A groundbreaking study led by Dr. Rebecca Hamilton at the University of Sydney challenges previous scientific consensus by revealing that the landscape of South East Asia during the Last Glacial Maximum over 19,000 years ago featured a diverse mosaic of closed and open forest types, rather than the prevailing belief in the dominance of dry savannah.
The research, published in the Proceedings of the National Academy of Sciences and conducted by an international team of scientists, carries significant implications for understanding the resilience of Asia’s tropical forests to climate change.
The findings indicate that maintaining a diversity of landscapes could enhance this resilience, offering a more varied resource base for both humans and migrating animals than previously recognized.
Dr. Hamilton, associated with the School of Geosciences at the University of Sydney, emphasized the urgency of conservation efforts in the face of climate change.
“Maintaining forest types that facilitate resilience should be a conservation objective for the region. Our work suggests that prioritizing protection of forests above 1000 meters (‘montane forest’) alongside seasonally dry forest types could be important for preventing future ‘savannization’ of Asia’s rainforests,” she explained.
“Savannization” refers to the transformation of forested areas into savannah ecosystems, typically characterized by open wooded plains. This shift is often triggered by climate variations, human interventions, or natural ecological dynamics.
To challenge the prevailing savannah model, which posited a uniform expansion of grasslands across tropical SE Asia during the Last Glacial Maximum, the researchers examined records from 59 paleoenvironmental sites in the region.
Analysis of pollen grains preserved in lakes indicated that, contrary to the assumptions of a uniform grassland, forests coexisted with expanding grasslands during that period.
Dr. Hamilton proposed a reconciling explanation, suggesting that during the Last Glacial Maximum’s cool and seasonal climate, montane forests above 1000 meters persisted and expanded in high-elevation regions.
Simultaneously, lowlands experienced a shift to seasonally dry forests, characterized by a naturally grassy understory.
The collaborative research effort involved scientists from the Max Planck Institute of Geoanthropology in Jena, Germany; Flinders University; Purdue University in the U.S.; University of the Philippines; and the Australian National University.
The researchers anticipate that the statistical methods developed for cross-comparing paleoecological records will prove valuable for examining past ecological changes in other regions.
