Remote Sensing of Tropical Rainforest Biomass Changes in Hainan Island, China from 2003 to 2018

Abstract

The largest area of tropical rainforests in China is on Hainan Island, and it is an important part of the world’s tropical rainforests. The structure of the tropical rainforests in Hainan is complex, the biomass density is high, and conducting ground surveys is difficult, costly, and time-consuming. Remote sensing is a good monitoring method for biomass estimation. However, the saturation phenomenon of such data from different satellite sensors results in low forest biomass estimation accuracy in tropical rainforests with high biomass density. Based on environmental information, the biomass of permanent sample plots, and forest age, this study established a tropical rainforest database for Hainan. Forest age and 14 types of environmental information, combined with an enhanced vegetation index (EVI), were introduced to establish a tropical rainforest biomass estimation model for remote sensing that can overcome the saturation phenomenon present when using remote sensing data. The fitting determination coefficient of the model was 0.694. The remote sensing estimate of relative bias was 2.29%, and the relative root mean square error was 35.41%. The tropical rainforest biomass in Hainan Island is mainly distributed in the central mountainous and southern areas. The tropical rainforests in the northern and coastal areas have been severely damaged by tourism and real estate development. Particularly in low-altitude areas, large areas of tropical rainforest have been replaced by economic forests. Furthermore, the tropical rainforest areas in some cities and counties have decreased, affecting the increase in tropical rainforest biomass. On Hainan Island, there were few tropical rainforests in areas with high rainfall. Therefore, afforestation in these areas could maximize the ecological benefits of tropical rainforests. To further strengthen the protection, there is an urgent need to establish a feasible, reliable, and effective tropical rainforest loss assessment system using quantitative scientific methodologies.

Crown Structure Metrics to Generalize Aboveground Biomass Estimation Model Using Airborne Laser Scanning Data in National Park of Hainan Tropical Rainforest, China

“…Hainan Island is rich in rainfall, rivers, and hydrological resources. Therefore, monitoring and recording an inventory of aboveground biomass of the island is beneficial to sustaining biodiversity, forest management, forest resources development, and the tourism industry [19,20]. The study area covers about 4900 km 2 , which is one-seventh of the area of Hainan Island.…”

Challenges and Opportunities in Aligning Conservation with Development in China’s National Parks: A Narrative Literature Review

“…Out of the 261 articles returned by our initial literature search, we identified 19 articles that focus on the interface between conservation efforts and local stakeholders in HTRNP (Table 3). These studies generally portray the park's primary ecological priority as preserving Hainan's rainforests (14 papers), specifically by conserving biodiversity [67] and protecting the source areas of the island's major rivers [68]. The literature places particular emphasis on HTRNP's role in protecting the remaining population of the endangered Hainan gibbons (5 papers).…”

“…The literature shows that locals living near HTRNP tend to have low income levels [4,83] and to rely on land-intensive economic activity for their livelihoods, including the cultivation of rubber plantations, crop farming, and livestock rearing [83]. Researchers have documented ecological damage resulting from unsustainable practices by locals (5 papers), including planting monoculture crops [20], and cutting into forest land to expand the land area occupied by private homes and associated economic activities [67]. Rainforest land has also been logged to create space for farmland and rubber plantations, the latter of which tends to damage critical ecosystem services such as soil retention and flood prevention [4].…”

Quantitative Assessment of Factors Influencing the Spatiotemporal Variation in Carbon Dioxide Fluxes Simulated by Multi-Source Remote Sensing Data in Tropical Vegetation

“…As a tropical forest area, Hainan Island (HN), China, boasts a large amount of wellpreserved tropical rainforests and abundantly planted forests, exhibiting a strong carbon sequestration capacity [30]. However, tourism pollution and rapid development have led to land desertification and water eutrophication, posing significant threats to the island's ecological environment [31].…”