Land use characterization and change detection of a small mangrove area in Banacon Island, Bohol, Philippines using a maximum likelihood classification method

Dixon Gevana,Leni Camacho,Antonio Carandang,Sofronio Camacho,임상준 한국산림과학회 2015 Forest Science And Technology Vol.11 No.4

Geospatial information of small mangrove islands in the Philippines is usually lacking. Such information is vital to monitor mangrove cover change and craft plans for their sustainable management. This study was conducted to provide some land use information about Banacon Island in Bohol province. The island is renowned for its vast mangrove plantations, community-initiated reforestation, and double reef system. To determine the different forest land uses therein, the study employed a maximum likelihood classification method using two Landsat images of different periods. Results revealed three distinct forest land uses, namely: dense mature stand; dense intermediate stand; and sparse mangrove area. Land use change detection analysis was also conducted. Findings suggest that mangrove cover has generally improved from 1993 to 2004, as seen in the expansion of dense plantations over sparsely vegetated areas. Such change is attributable to continuous reforestation activities by the local community. Minor deforestation was also recorded due to various natural and anthropogenic causes. Comparing the area of deforestation with the increase in plantations, the results suggest that reforestation has compensated or exceeded the rate of cover loss. In order to further improve the geospatial results, the study recommends the use of high resolution images covering other years for better analysis of land use change.

GIS를 이용한 산지하천의 침식위험도 평가

이은재,임상준,Dixon Gevana,이상호 한국산림공학회 2012 한국산림공학회지 Vol.10 No.3

본 연구에서는 산지하천의 잠재적인 침식발생 정도 및 침식위험성을 평가하기 위하여 침식위 험지수(EHI; erosion hazard index)를 기초로 GIS 분석기법을 이용하여 소유역별로 산지하천의 황폐화를 평가하였다. 또한, 산지하천에 대한 수리·수문학적 인자와 형태적 특성을 현장 조사하 여 이들 인자와 산지하천의 침식위험지수(EHI)와의 관계를 분석하였다. 그 결과 침식위험지수 (EHI)가 0.5보다 큰 값을 가지는 산지하천구간은 침식에 대해 취약하다고 평가할 수 있다. 이러 한 하천에서는 대부분 하천의 본류연장은 비교적 짧으며, 산지하천 내에 거력(boulder)이 많이 분포하고 급경사 지형이 나타나며, 하도단면 형태지수는 작아지는 것으로 나타났다. The objectives of this paper is to assess the erosion susceptibility of mountain streams using GIS approach. The Erosion Hazard Index(EHI) was introduced to identify the potential of the denuded torrential stream. EHI values of streams can be derived from watershed characteristics, landuse, soil, and stream morphology. GIS-based EHI map for the study area was developed in this study. Field survey was also conducted to investigate bankfull depth and width, stream gradient, and streambed material of the stream. A total of 39 streams were selected to examine the relation between EHI and hydrologic, hydraulic, morphological characteristics of the watershed. Results showed that the close relationships between the EHI values to length of the main stream, watershed area, and stream slope of the study area.

Tree biomass and carbon stock of a community-managed mangrove forest in Bohol, Philippines

Leni D. Camacho,Dixon T. Gevana,Antonio P. Carandang,Sofronio C. Camacho,Edwin A. Combalicer,Lucrecio L. Rebugio,윤여창 한국산림과학회 2011 Forest Science And Technology Vol.7 No.4

Mangrove plays a significant role in climate change mitigation particularly in carbon absorption and minimizing the detrimental impacts of sea level rise, salt-water intrusion and tidal surges. In Bohol Province, Philippines, a small coastal island community known as Banacon is one of the successful cases in mangrove reforestation. Recognizing the site’s potential for a carbon sequestration project, a biomass and carbon stock assessment of mangrove trees was done. Using standard sampling techniques and allometric equations, tree carbon storage was measured across stand ages, namely 15-, 20- and 40-year-old plantations. Mature natural stands were also included in the assessment. By estimate, the 40-year-old plantation has the largest carbon density with 370.7 ton ha71, followed by the 15-year-old plantation with 208.5 ton ha71, 20-year-old plantation with 149.5 ton ha71, and lastly by natural stand with 145.6 ton ha71. Overall, Banacon mangroves are in a vigorous condition of storing vast amount of carbon. Local community and government should therefore sustain their commitment in coastal reforestation activities in order to enhance the mangrove carbon stocks. Policies and programs that can help provide incentives and livelihoods to local people who are largely dependent on mangroves should likewise be explored in order to sustainably reap the economic and ecological benefits of conserving mangrove forest.

Economic valuation for sustainable mangrove ecosystems management in Bohol and Palawan, Philippines

Antonio P. Carandang,Dixon T. Gevana,Leni D. Camacho,Josefina T. Dizon,Sofronio C. Camacho,Catherine C. de Luna,Florencia B. Pulhin,Edwin A. Combalicer,Floribel D. Paras,Rose Jane J. Peras,Lucrecio L. 한국산림과학회 2013 Forest Science And Technology Vol.9 No.3

The study used the total economic value as a framework for estimating the values of the different uses of mangroves in Palawan and Bohol, Philippines. Market surveys were conducted to estimate the revenues from the major mangrove products collected in the two study sites. Contingent valuation method and travel cost method questionnaires were used in the survey to determine the biodiversity and recreational values (in Philippine pesos or PHP). Results of the market survey showed that the highest direct use value per year was estimated for Banacon site in Bohol with PHP 33.368 million per year as compared to Kamuning site in Palawan (PHP 25.521 million). The highest value of benefit for Banacon came from crab catch with PHP 13.23 million. Mollusk catch gave higher benefits to Kamuning, amounting to PHP 17.65 million. In terms of the values of benefits from shrimp and fish catch, the values for Banacon were higher than those in Kamuning site (PHP 8.06 million and PHP 6.38 million, respectively for Banacon, and PHP 4.32 million and PHP 0.16 million, respectively, for Kamuning). Nipa thatch was the source of the third highest value of benefit for Kamuning amounting to PHP 2.42 million. The result of the contingent valuation analysis done (combining the data sets from Palawan and Bohol) using a least-squares method (i.e., bid function approach) showed a mean willingness-to-pay amount of PHP 44/month per individual. The different factors affecting the willingness to pay (25% level) include education, income and information (new). In terms of the recreation/ecotourism value of mangroves, the estimated values in Banacon, Bohol, and Kamuning, Palawan, were PHP 83,079 and PHP 2769, respectively.

Economic Implications of Different Management Opportunities in Makiling Forest Reserve (MFR), Philippines

( Leni D Camacho ),( Antonio P Carandang ),( Marilyn S Combalicer ),( Sofronio C Camacho ),( Dixon T Gevana ),( Yeo Chang Youn ) 한국산림경제학회 2011 산림경제연구 Vol.18 No.1

Opportunity costs incurred in devoting the areas of MFR to agroforestry, grassland and timber production and combinations of them as well as the willingness to accept incentives of farmers to promote conservation were evaluated using the Net Present Value approach and contingent valuation. The main goal of the study is to determine the economic implications of different management options in the Makiling Forest Reserve (MFR) in the Philippines. Economic linkages between the local people and the conservation program in the area were also assessed. In this study, it was found that the analysis of the different options for MFR indicates that the conservation of remaining natural forests in tandem with agroforestry in all open areas yielded the highest strewn of benefits. Therefore, appropriate strategies that would further integrate local economic concerns in agroforestry and natural forest conservation arc necessary. It is recommended that the local people and the government seek optimal management opportunities in the conservation of MFR by partnering in the further development, restoration, and protection of the reserve.