What was the impression when westerners first arrived in Hong Kong in the 17th century? “No trees, much grass!“ was their comment. Although the original vegetation of Hong Kong no longer exists after decades of urban development, we have a large area of country parks and mountain ranges covered with trees and secondary forest.
Most of all, we have a total area of 510 hectare of mangroves lying around the coastal area of the city. Let's take a quick look at this horticultural highlight.
Why isn't the mangrove (literally "Red Tree" in Chinese) red?
The Chinese name for the mangrove came from the rhizophoraceae plants. The wood from rhizophoraceae is reddish; therefore, this family of plants is also called “red trees.”
What are mangroves and where do they live?
Mangroves are one of the coastal natural phenomena seen in river mouth zones in subtropical areas. They live mainly in muddy wetlands of loose and moist soil, especially in river bays. Mangroves are evergreen plants, and the term mangrove refers to sea-side plant communities of trees and shrubs divided into two species: true mangroves and associate mangroves. In Hong Kong, there are eight species that distribute mainly in the northwest around the Deep Bay wetland, namely the Kandelia obovata – Aegiceras corniculatum – Avicennia marina community, Acanthus ilicifolius community and the Acrostichum aureum community. This is currently the second largest wetland in southern China.
Mangroves as firewood
Mangroves provide habitat, nesting and breeding sites, and feeding grounds for countless species of birds and marine fauna. Fish, shrimp, crabs and other aquatic organisms can inhabit the mangrove tree trunk, leaves, root surface, the mud surface and also burrow into the mud. The root systems of mangrove species absorb inorganic substances and reduce water pollution. They also protect the coastline from wave erosion. A few decades ago, villagers living along the west coast of Hong Kong always used mangrove wood for fuel to cook. In Southeast Asian countries like India, Bangladesh, the Philippines, Malaysia and Indonesia, quite a lot of people living offshore are still using mangrove wood as cooking fuel.
Preserve our wetland forest
But on the top of it all, a mangrove forest is a beautiful environment. It is pitiful that we humans, intentional or otherwise, ignored the destruction and impacts to the environment. Facing the pressure from rural area developments such as reclamation and urbanisation and various kinds of pollution, the mangrove habit is shrinking. Many of the wetland areas are filled and used as open storage, scrap yard or rebuilt as parts of new towns. As a result, the original mangrove shrubs are disappearing. Not only in Hong Kong, but also in Thailand, the Philippines and Vietnam, more than one half of mangrove habitats have disappeared.
In recent decades, the conservation of these habitats has begun to receive increased attention in Hong Kong. In 1995, mangroves were added to the international Convention on Wetlands of International Importance list. Also, the government has designated marine parks and marine reserves to protect marine habitats in Hong Kong. At present, the mangrove at Hoi Ha Wan Marine Park is protected meaning collecting organisms is prohibited. Some local conservation groups such as The Conservancy Association have also planted mangrove seedlings in the Tung Chung bay area. The Department of Geography Resource Management of Chinese University has developed a Mangrove Species Mapping and Leaf Area Index Modeling using optical and microwave remote sensing technologies. This project promotes an efficient and long-term monitoring mechanism for mangrove studies in Hong Kong. It will also contribute to existing knowledge of remote sensing technologies and mangrove research in the territory.
To preserve this last piece of wetland forest in the city, we must do our utmost to treasure it in a sustainable manner.
Learn more about vegetation in Hong Kong by visiting Hong Kong Herbarium's website.