BIOTROPIKA Journal of Tropical Biology
https://biotropika.ub.ac.id/
Vol. 11 | No. 3 | 2023 | DOI: 10.21776/ub.biotropika.2023.011.03.01 MANGROVE DENSITY MAPPING FOR SUSTAINABLE UTILIZATION AND MANAGEMENT IN KLAWALU MANGROVE TOURISM PARK, SORONG CITY
Thomas Frans Pattiasina1)*, Ihwan Tjolli2), Aplena Ellen Bless2), Krisma Lekitoo3) ABSTRACT
Data and information on resource utilization supported by vegetation mapping are the basis for developing a sustainable mangrove management strategy. This study aims to map the vegetation density and identify the use of mangroves by the community in the Klawalu Mangrove Tourism Park (Taman Wisata Mangrove Klawalu-TWMK) Sorong City. The satellite imagery used is Sentinel 2A level 1C. Image pre-processing includes atmospheric correction, geometric correction and image cropping. Determination of the extent and distribution of mangrove vegetation is carried out by applying the color composite method and mangrove boundary delineation. Mangrove vegetation density mapping was carried out by applying the Normalized Difference Vegetation Index (NDVI) method. Identification of the species and intensity of mangrove utilization was carried out through observation and interviews with respondents who were determined purposively.
Based on the results of the analysis, the total area of mangrove vegetation in TWMK and its mapped surroundings is 144.64 ha. Of this area, 69.01 ha (47.71%) is classified as very dense, 34.96 ha (24.17%) is classified as dense, and 24.23 ha (16.75%) is classified as moderate, 12. 94 ha (8.95%) is classified as sparse, and 3.5 ha (2.42%) is classified as very sparse. The intensity of resource utilization from the mangrove ecosystem is quite high, especially the utilization of mangrove wood and coral mining. Awareness/education efforts need to be continued, as well as alternative livelihood solutions to reduce the heavy dependence on mangrove resources.
Keywords: ecosystem, resources, ecotourism, livelihood, degradation
INTRODUCTION
Mangrove ecosystems are often referred to as brackish forests or mangrove forests, which are tropical forest types that typically grow along beaches or river mouths that are still affected by tides. The definition of a mangrove ecosystem, in general, is a tropical coastal vegetation community dominated by several species of mangrove trees that grow and develop in tidal muddy coastal areas [1, 2]. When compared to other forest ecosystems, mangrove ecosystems have high biodiversity and productivity [3, 4].
Mangroves have a very important function as providers of environmental services and to support the economy of the people around them.
As providers of environmental services, mangroves can prevent coastal erosion/abrasion, seawater intrusion, reducing pollutants from rivers before going to the sea, and provide places to live and breed various types of aquatic and terrestrial animals, and oxygen producers [5]. Meanwhile, as a support for the economy, mangroves have high economic value, namely as a raw material for charcoal, the presence of various biota with high selling value, and the characteristics of their ecosystem which are typical for nature tourism or educational tourism [6].
The mangrove ecosystem in Sorong City, West Papua Province, has provided ecological services as well as economic benefits for local
communities from generation to generation.
However, in line with the increase in population and development activities, which are generally concentrated in coastal areas, threats to the sustainability of mangrove ecosystems are becoming an important issue. Mangrove land conversion for various purposes, as well as excessive and uncontrolled use of mangrove forests, is a problem in mangrove management in Sorong City.
The Sorong City Government has done various efforts to preserve mangrove forests in the coastal areas of Sorong City. In May 2019, the Sorong City Government, in collaboration with the Ministry of Tourism and Creative Economy, inaugurated the Klawalu Mangrove Tourism Park (Taman Wisata Mangrove Klawalu - TWMK) in Sorong City, covering an area of 24.5 ha. The purpose of developing the TWMK in Sorong City is as a recreation facility in the form of ecotourism for the community and an effort to preserve the mangrove ecosystem. In order to support the government's efforts in managing the TMWK ecotourism area, scientific studies need to be carried out, including those related to the condition of mangrove vegetation in the area. This study aims to map the density of mangrove vegetation, as well as identify the type and intensity of utilization by the community as a
Submitted : November, 18 2023 Accepted : January, 9 2024
Authors affiliation:
1) Faculty of Fisheries and Marine Science, Univesity of Papua
2)Center for Environmental Research, University of Papua
2)Research Center for Plant Conservation, Botanic Gardens and Forestry, National Research and Innovation Agency
Correspondence email:
How to cite:
Pattiasina, TF, Tjolli I, Bless AE, Lekitoo K. 2024. Mangrove density mapping for sustainable utilization and management in Klawalu Mangrove Tourism Park, Sorong City. Biotropika: Journal of Tropical Biology 11 (3): 126-132.
database to support the management of mangrove ecosystems in the TWMK area of Sorong City.
METHODS
Study area. This research was conducted in January-February 2021 at the Klawalu Mangrove Tourism Park (Taman Wisata Mangrove Klawalu - TWMK) Sorong City, West Papua Province.
Geographically, TWMK is located at position 0°54'47.92" South Latitude and 131°18'27.39"
East Longitude. Administratively, this area is part of the Kelurahan Klawalu area, East Sorong District, located about 2 km southwest of the main road at km 12, Sorong City (Figure 1). TWMK is a new tourist destination built by the Sorong City Tourism Office. Mangrove vegetation in the area is a secondary forest vegetation. Mapping the distribution and density of mangroves in this study is not limited to TWMK locations; it also includes the area around TWMK to provide a broader picture of mangrove health conditions.
Satellite image pre-processing. Satellite imagery used in mapping the distribution and density of TWMK mangroves is Sentinel 2A level 1C imagery. Sentinel 2A has a Multi-Spectral Instrument (MSI) sensor with 13 spectral bands, of which four bands have a spatial resolution of 10 m, six bands have a resolution of 20 m, and three bands have a resolution of 60 m with a swept area of 290 km (Table 1). The pre- processing process includes atmospheric correction, geometric correction and image cropping. The histogram adjustment method is applied in atmospheric correction. The basic principle of this method is that the minimum value of each channel is used to reduce the pixel values so that the minimum pixel value is 0 (zero). The geometric correction method applied is Image to map rectification through a linear geocoding process to rectify the image into a datum and map projection using the ground control point (GCP) from the Indonesian topographical map. Accuracy information or the Root Mean Square Error (RMSE) value from the geometry correction results refers to SNI regarding map accuracy. Furthermore, image cropping is performed to limit the image only to the area under study.
Satellite image processing and vegetation density mapping. Satellite image processing and mangrove vegetation density mapping were applied according to [8] and [9]. This process begins with compiling the necessary color composites to facilitate image interpretation. For this Sentinel 2A image, the color composites that help display mangrove vegetation clearly are the
composites of band 8, band 11, and band 4. Band 8 is the NIR (near infrared) channel, band 11 is the SWIR (shortwave infrared) channel, while band 4 is the Red channel (red light). With this composite, mangrove vegetation will appear dark red. The next stage is to delineate the mangrove boundaries, where the result is a polygon map of the mangrove area in the TWMK area and its surroundings.
The Normalized Difference Vegetation Index (NDVI) vegetation index was applied to map mangrove density. NDVI is a mathematical combination between the red and near-infra-red (NIR) bands [10]. According to [8] and [10], the NDVI calculation formula is:
𝑁𝐷𝑉𝐼 = (𝐵𝑎𝑛𝑑 8 (𝑁𝐼𝑅) − 𝐵𝑎𝑛𝑑 4 (𝑅𝑒𝑑) (𝐵𝑎𝑛𝑑 8 (𝑁𝐼𝑅) + 𝐵𝑎𝑛𝑑 4 (𝑅𝑒𝑑) NDVI values range from -1 to 1. Low (negative) NDVI values identify areas of water bodies, rocks, and sand. The NDVI value representing vegetation is in the range of 0.1 to 0.7. If the NDVI value is above this value, it indicates a better level of health of the vegetation cover, while an NDVI value of 0 generally indicates empty land. Next, the determination of the mangrove density value uses the NDVI calculation results. The NDVI class values were then reclassified quantitatively into five (5) classes, namely very dense, dense, moderate, sparse and very sparse. The calculation of density class intervals is based on the following formula [11]:
𝐶𝐼 = (𝑚𝑎𝑥 − 𝑚𝑖𝑛) 𝐶 where:
CI = Class interval max = Maximum value min = Minimum value
C = Number of classes required The result of this process is visualized in a map of the vegetation density classification in the TWMK area and its surroundings. This map is then superimposed with a polygon map of the mangrove area in the TWMK area and its surroundings. The result is a special density map of mangrove vegetation in the TWMK area and its surroundings.
Collecting and analyzing mangrove utilization data. Interview and observation methods were applied in field surveys to take inventory of mangrove utilization activities by the community. The selection of respondents as the research sample was carried out purposively, with the consideration that the respondents were
Table 1. Band, wavelength and spatial resolution of Sentinel-2 imagery [7]
Sentinel-2 Band Wavelength (µm) Spatial Resolution (m)
Band 1 - Coastal aerosol Band 2 - Blue
Band 3 - Green Band 4 - Red
Band 5 - Vegetation Red Edge Band 6 - Vegetation Red Edge Band 7 - Vegetation Red Edge Band 8 - NIR
Band 8A - Vegetation Red Edge Band 9 - Water vapour
Band 10 - SWIR – Cirrus Band 11 - SWIR
Band 12 – SWIR
0.443 0.49 0.56 0.65 0.705
0.74 0.783 0.842 0.865 0.945 1.375 1.61 2.19
60 10 10 10 20 20 20 10 20 60 60 20 20 specific so that the determination had to be made
purposively. Respondents are people who directly use the mangrove forest in TWMK, and other respondents are visitors to TWMK who generally live in the Sorong Raya area. The number of respondents interviewed was 24 people, consisting of 15 respondents who were active around TWMK and nine respondents who were visitors to TWMK (tourists). In collecting data, key informants were also used, namely TWMK officials or managers. Data analysis was carried out using a descriptive approach to describe conditions, potentials, and patterns of utilization of mangrove forest resources, as well as community costs, revenue, and income from each resource utilization activity in the mangrove ecosystem.
RESULTS AND DISCUSSION
Mangrove distribution and density. In general, the mangroves around the TWMK location are spread southward from the direction of the big river towards the land until they reach a maximum distance of about 1.4 km. The mangrove vegetation is spread around the two small rivers and even covers the area around the two small rivers. As illustrated in the map in Figure 2 below, mangrove vegetation cover classified as very dense is found in the southern part, bordered by large rivers, all the way to the land in the east. On the other hand, dense and moderate mangrove vegetation is found in the middle part of the road in the north and the big river in the south, and partly in the small river on the east side. Meanwhile, the condition of mangrove vegetation cover, which was sparse and very sparse, is found between or on the sidelines of dense and moderate vegetation.
The area of mangroves in TWMK and its surroundings, which is mapped, is 144.64 ha. Of this area, 69.01 ha (47.71%) is classified as very dense, 34.96 ha (24.17%) is classified as dense,
and 24.23 ha (16.75%) is classified as moderate.
Meanwhile, the mangrove area of 12.94 ha (8.95%) is classified as sparse density, and 3.5 ha (2.42%) is classified as very sparse (Figure 3).
Even though the proportion of very dense vegetation cover is higher than the other classes, attention must be paid to the sparse and very sparse density classes, which, combined with the moderate class, have reached around 31% of the mapped mangrove area. By means of unwise and uncontrolled utilization, it can be predicted that this percentage will increase rapidly in a short period.
Utilization of mangroves by the community.
The utilization of the mangrove forest ecosystem around TWMK Kota Sorong by the local community consists of 3 categories of utilization, namely, (1) utilization of forest products in the form of firewood; construction wood, flagpoles wood or banners, nipah roofing; (2) utilization of fishery products, namely crabs, shellfish (bia); (3) utilization of other resources in the form of corals.
Among these forms of utilization, the largest proportion is the collection of coral (28.09%), followed by the taking of wood for construction (26.21%) and firewood (14.64%). On the other hand, the smallest proportions were catching mangrove crabs, using them for roofing and collecting shells (Table 2). The use of mangroves by the people around TWMK has been going on for a long time. In utilizing mangrove forests, there are those who work or take them individually and those who work in groups. This group work usually occurs when a large quantity of wood or coral is received or when a buyer requires it to be provided as soon as possible.
The intensity of utilization of mangrove wood and coral reefs is quite high. This is shown by collecting mangrove wood and digging corals, which occur almost every day. In addition, there are times when buyers come and/or order in advance according to the amount needed.
Figure 2. Map of mangrove distribution and density in TWMK and surrounding areas
Figure 3. Percentage of mangrove area in the TWMK and surrounding areas by density class
The average price of firewood is Rp. 600,000 per truck, while the price of coral is Rp. 700,000 per truck. The price of construction wood is Rp.
30,000 per stick. Meanwhile, small-size wood costs Rp. 15,000 per stick. This type of wood is generally used for flagpoles or banners. Thus, this size is in very high demand ahead of the Independence Day celebrations in August.
Based on field observations, locations with sparse and very sparse mangrove vegetation cover are locations where mangrove exploitation is relatively high by the local community (Figure 2).
At these locations, mangrove tree felling and coral reef extraction activities occurred. At these locations, there are also houses made of wood and tarpaulin, which serve as resting places for the community when carrying out mangrove logging and coral mining activities. The results of felled
mangrove wood and coral are sold in several locations in Sorong City (Figure 4).
Intense mangrove exploitation activities in the TWMK mangrove area and its surroundings are made possible by easy access to the mangrove area. The map in Figure 2 shows that the mangrove area is bordered by densely populated settlements to the east and is only about 100 meters away. Based on observations in the field, apart from roads that pass through the mangrove area, the community can easily enter the area by boat through small rivers or narrow canals, especially at high tide. The existence of communities around mangroves affects the level of utilization of existing resources in mangrove ecosystems. The greater the population living around the mangrove area, the greater the rate of deforestation and damage to the mangrove ecosystem [12, 13].
Table 2. The benefit value of the mangrove forest ecosystem around TWMK
No. Utilization Type Revenue per
Month (Rp) Total cost per month (Rp) Net income per month (Rp) Percentage (%)
1 Firewood 1640,000 25,841 1,614,159 25.27
2 Flagpole wood 961,000 25,841 935,159 14.64
3 Construction wood 1,700,000 25,841 1,674,159 26.21
4 Nipah roof 150,000 25,841 124,159 1.94
5 Coral for construction 1,820,000 25,841 1,794,159 28.09
6 Crab 30,000 25,841 4,159 0.07
7 Shellfish 266,667 25,841 240,826 3.77
Total Benefits 6,567,667 180,888 6,386,779 100
Source: Results of field data analysis
Figure 4. (A) Location of mangrove logging & coral reef collection; (B) Example of mangrove cutting; (C &
D) Results of felling and taking of coral; (E) Location of selling mangrove wood in Sorong City (Source:
field survey documentation)
Mangroves in Indonesia are generally under the authority of the government, where in the view of the community, mangroves are open access, so in conditions of easy access, mangroves will be used uncontrollably. This makes mangroves vulnerable to degradation [14].
Over-exploitation that causes mangrove degradation in the study locations also occurs in other areas in Indonesia. Over-exploitation of mangroves in Indonesia has been going on for a long time. Mangroves in Indonesia have been systematically exploited since 1800. The exploitation of mangroves is mainly for the purposes of cultivating brackish water shrimp and for the use of wood. Around the end of the 1960s, it was estimated that there had been loss of mangroves in Indonesia of more than 200,000 ha, most of which were in the western part of Indonesia, especially in Java and Sumatra. The drastic increase in mangrove loss began in 1970 when mangrove exploitation shifted to other areas outside Java and Sumatra [15]. Deforestation and mangrove degradation are mainly influenced by the rapid growth of the human population in
coastal areas, increasing human needs, limited employment opportunities and public knowledge and perceptions of mangrove ecosystems [16, 17, 18].
As the findings from this study show that the damage and degradation of mangroves is caused by excessive and unwise use by the community, awareness and education efforts for the community must be given top priority. The TWMK tourist area must function as a means of counseling and learning for the community, especially the younger generation, to foster their love for the mangrove ecosystem. TWMK can also function optimally as a forum for developing alternative livelihoods to reduce dependence on the use of mangrove ecosystems. If the community already has the right understanding about the importance of protecting and preserving mangrove forests, and getting economic support for their lives, then the objectives of mangrove conservation efforts, namely sustainable mangroves and their sustainable services for present and future generations, will undoubtedly be achieved.
CONCLUSION
The percentage of mangrove areas that belong to the very dense and dense vegetation class category is higher than the other density classes.
Even so, the area of mangroves belonging to the very sparse, sparse and moderate density class category has covered around 31%. The intensity of resource utilization from the mangrove ecosystem is quite high, especially the utilization of mangrove wood and coral mining.
Awareness/education efforts need to be continued, as well as alternative livelihood solutions to reduce the heavy dependence on resources from the mangrove ecosystem.
ACKNOWLEDGMENT
This research is part of the program “Study of Mangrove Biodiversity and Preparation of Educational Materials for Mangrove Ecosystems in the Klawalu Mangrove Tourism Park (TWMK), Sorong City, West Papua Province”, which is a collaboration between the Center for Environmental Research (PPLH) University of Papua Manokwari and Conservation International Indonesia (CII). We express our gratitude to the Sorong City Government, in particular the Sorong City Tourism Office. Appreciation is also conveyed to Mr. Agustinus Howay and his son.
who have assisted in the field survey activities.
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