A study on estimation of above ground biomass and its impact in Kirala Kale Sanctuary, Matara District, Sri Lanka using GIS and RS techniques

Abstract

This research was conducted with the objective of estimating Above Ground Biomass (AGB) using Geographical Information Systems (GIS) and Remote Sensing (RS) technology and analysing the impact of its variation, based on the core research problem of the increase in associated Land Surface Temperature (LST) due to the decrease in AGB in Kirala Kale Sanctuary in the Matara District, Sri Lanka. Landsat data were used as secondary data, while primary data were collected through field measurements (DBH), location mapping and interviews. The Kirala Kale Sanctuary is a wetland ecosystem covering an area of 337.32 hectares. Using satellite data and ArcGIS 10.8 software, Normalised Difference Vegetation Index (NDVI) was calculated for the years 1996, 2006, 2016 and 2024, and then AGB was estimated using an allometric equation. The AGB data derived from satellite imagery were validated through field measurements, revealing a significant positive correlation. According to the study results, the average value of AGB in 1996 was 19.17 Ton/ha, and it had decreased to 18.25 Ton/ha in 2006. It was emphasised that AGB has decreased by as much as 13.9 Ton/ha in 2016 and AGB has decreased to 13.634 Ton/ha in 2024. AGB has decreased by 9.5% during the period 1996 - 2024, and the increase in LST can be identified as the strongest impact. The temperature in the study area, which was 25.07°C in 1996, has increased to 30.14°C in 2024. Correlation analysis between AGB and LST revealed a negative correlation. In the main affected area, Matara city, an increase in maximum temperature from 31.16°C in 1996 to 32.96°C in 2024 can be detected. As a final conclusion, the effect of AGB reduction on the increase in LST is emphasised.