It is said that freshwater marshes are the most serene place in the world, where water and soil strikes a delicate balance. This precious ecosystem, extremely rich in biodiversity, is home to numerous wildlife and plants, thereby bringing great benefits to human beings. These freshwater marshes help to protect and improve water quality, provide nurseries to fish, store floodwaters, and many more.
Unfortunately, this valuable habitat is vulnerable to active anthropogenic threats all around the world, particularly in Hong Kong. Landfilling, pollution and certain unsustainable recreational activities are among the threats faced by the depleting freshwater marsh resources. Despite this, human beings are not to blame fully for the disappearing freshwater marshes. Natural succession may attribute to such a decline as well. For example, in the early 1980s to 1990s, the whole lowland plain in Shui Hau was actually covered by marshes given that a large swathe of paddy farmlands got abandoned. In fact, for the period between the 1980s and 2017, the freshwater marshes in Shui Hau mostly survived amid the rapid urban development. The sad fact is that the marsh habitat in Shui Hau is reducing in size by about 15% every 5 years because of natural succession.
How does natural succession happen? Given the natural inflow of soil, the incoming organic matters cause the build-up of dead plant materials, which in turn absorbs moisture from the ground and restricts water flow to various parts of the marsh. The marsh area in Shui Hau becomes increasingly dry as a result. Such being case, the once open and extensive marsh habitat eventually gets replaced by seasonally wet grassland and dense shrubland.
So is the diminishing size of freshwater marshes attributable to the natural or other anthropogenic factors? Whatever the answer will be. Any unmanaged marshes will inevitably disappear. In a bid to sustain such unique ecosystems, it is imperative to implement active wetland management measures, including habitat restoration and management of water resource allocation. It may be concluded from the above that freshwater marshes are just like Hong Kong's "unpolished diamond". So the next time you explore our freshwater marshes, why not appreciate the wonder of such habitats and disseminate the message in the community?
