Maintaining Asian Forest Diversity to Combat Climate Change Impact

The study conducted by an international team of scientists, led by Dr. Rebecca Hamilton from the University of Sydney, has discovered that the previous scientific consensus regarding the dominance of dry savannah in South East Asia during the Last Glacial Maximum over 19,000 years ago was incorrect. Instead, the researchers found that a mosaic of diverse closed and open forest types existed during that period.

This new finding suggests that Asia’s tropical forests may be more resilient to climate change than previously believed, provided that a diverse landscape is maintained. The study also reveals that humans and animals migrating across the region would have had a more diverse resource base than previously understood.

The research, published in the Proceedings of the National Academy of Sciences, aims to address concerns about the impact of climate change on tropical rainforests in regions like South East Asia. Dr. Hamilton emphasizes the importance of prioritizing the protection of forests above 1000 meters, known as montane forests, alongside seasonally dry forest types. This approach could help prevent the future “savannization” of Asia’s rainforests.

Savannization refers to the transformation of a landscape, typically a forested area, into a savannah ecosystem, which involves open wooded plains. This change is often induced by climate variations, human interventions, or natural ecological dynamics.

To reach their conclusion, the researchers analyzed records from 59 paleoenvironmental sites across tropical Southeast Asia. They tested the so-called savannah model, which assumed that a large, uniform grassland expanded across the region during the Last Glacial Maximum. However, the team found that records from pollen grains preserved in lakes showed that forests persisted during this period alongside an expansion of grasslands.

Dr. Hamilton and her team suggest that the discrepancies between the savannah model and their findings can be reconciled if montane forests (above 1000 meters) persisted and expanded in high-elevation regions during the cool and seasonal climate of the Last Glacial Maximum, while lowlands experienced a shift to seasonally dry forests, which naturally have a grassy understory.

The study involved collaboration with 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 believe that the statistical methods developed to cross-compare the many paleoecological records will be useful for regional testing of other past ecological changes.