Can the Ecological Redline Policy Conserve Mangrove More Effectively? Assessment on the Coverage and Carbon Storage in Mangrove of Southern China

Abstract

Mangrove ecosystems are famed for their crucial ecological functionalities in moderating the global carbon cycling process. In 2017, the Chinese government implemented the Ecological Redline Policy (ERP) nationwide to protect various ecological functions. However, there is a lack of multi-temporal, high-resolution spatial studies evaluating the effectiveness of ERP in mangrove protection, which hinders sustainable mangrove management. This study focuses on mangroves in Guangdong Province, China, which has the most extensive mangrove distribution in the country, during 2013, 2017, and 2021 using Landsat-8 OLI images (30 m). Field surveys provided data on floral components, forest structure, and biomass of mangrove sites. Subsequently, we assessed the current storage of blue carbon in mangroves using an InVEST Carbon Storage and Sequestration model. Additionally, we estimated the future capacity of blue carbon storage and sequestration under different scenarios of mangrove management. The results revealed a total increase of 2094 ha in mangrove area, with approximately 65.2% of mangroves currently included in the ERP zoning plan. Compared to the Non-Redline zone, the mangrove increment under ERP was higher (1365.55 ha) but with a lower growth rate (20.7%). Conversely, the Non-Redline zone exhibited an increment of 729.32 ha with a growth rate of 38.3%. Furthermore, around 80.0% of carbon storage in mangroves was managed within ERP zones, where the biomass and carbon per unit were at least twice as high as those in the Non-Redline zone. The study suggested that the prevailing ERP planning in China could substantially enhance the function of blue carbon sequestration in mangroves. However, it was evident that the current ERP does not fully meet strategic needs, and it also highlighted the need for optimized planning to minimize tradeoffs between environmental quality and development.

Keywords: mangrove, Ecological Redline Policy, conservation, function