by Eric Wikramanayake
Wetlands don’t look like much. They lack the majesty of rainforests, the scorching intensity of deserts, or the awe-inspiring expanses of grasslands that meld with the horizon. But wetlands are rightfully recognised as among the most important ecosystems, ranking up there with rainforests, for the biodiversity they harbour, and the ecosystem services they provide.
Wetlands occur at the intersection of water and land and can cover a gamut of different ecosystems; from marshes and swamps to coastal mangroves. Because they remain flooded for long periods, they support a unique ecological community comprising aquatic plants that flourish in standing or slow-flowing water. Many are emergent, i.e., rooted in water and mud, but emerges from the water surface to blur the water-air interface that is obvious in lakes or streams. The faunal community includes a mix of aquatic and terrestrial species although many also transcend the water-air divide. Fishes, crabs, frogs, snails and aquatic insects live in the water, but even some fishes such as mudskippers and walking perches, break through the divide to emerge from the water, just as some birds such as cormorants and kingfishers and mammals such as otters and fishing cats dive into the water in search of food.
Wetlands are also incredibly important for the ecosystem services they provide people, to sustain their socio-economic needs and to support economic development, infrastructure, and consequentially, stable governance. Wetlands purify and replenish water, provide food for billions of people, and act as sinks to absorb damaging flood water while storing water during droughts. The coastal wetlands, including mangroves, buffer the coastlines from storms, which are expected to become more severe and frequent under projected climate change scenarios. The mangroves and other coastal wetlands can attenuate strong waves and surges and prevent destructive waves from reaching far inland, causing millions of dollars in economic losses as well as potential loss of life and livelihood.
But wetlands have been extensively converted the world over. According to the 2020 Living Planet Index — the longest-running study produced jointly by WWF and the Zoological Society of London to monitor how rapidly we are losing our planet’s biodiversity — nearly 90 per cent of wetlands across the globe have been lost and are still being destroyed three times faster than forests. In East and Southeast Asia, more than 80 per cent wetlands are now considered threatened due to human activity. Closer to home, in the Pearl River Delta area, almost all wetlands have been converted, and only a few isolated, scattered patches remain.
In Hong Kong, wetlands, including freshwater, intertidal, natural and human-modified systems, represent just about five per cent of the land area. But these remaining wetlands support a wide array of flora and fauna that hold high ecological value. The internationally renowned Mai Po Inner Deep Bay Ramsar Site is a very important feeding and resting grounds for hundreds of thousands of migratory birds that use the 14,000 kilometre-long East Asian-Australasian Flyway.
Most of the coastal infrastructure, from housing estates and commercial centres to promenades, have been built on what used to be wetlands. The remaining wetlands are being filled in with rubbish and waste from construction sites. Other areas are being converted into vehicle parking areas or caravan sites that bring some economic revenue to the owners but disregard the economic costs to the community — from potential floods that may be caused by filling in these flood retention areas to the loss of recreation values that can be enjoyed by a larger group of stakeholders represented by all Hong Kongers who visit these ecosystems.
It’s time to save these remaining wetlands — for the sake of the important biodiversity they support, but also to save Hong Kong from the ravages of climate change. Just over two years ago, Typhoon Mangkhut gave us a glimpse of what the future holds. Climate scientists predict that similar high-energy storms will soon become more frequent and more severe. The coastal wetlands will be a powerful weapon to ameliorate the impacts from these storms and save the coastlines from erosion and the inland areas from severe flooding.
WWF-Hong Kong places a high priority on protecting and restoring Hong Kong’s wetlands and freshwater systems. For almost four decades, WWF in collaboration with the Agriculture, Fisheries and Conservation Department, has been managing Mai Po Nature Reserve, the core area of this Ramsar site. But in its new strategy, WWF has also turned its attention to the other remaining wetlands in Hong Kong and the stream systems that feed and sustain the ecology of these wetlands.
A key area of focus will be South Lantau, which still has a relatively pristine natural landscape. WWF’s strategy is to implement a ‘Ridge to Rock Reef’ approach to conserve the landscape of watersheds in South Lantau as a model landscape, with ecological connectivity from the mountain ridges that are the sources of the streams to the coastal wetlands that include the marshes and mangroves, to the sand and mudflats in Shui Hau, which support important biodiversity and natural resources, such as clams and the Chinese horseshoe crab.
WWF is now in the process of using satellite imagery to map the existing wetlands across Hong Kong to create a baseline map. We mark World Wetlands Day on 2 February by calling on the Hong Kong Government to use this baseline to adopt a policy of no further conversion of local wetlands and commit to conserving the existing ones for community benefit with community stewardship, for a climate-resilient Hong Kong.
Dr Eric Wikramanayake is Director of Wildlife & Wetlands at WWF-Hong Kong.