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| Credit: Dr. Rebecca Hamilton, The University of Sydney. |
Led by Dr. Rebecca Hamilton at the University of Sydney, an international team of scientists has challenged previous scientific consensus regarding the dominant landscape during the Last Glacial Maximum over 19,000 years ago in Southeast Asia. Contrary to the belief that dry savannah prevailed, the researchers discovered a diverse mosaic of closed and open forest types.
These findings suggest that Asia's tropical forests may exhibit greater resilience to climate change if a variety of landscapes is preserved. The research, published in the Proceedings of the National Academy of Sciences, also indicates that migrating humans and animals in the region had access to a more varied resource base than previously thought.
Dr. Hamilton, from the School of Geosciences at the University of Sydney, emphasized the importance of conservation efforts in the face of climate change. She proposed that safeguarding diverse forest types, particularly montane forests above 1000 meters, alongside seasonally dry forest types, should be a priority to prevent the potential 'savannization' of Asia's rainforests. Savannization refers to the transformation of a forested area into a savannah ecosystem, often influenced by climate fluctuations, human activities, or natural ecological processes.
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| Credit:Dr. Rebecca Hamilton, The University of Sydney. |
To scrutinize the validity of the savannah model, which posits the prevalence of a vast, uniform grassland in tropical Southeast Asia during the Last Glacial Maximum, researchers examined data from 59 paleoenvironmental sites across the region. Contrary to the model's assumptions, their analysis of preserved pollen grains in lake sediments revealed a coexistence of forests and expanding grasslands, as indicated by various biochemical signatures.
Dr. Hamilton explained that these apparent contradictions could be reconciled by considering the persistence and expansion of montane forests (above 1000m) in high-elevation areas, while lowlands underwent a transition to seasonally dry forests with naturally grassy understories, facilitated by the cool and seasonal climate of the Last Glacial Maximum.
The collaborative 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 comparing numerous paleoecological records will prove valuable for examining other instances of past ecological changes in the region.
The study, authored by Rebecca Hamilton et al., titled "Forest mosaics, not savanna corridors, dominated in Southeast Asia during the Last Glacial Maximum," is featured in the Proceedings of the National Academy of Sciences (2023).DOI: 10.1073/pnas.2311280120. doi.org/10.1073/pnas.2311280120