Browsing by Author "Dangalla, N.K."

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Application of PRA tool to study fish diversity variations due to small tank renovation - A case study from Galgamuwa D.S Division
(Research Symposium 2009 - Faculty of Graduate Studies, University of Kelaniya, 2009) Nishantha, K.P.L.; Najim, M.M.M.; Dangalla, N.K.
Small tank renovation has been practiced with the intention of improving agricultural productivity and alleviation of rural poverty in Sri Lanka since the independence. Small tank renovation process influences changes in aquatic habitat that could have impacts on the fauna and flora in the tank systems. Small tank renovation process does not consider the possible changes that could take place on aquatic fauna and flora. This study was conducted to assess the variations that took place in bird diversity in the small tanks due to tank renovation utilizing Participatory Rural Appraisal (PRA) and questionnaire survey. Twelve small tanks from Galgamuwa D.S. Division that were renovated within last 15 years were selected using stratified random sampling technique. Randomly selected 150 farmers responded to the questionnaire survey while 400 farmers were engaged in the 12 PRA surveys conducted to cover the 12 study tanks. Results from the questionnaire and PRA surveys were used to assess the presence and abundance of fish before and after tank renovation. Tank renovation has changed the living environment of the fish and brought in some changes in the fish population. The population of carnivores has decreased due to tank renovation according to the statistical analysis. This could be due to silt deposition on gills and eggs of those species during the renovation process. The population of the omnivores has increased while fish like barbs has also increased due to reduction of the predators.
Bird diversity variation due to small tank renovation in dry zone of Sri Lanka – A case study from Galgamuwa D.S Division
(Research Symposium 2009 - Faculty of Graduate Studies, University of Kelaniya, 2009) Nishantha, K.P.L.; Najim, M.M.M.; Dangalla, N.K.
Tank renovation programs implemented in Sri Lanka were intended to increase agricultural productivity but did not take into account the possible impacts on the fauna living in the tank environment. Tank renovation programs in Sri Lanka might have influenced changes in avian fauna inhabited around a tank environment. Therefore, a study was conducted to assess the variations that took place in bird diversity in and around the tanks due to tank renovation. Twelve small tanks from Galgamuwa D.S. Division were selected using stratified random sampling technique. Randomly selected 150 farmers responded to the questionnaire survey while 400 farmers were engaged in the 12 Participatory Rural Appraisal (PRA) surveys conducted to cover the 12 study tanks. Results from questionnaire and PRA surveys were used to assess the presence and abundance of birds before and after the tank renovation. Questionnaire survey identified that Cormorant species population has increased with the tank renovation. Fifty nine percent of farmers said that Cormorant (Phalacrocorax niger) could be seen rarely before the renovation but 85% of them reported that there is an increase of the Cormorant population after the renovation. Removal of tank vegetation has given them a favorable environment to catch their pray. The White-breasted Water hen (Amauronis phoenicurus) and Purple Swamp (Porphyrio porphyrio) that used the tank vegetation as the habitat and breeding site are reduced due to tank renovation. This has reduced the environment suitable for egg laying. PRA analysis identified an increase of Lesser Whistling Teal (Dendrocygna javanica) in some tanks and a decrease in some other. This study showed that tank renovation could influence the presence of different bird species due to the changes that take place in and around tank environments due to the tank renovation programs.
Changes in amphibian and reptile species living around tank environments due to r enovation of small tanks in the dry zone of Sri Lanka – A case study from Galgamuwa D.S Division
(Research Symposium 2009 - Faculty of Graduate Studies, University of Kelaniya, 2009) Nishantha, K.P.L.; Najim, M.M.M.; Dangalla, N.K.
Small tank renovation programs were implemented in Sri Lanka to increase the land area under cultivation. The renovation activities could have positive and negative impacts. The environmental impacts due to tank renovation have not been studied in Sri Lanka. Therefore, a study was conducted to assess the changes that took place in amphibian and reptile species living in and around the tanks due to tank renovation. Twelve small tanks from Galgamuwa D.S. Division were selected using stratified random sampling technique. Randomly selected 150 farmers responded to the questionnaire survey while 400 farmers were engaged in the 12 Participatory Rural Appraisal (PRA) surveys conducted to cover the 12 study tanks. Results from questionnaire and PRA surveys were used to assess the presence and abundance of amphibians and reptiles before and after tank renovation. Some amphibians and reptiles lived in the tank environment have either reduced in population or disappeared after the renovation. Significance testing at 95% confidence level revealed that tortoise and water monitor populations have reduced after the tank renovation. Eighty seven percent (87%) and 72% of the farmers responded that tortoises and monitors were abundant before the tank renovation, respectively in the tank environment while only 47% and 42% agree to it, respectively after the tank renovation. According to the PRA analysis, before the tank renovation, the monitor was the second abundant but it has reduced to the sixth most abundant species after the tank renovation. Bulnawa tank was identified as the tank with the highest population of reptile species before the renovation process but after the renovation Medawachchiya and Mahagalkadawala showed higher populations. This study showed a decrease in the population of reptiles after the renovation but the amphibians do not show any variation in population
Changes in mammal abundance due to small tank renovation – A Case Study from the Dry Zone of Sri Lanka
(Research Symposium 2010 - Faculty of Graduate Studies, University of Kelaniya, 2010) Dangalla, N.K.; Najim, M.M.M.; Nishantha, K.P.L.
The tank renovation programs in Sri Lanka were implemented with the sole objective of increasing agricultural productivity without considering the possible impacts on the environments. A study was conducted to assess the impact of tank renovation on mammal diversity around renovated tanks. Twelve small tanks from Galgamuwa D.S. Division were selected using stratified random sampling technique. The questionnaire survey was responded by 150 randomly selected farmers while 400 farmers were engaged in the 12 PRA surveys covering each study tank. Results from these surveys were assessed to evaluate the abundance of mammals before and after the tank renovation. According to the questionnaire survey deer, mongoose species and sambur populations have decreased with tank renovation. Twelve percent of the respondents are with the opinion that many deers (Axis axis ceylonesis) could be seen before the tank renovation but 79 % of them reported that deer could not be seen abundantly after the renovation. According to the farmers responses, Sambur (Cervus unicolor unicolor) could not be seen after the tank renovation. The PRA analysis identified an increase in mammal species in Monnankulama tank while a decrease in Ihalagama tank. The other tanks did not show any changes in the overall mammal populations. The reduction in the population of these mammals could be due to the increased human, vehicular and machinery movements due to the tank renovation. In additions, regular removals of vegetation cover from the tank surroundings, increased crop cultivation and settlements could have contributed to the changes in mammal diversity. According to the PRA survey, least mammal density is reported from Pahala Pulanchiya, Inhale and Pahala Palukandawa, Kurundankulama and Diwullawa tanks. The main reason for the least population could be linked to the closeness to the main roads and the settlements.
Influence of small tank renovation on floral diversity around the renovated small tanks – a PRA analysis from the Dry Zone of Sri Lanka
(Research Symposium 2010 - Faculty of Graduate Studies, University of Kelaniya, 2010) Dangalla, N.K.; Najim, M.M.M.; Nishantha, K.P.L.
Small tank renovation programs not only influence agricultural productivity but also influence many other aspects ranging from social to environmental issues. The small tank renovation programs implemented in Sri Lanka have not considered the environmental changes that are associated with the renovation activities. A study was conducted to assess the influence of tank renovation on floral diversity in the renovated tank environments. Twelve small tanks from Galgamuwa D.S. Division were selected using stratified random sampling. A questionnaire survey was conducted among 150 randomly selected farmers while 400 farmers were engaged in 12 PRA surveys that covered each study tank. This study revealed that there are some significant influences on some of the plant varieties in the tank vicinity due to the tank renovation. Pongamia pinnata has shown a positive change due to tank renovation while Vitex leucoxylon, Cerbera manghas and Calotropis gignntea showed a negative change. Pongamia pinnata distribution in the tank environment has increased on both sides of the bund, Kattakaduwa, tank shore and in the catchment area, which is confirmed by the Mann-Whitney Test at a 95% significant level. Pongamia pinnata which is growing in the tank environment is spread through the tank environment as the seeds are transmitted through water. As this plant is a medicinal plant, the tank community usually does not remove it from the tank environment and showed an increase in abundance after the tank renovation process. Vitex leucoxylon, Cerbera manghas and Calotropis gignntea showed a negative change as those are removed from the tank environment during the tank renovation and seasonal tank maintenance programs as these plants do not offer any specific advantages to the tank community.. According to the t-test at 95% significant level, there is a difference (negative change) between the total rank marks of the plant species grown in the tank surroundings before and after the renovation of the tanks. This revealed that the tank renovation has influenced a reduction in the diversity of some plant species available around the tank environments.
Soil preferences of Tiger Beetles in selected location of Sri Lanka
(Biodiversity Secretariat, 2013) Dangalla, C.D.; Pallewatta, N.; Dangalla, N.K.
Village tank renovation induced changes in aquatic plant varieties
(Research Symposium 2010 - Faculty of Graduate Studies, University of Kelaniya, 2010) Dangalla, N.K.; Najim, M.M.M.; Nishantha, K.P.L.
Village tank renovation programs that were implemented in Sri Lanka aimed at increasing in agricultural productivity and alleviating rural poverty. However, those did not consider the probable changes on the surrounding environments. In this study twelve village tanks from Galgamuwa D.S. Division were selected using stratified random sampling technique to assess the renovation induced variations on floral diversity in and around the renovated tanks. A questionnaire survey was conducted among 150 farmers who were randomly selected. Twelve PRA surveys were conducted to cover all the sample village tanks employing 400 randomly selected farmers. Results from questionnaire and PRA surveys were assessed to evaluate the presence and abundance of plant species before and after the tank renovation. This study revealed that the plant varieties Nelumbo nucifera (Lotus), Nemphaea pubescens (Lilly), Nymphoides indica (Blue water Lilly), Pistia stratiotes (Diya gowa), Eichhornia crassipes (Water hyacinth), and Colocasia sp. are available in all the study tanks. Plant species Pistia stratiotes, Colocasia esculenta and Eichhornia crassipes are alien invasive plants which have been a major threat for the existence of the marshland environment and related hydro systems. As per the Mann-Whitney Test at 95% significant level, significant changes in the plant varieties were observed after the tank renovation. Tank renovation has positively controlled the aquatic plants available within the tank. Dredging of the tanks during the renovation process has resulted in the reduction in plant densities. Dredging and deepening the tanks has influenced the distribution of Nelumbo nucifera (lotus) by reducing its distribution. Distribution of Nymphoides indica (Blue water Lilly), Aponogeton crispus, (Kekatiya) Eichhornia crassipes (Water hyacinth) and Musa sapientum (Diyameneri) have significantly decreased due to tank renovation. The aggregated rank mark has reduced to 430 from 517 after the tank renovation and it shows a clear reduction in the distribution of plant species grown in the tanks.