Our Nature Reserves are ANCIENT
The distribution of flora and fauna in our SE Asia region is the result of the changing geology throughout the millions of years.
11,000 years ago, it would be possible to walk from Singapore to Sumatra and even Borneo and Java. Singapore was part of a large land mass called the Sundaland. During the ice age, sea level dropped more than 100 m below the present level, exposing the lower lying central portion.
This map below shows today’s land areas as well as parts of the seas that were once land (Sunda Land).
Can this explain why the species found in Singapore can also be found in Peninsula Malaysia and also Borneo?
Map of Southeast Asia showing current land areas and the late Pleistocene land area, as estimated from the 120m bathymetric line. From Heaney (in press), adapted from Kuenen (1950).
The Fascinating “Plot 13”
Among the ecologists in Singapore, “Plot 13” in CCNR is an exciting patch of the Primary forest that has not been touched by development all these years. The paper, “The Tree Communities of the Central Catchment Nature Reserve, Singapore” (1994) written by Mr Wong Yew Kwan et. al. stated their surprise in finding three Seraya or Shorea curtisii, in this patch of Lowland Dipterocarp Forest.
What is fascinating is this particular species of tree is a Primary forest species but not known to grow in the lowland. Instead it is typically found growing on Coastal Hill Forest from about 300 – 800 m above sea level according to Symington (1941). Seraya can be found in the hill forest of our BTNR naturally. The Seraya trees with their saplings close to them were found at 30 – 40 m
So why is it found in the lowland in CCNR?
Take a look at the map above again. The Central Catchment Area was an inland hill during the Pleistocene as sea levels were over 100 m lower than they are today. The Seraya that are found growing in “Plot 13” are the descendants of a possibly much larger population of Seraya growing on these mountain ridges some 15,000 years ago!
It is amazing that we have in our rain forest, relics of the ancient forest. The CRL will cut right under Plot 13 where these trees are found. They have survived the last Ice age, the axe from plantation owners and the Second World War. Will there fate be sealed by a train line in the 21th century?
[For more details refer to Pg 13 of NSS Discussion and Position Paper, 2013 and Wong Yew Kwan’s paper]
Why are the rain forests in this region more unique?
The extent of rain forest in South America and Africa has been determined mainly by variation in rainfall and temperature. In Indo-Australia, the land mass is discontinuous at the various ice ages, resulting in exceptionally high localized biological diversity of plants and animals. The changing sea level played a crucial role in the distribution of plants and animals besides rainfall and temperature.
“Human destruction of forest differs from past natural variation because it involves the removal of natural vegetation, rather than shifting its distribution” – Lawrence R. Heaney
“Current major vegetative types in Southeast Asia are evergreen tropical rain forest, seasonal or monsoon forest, montane forest, and natural savannah, as well as several more limited natural types and broad expanses of disturbed vegetation.1986).
Current conditions have historically supported more extensive tracts of forest than existed during the last glacial maximum, but human activity has reduced the actual current extent of rain forest cover (Whitmore, 1984) to what is probably the lowest level since the geological origin of the region. Human destruction of forest differs from past natural variation because it involves the removal of natural vegetation, rather than shifting its distribution, and because it is especially directed toward removal of lowland rain forest, which for most of the biota supports the greatest diversity. Increasing deforestation and fragmentation can serve only to increase the vulnerability of the rain forest’s entire biota.”
Reference
J. Severinghaus, E. Brook 1999. Abrupt Climate Change at the End of the Last Glacial Period Inferred from Trapped Air in Polar Ice. Science 286 (5441): 930–4.
L.R. Heaney 1990. A Synopsis of Climatic and Vegetational Change in Southeast Asia.
