Wetlands are key to securing a climate-resilient Northern Metropolis

Hong Kong’s wetlands play a vital role in flood protection but this function has been largely ignored
Respecting and tapping into the existing ecosystem can help protect the Northern Metropolis and other coastal areas in the region that are vulnerable to climate change

Joe Lee,David DudgeonandMichael Lau

Published: 9:30am, 18 Nov 2023

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Super Typhoon Saola and the record-breaking black rainstorm in September were stark reminders that, even in a modern city such as Hong Kong, we live within natural ecosystems. As a result of climate change, such extreme weather is happening more frequently, with greater intensity, and affecting more places around the world.

As a result, we must act urgently to enhance our city’s resilience. Much discussion has focused on the need to upgrade our existing infrastructure, which would involve hefty expenditure, many people, a protracted process and the emission of substantial greenhouse gases.

The planned Northern Metropolis encompasses a large area of floodplain wetland, mangrove and fish ponds in the northwestern New Territories, where flood risk is already a concern. Hong Kong’s wetland ecosystem is of international importance to the migratory water birds along the East Asia-Australasia Flyway.

According to the Northern Metropolis development strategy, the government plans to establish a comprehensive wetlands protection system of some 2,000 hectares. These wetlands have the highly beneficial effect of increasing the climate resilience of Hong Kong, but this function has been largely ignored.

These wetlands function as natural buffers that absorb rainwater and are adapted to being flooded. During the black rainstorm, they stored tremendous amounts of rainwater and protected adjacent buildings and roads from flooding. They then quickly returned to normal once the rains subsided and excess water drained away.

Pak Nai, on the coast of the northwestern New Territories, is home to mangroves, oyster beds and rich marine life, and is also known for its spectacular sunsets. Photo: Handout

The recently published Northern Metropolis Action Agenda disappointingly focuses far more on development and urbanisation than conservation of Hong Kong’s natural assets. Plans to develop wetlands in the northwestern New Territories raise questions about whether the government values the ecosystem services such as flood protection provided by wetlands and their role in sustaining livelihoods.

The once-envisioned coastal protection park from Tsim Bei Tsui to Pak Nai has been reduced to Lau Fau Shan only. It is worrying that the government has missed the opportunity to use nature-based solutions in advancing Hong Kong and the Northern Metropolis to become an international demonstration of a Wetland City, where nature and development coexist in harmony.

The existing wetlands and fish ponds of the northwestern New Territories offer nature-based solutions to many of Hong Kong’s environmental concerns. They have immense water storage capacity and can serve as natural detention tanks to lessen flooding risks. In addition, they can continue to be used to raise fish and other aquaculture products.

At the same time, these productive ecosystems support a host of water birds and other wildlife – notably the Eurasian otter – providing opportunities to citizens for leisure, eco-tourism and education. With conservation practices, proper management and appropriate facilities, Hong Kong’s wetlands have substantial potential to provide direct and tangible socioeconomic benefits for Hong Kong.

Eurasian otters are endangered in Hong Kong after decades of hunting and habitat loss. Photo: Shutterstock

Adapting to a greater frequency of extreme weather through increasing resilience is only one part of tackling the climate crisis. If greenhouse gases cannot be brought down quickly, global warming will get worse. Wetlands can help in managing carbon dioxide in the atmosphere by storing carbon in their ecosystem.

There are hundreds of hectares of mangroves in Deep Bay, providing an important carbon sink for some of the city’s emissions. According to a recent Chinese University study, one hectare of mangroves and their associated sediments can contain about 450 tonnes of carbon.

In recent years, the Deep Bay wetland ecosystem has shrunk because of urbanisation. Of particular concern is the reduction of intertidal mudflats, which are the prime feeding ground for migratory waterbirds, including rare species such as the spoon-billed sandpiper and black-faced spoonbill, which are globally threatened.

The potential to increase the area of mangroves therefore lies in fish ponds, which were originally created from impounding coastal habitat within the Deep Bay wetlands. An estimated 200 to 300 hectares of fish ponds have been abandoned or become inactive. They have the potential to be restored and managed as an integrated mangrove-aquaculture system that provides benefits such as fish production, flood protection, wildlife conservation and carbon sequestration.

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In addition, the mangroves fringing the coast offer protection from sea level rises and storm surges, which will become increasingly important as the climate changes and typhoons become more frequent and severe.

To fully realise the flood alleviation service provided by wetlands in the northwestern New Territories, the Development Bureau and Drainage Services Department must incorporate them in the design of drainage and flood storage systems for the Northern Metropolis. It would also be timely to initiate pilot field research on how to optimise carbon capture, aquaculture production and biodiversity enhancement within inactive ponds on government land.

The knowledge and experience gained would be invaluable for the planning and management of future wetland conservation parks envisaged for the Northern Metropolis. These lessons should also be shared across the Greater Bay Area and other coastal areas in the region which share similar climate vulnerability.

We have learned the hard way that undertaking development without taking heed of nature’s way has caused the climate crisis we have to face now. To realise the “ecological civilisation” proposed by President Xi Jinping, we must work with nature.

Shing Yip (Joe) Lee is an adjunct professor at the Chinese University of Hong Kong and chair of the mangrove specialist group at the International Union for Conservation of Nature (IUCN) Species Survival Commission

David Dudgeon is emeritus professor of ecology and biodiversity at the University of Hong Kong and chairman of Mai Po Management Committee, WWF-Hong Kong

Dr Michael Lau is founder of the Hong Kong Wetlands Conservation Association and adjunct professor at the School of Biological Sciences, the University of Hong Kong

This article also received support from prominent scholars and representatives of green groups, see here