Muthurajawela is an accidental wetland. It was never supposed to be a haven for wetland birds, nor was it ever a home for Mangroves in Sri Lanka. In fact, it was originally a vast agricultural landscape, with thousands of farmers and labourers working the land endlessly to plant and harvest the staple crop of Sri Lanka, rice.
The Dilmah One Earth Nature Club decided to go and discover the wonder of Muthurajawela, a simple half an hour drive away from Colombo. The first order of business was to learn about the history of Muthurajawela. Actually, first we had an awesome cup of tea. Then we moved to the history.
The Muthurajawela Marsh and the Negombo Lagoon forms a single coastal ecosystem. The Negombo Lagoon was actually the most important seaport in the country during the Kotte Period. This port was controlled by Portuguese and subsequently Dutch invaders since 1505, and it was the Dutch why wanted to build systems of transportation further inland, to facilitate movement of goods from and towards Colombo.
The newly dug canal system proved disastrous for paddy cultivation in the area, because the salt water intrusion to the fields increased exponentially, inundating the land and creating saline conditions unsuitable for cultivation.
The final canal, Hamilton Canal, was such a counter productive effort, that the locals call it Moda Ela (Fool’s Canal) to this day.
Muthurajawela is now host to a wide variety of flora and fauna, including many bird species, both native and migrant. Mangroves grow abundantly all along the Marsh waters.
“Mangroves” in itself is an umbrella term for many different, taxonomically unrelated species of wetland plants, which are specially adapted to the highly saline conditions. Some of the species are Excoecaria agallocha, Acanthus ilicifolius and Sonneratia caseolaris.
Mangroves in Muthurajawela have many important functions. They act as biological filters. A lot of industrial and domestic waste drains into the wetland, and the sediment and toxic materials are trapped and absorbed by mangroves. Thus siltation and nutrient overload in the water is prevented.
They are also important as flood water buffers, because they slow down fast flowing waters of the runoff from higher grounds during the rainy season, and prevents velocity induced damage to the Negombo Lagoon.
Mangroves also act as breeding grounds for many wetland species, and protects them during the juvenile stages.
All this and more was taught to the One Earth members as they cruised along the Hamilton Canal, and many wetland birds, such as purple swamphens, herons, cormorants and kites were also spotted.
It was an enlightening visit, which highlighted the economic and ecological benefits of protecting and restoring the largest expanse of wetland ecosystem just outside our city limits.
- www.lankalibrary.com/natural/muthu.htm (29th August 2016)
- A.R. Gunawardana et all (2016) Above Ground Biomass Estimation of Mangroves Located in Negombo. Tropical Agricultural Research Vol. 27(2): 137-146
- IUCN Case Study (2003) Muthurajawela Marsh Sri Lanka