香港蓮華島海底默默恢復珍貴植物吸引綠海龜

HKU researchers and island residents team up to restore plummeting levels of a vital vegetation to attract green turtles and other animals The city’s seagrass meadows have plummeted by 60 per cent over the past two decades. Photo: Claudia Hinterseer On a sunny July afternoon along the shores of Hong Kong’s Lamma Island, the receding tide reveals an unassuming patch of greenery that scientists describe as the “ultimate underwater superheroes” for boosting marine biodiversity. Seagrass – an easily overlooked marine plant – can lock away climate-warming carbon 35 times faster than tropical rainforests. But levels of this vital vegetation in local waters have plummeted by 60 per cent over the past two decades, while sightings of local green turtles, which feed on it, have also dropped significantly. According to the latest government figures, local live sightings of green turtles dropped from 17 in 2019 to seven in 2025. Strandings have also declined, falling from 16 in 2018 to two this year. In a bid to turn the situation around, researchers are working with villagers to plant more seagrass. “Seagrasses are the ultimate underwater superheroes,” said Juan Diego Gaitan-Espitia, an associate professor of biological sciences at the University of Hong Kong (HKU). “Without these quiet champions, both the global fight against climate disruption and the very livelihoods of coastal populations will be threatened.” Hong Kong is home to five seagrass species, the most widespread being Halophila ovalis , also known as “spoon grass” due to its pale green, delicate, spoon-shaped leaves. According to the Agriculture, Fisheries and Conservation Department (AFCD) , the marine plant can be found along shallow, sheltered marine coastlines and river deltas, such as Ham Tin, Lai Chi Wo and Sheung Pak Nai. Seagrass meadows are also believed to provide nursery habitats for the local endangered horseshoe crab population. But Gaitan-Espitia said that human activities, such as land reclamation and pollution, alongside limited plant dispersal and typhoons, had led to a 60 per cent decline in seagrass levels in Hong Kong since 2000. A HKU team documented the seagrass’s decline and local extirpation in some areas by analysing monitoring surveys in Hong Kong since 2018 and comparing historical records from scientific publications dating back to 2000. Unhandled type: inline-plus-widget {"type":"inline-plus-widget"} In April and June, the team engaged villagers and volunteers to plant seagrass at a mudflat in Sok Kwu Wan on Lamma Island – an experimental effort to create a new seagrass site, known as “afforestation”, in 2023. The experiment stemmed from the team’s ongoing seagrass restoration project across various sites since 2020. The Hong Kong Biodiversity Strategy and Action Plan outlines restoration of seagrass beds as a priority project that aligns with national and global initiatives. Gaitan-Espitia said afforestation and restoration methods could be combined to revitalise seagrass habitats. Juan Diego Gaitan-Espitia has said human activities, alongside limited plant dispersal and typhoons, have led to a 60 per cent decline in seagrass levels in Hong Kong since 2000. Photo: The Swire Institute of Marine Science of the University of Hong Kong “If we restore the seagrass but the pollution or land reclamation is still there, the seagrasses will disappear again with our intervention,” he said. “Afforestation finds suitable habitats for seagrass that can protect and help it recover in the long term.” The idea to plant seagrass was sparked by island resident Wendy Chan Wing-fung, who recalled older villagers sharing memories of green turtles paddling nearby. Hoping to restore that memory, Chan, the daughter of a local fisherman, sought approval from the island’s rural committee and reached out to Gaitán-Espitia, who found the mudflat was a viable site for seagrasses to thrive. Rainbow Leung, a doctoral researcher studying seagrass ecology and restoration, said seagrass seedlings were cultured in multiple nurseries, including a laboratory at HKU’s Swire Institute of Marine Science, before being transplanted to the site. Chan, who also founded social enterprise Life Jungle, offered some of her family’s fish rafts to the researchers for cultivating seagrass seedlings and co-hosted workshops for volunteers to help anchor seagrass pots into the mudflats. The goal is to cover at least two hectares (4.94 acres) with seagrass in the intertidal area. Leung, who conducted monitoring surveys at the site, noted that local fauna was already flourishing in the area. “We found a diverse group of organisms, including snails, clams and hermit crabs,” she said. Gaitan-Espitia said that other environmental benefits of seagrass include cleansing the ocean water of harmful pathogens and buffering shores against destructive erosion. While such underwater meadows only occupy about 0.2 per cent of the world’s ocean floors, they can store up to 18 per cent of ocean carbon. While it would take years to quantify the environmental and ecological impact of the seagrasses in Sok Kwu Wan, Gaitan-Espitia noted that green turtles had already been spotted on three occasions in June, with two sightings recorded on the same day. “This is promising particularly because they are around the nesting area and the community has engaged in their protection,” he said. The green turtle is the only sea turtle species that nests locally and is protected under the Wild Animals Protection Ordinance in Hong Kong. The AFCD said Lamma Island’s Sham Wan Beach was the only site in Hong Kong where green turtles laid eggs from time to time, although no nesting was recorded from 2018 to 2026. Public access to the beach is restricted between April and October as part of local efforts to protect the species. The green turtle is the only sea turtle species that nests locally and is protected under the Wild Animals Protection Ordinance in Hong Kong. Photo: Handout Gaitan-Espitia explained that green turtle sightings and strandings could have dropped due to boat strikes, plastic pollution or turtles relocating to better habitats, but stressed food availability and habitat quality were most important to their survival. Aside from green turtles, Chan said she had also started seeing egrets and other animals gracing the seagrass meadows. “It just fills me with gratitude,” she said.