Abstract
Abstract. The mangrove forests of Lawaan-Balangiga in Eastern Samar lost significant cover due to the Typhoon Haiyan that struck the region in 2013. The mangroves in the area have since shown signs of recovery in terms of growth and spatial coverage, but these widely varied with locations. This study aims to further examine the status of recovery of mangroves across different locations by analysing the time series trends of selected vegetation and moisture indices: Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Modified Soil Adjusted Vegetation Index (MSAVI), and Normalized Difference Moisture Index (NDMI). These indices were extracted from Landsat 8 surface reflectance images, spanning 2014 to 2020, using Google Earth Engine (GEE). The time series analyses showed similar NDVI, MSAVI and NDMI values and trends after the 2013 typhoon event. The trend slopes also indicated high correlation (0.91 – 1.00) between and among the indices, with NDVI having the highest correlation with MSAVI (∼1.00). The study was able to corroborate the previous study on mangroves in Lawaan-Balangiga, by presenting positive trend results in the identified recovered areas. These trends, however, would still have to be validated by collecting and comparing biophysical parameters in the field. The next step of the research would be to identify the factors that contribute to the varying rates of recovery in the areas and to evaluate how this can affect the carbon sequestration rates of recovering mangroves.
Highlights
1.1 The ecosystem services of mangrovesMangroves are a group of trees and shrubs that grow in the coastal intertidal zone, making up for one of the most productive ecosystems in the world (IUCN, 2021; NOAA, 2021)
Mangroves are effective in providing coastal protection to communities, through its aerial roots that trap and retain sediments, preventing erosion; its roots, trunks and canopies can significantly reduce the force of wind, waves and flood waters (Losada et al, 2017)
Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Modified Soil Adjusted Vegetation Index (MSAVI), and Normalized Difference Moisture Index (NDMI) were calculated and added as bands to each image which were masked for clouds
Summary
Mangroves are a group of trees and shrubs that grow in the coastal intertidal zone, making up for one of the most productive ecosystems in the world (IUCN, 2021; NOAA, 2021). They are vulnerable environmental resources that provide significant economic goods and services that contribute to human well-being (Conservation International, 2008). When super typhoon Haiyan struck the country in 2013, it was packing winds registered over 300 kph—one of the strongest in history for the landfall of a cyclone (FAO, 2021) It made several landfalls along the Visayas group of islands. Even local narratives (Delfino et al, 2015; The World, 2021) recognize the critical role that mangroves have in the protection of the community
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