Integrated evaluation of Ecosystem Services in Prawn-Rice rotational crops, Vietnam

Abstract

The hydrologic condition in Kien Giang province on the west coast of Vietnam's Mekong Delta is unique in the sense that it has extensive saline water intrusion during the dry season every year. Instead of a triple crop scheme like other areas in the Delta, a prawn and rice rotational cultivation scheme was initiated to facilitate agricultural production in Kien Giang. In this paper, the ecosystem services (ES) generated from the agriculture ecosystem under the prawn and rice rotational crops (PRRC) were assessed using an integrated approach. The specific ES identified here include water and nutrition regulation in the soil together with climate regulation in favor of the cultivated crops. A multi-disciplinary approach including remote sensing, GIS, social surveys and statistical analysis was adopted to comprehensively evaluate the geographical, biophysical, economic and social aspects of the ES. Firstly, Landsat 8 images were processed with Normalized Difference Vegetation Index (NVDI) and Modified Normalized Difference Water Index (MNDWI) to identify the areas cultivating PRRC. The accuracy of image classifi- cation was assessed by ground truthing and we found an 80% coincidence between the simulated results and the field observations. Then, the social survey was conducted using face to face interviews at 50 local households to collect data related to farming practices. Economic values of ecosystem services were obtained using the revised market methods by annual crop yields per unit area. The mean estimated value of ES provided through the PRRC was 1300 USD/ha/year (standard deviation of 600 USD/ha/year) which accounted for 38.1% and 59.4% of the averaged economic revenue and net benefit, respectively. The analysis of social survey data revealed the factors having the greatest effects on ecosystem services values were selling prices of prawn and farming experiences. Finally, results were synthesized with GIS to describe how ES values vary across the research area which facilitates effective communication of the importance of ES concepts to policy makers regarding land use planning and natural resources management decision.