The mystery of the Sunda shelf vegetation during the last glacial period

Changes in the vegetation of the Sunda shelf exposed during the last ice period at low sea level have important implications for global carbon cycle impacts. However, the results of current vegetation reconstructions are still highly controversial. A paleo-vegetation reconstruction was conducted using the available carbon isotope and pollen records of the last ice age in the Sunda shelf region. Compared to the Holocene, the distribution range of tropical rainforests contracted toward the equator during the last glacial period, showing an uneven zonal distribution pattern, while the herbaceous vegetation expanded in the regions far from the equator. The southward shift of the Intertropical Convergence Zone and the overall decrease of precipitation in the Sunda shelf region due to the El Niño-like state of the tropical Pacific Ocean are important reasons for this phenomenon. Mountains play an essential role in the evolution of the vertical distribution structure of vegetation during the ice age. In the wet and cold regions, montane rainforests expanded downward, while in the dry and cold regions, mountains played the role of rainforest refuges. The reconstruction of ancient vegetation on the Sunda shelf still faces difficulties such as cryptic vegetation and limitations of vegetation indicators, and more work is needed to improve it.