarkably high diversity and extraordinary endemism. It is the only area of seasonal lowland climate between western Malaysia (Sumathra, Malay Peninsula, Borneo and Philippines) and eastern coastal Madagascar. [6]
According to the National Red List said, Sri Lanka counts 253 land species, 245 species of butterflies, 240 birds, 211 reptiles, 748 evaluated vertebrates and 1,492 invertebrates. [7] Forest coverage is about 70% tropical dry monsoon forests, 15% tropical moist monsoon forests and 5% tropical lower montane forests. By the dawn of the 19th century, Sri Lanka's forest cover was estimated at up to 70% of the total land area. Since then, the forest cover has decreased progressively over time.
Based on a global yardstick of concentrations of exceptional terrestrial biodiversity under threat, Sri Lanka and Western Ghats of southwestern India have been grouped together as one of the 34 global hotspots of biodiversity, implying that biologically they are among the richest and at the same time the most endangered terrestrial biogeographic region in earth. [8]
Sri Lanka is in the north-equatorial tropical zone. Therefore it experiences a climate with high rainfall and temperature which permits the county to be broadly classified into groups as follows.
Climatic zone | Temperature | Rainfall | Altitude | Forests | Grasslands |
---|---|---|---|---|---|
Arid zone | 32–36 °C | <1,000 mm | <300 m | Tropical thorn scrubs | Arid |
Dry zone | 28–32 °C | 1,000–1,500 mm | <500 m | Tropical dry mixed evergreen forests | Damana grassland |
Talawa grassland | |||||
Savanna | |||||
Intermediate zone | 24–28 °C | 1,250–2,000 mm | 500–1,500 m | Tropical moist evergreen forests, Tropical sub montane forest | Savanna |
Dry patana | |||||
Wet zone | 16–28 °C | >2,000 mm | 300–1,000 m | Tropical lowland wet evergreen | Talawa |
900–1,500 m | Tropical sub-montane | Dry patana | |||
>1,500 m | Tropical upper montane | Wet patana |
The tropical wet lowland rainforests are found below 900 m elevation in the south western quarter of the country. The mean annual temperature is about 28 °C, and the mean annual rainfalls varies between 2,000–5,000 mm in different locations without any dry period. The humidity is very high. These forests are characterized by a tall canopy, sub canopy and a sparse shrub layer consisting mostly of the saplings of canopy trees. Sometimes an emergent layer is also seen above the canopy. The vegetation is filled with a network of woody lianas that reach to the canopy layer. A diverse population of epiphytic lichens, mosses, liverworts ferns, orchids are found while many fungi inhabit decaying woods and soil. High endemism of floral and faunal diversity can be seen in these forests. ( Sinharaja, Nakiyadeniya and Kanneliya are some examples for wet lowlands rainforest) These forests are disturbed due to expansion of tea cultivation, agriculture, industrial and residential development. [10]
Some tree species found in the wet lowland rain forests are;
Some animal species found in the wet lowland rainforests are purple-faced langur, red slender loris, golden palm civet. [11]
They occur at elevations above 1,500 m above mean sea level. The average temperature is about 16 °C and rainfall is about 2,000 mmm without any dry period. The humidity is high as lowland rainforests. These forests are characterized by a short canopy of about 13 m, with a dense shrub layer. There are trees with umbrella-shaped rounded crowns and twisted branches having leathery small leaves to accommodate the strong winds that prevail in the montane zone. High density of epiphytes cover the branches and stems of trees. Some plants found in these forests are;
Some animals that inhabit montane rainforests of Sri Lanka are yellow-eared bulbul, Sri Lanka highland shrew (Suncus montanus), sambar (Rusa unicolor unicolor). [11]
Montane forests are distributed in the Central Highlands including Knuckles range, Pidurutalagala, Hakgala. Montane forests were greatly affected due to tea cultivation.
These forests have a mean annual temperature of about 29 °C and rainfall around 1,000 mm- 1,500 mm most of which falls during the northeast monsoon periods. There is a marked dry spell from May to August. Above forests are distributed in areas below 300 m altitude. These forests are characterized by having sparse canopy, a sub canopy and a well-developed shrub/herb layer. Some plant species naturally found in these forests are [12]
Some of the canopy trees are deciduous during the dry spell of the year. These forests harbour the largest elephant populations in Asia. The mammal fauna includes Panthera pardus kotiya , Melursus ursinus , Axis axis ceylonensis . Most of the forest are protected ad National parks such as Yala National Park, Wilpattu National Park, Wasgamuwa National Park, Maduru-Oya national park, Ritigal Strict Nature reserve and many sanctuaries and forest reserves. These forests are disturbed by 'chena' cultivation, human settlements, extraction of timber, poaching etc. [10]
These are called "scrubs" than "forests" as large trees are sparse and the vegetation is mainly consists of thorny shrubs. They are found in arid lowlands. The mean annual temperature is around 31 °C and rainfall is below 1,000 mm with a longer dry period. Due to the dry conditions, many fauna species can't be found. However Axis axis ceylonensis, Panthera pardus kotiya, Elephas maximus maximus can be seen in these areas. They are distributed near Hambantota, Yala, Mannar, Puttalam areas and disturbed due to various development pressures. [12]
The following plant species are commonly found;
Savannas have a thick grass cover and few scattered trees. These are common on hill slopes of the dry or intermediate zone. The thin layer of soil on hill slopes can not support the growth of trees and the grass cover of savannas helps to bind soil particles and reduce erosion of soil. Periodic fires are common to this ecosystem as the dried grass cover easily catches fire in dry period of the year. They have trees with fire-resistant species. Savannas are seen in Bibile, Monaragala, Mahiyanganaya, Wellawaya and Horton Plains areas. These are distributed by periodic fires set by villagers for various reasons. [12]
Some plant species found in Savanna are trees are;
There are two type of 'patana' found in Sri Lanka; 'wet patana grassland' and 'dry patana grassland' based on the rainfall pattern and soil of the site. 'Wet patana' grass lands are found in areas above 1,500 m from the sea level with mean annual rainfall of over 2,000 mm. Temperature range from 5 °C to 18 °C. Mist, fog and frost and frost are common in these areas and do not experience any dry period. The grasses do not reach more than 1 m height and are called 'tussock grasses' which include the Chrysopogon nodulibarbis and Arundinella villosa. The animals include a large Sri Lankan sambar and wild boar population and few Sri Lankan leopards (Panthera pardus kotiya). Extensive 'wet patana' are found only in Horton plains. 'Dry patana' are found in altitudes between 500 m to 1,600 m. They receive a rainfall about 1,400 to 2,000 mm with a definite dry period. Temperature ranges from 18 °C to 24 °C. The vegetation is made up of grasses that grow up to 1–2 m height such as Cymbopogon nardus and Themeda tremula. 'Dry patana' is common on hill tops in Hanthana, Gampola, Welimada and Haputale. [12]
Wetlands are simply habitats with permanent or temporary accumulation of water with associated plant and animals. According to the Ramsar Convention, [13] wetlands are defined as areas of marsh, fen, peatland or water, whether natural or salt, including areas of marine water the depth of which at low tide not exceed six metres. [14]
Inland freshwater marshlands are low-lying areas that receive water through surface runoff, ground water seepage or flood water from rivers. These contain peat (partially decomposed organic matter), and water-logged sticky clay soil. Many water birds, amphibians and fresh species inhabit these areas. Plants that have adapted to grow in shallow stagnant water such as Colocassi spp., Aponogeton spp., species are abundant in inland marshlands. Freshwater swamp forests are not common in Sri Lanka. It is a place where forest vegetation is inundated for a short period of time in the year as seen in Waturana swamp at Bulathsinhala located in the 'Kalu Ganga' river basin. [15]
Generally 'villus' are the flood plains of the reservoirs. 'Villu' grasslands possess a special link with the wildlife in the area, especially elephants and bird population. The vegetation is dominant with grasses (members of Poaceae )and sedge (member of Cyperaceae ). 'Villu' grasslands are located in areas such as Mahawelli flood plains, Wilpattu National Park. [15]
Lagoons are coastal wetlands generally separated from the sea by a sand barries. [16] (eg. Negambo and Bundala lagoons) Estuaries are formed in places where rivers enter the sea and does not contain a sand barriers separating it from seas.(eg. Madu Ganga/Benthota) The daily tidal fluctuation is a characteristic of these places. [17]
Mangroves ecosystem is an intertidal vegetation that covers fringes of the lagoons and estuaries. They share characteristics usually of saline/brackish water, loose soil and anoxic conditions. The vegetation is also exposed to intense sunlight. Mangrove plants could be categorized into groups; true mangroves that occur towards the boundary between sea and land and mangrove associated that occur more towards inland common true mangrove species are; [18]
Common mangrove associate are;
To protect from sunlight leaves of the mangrove have a thick cuticle to reflect sunrays and/ or cut off excess radiation. Some have salt glands to secrete excess salts that are absorbed by the plants. There are special roots to intake atmospheric oxygen. Seeds of some mangroves germinate while attached to the mother plant ("vivipary"). This helps the seed to establish successfully soon after falling from the tree. Mangroves provide a unique habitat mainly for many crustaceans and mollusks. Mangroves are found in Puttalam, Batticaloa, Trincomalee, Galle, Bentota and Negambo. [14]
Salt marshes are marshlands restricted to the arid coastal regions of the country where soil dries up to form crystals of salts during the dry season. Low rainfall, high wind, high temperatures and losses sand blowing with salt are some of the major characteristics found in this ecosystem. The vegetation has only few plant and animal species. Plant are short, contain fleshy succulent plant bodies one common plant species is Salicornia spp. salt marshes are common in Puttalam, Mannar, Hambantota and Vakarai areas. [19]
In large lagoon areas with low wave action, the floor of the shallow sea is occupied by sea grasses. These are not grass species but appear like grasses due to the shape of leaves. (eg. plant species such as Halodule spp. and Halophyla spp. are common sea grasses found in Sri Lanka) Especially from Kalpitiya to Mannar. Sea grasses grow in a compact cluster and provides the sea bed a favourable habitat for breeding of many fish species. However, these areas are often disturbed by the fisheries activities as these are the parking areas of fishing boats. [14]
Coral reefs are one of the natural wonders of Sri Lanka. Coastline of about 1,585 km, has nearshore coral reefs of varying quality along 2% of the liner coast. The most extensive coral reefs occur off the north west and east coast up to and around the Jaffna Peninsula. The greatest extent of true corals in Sri Lanka lie in patchy reefs from Vakalai to the Kalpitiya peninsula. These offer the most varied reef access from snorkelling on shallow reefs to scuba diving on deeper reefs. Patchy coral reefs are also found on the western and eastern seaboards at a distance of about 15–20 km from the shore, at an average depth of 20m. Passekudah and Trincomalee have the best coral reefs on the Eastern Maritime Province seaboard. Hikkaduwa, Unawatuna, Rumassala and Matara have the main fringing reefs along the southern coast. Little Basses and Great Basses off the south coast have the best barrier like reefs in Sri Lanka. [20]
Sri Lanka has an extensive network of rivers, which drains a total of 103 distinct natural river basins. The river basins originating in the wet highlands are perennial, while many of those in dry zone are seasonal. There is hardly any vegetation to be found in running water. [15]
There are no natural lakes in Sri Lanka, but there are numerous ancient irrigation tanks mainly scattered in the low land dry zone. Typical irrigation tanks include Parakrama Samudra, Kala Wewa, Minneriya Wewa" and Tissa Wewa.
The long sea shore of Sri Lanka varies in nature. The most common sea shore type is sandy seashores. The seashore areas share the characteristics of high temperature throughout, and slat spray and high winds especially during the monsoon seasons. Most of the sea shore plants have adapted to these conditions. Examples for these plants are, [19]
The vegetation gradually become stable a distance away from the tide mark, with the stabilization of the soil. In these areas plant species such as,
Sand dunes are characterized by stunted or creping vegetation on large masses of sand. The sand dune structure is determined by wind speed and direction. Dunes are raised beaches of sand and are characteristic of certain coastal areas in the arid zone. Example: near Mullativu, Trincomalee, Kalpitiya, Yala etc. [17]
In 1882, 82% of Sri Lanka was forested. [2]
Between 1990 and 2000, Sri Lanka lost an average of 1.14% of its forest per year. [2]
In total, between 1990 and 2005 alone, Sri Lanka lost 17.7% of its forest cover. [2]
Large scale agricultural and settlement schemes without the recognition given for wild animal habitats and their migration patterns have been a major driver of deforestation and degradation, particularly in the dry zone, during the last century. Planted crops, such as sugar cane, banana, maize and paddy, in an unplanned manner, have led to ever-increasing human-elephant conflicts. Sri Lanka current forest cover 16.5% in 2019 down form 29.7% in 2017. [21]
The Mascarene Islands or Mascarenes or Mascarenhas Archipelago is a group of islands in the Indian Ocean east of Madagascar consisting of islands belonging to the Republic of Mauritius as well as the French department of La Réunion. Their name derives from the Portuguese navigator Pedro Mascarenhas, who first visited them in April 1512. The islands share a common geological origin beneath the Mascarene Plateau known as the Mauritia microcontinent which was a Precambrian microcontinent situated between India and Madagascar until their separation about 70 million years ago. They form a distinct ecoregion with unique biodiversity and endemism of flora and fauna.
Horton Plains National Park is a national park in the central highlands of Sri Lanka that was designated in 1988. It is located at an elevation of 2,100–2,300 m (6,900–7,500 ft) and encompasses montane grassland and cloud forest. It is rich in biodiversity and many species found here are endemic to the region.
The Vanuatu rain forests are tropical and subtropical moist broadleaf forests ecoregion which includes the islands of Vanuatu, as well as the Santa Cruz Islands group of the neighboring Solomon Islands. It is part of the Australasian realm, which includes neighboring New Caledonia and the Solomon Islands, as well as Australia, New Guinea, and New Zealand.
Yala (යාල) National Park is the most visited and second largest national park in Sri Lanka, bordering the Indian Ocean. The park consists of five blocks, three of which are now open to the public. There are also two adjoining parks, Kumana National Park or 'Yala East' and Lunugamvehera National Park. The blocks have individual names, such as Palatupana. It is situated in the southeastern region of the country, in the Southern Province and Uva Province. The park covers 979 square kilometres (378 sq mi) and is located about 300 kilometres (190 mi) from Colombo. Yala was designated as a wildlife sanctuary in 1900, along with Wilpattu, designated in 1938, as the first two designated national parks in Sri Lanka. The park is best known for its variety of wildlife and is important conservation of Sri Lankan elephants, Sri Lankan leopards and aquatic birds.
The East Deccan dry evergreen forests is an ecoregion of southeastern India. The ecoregion includes the coastal region behind the Coromandel Coast on the Bay of Bengal, between the Eastern Ghats and the sea. It covers eastern Tamil Nadu, part of Puducherry and south eastern Andhra Pradesh.
The Gulf of Mannar is a large shallow bay forming part of the Laccadive Sea in the Indian Ocean with an average depth of 5.8 m (19 ft). It lies between the southeastern tip of India and the west coast of Sri Lanka, in the Coromandel Coast region. The chain of low islands and reefs known as Adam’s Bridge or Rama Setu, which includes Mannar Island, separates the Gulf of Mannar from Palk Bay, which lies to the north between India and Sri Lanka. The estuaries of Thamirabarani River and Vaippar River of South India and the Malvathu Oya of Sri Lanka drain into the Gulf. The dugong is found here.
The Hawaiian tropical rainforests are a tropical moist broadleaf forest ecoregion in the Hawaiian Islands. They cover an area of 6,700 km2 (2,600 sq mi) in the windward lowlands and montane regions of the islands. Coastal mesic forests are found at elevations from sea level to 300 m (980 ft). Mixed mesic forests occur at elevations of 750 to 1,250 m, while wet forests are found from 1,250 to 1,700 m. Moist bogs and shrublands exist on montane plateaus and depressions. For the 28 million years of existence of the Hawaiian Islands, they have been isolated from the rest of the world by vast stretches of the Pacific Ocean, and this isolation has resulted in the evolution of an incredible diversity of endemic species, including fungi, mosses, snails, birds, and other wildlife. In the lush, moist forests high in the mountains, trees are draped with vines, orchids, ferns, and mosses. This ecoregion includes one of the world's wettest places, the slopes of Mount Waiʻaleʻale, which average 373 in (9,500 mm) of rainfall per year.
The environment of Sri Lanka exhibits a remarkable biodiversity.
The Deccan thorn scrub forests are a xeric shrubland ecoregion of south India and northern Sri Lanka. Historically this area was covered by tropical dry deciduous forest, but this only remains in isolated fragments. The vegetation now consists of mainly of southern tropical thorn scrub type forests. These consist of open woodland with thorny trees with short trunks and low, branching crowns; spiny and xerophytic shrubs; and dry grassland. This is the habitat of the great Indian bustard and blackbuck, though these and other animals are declining in numbers; this area was at one time home to large numbers of elephants and tigers. Almost 350 species of bird have been recorded here. The remaining natural habitat is threatened by overgrazing and invasive weeds, but there are a number of small protected areas which provide a haven for the wildlife. Trees in these forests have adapted to not require much water.
The Sri Lanka dry-zone dry evergreen forests are a tropical dry broadleaf forest ecoregion of the island of Sri Lanka.
The Shoalwater Bay Military Training Area is a heritage-listed military installation at Byfield Road, Byfield, Shire of Livingstone, Queensland, Australia. It is a large, relatively undisturbed and intact natural system with a wide variety of coastal landforms and a high level of biodiversity. It contains a diverse range of marine and coastal wetland landscapes, vegetation types and ecosystems. It was added to the Australian Commonwealth Heritage List on 22 June 2004.
A tropical marine climate is a tropical climate that is primarily influenced by the ocean. It is usually experienced by islands and coastal areas 10° to 20° north and south of the equator. There are two main seasons in a tropical marine climate: the wet season and the dry season. The annual rainfall is 1000 to over 1500 mm. The temperature ranges from 20 to 35 °C. Under the Köppen climate classification, a "tropical marine climate" would fall under Af or Am, tropical rainforest or tropical monsoon climate. The trade winds blow all year round and are moist, as they pass over warm seas. These climatic conditions are found, for example, across the Caribbean, the eastern coasts of Brazil, Madagascar and Queensland; and many islands in tropical waters.
The Sri Lanka lowland rain forests represents Sri Lanka's Tropical rainforests below 1,000 m (3,281 ft) in elevation in the southwestern part of the island. The year-around warm, wet climate together with thousands years of isolation from mainland India have resulted in the evolution of numerous plants and animal species that can only be found in rain forests in Sri Lanka. The thick forest canopy is made up of over 150 species of trees, some of the emergent layer reaching as high as 45 m (148 ft). The lowland rain forests accounts for 2.14 percent of Sri Lanka's land area. This ecoregion is the home of the jungle shrew, a small endemic mammal of Sri Lanka. Sri Lanka has the highest density of amphibian species worldwide. Many of these, including 250 species of tree frogs, live in these rain forests.
Bundala National Park is an internationally important wintering ground for migratory water birds in Sri Lanka. Bundala harbors 197 species of birds, the highlight being the greater flamingo, which migrate in large flocks. Bundala was designated a wildlife sanctuary in 1969 and redesignated to a national park on 4 January 1993. In 1991 Bundala became the first wetland to be declared as a Ramsar site in Sri Lanka. In 2005 the national park was designated as a biosphere reserve by UNESCO, the fourth biosphere reserve in Sri Lanka. The national park is situated 245 kilometres (152 mi) southeast of Colombo.
Pigeon Island National Park is one of the three marine national parks of Sri Lanka. The national park is situated 1 km off the coast of Nilaveli, a coastal town in Eastern Province, encompassing a total area of 471.429 hectares. The island's name derives from the rock pigeon which has colonized it. The national park contains some of the best remaining coral reefs of Sri Lanka. Pigeon Island was designated as a sanctuary in 1963. In 2003 it was re-designated as a national park, making it the 17th such park in Sri Lanka. The island was used as a shooting range during the colonial era. Pigeon Island was one of the several protected areas affected by the Indian Ocean tsunami in 2004.
The Arnhem Land tropical savanna is a tropical and subtropical grasslands, savannas, and shrublands ecoregion in Australia's Northern Territory.
Flood Plains National Park is one of the four national parks set aside under the Mahaweli River development project in Sri Lanka. The park was created on 7 August 1984. The national park is situated along the Mahaweli flood plain and is considered a rich feeding ground for elephants. Flood Plains National Park is considered an elephant corridor for the elephants migrate between Wasgamuwa and Somawathiya national parks. The park is situated 222 kilometres (138 mi) north-east of Colombo.
Environmental issues in Sri Lanka include large-scale logging of forests and degradation of mangroves, coral reefs and soil. Air pollution and water pollution are challenges for Sri Lanka since both cause negative health impacts. Overfishing and insufficient waste management, especially in rural areas, leads to environmental pollution. Sri Lanka is also vulnerable to climate change impacts such as extreme weather events and sea level rise.
The Maldives–Lakshadweep–Chagos Archipelago tropical moist forests is a tropical moist broadleaf forest ecoregion in South Asia. It spans a chain of coralline islands in the Indian Ocean, including Lakshadweep, a union territory of India; the Maldives, an independent country; and the British Indian Ocean Territory, an overseas territory of the United Kingdom.
The Tongan tropical moist forests is a tropical and subtropical moist broadleaf forests ecoregion that includes the Tonga archipelago and Niue.
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