Prof. Cannon is lead author on a recent publication in the Proceedings of the National Academy of Sciences (U.S.A.) that presents a spatially explicit model of rainforest distribution through the last million years in Sundaland.  Sundaland is the ‘sub-continent’ of the major islands of Indonesia and Malaysia which were joined during previous ice ages but much of which is now submerged due to the higher sea levels after the ice melted.  Sundaland is widely recognized as a major biodiversity hotspot and helped to inspire the biological insights of the father of biogeography and co-founder of the theory of natural selection, Alfred Russel Wallace.

The publication, entitled “The current refugial rainforests of Sundaland are unrepresentative of their biogeographic past and highly vulnerable to disturbance”, illustrates that the current situation, where the islands are separated by the shallow South China Sea, is extremely unusual given the actual history of the region.  During most of the last million years, the islands were all joined in a single and much larger landmass.  Paleoclimate models strongly indicate that much of this landmass would have been covered with evergreen rainforests, forming an Amazon-like basin.  With the onset of the current climate conditions, with a much warmer globe and higher sea levels, forests have been forced to retreat onto the islands, becoming much smaller and more fragmented than they have been in the past.

These dynamics are widely recognized and well understood in North America and Europe but Dr. Cannon’s publication demonstrates that the dynamics in Sundaland are exactly in the opposite phase as those in the northern latitude.  This means that during the ice age, rainforest is at its greatest extent, while during the warm periods, like now, rainforest is at its lowest extent and exists only in refugia.  While we understand the expansion of populations out of refugia, we know almost nothing about how refugia are foremd.  This is a critical question confronting ecologists and biogeographers in Southeast Asia and the work led by Dr. Cannon provides a powerful tool for exploring these dynamics.

Finally, the results of this model have major conservation implications.  Much has been written about the decline and degradation of Southeast Asia’s rainforests.  The rate of conversion from natural forests to intensive plantation forest has remained high for many years.  This conversion reduces and fragments the rainforest, leaving little habitat for endangered species like orangutans and gibbons and sun bears and clouded leopards.  What this model highlights is the critical fact that the human conversion of Sundaland’s forests is occurring only a few thousand years after a major natural reduction and fragmentation of forest area occured due to changing climate and rising sea levels.  So, all of these endangered species were already at probably historical lows in their population and already highly vulnerable to population extinction.  And now, humans are adding insult to injury, in a sense.

The paper is available at the Early Edition site at PNAS:

http://www.pnas.org/content/early/2009/06/18/0809865106.abstract