Seasonal and Interannual Variabilities of Philippine Vegetation as Seen from Space
Gay Jane P. Perez1 and Josefino C. Comiso2
1Institute of Environmental Science and Meteorology
University of the Philippines Diliman, Quezon City 1101 Philippines
2Earth Sciences Division, NASA Goddard Space Flight Center
Maryland, USA 20771
corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it. or This email address is being protected from spambots. You need JavaScript enabled to view it.
ABSTRACT
Seasonal and interannual variabilities of the Philippine vegetation cover were studied using the Normalized Difference Vegetation Index (NDVI) data derived from the Moderate Resolution Imaging Spectroradiometer (MODIS). Because of persistent cloud cover, the NDVI dataset was enhanced to ensure temporal consistency needed for time series studies. The resulting data was validated and shown to agree with higher resolution satellite data and follow the expected features that are dictated by location and season. General locations of forest areas and agricultural regions were identified using the 250-m resolution NDVI 16-day composites. Analyses of the vegetation dataset for the period 2000 to 2011 showed large seasonal variability in lowlands, which generally consist of agricultural areas, while moderate seasonality was observed in the high lands where the vegetation consists primarily of forests. High NDVI values were observed during the wet season (June to November), while low NDVIs were recorded in the dry/hot season (March to May). Large interannual variability during the dry/hot season was observed and NDVI is shown to exhibit good correlation with land surface temperature. An anomalously low NDVI at agricultural areas in 2010, representing not just less healthy plants but also reduced vegetation cover, is linked to the anomalously high surface temperature recorded in 2010 and low precipitation rate in the region. This work successfully demonstrates that changes in Philippine vegetation cover can be assessed and monitored using MODIS NDVI or similar data. It also shows that data can be used to detect agricultural regions that are likely to be most vulnerable to global warming.
INTRODUCTION
The Philippines has a total land area of about 300,000 km2, 40.1% of which is covered by agricultural lands while 25.7% is covered by forest (World Development Indicators 2013). Philippine agriculture represents 1/5 of the total economy (18% of GDP) and generates 1/3 of the country’s total employment (National Statistics Office 2002). On the other hand, the Philippine forest is critical in sustaining the high biodiversity in the region, . . . . . . . . . . . . .
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