Relevance of the Coastal Hill Forest to the Marine Environment of Chek Jawa

Introduction
Rising steeply from the sandy beach to a height of 21m, the coastal hill at Chek Jawa may seemed remotely connected to the shallow sea beneath, where lush meadows of seaweed and sea grasses thrived in the shallow, well-lit and nutrient-rich waters. However, the link is very much alive though not easily perceivable unless one witnesses how rainwater runs down the hill during a monsoon downpour. 

Export of nutrients to the marine environment

Dissolved nutrients, along with guano, leaf detritus and rock minerals, trickle down with the rainwater to the beach below, where it is released slowly through the sand to the sea, and readily absorbed by the marine flora or consumed by detritus feeding fauna. 

Leached nutrients (Trono, 1997) and leaf detritus (Odum and Heald, 1975) are two of the most important elements in the food web that associating landforms (including mangrove) contribute to the vitality of the inter-tidal zone. The abundance of marine flora and fauna in Chek Jawa bears testimony to the importance of the coastal hill as a keystone community in the marine environment. 

Physical buffer and natural breakwaters 

Physically, the steep coastal hill is imposing. It is a natural fortress make up of large igneous boulders that goes right down to the beach, and act effectively as a buffer against casual intrusion to the sandy beaches from inland. The obscurity as well as the relatively undisturbed state of Chek Jawa owes much to this rugged feature that are almost impregnable when aided by the long hours of high tides. 

The coastline integrity of Chek Jawa owes much to the series of protective finger-like boulders jutting out to sea at the base of the hill. Like natural breakwaters, they offer protection against accretion of the sandy beach. Without doubt, the coastal morphology of Chek Jawa, predominantly truncated by these mighty boulders, had evolved with the tidal flow to create the unique marine features (including the lagoon) that we find today. 

Unique flora and beach-dependent terrestrial fauna 

Apart from being an ecological and protective partner to the marine environment, the rocky coastal hill forest is a special habitat by itself. It harbors a very unique primary flora that is distinctly different from the terrestrial vegetation found further inland. These are tenacious survivors in the plant kingdom, as equally adaptable as plants found in the deserts. Coastal trees such as the Seashore Nutmeg, Sea Mangosteen and the Sea Olive are constantly exposed to strong dry winds, salt sprays, high solar radiation and temperature, and scrounging a living from nutrients obtain from its own leaf detritus and animal guano. 

These are amongst the last remaining stand of littoral plants that have survived the centuries undisturbed, on extremely shallow soil found atop rock ledges and crevices, and sandy substrates. One such rare tree, Mischocarpus sundaicus, once common in Geylang, Changi and Ubin, cannot be found elsewhere in mainland Singapore now. 

A flock of over 50 native Red Junglefowls inhabits and breeds in this quiet coastal forest. At low tide, they flock to the beach to eat worms, mollusks and other organisms. They are dependent on the beach for food. The coastal forest, in turn, depends on them and other rooting birds for their nutrient-rich guano. The activities and life history of these animals are thus not compartmentalized or confined in their own habitat. Food webs are very complex and cross invisible ecological lines that separate adjacent ecosystems. 

In conclusion, Chek Jawa's six special habitats, namely coastal hill forest, sandy beaches, mangrove, lagoon (sand/mud flats), coral rubble and the rocky shore, represent an integrated system or community of linked ecosystems.  Physical and biological alterations will pose and adverse and irreversible consequence to the ecological balance in what is recognised as the marine environment of Chek Jawa. 

Footnote: 

The above paper was written for the group submission put together on the invitation by the Minister of National Development, Mr. Mah Bow Tan, in 2002. Lead authors were Professor Teh Tiong Sa, N. Sivasothi and my good self, with contributions from Ria Tan, Francis Lim and Yap Hui Boon.