HA 007: Guardians of the Pearl River Delta

Hope for Hong Kong's mangrove forests

Words and images by Katherine Cheng | Website | Instagram

This story was originally published on China Dialogue under a Creative Commons license (CC BY ND NC). Also available in Chinese/中文.

Nestled deep within one of the many bays of the Pearl River delta, a densely populated region at the confluence of the Pearl River and the South China Sea, a rare patch of mangrove forest can be found hidden between the towering skyscrapers on the Hong Kong–Shenzhen border. Egrets laze in the sun as small crabs scuttle at their feet, a mountainous skyline of construction cranes looming behind them.

Mangroves are small trees that grow along the coastlines of more than 100 countries in tropical and subtropical regions. They were once widespread on the Pearl River delta and around the inlets and islands of the neighbouring Hong Kong Special Administrative Region (SAR). Now there are only about 60 small patches remaining in Hong Kong – the largest is at Mai Po, at the head of Deep Bay (also known as Shenzhen Bay).

Across the Mai Po mudflats, the high-rise buildings of Shenzhen are a hard-to-miss reminder of urban spread along this coastline. (Katherine Cheng/China Dialogue)
Although litter can often be found around the mossy roots of the Yim Tin mangroves, they remain a haven for wildlife, such as this crab. (Katherine Cheng/China Dialogue)

Over the past 50 years, 50% of the world’s mangroves have been lost. This is due to a combination of factors, including coastal reclamation, urbanisation, unsustainable aquaculture practices and pollution.

Hong Kong is not exempt from these ecological stressors. With space limited, urban development looms ever on the horizon. This is clearly in evidence in Starfish Bay in the New Territories, where a new housing development towers over the beach. Long-time resident Mr So is only too aware of the issues: “There’s too much pollution, and look at all these new buildings that have been built nearby. It’s changed so much.”

Mr. So untangles a fishing net on Starfish Bay beach. Fish haven’t been easy to catch since the new tower blocks behind him were built. (Katherine Cheng/China Dialogue)
Not far from Three Fathoms Cove at Starfish Bay, a newly built housing complex towers over the beach. At high tide, the water reaches the thin strip of mangroves providing a buffer between the beach and the buildings. Originally named after its rich biodiversity, starfish are no longer easy to find in the bay due to rapid urban development. (Katherine Cheng/China Dialogue)

The loss of mangroves means more than just the loss of another species of plant. Walking through the Mai Po Nature Reserve at low tide, it’s clear how important this ecosystem is. The tangled, gnarly roots are teeming with life, a haven between fish ponds and exposed mudflats.

Mangroves are highly tolerant to salt, using different mechanisms to extract the fresh water they need from the seawater they live in. Their complex root systems are also adept at binding the sediment brought in by the rising tide. (Katherine Cheng/China Dialogue)
The protected mangroves of the Mai Po reserve in the north of Hong Kong are a richly biodiverse habitat supporting numerous species. With its many hides, the reserve is also popular with nature lovers, many on the lookout for birds like this black-faced spoonbill (Platalea minor). (Katherine Cheng/China Dialogue)
Dr Xianji Wen, director of the Mai Po Nature Reserve and Regional Wetlands, waits with a handful of grass to feed “Ah Bo”, a water buffalo being kept on the reserve. Larger animals have an important role to play in maintaining ecosystem health. Ah Bo, who was named by the public through an online competition, helps keep the grass down so that other species of plant, such as mangrove, can grow. (Katherine Cheng/China Dialogue)

Given the myriad threats to the Mai Po mangrove forest and all the actors in its ecosystem, Mai Po was designated a Wetland of International Importance under the Ramsar Convention in 1995, thereby helping to shield the forest and surrounding mudflats from damage. It is part of a Hong Kong success story, albeit a limited one, where after years of degradation, the mangroves are now making a recovery in the region.

A researcher from the Chinese University of Hong Kong collects samples of mangroves and mud in the Mai Po reserve. She is studying the diet of mangrove crabs, an important part of the mangrove ecosystem. The scientific research supported by the reserve plays a key role in efforts to conserve mangroves, both in Hong Kong and on the Chinese mainland. (Katherine Cheng/China Dialogue)
A mangrove sapling growing in Three Fathoms Cove. With its mangroves, mudflats and sandy shores, this is one of Hong Kong’s most ecologically diverse locations. Hong Kong has lost almost all of its mangroves due to coastal development. (Katherine Cheng/China Dialogue)

Benefits of that recovery have implications far beyond a healthy ecosystem. Eddie Leung, assistant manager of WWF’s Mai Po Habitat and Infrastructure programme, explains that, when seen as a nature-based solution, the mangrove ecosystem “addresses coastal erosion, prevents typhoon damage, provides a rich nursery for biodiversity, and more recently, is known for storing carbon.” For people who live in low-lying areas, this means the trees not only help protect their homes from flooding, but also provide a source of income through the fish stocks they nurture.

This elderly resident of Tai O, a fishing village on the western side of Hong Kong on Lantau island, sells traditional salted fish for a living. Fishing around Tai O benefitted greatly when a new patch of mangroves was planted on abandoned salt pans next to the village between 2005 and 2007. (Katherine Cheng/China Dialogue)
A floating fish farm in Three Fathoms Cove, home to one of Hong Kong’s few remaining areas of mangroves. If practised sustainably, aquaculture can benefit from the ecosystem services mangroves provide. A richly biodiverse habitat, these intertidal forests offer a safe haven for fish to breed and raise their young, and also help clean the water of pollutants. (Katherine Cheng/China Dialogue)

To conserve mangroves, protected areas and restoration projects are vital. But for Hong Kong’s mangroves to continue to recover, and for these coastal forests to start making a come-back elsewhere – including on the Chinese mainland – best practice needs to be followed. Reserves need to be properly monitored and policed. And planting should only occur in areas suitable for mangroves, using only suitable local species.

Directly north of Three Fathoms Cove at Lai Chi Wo, a remote part of the Plover Cove Country Park, a patch of unprotected mangroves thrives in mudflats, seen here exposed at low tide. Hong Kong University researcher Brian Morton has described this patch as “the most intact mangrove in all of China”, recommending it be protected as a World Heritage Site. (Katherine Cheng/China Dialogue)

What’s happening in Hong Kong shows there is hope for mangroves. But much more needs to be done if we want to prevent this vital coastal ecosystem from disappearing by the end of the century.