Monitoring Changes in Rice Cultivated Area from SAR and Optical Satellite Images in Ben Tre and Tra Vinh Provinces in Mekong Delta, Vietnam

Kirsi Karila,Anssi Krooks,Sanna Kaasalainen,Olli Nevalainen,Mika Karjalainen

doi:10.3390/rs6054090

Abstract

The objective of this study was to obtain up-to-date information on land use and to identify long term changes in land use, especially rice, aquaculture and other crops in Ben Tre and Tra Vinh provinces in Vietnam’s Mekong Delta. Long-term changes in land-use of the study area have not been studied using long time series of SAR and optical Earth observation (EO) data before. EO data from 1979–2012 was used: ENVISAT ASAR Wide Swath Mode, SPOT and Landsat imagery. An unsupervised ISODATA classification was performed on multitemporal SAR images. The results were validated using ground truth data. Using the Synthetic Aperture Radar (SAR) imagery maps for 2005, 2009 and 2011 were obtained. Different rice crops, aquaculture and fruit trees could be distinguished with an overall accuracy of 80%. Using available optical imagery the time series was extended from 2005 to 1979. Long-term decrease in the rice acreage and increase in the aquaculture acreage could be detected.

Highlights

Rice is one of the most important nutrition components in the world and a supply of stable food in many countries, especially in Southeast Asia
The Synthetic Aperture Radar (SAR) data consisted of 37 ENVISAT ASAR WSM (Wide-Swath Mode) images acquired between December 2004 and March 2012 (Table 1)
The most reliable results were based on SAR imagery, the reason being that the SAR data was multitemporal covering the whole year

Summary

Introduction

Rice is one of the most important nutrition components in the world and a supply of stable food in many countries, especially in Southeast Asia. Up-to-date information on areas under rice cultivation and changes in the cultivated area is essential for national political decision-makers and for international trade organizations for planning and monitoring purposes. Due to the human population growth the global food security has to be ensured. Awareness of changes in rice growing conditions is beneficial for estimating the long term impacts of climate change on the rice production. According to the International Rice Research Institute, Vietnam is the leading producer of rice in the world; the Mekong Delta region being the most important rice production area [1]. In some of the coastal parts of the Mekong Delta region, United Nations International Fund for Agriculture (IFAD)

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