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Multiscale analysis of land use and land cover changes in Sri Lanka by remote sensing: the impacts of post-war infrastructure development in the last 20 Years (2002-2022)
(National Science Foundation: Colombo, 2024-01-02) Andrieu, J.; Anupama, K.; Bautes, N.; Benabou, S.; Crook, O-J.; Gunasekara, V.; Jayasingam, T.; Jayathilaka, C.; Kodikara, K.A.S.; Lombard, F.; Madarasinghe, S.K.; Mathiventhan, T.; Muthusankar, G.; Premathilake, R.; Proisy, C.; Vanniasinkam, N.; Weeratunge, N.; Wickramaarachchi, N.; Mathevet, R.
On a worldwide scale, land use and land cover changes (LULCC) is a major driver of global change and biodiversity erosion. This study aims to monitor at the scale of Sri Lanka, LULCC and vegetation dynamics, to identify the main changes and their drivers. It places emphasis on multiscale geospatial monitoring with satellite data but also mobilises the interdisciplinary knowledge of a research programme. First, national scale data allows the identification of major changes with the MODIS NDVI dataset using Mann-Kendall tests and time profile analysis. A second local scale was mobilised with a systematic diachronic visual interpretation of high-resolution images on Google Earth. The third step, a macro-regional scale focus on the South and East coasts, used LANDSAT imagery (Stacked K-means) verified by field studies (botanical and vegetation analysis, and interviews). About 92.5% of the island of Sri Lanka is stable or presents no significant trends in the vegetation cover. 5% show a significant positive (greening) trend between 2000 and 2020 around the Puttalam lagoon, west of the Samanalawewa Reservoir, in the Udawalawe National Park, east and north of Ella, and the Nuwaragala Forest Reserve. Only about 2.5% (165,000 ha) of the Island shows a negative significant trend mainly in the periphery of Colombo and Trincomalee. The first driver is a set of national planning decisions in terms of infrastructure development (including urban growth, housing programmes and agricultural fields, and the management of protected areas). The second driver comes under rural dynamics with increasing tree density in rural landscapes over the Uva Province. Infrastructure development initiated by the state, creates both underlying conditions for other activities and negative impacts on coastal ecosystems, such as degradation of wetlands (including protected areas).
Assessment of tree cover density of Sri Lanka using visual interpretation of open-source high-resolution imagery and geographic information system interface mapping
(National Science Foundation: Colombo, 2024-01-02) Premakantha, K.T.; Chandani, R.P.D.S.; Silva, G.G.J.R.; Gunatilaka, R.P.S.I.K.; Pushpakumara, D.K.N.G.
Trees are found in various formations, ranging from individual trees to randomly occurring tree clusters and systematically established tree plantations, as well as natural forests. Accurate information about trees, their distribution and density is crucial for the development of national policies, strategies, and management decisions related to tree planting, and environmental management. While some organizations and individuals have mapped forests, home gardens, and trees outside forests at different scales, the lack of comprehensive and systematic spatial distribution data on trees and tree cover density in Sri Lanka has been a significant challenge for policymakers. To address this issue, this study utilized the tree cover mapping (TCM) tool developed by U.S. Geological Survey. High-resolution images were visually interpreted within a geographic information system interface to map tree cover. The TCM tool employed a systematic sample grid, with a sampling interval of 200 m. The study encompassed 1.64 million sampling units, and mapping and interpretation were conducted at a scale of 1:3000. The resulting tree density map had a resolution of 200 m. Results show that 78% of the country’s land area has a tree cover density exceeding 10%, resembling open and sparse forests, while 64% of the country exhibits a tree cover density exceeding 40%, comparable to dense forest areas. The study found that although forest cover was limited in districts such as Colombo, Gampaha, and Jaffna, these areas still displayed a significant level of tree cover density, offering services and functions similar to those provided by forests.
1992_Vidurava 14 (03 & 04) English
(Colombo : Natural Resources, Energy and Science Authority of Sri Lanka ; Vidurava Issue, 1992) Silva, S.K.H.; Somapala, E.G.; Pathirana, R.
1992_Vidurava 14 (02) English
(Colombo : Natural Resources, Energy and Science Authority of Sri Lanka ; Vidurava Issue, 1992) Yapa, P.A.J.; De Alwis, A.; Wickramasinghe, R.H.
1992_Vidurava 14 (01) English
(Colombo : Natural Resources, Energy and Science Authority of Sri Lanka ; Vidurava Issue, 1992) Natural Resources, Energy and Science Authority of Sri Lanka