The status of Belitong Island as a UNESCO Global Geopark demands a deep understanding of the interactions between its geological heritage and the ecological systems that sustain it. A primary challenge is maintaining coastal stability against the pressures of climate change and historical land-use legacies. A 25-year quantitative analysis (2000-2025) of shoreline dynamics in two contrasting areas—Sijuk and Manggar—provides decisive empirical evidence of the key factor driving coastal resilience.
A Natural Comparative Test: Sijuk vs. Manggar
This research compared two coastal systems to isolate the impact of mangrove cover.
- The Control System (Sijuk): This area is characterized by a healthy and extensive mangrove ecosystem, with a stable forest cover exceeding 700 hectares. It serves as the baseline for a resilient coastal condition.
- The Impacted System (Manggar): This area exhibits a post-mining landscape with a degraded and fragmented mangrove cover of only around 400 hectares, representing a vulnerable coastal condition.
Using multi-temporal satellite data from the Landsat archive processed via the Google Earth Engine, shoreline changes in both locations were systematically measured to identify rates of erosion (land loss) and accretion (land gain).
Quantitative Findings: The Direct Correlation Between Mangroves and Coastal Stability
Comparative of Accretion Area of Mangrove Forest in Sijuk and Manggar (2000-2025).
Comparative of Erossion Area of Mangrove Forest in Sijuk and Manggar (2000-2025)
The data reveal a powerful and unambiguous correlation between mangrove health and shoreline dynamics.
- In Sijuk, Proven Resilience: The coastline with healthy mangroves demonstrated a dominant and sustained process of accretion. Analysis projects a net land gain of over 71 hectares by 2025. The rate of erosion in this area was minimal, recorded at less than 1.2 hectares over the same period, rendering it statistically insignificant. This proves that an intact mangrove ecosystem not only protects but actively builds and fortifies the coastline.
- In Manggar, Measured Vulnerability: Conversely, the degraded coastline experienced persistent, large-scale erosion on an escalating trend. Total land loss in Manggar is projected to exceed 32 hectares by 2025. This figure is orders of magnitude greater than the erosion in Sijuk, indicating severe instability and high vulnerability to wave energy and sea-level rise.
The Biophysical Mechanisms Behind Resilience
These findings are explained by two primary biophysical functions of mangroves:
- Energy Dissipation: The dense and complex mangrove root structure acts as a natural shield, effectively attenuating and absorbing wave energy, drastically reducing its impact before it reaches the shore.
- Sediment Trapping: The unique root system slows water flow, allowing sediment particles (mud and sand) to be deposited. This process gradually builds land elevation and promotes shoreline progradation (accretion).
The absence of this “green infrastructure” in Manggar leaves its coastline directly exposed to marine hydrodynamic forces, resulting in chronic erosion.
Critical Implications for Belitong as a UNESCO Global Geopark
These results compel a fundamental critical assessment for the management of Belitung:
- Resilience is Not an Abstract Concept: It is a quantifiable ecological function. This data demonstrates that investing in mangrove conservation and restoration is the most effective and measurable ecosystem-based adaptation strategy to protect the island’s geological and social assets.
- Environmental Legacies Carry Long-Term Costs: The degradation in Manggar is clear evidence that the environmental impacts of past extractive activities continue to create tangible vulnerability today. This underscores the necessity of integrating the full cost of ecological restoration into all future development planning.
- The Geopark’s Integrity Depends on Healthy Ecological Systems: Belitung’s geological uniqueness cannot be preserved in a vacuum. The Geopark’s long-term sustainability is contingent upon the health of functional ecosystems, like mangroves, that protect it from physical degradation. Mangrove protection is therefore not an option, but a prerequisite.
In conclusion, this analysis provides a robust scientific basis that mangroves function as the critical infrastructure determining the coastal resilience capacity of Belitong. Safeguarding Sijuk and rehabilitating Manggar is not merely an act of conservation; it is a strategic imperative for securing the ecological, social, and economic future of the island as a world-class Geopark.
The findings of this research were presented at the Young Forest Scientists Awards Program, hosted by the Asian Forest Cooperation Organization (AFoCO) in Seoul, Republic of Korea, 29-30 September 2025.
Correspondence Author: Kharisma Rinandyta