Heshan Lin

Fujian has one of China’s most tide-dominated and heavily engineered coasts, yet no segment-scale vulnerability assessment exists. We assessed 2449 km of mainland shoreline in 1 km segments using the classic six-variable coastal vulnerability index, from public data. Change rates came from thirty annual Landsat-based shorelines, giving a complete index for 2293 segments. The very high vulnerability class (defined by provincial quartiles) is predominantly concentrated in Putian (51.9 percent) and Quanzhou (42.8 percent). Those differences follow shoreline type. Eighty percent of the remaining 115 km of sandy shore is very high, against 53 percent of rocky shore in the low class. An exact decomposition gives each segment a dominant contributor from tide in Ningde to waves in Zhangzhou. Thirty percent of the 1.70 million people within 1 km of the coast live behind the very high quarter. Eleven sensitivity runs move individual segments, but none breaks the link to shoreline type, and Putian and Quanzhou lead even without the rate variable. The two published conventions for scoring tidal range rank different prefectures first, and each matches a different hazard. The storm-framed convention leads with Zhangzhou, where 99.7 percent of the province’s 2020 storm-surge damage fell.

Satellite-derived shorelines (SDS) reconstruct storm-scale beach change, but their accuracy degrades on macrotidal coasts. The prevailing storm-response and recovery framework, moreover, was built on microtidal, swell-dominated coasts. We combine CoastSat multi-mission shorelines (Sentinel-2, Landsat 7–9, 2015–2026) with EOT20 tidal correction, data-driven slope inversion and an expert-in-the-loop beach registry at five sites on the macrotidal (4–7 m) coast of Fujian, China, validate them against 19 sub-metre reference waterlines (18 yielding paired offsets), and apply them to 19 typhoons. Validation resolves the SDS error into a structure: unbiased near mean sea level, a slope-scaled landward bias of ~7–45 m toward low tide, and undefined below a beach-face/low-tide-flat break near −1.5 m, motivating a tide-gated protocol that cuts series scatter to 7–19 m. Typhoon retreats (median 15–16 m) vary systematically with landfall and embayment geometry, whereas offshore wave metrics and backshore hardening show no consistent event-scale control. Recovery is gated by the monsoon calendar: half-restored within weeks in summer, arrested through the northeast monsoon, and completed only the following March–June. This departs from the exponential recovery of mid-latitude coasts. The protocol and event catalogue provide a template for other macrotidal, typhoon-exposed coasts.

Digital elevation models (DEMs) are foundational for critical tasks such as flood inundation simulation, disaster risk assessment, and ecosystem monitoring in coastal zones, yet their vertical accuracy is significantly compromised by complex terrain and surface characteristics. This study quantitatively decomposes the vertical errors of three 30 m global DEMs (COP30, NASADEM, and AW3D30) across the subtropical coastal region of Southeast China using ICESat-2 ATL08 data as a reference. By integrating an eXtreme Gradient Boosting (XGBoost) model with SHapley Additive exPlanations (SHAP), we successfully decoupled systematic biases from random noise. The results show that NASADEM achieved the lowest RMSE (7.775 m), followed by COP30 and AW3D30. While the Terrain Ruggedness Index (TRI) and categorically encoded Land Cover were identified as the universally dominant error drivers across all datasets, explainable analysis revealed distinct secondary mechanisms: X-band COP30 is notably susceptible to canopy height, exhibiting significant positive bias in forests exceeding 15 m; C-band NASADEM shows a systematic bias related to topographic position, typically overestimating ridges and underestimating valleys; and optical AW3D30 is significantly affected by stereo-matching errors. Furthermore, the analysis quantified a systematic error component of ~40%. These findings provide a data-driven basis for DEM selection and highlight that accuracy improvements should prioritize vegetation removal for radar DEMs and enhanced stereo-matching for optical models.

Accounting for Gross Ecosystem Product (GEP) is a crucial approach for quantifying ecological value, assessing the contributions of ecosystems to human well-being, and supporting sustainable development decision-making. For the Pingtan Comprehensive Experimental Zone, an island-centered administrative region, we developed a GEP indicator system and accounting framework tailored to islands for integrated accounting of terrestrial and marine ecosystems. We used a functional value approach that combines biophysical models with statistical data and conducts physical and monetary accounting in two steps. The accounting methods and procedures were refined to exclude resource and labor inputs from production processes and eliminate external contributions. From 2015 to 2023, the GEP increased by 9.118 billion CNY, representing an increase of 133.03%. The total GEP exhibited a phased rapid–slow–rapid fluctuation pattern over time. The value structure shifted from being dominated by material supply services to being dominated by cultural services. The high-value areas of flood regulation exhibited a clear expansion trend, whereas water conservation and climate regulation showed a fragmented decline. Carbon sequestration, oxygen release, and soil retention remained relatively stable. The findings support evaluating the effectiveness of ecological conservation, implementing ecological compensation, and formulating sustainable development policies in the Pingtan Comprehensive Experimental Zone.

As an indispensable part of the marine ecosystem, the health status of the sea affects the stability and enhancement of the overall ecological function of the ocean. Clarifying the future land and sea utilization pattern and the impacts on the carbon stocks of island ecosystems is of great scientific value for maintaining marine ecological balance and promoting the sustainable development of the island ecosystem. Using Pingtan Island as an example, we simulate and predict changes in island utilization and carbon stocks for historical periods and multiple scenarios in 2030 via the PLUS-InVEST model and the marine biological carbon sink accounting method. The results show that (1) from 2006 to 2022, the carbon stock of Pingtan Island decreased by 7.218 × 10⁴ t, resulting in a cumulative economic loss of approximately USD 13.35 million; furthermore, from 2014 to 2018, the implementation of many reclamation and land reclamation projects led to a severe carbon stock loss of 6.634 × 10⁴ t. (2) By 2030, the projected carbon stock under the three different policy scenarios will be greater than that in 2022. The highest carbon stock of 595.373 × 10⁴ t will be found in the ecological protection scenario (EPS), which will be 4.270 × 10⁴ t more than that in 2022. With the strong carbon sequestration effect of the ocean, the total social carbon cost due to changes in island utilization is projected to decrease in 2030. (3) The factors driving changes in island utilization will vary in the design of different future scenarios. The results of this study not only provide a solid scientific basis for the sustainable development of island areas, but they also highlight the unique contribution of islands in the field of marine ecological conservation and carbon management, contributing to the realization of the dual-carbon goal.

With the acceleration of urbanization and industrialization, regional development is becoming increasingly disordered. Thus, how to balance economic development and ecological protection is a key question. To comprehensively evaluate land development suitability, an evaluation index system for construction land and farmland suitability was established in this study based on natural and social-economic information. After selecting an island in China as the main case study in this work, the reference method was applied in grading and value assigning for all indices. In addition, the analytic hierarchy process and expert evaluation method were used to determine the index weighting. After scenario analysis was adopted in the study to analyze the impact of the policy orientation on the suitability evaluation, we finally evaluated the landscape ecological quality of different scenarios. Results showed the landscape ecological quality of a coordinated development scenario was the highest. The results indicated that coordinated development which takes the ecological protection and urban development into account may be a better choice for land planning.