Mai Po Mudflats: A Hidden, Vanishing World
by Thomas Gomersall
Apart from the gei wai, reedbeds and lily ponds, one of the most outstanding features of Mai Po is the barbed wire-topped fence that straddles the road running through the west of the reserve. To the casual observer, it may seem like an obtrusive eyesore in an otherwise relatively pristine environment. But to those who know what lies on the other side, it is the border of a fascinating world that relatively few people — even birdwatchers — get to see.
Just beyond this fence is the Frontier Closed Area (FCA) of Mai Po, a vast expanse of dense mangrove forests and open coastal mudflats lying between the gei wai and the mainland city of Shenzhen. As it is a restricted area, the easiest way to visit is by joining WWF’s weekend mangrove boardwalk tour between October and May, a trip that’s well-worth it.
As soon as you step through Gate 107 between Gei Wai 12 and 13, the first thing that greets you is the floating boardwalk that rests on large plastic barrels bobbing up and down in the tea-coloured water. How quickly you get from the gate to the bird hide will depend partly on how fast you’re willing to walk along this swaying line of narrow planks with only a single handrail for support. But given that none of the people on the tour I went on — all of whom were going much faster than me — fell in, odds are that the risk of an accident is pretty slim.
Eventually, you reach solid ground and from here it’s a straightforward walk to the hide. Along the way, be sure to keep your eyes on the mud beneath the boardwalk for fiddler crabs. The burrows of these stalk-eyed crustaceans pepper the ground here, and the sight of a male with his comically oversized claw (which he uses to attract females and fight for a territory) is sure to impress.
Finally, you get your first sight of the bird hide, nestled among the mangrove trees like a fairy tale cottage. But it’s nothing compared to what awaits you when you get inside, open the windows and get your first glimpse of the open mudflats.
The best time to visit is at high tide, when the birds tend to come closer to the hide. But whatever the tidal level, the mudflats are always a hive of activity. Every winter they play host to more than 50,000 waterbirds, from the commonplace herons and avocets, to mudflat specialties like curlews, godwits and plovers. All here for a feast.
And what a feast it is. As well as fiddler crabs, the mangrove forests provide a refuge and breeding ground for large numbers of shrimps, fish and other aquatic organisms, many of which also move out on to the mudflats. For the birds, being here is like walking on a giant buffet table and they don’t hold back from it. Whether it’s red knots furiously probing the mud, curlews sucking up worms like spaghetti or avocets daintily sweeping their beaks through the shallows, there’s surely nowhere in Hong Kong where you can more easily see feeding behaviour in wetland birds. Occasionally, there’s even some extra drama added when a harrier or greater spotted eagle soars overhead and the waterbirds beat a hasty retreat en masse.
It’s a beautiful sight. But unfortunately, this extraordinary place is under threat. Coastal urbanisation in Shenzhen has led to the creation and dumping of large amounts of sediment, adding to the already large amounts of sediment naturally carried by the Pearl River. Some of this excess sediment is deposited in the mudflats at Mai Po, where it gets trapped by the roots of the mangrove trees and gradually builds up and stabilises into solid ground. This allows for the colonisation of more mangroves, which turn more sediment into dry land, shrinking the area of mudflat habitat even further and faster than it would naturally (1).
Illegal fishing also presents a problem, particularly of mudskippers. Recently these fish have become a gourmet dish in the mainland, where there have been several reports of mainland fishermen venturing out on to the mudflats to catch them, distressing the birds and potentially depriving them of a staple food source (2).
The environmental impact of these threats is big and has already had serious effects on Mai Po’s wildlife. Monitoring data from the Agriculture, Fisheries and Conservation Department (AFCD) and Hong Kong Birdwatching Society has shown a decline in the numbers of birds visiting the mudflats, with some species like the common shelduck and Dalmatian pelican having stopped coming altogether. While this trend may be driven in part by shifting distributions of birds due to climate change, the loss of mudflat habitats to sedimentation and reclamation has almost certainly played a huge role in it, too (3).
While little can be done to completely stop the sedimentation process, WWF-Hong Kong has been working to control vegetation in front of the bird hides to maintain an open mudflat as a feeding site for waterbirds. Mangrove seedlings, sedges and grasses are removed every summer to prevent the establishment of plants on the mudflats. Sightings by birdwatchers of illegal fishing activity are also collected on a weekly basis and shared with the AFCD to inform them of when fishing activity is at its highest and adjust their patrol schedule accordingly. Additionally, WWF is working with other nature reserves in the mainland to create management schemes for all mudflat habitats along the coastline in China to ensure that they can all be protected in the way that is best for the wildlife that depends on them.
Sources:
1.Liu, M., Zhang, H., Lin, G., Lin, H., & Tang, D. (2018). Zonation and directional dynamics of mangrove forests derived from time-series satellite imagery in Mai Po, Hong Kong. Sustainability, 10(6), 1913.
2.https://www.info.gov.hk/gia/general/201807/04/P2018070400537p.htm
3.Banson Leung, Wetland Officer, WWF-Hong Kong
