“One foot on the land, the other in the sea.” Such are the amazing amphibious plants that thrive in mangroves among the intertidal zones of the tropical and subtropical coasts. Their well-developed root systems and tenacious resistance to severe weather position them as “forest sentinels”, protecting the safety and offshore biodiversity of our coastlines. As an important component of coastal wetland ecosystems, mangrove wetlands play critical roles in decontaminating water of pollutants and urban waste, supporting biodiversity, maintaining food chains in estuarine coasts, sustaining offshore fisheries, promoting siltation, sheltering shorelines, sequestering carbon, and abating climate change. Threats to mangroves have multiplied in recent years, often exacerbated by human influences: influxes of sewage and other pollutants, invasions of alien species, expansions of aquaculture and construction of ports, and disruptions in the natural balance of water and salt in coastal inlets and seas. Coupled with long-term overuse of mangrove resources, these threats have caused the area of mangroves in China to plummet. Many mangrove species have become endangered, entering into an unprecedented period of crisis.
One group of scientists at Tsinghua University works day after day in the mud and the sea breeze, striving to better understand the mangrove forests and counter these emerging threats to their existence. These scientists are members of Professor Lin Guanghui’s research group in the Department of Earth System Science. As the 22nd “World Wetlands Day” (February 2) approaches, we take a moment to share their stories.
Prof. Lin Guanghui is a former student and follower of academician Lin Peng, long recognized as the “father of Chinese mangroves”. Recognizing the urgent need to protect and restore coastal mangroves in China, Prof. Lin returned to his motherland more than 10 years ago to form a team focusing on wetland research and conservation. He has led his team members to visit almost all coastal wetland areas along the southeastern coast of China, and has devoted his team to the restoration and protection of Chinese coastal wetlands, especially mangrove wetlands.
During recent years, Prof. Lin’s research team has successively implemented a series of major research projects focusing on coastal wetlands, with funding from the Ministry of Science and Technology (MOST) National Key Basic Research Program (or “973” program) for Global Change, the National Natural Science Foundation of China (NSFC), and the State Oceanic Administration (SOA). Under these projects, the team has conducted extensive research into the biogeochemical processes of carbon exchange and the ecological restoration of coastal wetlands.
The team has focused especially on mapping biogeochemical processes in the coastal carbon cycle, including carbon exchange at the land-sea interface, carbon turnover processes beneath the soil surface, the impact of human activities on greenhouse gas emissions, the decomposition and conversion of marine organic carbon, the response of net primary productivity to extreme climatic events, and feedbacks between the carbon cycle and climate change, among other topics. The results of this research have substantially advanced scientific understanding of the mechanisms and intrinsic principles of the global carbon cycle, and helped to establish the importance of coastal wetlands within this global context.
Focusing on the cycling of major biogenic elements in several prevalent types of coastal wetlands, the team evaluated how different approaches to mangrove restoration affect the carbon sequestration capacity and the storage of nitrogen and phosphorus nutrients in mangrove wetlands. Careful analysis of the ecological functions and purposes of restoring different types of coastal wetlands has helped the research team to develop novel methods for assessing the effectiveness of efforts aimed at conserving these valuable and underappreciated natural resources.
Prof. Lin continues to lead a dedicated team working on the forefront of coastal wetland research and protection. The next step for this team will focus on the mangrove wetlands of Hainan province, which feature great biodiversity and multiple community types. Unique among the mangrove-containing regions of China, Hainan has historically possessed all species of mangroves found in China, including rare epiphytes and parasitic plants that have not been observed in other provinces or autonomous regions. However, mangrove forests in Hainan have been destroyed at large scales by human activities from 1950 to 2000, with the area of mangroves reduced by 62% and dramatic drops in species diversity. Thus, new surveys and targeted efforts to conserve mangrove resources in Hainan are urgently needed. Through this research, the team will be able to reveal the structural characteristics and dynamic interactions among the communities of mangrove plants, zoobenthos, and microorganisms that inhabit the mangrove ecosystems of Hainan. The survey will clarify the current distribution, quantity, and vitality of mangrove communities on Hainan island in the context of historical data.
While the tide ebbs and flows, the scholars of Tsinghua University’s wetlands ecology lab will continue to strive to be “guardians of the mangroves”, cherishing both the opportunity and the responsibility that this entails. Like the mangrove, they will stand firm in the face of challenges, endeavoring to leave the coastal wetlands of southern China healthier and more vibrant in their wake.