Thilina Jayarathne
All species play a role within an ecosystem as, (i) Primary producers (ii) Primary consumers (iii) Predators, and (iv) Decomposers. Primary producers absorb energy from the environment mainly from sun light an inorganic substances CO2 and H2O, produce Organic molecules such as C6H12O6 in their living cells which contain pigments. The primary consumers feed on them, they are herbivores. the Predators consume flesh meet on herbivores. Decomposers decompose dead organic materials in to inorganic particles and contribute for the material cycle. For many species the role is not unique. But some species play a unique & important role in ecosystem function & their removal results changes in that system.
Key Stone species is a species which affects the survival and abundance of many other species in the community in which it lives. The removal of such species can have a profound effect on the ecosystem in which they live, and sometimes even on the physical structure of the environment. And often the importance of these species is not evident until they disappear. Keystone species are less abundant, but they exert strong effects on the community they inhabit. There are Four types of Key Stone Species, (i)Organisms Controlling Dominants (ii)Resource Providers (iii)Keystone Mutualists (iv)Ecosystem Engineers.
Organisms Controlling Dominants Promote coexistence by reducing competition among other species for limiting resources in an Eco-system. Best examples are Predators which control the herbivores population and Herbivores which controls the plant composition. Resource Providers Provide continuous reliable source of food for many kinds of creatures. If it is removed unable to bridge the gap of supply. The best example is Fig tree. Mutualism is an interaction between 2 organisms. Both are inter dependent. They depend for Pollination (plants & animals) & Dispersal (plants & animals). If It fails it can be led to Reproductive failures, Loss of genetic diversity, Change in plant and animal population dynamics, Local extinctions without replacement, Loss of animal species reliant on fruits and seeds, Long terms species loss (trees). Ecosystem engineers are keystone species who physically modifies habitats. Best example is Elephants which maintain grasslands. Most exotic invasive species are ecosystem engineers in their invaded locations.
Loss of a Key Stone Species Can create a series of linked extinction events known as an extinction cascade. Returning the keystone species to the community may not necessarily restore the community, if other component species & physical environment have already lost.
Thursday, September 28, 2006
Threatened Plant Species & their Conservation in Sri Lanka.
Gayesha Jayasinghe
Plants are a vital part of the world’s biological diversity & an essential resource for human well being. Beside the crop plants that provide our basic food & fibers, many thousands of wild plants have great economic & cultural importance & potential, providing food, medicine, fuel, clothing & shelter for vast number of people throughout the world. Plants also play a key role in maintaining basic ecosystem functions & are essential for the survival of the world’s animal life.
Yet, despite our reliance on plants, crisis point has been reached. Although much work remains to be carried out to evaluate the status of the plants, it is clear that about species are threatened in Sri Lanka. There are 280 plant species are threatened in Sri Lanka.
Plants are endangered by a combination of factors; over collecting, unsustainable agriculture & forestry practices, urbanization, pollution, land use changes, & the spread of invasive alien species & climate change.
The IUCN Red List is the world’s most comprehensive inventory of the global conservation status of plant & animal species. It uses a set of criteria to evaluate the extinction risk of thousands of species & subspecies. The Red List can answer commonly asked questions such as, how threatened is a particular species? What are the threats to a species? etc. There are nine categories in the IUCN Red List system. In that categories there are Critically Endangered, Endangered and Vulnerable. Those are collectively called as “Threatened”. These criteria are based on biological factors related to extinction risk & include: decline, population size, area of geographic distribution & degree of population & distribution fragmentation. So we need conservation methods to protect these threatened plant species. The conservation can be divided in to In-situ conservation & Ex-situ conservation. In-situ conservation means “on site conservation”. It is the process of protecting on threatened plant species in its natural habitat. Ex-situ conservation may be used on some or all of the population, when In-situ conservation is too difficult or impossible. As a example we can consider about medicinal plants. About 80 medicinal plants are in threatened. Sri Lankan government takes necessary actions to conserve these. “Conservation & Sustainable use of Medicinal plants” project is an example for it. There are many policies to protect these plant species. “The Fauna & Flora protection ordinance” is the most important one.
There are many constrains to conserve these threatened plants in Sri Lanka. So we have to identify those constrains & give our maximum effort to protect them. Because those are main part in the biodiversity of Sri Lanka.
Plants are a vital part of the world’s biological diversity & an essential resource for human well being. Beside the crop plants that provide our basic food & fibers, many thousands of wild plants have great economic & cultural importance & potential, providing food, medicine, fuel, clothing & shelter for vast number of people throughout the world. Plants also play a key role in maintaining basic ecosystem functions & are essential for the survival of the world’s animal life.
Yet, despite our reliance on plants, crisis point has been reached. Although much work remains to be carried out to evaluate the status of the plants, it is clear that about species are threatened in Sri Lanka. There are 280 plant species are threatened in Sri Lanka.
Plants are endangered by a combination of factors; over collecting, unsustainable agriculture & forestry practices, urbanization, pollution, land use changes, & the spread of invasive alien species & climate change.
The IUCN Red List is the world’s most comprehensive inventory of the global conservation status of plant & animal species. It uses a set of criteria to evaluate the extinction risk of thousands of species & subspecies. The Red List can answer commonly asked questions such as, how threatened is a particular species? What are the threats to a species? etc. There are nine categories in the IUCN Red List system. In that categories there are Critically Endangered, Endangered and Vulnerable. Those are collectively called as “Threatened”. These criteria are based on biological factors related to extinction risk & include: decline, population size, area of geographic distribution & degree of population & distribution fragmentation. So we need conservation methods to protect these threatened plant species. The conservation can be divided in to In-situ conservation & Ex-situ conservation. In-situ conservation means “on site conservation”. It is the process of protecting on threatened plant species in its natural habitat. Ex-situ conservation may be used on some or all of the population, when In-situ conservation is too difficult or impossible. As a example we can consider about medicinal plants. About 80 medicinal plants are in threatened. Sri Lankan government takes necessary actions to conserve these. “Conservation & Sustainable use of Medicinal plants” project is an example for it. There are many policies to protect these plant species. “The Fauna & Flora protection ordinance” is the most important one.
There are many constrains to conserve these threatened plants in Sri Lanka. So we have to identify those constrains & give our maximum effort to protect them. Because those are main part in the biodiversity of Sri Lanka.
Friday, September 22, 2006
Wildlife Conservation in Sri Lanka
W.M.K.S.Chandrarathne
The theme of wildlife conservation has been an ancient concept in Sri Lanka.It was considered noble in keeping with the teaching of Goutham Buddha and later essential to the Island.
The first attempt to stop the destruction of wildlife resources of Sri Lanka was made in 1889, by the conservation of forests, Colonel Clark R.A. He has enact " An ordinance to prevent Wanton destruction of elephants, buffaloes and other games" and "An ordinance to readjust the customs duties livable on firearms and to impose and export duty on certain hides and horns". For the protection of flora and fauna Ordinance, No 2 of 1937 was provide to the necessary rules and regulations. Under this ordinance the wildlife department separate in 1949. And establish new protected areas such as; Strict Nature Reserves, National Parks, Nature Reserves, Jungle corridors,Refuge,Marine Reserves ,Buffer Zones and Sanctuaries. The above ordinance amended in 1993 act no 49. After that under the Flora and Fauna ordinance, National parks 20, Strict nature reserves 03, Nature reserves 04,elephant corridors, and Sanctuaries. Haggala, Yala block 11, and Ritigala are the strict nature reserves; and the largest national park is the wilpattu national park, second largest national park is the Yala.And last gazzeted national park is Angammadilla in 05/07/2006.
In Sri Lanka, main conserve animal is the elephant which is the flagship species in the country and becoming threatened. Other major animals such as samber, deer, sloth bear, and Leopard were also protected. According to the survey of prof.Santiapillai in 2000, elephant population recorded as 4000 - 5000 .Most of this elephant population saturated in dry zone. And it case to human elephant conflict also. Because of the destroying forests food, water and shelter are not enough to for the population. Year by year elephant mortality goes to high, because of gunshot injuries, electricution, poisoning, landmines accidental fall into wells and pits,colission with trains and natural causes. For the conservations of elephants, the department of wildlife conservation has identified several areas where the human - elephant conflict has become serious. And given the facilities to control the conflict. When some elephants become rogue, they are tranquilized and translocate to another place and, when some baby elephants are remote in the jungle or village, bring to the Udawalawa elephant rehabilitation center.
Conservation measures adapted for; mitigation of human - elephant conflict, controlling ivary poaching, establishment of new national parks, establishment of elephant corridors, Increasing the extent of conservation areas, habitat enrichment activities, translocation of elephants, elephant drives and electric fencing. Ex-situ conservation and integrated elephant conservation with economic developments. Apart from that wildlife policy and international conservation laws and regulations such as CITES, BON convention, RAMSAR convention, are helps to conservation. And education programmes, NGO's also give the support to conservation. By the conserve wildlife, it gives recreation and scientific values to the nature.
And other projects such as turtle conservation project, lepord conservation project and bear conservation project given the support to the wildlife. And foreign donar agencies such as ADB, World Bank and GEF give the financial support to conservation.
The theme of wildlife conservation has been an ancient concept in Sri Lanka.It was considered noble in keeping with the teaching of Goutham Buddha and later essential to the Island.
The first attempt to stop the destruction of wildlife resources of Sri Lanka was made in 1889, by the conservation of forests, Colonel Clark R.A. He has enact " An ordinance to prevent Wanton destruction of elephants, buffaloes and other games" and "An ordinance to readjust the customs duties livable on firearms and to impose and export duty on certain hides and horns". For the protection of flora and fauna Ordinance, No 2 of 1937 was provide to the necessary rules and regulations. Under this ordinance the wildlife department separate in 1949. And establish new protected areas such as; Strict Nature Reserves, National Parks, Nature Reserves, Jungle corridors,Refuge,Marine Reserves ,Buffer Zones and Sanctuaries. The above ordinance amended in 1993 act no 49. After that under the Flora and Fauna ordinance, National parks 20, Strict nature reserves 03, Nature reserves 04,elephant corridors, and Sanctuaries. Haggala, Yala block 11, and Ritigala are the strict nature reserves; and the largest national park is the wilpattu national park, second largest national park is the Yala.And last gazzeted national park is Angammadilla in 05/07/2006.
In Sri Lanka, main conserve animal is the elephant which is the flagship species in the country and becoming threatened. Other major animals such as samber, deer, sloth bear, and Leopard were also protected. According to the survey of prof.Santiapillai in 2000, elephant population recorded as 4000 - 5000 .Most of this elephant population saturated in dry zone. And it case to human elephant conflict also. Because of the destroying forests food, water and shelter are not enough to for the population. Year by year elephant mortality goes to high, because of gunshot injuries, electricution, poisoning, landmines accidental fall into wells and pits,colission with trains and natural causes. For the conservations of elephants, the department of wildlife conservation has identified several areas where the human - elephant conflict has become serious. And given the facilities to control the conflict. When some elephants become rogue, they are tranquilized and translocate to another place and, when some baby elephants are remote in the jungle or village, bring to the Udawalawa elephant rehabilitation center.
Conservation measures adapted for; mitigation of human - elephant conflict, controlling ivary poaching, establishment of new national parks, establishment of elephant corridors, Increasing the extent of conservation areas, habitat enrichment activities, translocation of elephants, elephant drives and electric fencing. Ex-situ conservation and integrated elephant conservation with economic developments. Apart from that wildlife policy and international conservation laws and regulations such as CITES, BON convention, RAMSAR convention, are helps to conservation. And education programmes, NGO's also give the support to conservation. By the conserve wildlife, it gives recreation and scientific values to the nature.
And other projects such as turtle conservation project, lepord conservation project and bear conservation project given the support to the wildlife. And foreign donar agencies such as ADB, World Bank and GEF give the financial support to conservation.
Environmental Impacts of Shrimp Farming in Sri Lanaka
Duminda Perera
The problems related to the environment in the shrimp farming industry in Sri Lanka arose mainly from over–emphasis on high production, economic viability and foreign income generation without full consideration of the environmental impacts caused by over-crowding of farms. At the inception, there was no proper zoning plan to facilitate development of an environmentally sound industry. Lack of a proper zoning plan for the northwestern and western provincial coastal belts led to many social problems and destruction of ecologically sensitive areas, such as mangroves and mud flats.
Destruction of mangroves leaves coastal areas exposed to erosion, flooding and storm damage alters natural drainage patterns, increases salt intrusion and removes critical habitats for many aquatic and terrestrial species, with serious implications for biodiversity, conservation and food security. Mangrove estuaries are also specially rich and productive ecosystems and provide the spawning grounds for many species of fish including many commercially important ones.
Nutrient rich effluents of shrimp farms are typically discharged into the environment seriously upsetting the ecological balance. These waste waters contain significant amounts of chemical fertilizers, pesticides and antibiotics that cause severe pollution of the environment.
Other main environmental impacts are pollution and depletion of drinking water, retention of flood water and more frequent floods in the area. Agricultural activities of the area is also seriously affected due to conversion of agricultural lands in to ponds, salinization of water, deposition of salt in the soil and lowering of the water table.
The problems related to the environment in the shrimp farming industry in Sri Lanka arose mainly from over–emphasis on high production, economic viability and foreign income generation without full consideration of the environmental impacts caused by over-crowding of farms. At the inception, there was no proper zoning plan to facilitate development of an environmentally sound industry. Lack of a proper zoning plan for the northwestern and western provincial coastal belts led to many social problems and destruction of ecologically sensitive areas, such as mangroves and mud flats.
Destruction of mangroves leaves coastal areas exposed to erosion, flooding and storm damage alters natural drainage patterns, increases salt intrusion and removes critical habitats for many aquatic and terrestrial species, with serious implications for biodiversity, conservation and food security. Mangrove estuaries are also specially rich and productive ecosystems and provide the spawning grounds for many species of fish including many commercially important ones.
Nutrient rich effluents of shrimp farms are typically discharged into the environment seriously upsetting the ecological balance. These waste waters contain significant amounts of chemical fertilizers, pesticides and antibiotics that cause severe pollution of the environment.
Other main environmental impacts are pollution and depletion of drinking water, retention of flood water and more frequent floods in the area. Agricultural activities of the area is also seriously affected due to conversion of agricultural lands in to ponds, salinization of water, deposition of salt in the soil and lowering of the water table.
Thursday, September 21, 2006
Flowering Plant Diversity in Sri Lanka, with special reference to Endemism and Nomenclature
Pradeep Rajatewa
Sri Lanka has considerably high diversity of flowering plants. According to the recent checklist published in 2001, in Sri Lanka there are 214 flowering plant families, 1,522 genera and 4,143 species. Of the total number of species, about 75% are indigenous and about 25% are exotic. Of the total number of indigenous plant species 27.53% are found to be endemic to Sri Lanka. 75% of Flowering plants belong to the sub class - Dicoteledonae and rest belongs to the sub class - Monocoteledonae. Above mentioned numbers and percentages can vary slightly, due to the incompletion of the checklist. There are enough evidences to suggest the total number of flowering plant of Sri Lanka may exceed 4,500. In this it is study considered that there are 4206 plant species in Sri Lanka for further analysis.
Sri Lanka has the 871 endemic flowering plant species and 827 of them do not have lower taxa, but 44 species have. It includes 2 forma (1 sp), 26 sub species (13 sp) and 60 verities (30 sp). Apart from that, 15 subspecies (14 sp.), 46 verities (31 sp) and 2 forma (1 sp) are endemic to Sri Lanka. Within this 871 endemic species more than 12 point endemics included. Available literature is not enough to reveal all the point endemics. It is believe that Sri Lanka has 17 endemic genera. On recent study shows 3 of them are not endemic genera. It is difficult to find the endemism of another two genera because there generic name has been changed.
Nomenclature of the plants of Sri Lanka started from the period of eminent taxonomist Carols Linnaeus in 17 th century. But till today there are no any analysis have been made of the nomenclature. This study is attempted to fill this gap. According to this study 1612 plant names were changed. It includes 315 introduced plants and 248 endemic plants. Carols Linnaeus was the leading taxonomist who describes the highest number of flora that find in Sri Lanka. There are 542 species. But it includes very few endemics. Thwaitesi has described the highest numbers of endemic species. His total descriptions is 298 and 240 of them are endemic. Alston and Henry Trimen were the other taxonomists who described over 50 species. Only 6 Sri Lankan authors were able to describe the plant species (22 sp.). D.M.A. Jayaweera is the leading person among them who described 9 species.
There are only 2490 specific epithets used for 4206 plant species. zeylanica is the most commonly used specific epithet. It used for 72 times. Another 11 epithets that related to the epithet zeylanica has used 74 times (synonyms for Sri Lanka). indica and thwatesii are the next mostly used epithets. Another 25 epithets have Sri Lankan origin. It includes 7 Sinhala names that use for the related plants, 12 places or the area name that find the relevant plant species and 6 epithets mentioned the eminent taxonomist or the people’s name that have Sri Lankan origin.
Sri Lanka has considerably high diversity of flowering plants. According to the recent checklist published in 2001, in Sri Lanka there are 214 flowering plant families, 1,522 genera and 4,143 species. Of the total number of species, about 75% are indigenous and about 25% are exotic. Of the total number of indigenous plant species 27.53% are found to be endemic to Sri Lanka. 75% of Flowering plants belong to the sub class - Dicoteledonae and rest belongs to the sub class - Monocoteledonae. Above mentioned numbers and percentages can vary slightly, due to the incompletion of the checklist. There are enough evidences to suggest the total number of flowering plant of Sri Lanka may exceed 4,500. In this it is study considered that there are 4206 plant species in Sri Lanka for further analysis.
Sri Lanka has the 871 endemic flowering plant species and 827 of them do not have lower taxa, but 44 species have. It includes 2 forma (1 sp), 26 sub species (13 sp) and 60 verities (30 sp). Apart from that, 15 subspecies (14 sp.), 46 verities (31 sp) and 2 forma (1 sp) are endemic to Sri Lanka. Within this 871 endemic species more than 12 point endemics included. Available literature is not enough to reveal all the point endemics. It is believe that Sri Lanka has 17 endemic genera. On recent study shows 3 of them are not endemic genera. It is difficult to find the endemism of another two genera because there generic name has been changed.
Nomenclature of the plants of Sri Lanka started from the period of eminent taxonomist Carols Linnaeus in 17 th century. But till today there are no any analysis have been made of the nomenclature. This study is attempted to fill this gap. According to this study 1612 plant names were changed. It includes 315 introduced plants and 248 endemic plants. Carols Linnaeus was the leading taxonomist who describes the highest number of flora that find in Sri Lanka. There are 542 species. But it includes very few endemics. Thwaitesi has described the highest numbers of endemic species. His total descriptions is 298 and 240 of them are endemic. Alston and Henry Trimen were the other taxonomists who described over 50 species. Only 6 Sri Lankan authors were able to describe the plant species (22 sp.). D.M.A. Jayaweera is the leading person among them who described 9 species.
There are only 2490 specific epithets used for 4206 plant species. zeylanica is the most commonly used specific epithet. It used for 72 times. Another 11 epithets that related to the epithet zeylanica has used 74 times (synonyms for Sri Lanka). indica and thwatesii are the next mostly used epithets. Another 25 epithets have Sri Lankan origin. It includes 7 Sinhala names that use for the related plants, 12 places or the area name that find the relevant plant species and 6 epithets mentioned the eminent taxonomist or the people’s name that have Sri Lankan origin.
Sunday, September 10, 2006
Importance and Management Constraints of Elephant Transit Home, Udawalawa, Sri Lanka
Isuru Jayasundara
Sri Lankan elephant (Elephas maximus maximus ) is considered as a major endangered species and their survival in the natural habitat is threatened due to expansion of various human informal activities. Therefore the human and elephant conflict is increasing and as a result of that elephants in natural forests are constantly being destroyed and baby elephants become orphaned or abandoned.
Elephant Transit Home (Eth Athuru Sevena) is an elephant orphanage maintained by the Department of Wildlife Conservation (DWC) for protecting the orphaned baby elephants in Sri Lanka. This has been established in 1995 in Udawalawa National Park. Main purpose of this ETH (Elephant Transit Home) is taking care of orphaned baby elephants until they become young and release them into their natural habitat.
When a small elephants become abandoned or orphaned, it is difficult them to survive in their natural habitats, because of some carnivorous animals. On the other hand they may face many problems such as falling into abandoned pits and malnutrition. But if the herd is with them, adults in the herd try to save calves from dangerous incidents. If smalls can not escape from these troubles even with the help of adults, they get orphaned. Sometimes the baby elephant can be orphaned after its mother’s death. (This mostly happens, because of human activities, such as killing elephants)
DWC has to pay attention to provide shelter to the orphaned baby elephants and maintain them in good health condition. After living about 4 1/2 years of time they are released to the forest. All released elephants are then monitored for three years. Therefore this makes further conserve of our elephants. Actually this is a kind of ex-situ conservation method to conserve several genotypes of elephants found in different places of the country. Through this the production of improved novel genetic combinations is also provoked. In addition to that regular awareness programmes on elephants are also conducted in these premises.
Government has to make sound allocations to improve the facilities of ETH and for its maintenance. Therefore DWC has decided to seek private sector assistance. Launching a Foster Parent Scheme for baby elephants is one of such efforts. DWC is facing some problems in releasing the elephants to forests. Udawalawa National Park is highly suitable as it is enriched with food and covered by an Electric fence. But nearly fifty elephants have been released to this park up to now. As Udawalawa National Park is not very large, DWC will have to search another area for future uses. But most of parks do not have the environmental conditions like in Udawalawa national Park. In addition, there are some problems in monitoring or released animals.
ETH is doing a great work to conserve our elephants. We too must promote greater awareness and pay a hefty price to conserve this priceless ecological jewel for the benefit of our future generation.
Sri Lankan elephant (Elephas maximus maximus ) is considered as a major endangered species and their survival in the natural habitat is threatened due to expansion of various human informal activities. Therefore the human and elephant conflict is increasing and as a result of that elephants in natural forests are constantly being destroyed and baby elephants become orphaned or abandoned.
Elephant Transit Home (Eth Athuru Sevena) is an elephant orphanage maintained by the Department of Wildlife Conservation (DWC) for protecting the orphaned baby elephants in Sri Lanka. This has been established in 1995 in Udawalawa National Park. Main purpose of this ETH (Elephant Transit Home) is taking care of orphaned baby elephants until they become young and release them into their natural habitat.
When a small elephants become abandoned or orphaned, it is difficult them to survive in their natural habitats, because of some carnivorous animals. On the other hand they may face many problems such as falling into abandoned pits and malnutrition. But if the herd is with them, adults in the herd try to save calves from dangerous incidents. If smalls can not escape from these troubles even with the help of adults, they get orphaned. Sometimes the baby elephant can be orphaned after its mother’s death. (This mostly happens, because of human activities, such as killing elephants)
DWC has to pay attention to provide shelter to the orphaned baby elephants and maintain them in good health condition. After living about 4 1/2 years of time they are released to the forest. All released elephants are then monitored for three years. Therefore this makes further conserve of our elephants. Actually this is a kind of ex-situ conservation method to conserve several genotypes of elephants found in different places of the country. Through this the production of improved novel genetic combinations is also provoked. In addition to that regular awareness programmes on elephants are also conducted in these premises.
Government has to make sound allocations to improve the facilities of ETH and for its maintenance. Therefore DWC has decided to seek private sector assistance. Launching a Foster Parent Scheme for baby elephants is one of such efforts. DWC is facing some problems in releasing the elephants to forests. Udawalawa National Park is highly suitable as it is enriched with food and covered by an Electric fence. But nearly fifty elephants have been released to this park up to now. As Udawalawa National Park is not very large, DWC will have to search another area for future uses. But most of parks do not have the environmental conditions like in Udawalawa national Park. In addition, there are some problems in monitoring or released animals.
ETH is doing a great work to conserve our elephants. We too must promote greater awareness and pay a hefty price to conserve this priceless ecological jewel for the benefit of our future generation.
Aquatic Weeds in Sri Lanka
Darshani Samarakkody
Sri Lanka is an agricultural country with a population of 19 million people. Farmers and farming communities rely on a multitude of reservoirs for water as the country knows prolonged dry periods. There are some 50000 reservoirs in Sri Lanka ranging in size from 10Km2 to 1045 Km2, which have been constructed over the past 3000 years mainly for irrigati. The rural communities in Sri Lanka depend on inland water for rice and vegetable production, animal protein as well as fresh water supply. In recent years, moreover the country has seen a rapid increase in the number of dams, reservoirs and canals resulting from development of irrigation and hydroelectric projects. Recent observation and reports have demonstrated that both natural and artificial water bodies in Sri Lanka have become infected with the aquatic weeds.
In its native range water weeds is largely restricted to costal lowlands and along the margins of lagoons and slow moving waters. It occur low densities, only becoming a problem where the hydrological regime of a water body has been altered by human activities, or where the level of nutrients in the water has been increased. They provide a habitat for vectors of several diseases, increase the areas at risk as a result of flooding, and affect drinking water supply, inland fisheries and rural transport. The mosquito populations have increased at an alarming rate during the last five years due to the large mat of floating weed infestations in coastal districts.
Programms to control its growth have been initiated in most countries where it occurs. Chemical and mechanical control measures have been used to combat water weeds, but are expensive and ineffective on all but small infestation. Eradication of the weed has been rare because of its rapid growth rate and its ability to reinfest from seeds or isolated plants. Increasing concern about the financial and environmental costs associated with herbicidal control measures and their limited effectiveness has led to growing interested in the use of biological control. Biological control of water weeds offers sustainable, environmentally-friendly, long-term control and is the only feasible method to provide some level of control to those infestations which cover huge areas, are difficult to access and / or do not warrant the high cost of physical or chemical control.
The area colonized by this weeds appear to have increased in the recent years as the Government suffers from foreign exchange difficulties, lack of aquatic management knowledge, expertise and programms. Thus aquatic weeds have received very little attention in Sri Lanka so far.
Sri Lanka is an agricultural country with a population of 19 million people. Farmers and farming communities rely on a multitude of reservoirs for water as the country knows prolonged dry periods. There are some 50000 reservoirs in Sri Lanka ranging in size from 10Km2 to 1045 Km2, which have been constructed over the past 3000 years mainly for irrigati. The rural communities in Sri Lanka depend on inland water for rice and vegetable production, animal protein as well as fresh water supply. In recent years, moreover the country has seen a rapid increase in the number of dams, reservoirs and canals resulting from development of irrigation and hydroelectric projects. Recent observation and reports have demonstrated that both natural and artificial water bodies in Sri Lanka have become infected with the aquatic weeds.
In its native range water weeds is largely restricted to costal lowlands and along the margins of lagoons and slow moving waters. It occur low densities, only becoming a problem where the hydrological regime of a water body has been altered by human activities, or where the level of nutrients in the water has been increased. They provide a habitat for vectors of several diseases, increase the areas at risk as a result of flooding, and affect drinking water supply, inland fisheries and rural transport. The mosquito populations have increased at an alarming rate during the last five years due to the large mat of floating weed infestations in coastal districts.
Programms to control its growth have been initiated in most countries where it occurs. Chemical and mechanical control measures have been used to combat water weeds, but are expensive and ineffective on all but small infestation. Eradication of the weed has been rare because of its rapid growth rate and its ability to reinfest from seeds or isolated plants. Increasing concern about the financial and environmental costs associated with herbicidal control measures and their limited effectiveness has led to growing interested in the use of biological control. Biological control of water weeds offers sustainable, environmentally-friendly, long-term control and is the only feasible method to provide some level of control to those infestations which cover huge areas, are difficult to access and / or do not warrant the high cost of physical or chemical control.
The area colonized by this weeds appear to have increased in the recent years as the Government suffers from foreign exchange difficulties, lack of aquatic management knowledge, expertise and programms. Thus aquatic weeds have received very little attention in Sri Lanka so far.
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