This year World Wetland Day's theme is "Protecting Wetlands for Our Common Future". It is crucial to recognize the vital role wetlands play. Water sustains life and wetlands make our existence on Earth possible. Moreover, they contribute to climate adaptation by absorbing and storing stormwater. They are key components of the Earth’s climate system and store more carbon than any other ecosystem.

Wetlands are highly productive and biodiverse. They serve as nurseries for many fish and shellfish populations that are important for ecological balance and commercial fishery. 40% of all known plant and animal species live or breed in wetlands, including many endangered species. However, they are among the most threatened ecosystems. At least 35% of the wetlands in the world were lost since 1970 and the rate is accelerating. This has led to 25% of all wetland species facing extinction.

The largest wetland system in Hong Kong is in Deep Bay in Northwest New Territories. It is part of the Pearl River estuary with Shenzhen River and Kam Tin River empty into it. It is very shallow and vast expense of mudflat is exposed during low tide. A belt of mangroves grow along its shore. When the Sung Dynasty immigrants settled in the area, they converted some of the marshland into paddy fields to grow rice.

In the 1940’s, villagers started turning coastal marshes into tidal shrimp ponds called gei wais. A sea wall was established using the dug out mud. A sluice gate connecting to the sea was built. By opening it during high tide, shrimp larvae, fish fries and nutrients were flushed into the gei wai in which they grew naturally. Shrimp harvesting was conducted at night during low tide by putting a net across the opened sluice gate. Fish was caught in the winter when the gei wai was completely drained. This man-modulated tidal habitat supports many aquatic animals, water birds and the Eurasian Otter. Several new-to-science invertebrates have been recorded. The most recent discovery was a box jellyfish named in 2023.

In the 1970's, many of the paddy fields and gei wais in Deep Bay were converted to fish ponds to supply freshwater fish to the growing urban population. Fish ponds are artificial system that relies on stocking of fish fries, adding feeds and aerating the water. During harvesting, the pond would be drained gradually and the small fish and shrimps in the shallow water became easy prey for water birds. However, import from mainland China has made fish farming less profitable. Many of the fish ponds are now inactive or abandoned.

Over the years, the Deep Bay wetlands face many threats. In 1970's and 1980's, pig farm waste together with industrial effluents polluted the lowland rivers and Deep Bay. The water quality has laregly improved in recent years thanks to new regulations, water treatment facilities and coordination between Hong Kong and Shenzhen Governments.

Urbanisation on both sides of Deep Bay has reduced the size of the wetland system. To counter that, HK Government and Green Groups have acted to conserve the remaining wetlands. A key achievement is the establishment of the Mai Po Nature Reserve in 1983 driven by WWF-Hong Kong. Together with the Shenzhen Futien National Nature Reserve, they give protection to the Bay. Mai Po and Inner Deep Bay was designated as a Ramsar Site in 1995 because of its importance to migratory waterbirds. In addition, the Hong Kong Wetland Park was opened in 2006, allowing visitors to learn about wetlands. Government also provides funding support to management agreement schemes to preserve traditional fish pond practices. 

The Northern Metropolis poses a challenge to the future of the Deep Bay wetlands. Another challenge is climate change that is causing sea level rise, more intense rainstorms and stronger typhoons. These exacerbate the flooding risks of the whole area and affect the hydrology of the wetlands. Is it possible to maintain or even enhance the many values of the Deep Bay wetlands?

The Mai Po and Deep Bay wetlands shows success in optimising the ecological, educational and fisheries values through active management. The Northern Metropolis provides an opportunity to elevate that as Government promises to conserve and manage the remaining wetlands through the new Wetland Conservation Park system.

Now that the water quality in Deep Bay has improved, tidal wetlands in the form of gei wai should be restored so that the rich fisheries can be utilised. Technology should be applied so that water inside can be easily drained in advance of an incoming heavy rainstorm or tidal surge. This nature-based solution can increase the stormwater storage capacity and reduce the flooding risk to the nearby human habitation and infrastructure.

The world is facing a double crises of climate change and biodiversity loss. The wise use of Deep Bay wetlands by our predecessors created a combination of natural and man-made biodiverse habitats that also provides food and livelihood to the people. We can make them contribute to the climate resilience of the Northern Metropolis and offer plentiful opportunitities for people to enjoy. What is needed is to see the Deep Bay wetlands as a unique asset crucial for our future.

This morning I would like to dedicate a song “Sometimes when it rains” by Secret Garden to you all. I chose this song because rainfall is very important to us and also important to the wetlands. On the other hand, wetland is also important to ensure that we have plentiful and stable rainfall.