Sustainability of mangrove forest management in the former bauxite mining area on Bintan Island

Location of study

The research was carried out from June to November 2021 in Bintan Regency (Tembeling Tanjung and Wacopek Villages) and Tanjungpinang City (Senggarang Village and Air Raja Village) as presented in Figure 1. The location of the former bauxite mine is visible with reddish-yellow land openings with Mangrove ecosystem still found around the area. The sampling area is around the former bauxite mining area or outside the bauxite mining area.

Figure 1. Map of research sites on Bintan Island.

Data collection

The data used in this study include primary and secondary data. Primary biophysical data were obtained directly through field observations, while economic, social, institutional, and technological data were obtained using a Focus Group Discussion (FGD) involving 17 respondents. The selection of key respondents was carried out using a purposive sampling technique, namely experts in the field such as the village head/Lurah, community leaders, community organizations, and the government. Secondary data were obtained from the Tanjungpinang City Government, Bintan Regency, and related literature. The dimensions and attributes of the analysis on the sustainability of mangrove forest management on Bintan Island are presented in Table 1.

Data analysis

Sustainability analysis was carried out via the MDS (multidimensional scaling) approach using the software RAPFISH (Rapid Appraisal for Fisheries) 1.0⁸ which was modified into RApMEc (Rapid Appraisal for Mangrove Ecosystem) to evaluate the sustainability of mangrove forests in multidimensionality. The assessment of each attribute in Table 1 is based on categories/criteria/quality standards according to expert opinion/laws and regulations. Scores are given with a range of 0 (poor) to good (2 or 3). The sustainability index value of each dimension can be visualized in the form of a kite diagram and analyzed multidimensionally to determine the point or position of the sustainability of mangrove forest management. The grouping of sustainability index values is presented in the range of 0 (bad) to 100 (good), which consists of 0-25 (bad), 25-50 (poor), 51-75 (enough), and 76-100 (good).⁹ Leverage analysis was used to determine the leverage factor while Monte Carlo analysis was used to see the effect of errors in the scores of each attribute.¹⁰

Environmental conditions of the former mining area on Bintan Island

Bauxite mining activities on Bintan Island have continued to grow, reaching 1.1 million metric tons in 2013 and 1.6 million metric tons in 2019.¹ The general characteristics seen in ex-bauxite mining areas include severe land damage, missing soil layers, and a soil structure, texture, and density that does not support the development of root systems, thereby interfering with plant growth.¹¹ Pollutants detected in bauxite mines on Bintan Island typically include minor elements, namely Fe and Mn. In addition, the trace elements found in the area include Cu, Cr, Cd, Pb, Ni, and Zn. The reported values obtained from the analysis of metal contents in the area indicated non-compliance with the environmental quality standard.¹² The results from the previous study¹³ showed that the environmental conditions around the former bauxite mining area on Bintan Island are not polluted but have been contaminated with heavy metals from mining activities. The conclusion was derived based on the Pollutant Load Index (PLI) value which was <1 for Pb and Cr, and the Geo-Accumulation Index (I_geo) which was 0<I_geo<1 for Pb and Cr. On the other hand, it was reported that the sediment fraction in Carang River, Tanjungpinang City is dominated by sand (74.65-97.7%), while the Tembeling Tanjung and Wacopek in Bintan Regency are dominated by gravelly sand to slightly gravelly sand.¹⁴ And also the survey results and sediment analysis,¹³ the sediment fraction is dominated by sand and silt. This type of fraction is still classified as suitable for mangrove life, as evidenced by the results of observations in the field of mangrove life conditions that mangrove density is still found which is classified as rare to very dense. The environmental parameters assessed in the attributes include water quality based on the level of water pollution Quality standards used for the needs of marine biota.

Mangrove biophysical condition

The survey¹³ found 11 mangrove species at the site, namely Avicennia alba, A. marina, Rhizophora apiculata, R. mucronata, Ceriops tagal, Bruguiera gymnorhiza, B. cylindrical, Sonneratia alba, Xylocarpus granatum, X. mollucensis, and Lumnitzera littorea. The most dominant species were R. mucronata, R. apiculata, and A. marina with mangrove density values classified as moderate (1300 trees/Ha) to damaged (678 trees/Ha). Assessment of the damage level in mangrove trees revealed that 43.5% of the trees in the samples were found damaged with the remaining 56.5% found as healthy. The mangrove tree species with the largest Significance Index determined in the tree, sapling, and seedling strata was R. mucronata.

Based on the results from a study,¹³ the accumulation of heavy metal, Pb, in the sediment was found between 0.06 and 0.24 ppm. Besides, the concentration of Pb found in the leaves of R. mucronata was between 0.04 and 0.37 ppm, 0.05-0.71 ppm in the stems, and 0.08-0.87 ppm in the roots. On the other hand, the concentration of Cr in sediment was found between 0.01 and 0.04 ppm, with the concentration of Cr in the leaves of R. mucronata found between 0.02-0.09 ppm, 0.01-0.09 ppm in the stems, and 0.01-0.10 ppm in the roots.

Sustainability index

A Sustainability Index of 52.48 was obtained from an analysis using RApMEc, which was carried out based on 27 attributes. This value reflects the sustainable management of mangrove forests in the former bauxite mining area in a multidimensional manner. Sustainability index values for each dimension, stress value, and R² are presented in Table 2.

Table 2 shows that the small difference between the index values obtained from the MDS analysis and that of the Monte Carlo analysis indicates the relatively small scoring errors, relatively small variation in opinions, a stable repeated analysis process, and errors in data entry or lost data can be avoided. The results confirmed the validity of the MDS used in assessing the sustainability of mangrove forest management on Bintan Island. The validity of the results obtained from the MDS analysis was also demonstrated by the Goodness of Fit value, which was represented by the stress value and the coefficient of determination (R²) at the 95% confidence level. Table 2 shows that the stress value was less than 0.25 and the R² value was close to 1, demonstrating the statistically valid results obtained from the analysis and the sufficient number of attributes used which represented the actual condition adequately. The attributes used in the analysis were sufficient to assess the sustainability of mangrove forests, whereby the results demonstrated a high level of confidence in the RApMEc analysis. The multidimensional sustainability indices are shown in Figure 2.

Figure 2. Kite diagram of the five dimensions of RApMEc showing the mangrove management status score.

The sustainability of the ecological dimension is an indicator of the biophysical sustainability of mangrove forests related to environmental aspects such as physical, chemical, and biological. A sustainability index of 69.94 was obtained for the ecological dimension indicating quite a sustainable management in this aspect. This finding also demonstrates that the ecological dimension is sufficient to prove the sustainability in the mangrove forest management around the former bauxite mining area on Bintan Island. On the other hand, the leverage analysis revealed the five attributes related to the sustainability of the ecological dimension, namely 1) mangrove density, 2) substrate fraction, 3) sedimentation, 4) mangrove importance value index, and 5) metal bioconcentration factor. These attributes are presented in Figure 3. The environmental conditions around the former bauxite mining area are classified as uncontaminated but already contaminated by heavy metal content.¹³ This assessment is obtained from the calculation of the geoaccumulation index as the level of water pollution and environmental pollution load. However, based on the health level of the mangroves, it is classified as experiencing mild to moderate damage, with the sources of damage being roots (21%) as well as roots and lower stems (17%).¹³

Figure 3. Leverage of sustainability attributes ecological dimension.

The density level of various mangrove tree species deserve attention and should ideally be increased because they greatly affect the health of the mangrove forest, and consequently, the sustainability of the mangrove forest ecosystem on Bintan Island. Although the emergence of seedlings and saplings has been reported in the area, the Important Value Index indicates a disturbance in the mangrove community.¹³ The growth of mangrove seedlings and saplings must be preserved to maintain the availability of seeds for mangrove forest regeneration.

Sedimentation that occurs around the former bauxite mining area has been reportedly low. Sedimentation has resulted in the formation of red mud sediment in the mangrove area, indicating a very low organic content in the soil. Therefore, it is necessary to prevent the rate of erosion and sedimentation so the quality of the water and sediments in the former bauxite mining area can be improved, which consequently supports the life of the surrounding mangroves.

Based on the results from the analysis of the Bioconcentration Factor (BCF), it was found that R. mucronata and A. marina can absorb heavy metals, namely Pb and Cr present in the environment. Although the metal accumulation value was reportedly low, a test on the metal absorption mechanism revealed that R. mucronata is a hyperaccumulator of metals while A. marina was found the opposite.¹³ The BCF revealed the potential use of mangrove species for the accumulation of heavy metals from the former bauxite mining area to eliminate pollution.

A value of 17.62 was obtained to represent the sustainability status of the mangrove forest around the ex-bauxite mining area on Bintan Island, indicating unsustainability (bad). This value demonstrates that the management of mangrove forests around the former bauxite mining area has been experiencing pressure from an economic standpoint. This pressure could be due to the poor ability of mangrove natural resources and the surrounding ecosystems to provide environmental benefits and services. The results obtained from the leverage analysis showed that all attributes are the levers that require attention in the management of mangrove forests. The graph of economic dimension leverage is presented in Figure 4.

Figure 4. Leverage analysis of sustainability attributes in the economic dimension.

The values obtained for direct and indirect benefits of mangrove forests around the former bauxite mining area revealed that the current utilization of mangrove forests is not optimal.¹² Therefore, there is an immediate need to increase the economic value of mangrove forests, either directly or indirectly, so that people can also benefit from healthy mangrove forests. The status of the mangrove forest area around the former bauxite mining area does not prohibit its development based on usefulness values, especially for fisheries and environmental services.¹⁶

The dependence of the community around the mangrove forest is still very low as some people choose to be entrepreneurs. Fishermen are the only group of people in the community whose livelihood depends on mangrove forests. Moreover, the community does not view the mangrove forests as an asset in supporting their household economy. Awareness of the importance of mangrove forests must be raised so the community can benefit from the forests economically, either directly or indirectly.

Currently, the mangrove forest rehabilitation activities have mostly been funded by the CSR organizations located on Bintan Island such as the Ecology Foundation and Banyantree, PT. Various Mines. To date, such support still prevails on the island but is not yet optimally available. Furthermore, the support from CSR funding also influences the sustainability of mangrove forests on Bintan Island in terms of economic dimension. When funding is available, the management and utilization of mangrove forests by the community and the authority will run well.¹⁵

To improve the sustainability of the economic dimension in the mangrove forest management around the former bauxite mining area on Bintan Island, it is important to develop the economic values of the mangrove forests for community use and plan for integrated mangrove forest rehabilitation activities with various parties. The attribute of community dependence on the role of mangrove forests as a source of livelihood can be used as social capital to encourage communities to participate in the sustainable management of mangrove forests.^16–18

A value of 65.40 obtained from the analysis of the sustainability status of mangrove forests based on the social dimension indicated sustainability in the management. The level of public health and public perception of mangrove management were the two attributes that are sensitive and can greatly affect the social dimension. The graph of the leverage identified in the social dimension is presented in Figure 5.

Figure 5. Leverage attributes in the social dimension.

The level of public health and public awareness in the management of an area are both very important for the success of any efforts in managing the area. The perception of the coastal community greatly determines the level of understanding among the community about the importance of the mangrove area and its sustainable management for the survival of the community.^19–22

A value of 54.95 obtained from the analysis of the sustainability index for the legal and institutional dimensions indicated sustainability in the management. Based on the leverage analysis, only one of the five attributes, namely the legality of the mangrove forests and the bauxite mine was identified as the lever in the legal and institutional dimensions. The graph of the leverage is presented in Figure 6.

Figure 6. Leverage attributes legal and institutional dimensions.

The legality of mangrove forests and bauxite mining areas is necessary for resource management on Bintan Island. Within the mangrove ecosystem, many resources such as mangrove forests, fisheries, waters, and non-aquatic biota must be managed to ensure sustainability. In addition, Bintan Island is also rich in bauxite, one of the mineral resources.^23,24 The potential value of bauxite minerals can be exploited to support the economy of the locals. To avoid overlapping, it is necessary to make clear arrangements regarding area zoning, forms of utilization, and management efforts according to the laws or regional regulations. This attribute should be given great attention in the implementation of mangrove forest management policies, considering the influence of these attributes on the sustainability of the management of mangrove forest and ex-bauxite mining areas.

A value of 49.52 was obtained for the sustainability index of the technological dimension, indicating a lack of sustainability in the management. The value indicates the condition of the mangrove forest around the former bauxite mining area on Bintan Island, which is currently under pressure from the technological aspect. Based on leverage analysis, all attributes were identified as the levers. The chart of the leverage analysis is presented in Figure 7.

Figure 7. Leverage attributes in the technological dimension.

The technology for monitoring environmental pollution around the bauxite mining area is still inadequate in anticipating the impacts of erosion, abrasion, water quality degradation, and metal accumulation. Although the available mangrove rehabilitation technology is still simple, namely planting with a seed and fruit system and embroidery techniques, this technology has not been able to reduce threats that can reduce the factors and intensity of threats to the mangrove ecosystem around the former bauxite mining area on Bintan Island.⁶ One of the reasons is the absence of integration programs between local and central governments (cross-sector). In addition, the miners have also not practiced environmentally friendly mining techniques (good mining practice) as mining activities are still carried out with an open mining system without the implementation of any post-mining restoration efforts. These two in the technological dimension need great attention for the implementation of mangrove forest management policies to support the sustainability of mangrove forest management in the future.