World’s Largest Flowers at Risk of Extinction, Scientists Warn

An international team of scientists conducted the first comprehensive assessment of extinction risk for all known Rafflesia species. Their findings reveal that over 60% of the 42 known species face a severe threat of extinction. Rafflesia produce the world’s largest individual flowers, which can grow over 3 feet wide. However, most species have highly restricted ranges in Southeast Asia’s rapidly vanishing rainforests.

The study, by Pastor Malabrigo Jr. and colleagues, estimated that 25 Rafflesia species qualify as Critically Endangered based on small geographic range size and limited number of locations. The researchers also found that at least 67% of known habitats are outside of protected areas, making the plants even more vulnerable.

Rafflesia are unusual rootless parasitic plants that live inside vines of the genus Tetrastigma. This lifestyle makes them extremely difficult to propagate or transplant. Most species are only known from a single locality and have tiny populations.

Deforestation is the primary threat, as logging and land conversion for agriculture have destroyed vast areas of Southeast Asia’s tropical rainforests. Rafflesia species literally live on the edge – often in small forest fragments. Alarmingly, the paper documents probable extinctions of Rafflesia even before the plants were formally described by science. Malabrigo Jr. and colleagues write:

In situ conservation in Indonesia is challenging and interdependent on multiple variables, including economic growth, increasing pressure on habitats linked to land use, and a poor understanding of the ecology and distribution of most species; it is impossible to conserve populations not known to exist. Less-explored Kalimantan is likely to host poorly known species of uncertain taxonomic status. For example, three unassigned taxa were documented on Mount Sekerat in northeast Kalimantan (Meijer, 1997). Recently, a team from the Indonesian National Research and Innovation Agency (BRIN) examined the area and found no extant Rafflesia populations; they appear to have been lost to land conversion. Hitherto unreported, this is a highly concerning example whereby three species may have been lost before they were even known to science. 

Malabrigo Jr et al. (2023)

Dr Chris Thorogood, Deputy Director of the University of Oxford Botanic Garden and an author of the study, said: ‘This new study highlights how the global conservation efforts geared towards plants – however iconic – have lagged behind those of animals. We urgently need a joined-up, cross-regional approach to save some of the world’s most remarkable flowers, most of which are now on the brink of being lost.’

Yet, the assessment is not all negative. According to the study, community-led conservation initiatives have successfully protected some Rafflesia habitats, especially when they are sources of ecotourism revenue.

Adriane Tobias, a forester from the Philippines, said: ‘Indigenous peoples are some of the best guardians of our forests, and Rafflesia conservation programmes are far more likely to be successful if they engage local communities. Rafflesia has the potential to be a new icon for conservation in the Asian tropics.’

To prevent further losses, the researchers recommend strengthening taxonomy, expanding protected areas, propagating species ex-situ, and supporting community engagement. With Rafflesia facing existential threats across their range, the study argues that a multi-pronged approach is urgently needed to save these ecological wonders.

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Malabrigo, P., Jr, Tobias, A.B., Witono, J., Mursidawati, S., Susatya, A., Siti-Munirah, M.Y., Wicaksono, A., Raihandhany, R., Edwards, S. and Thorogood, C.J. (2023) “Most of the world’s largest flowers (genus Rafflesia) are now on the brink of extinction,” Plants, People, Planet. Available at: https://doi.org/10.1002/ppp3.10431.

Cover: Rafflesia kemumu in the rainforest of Sumatra. Image: Chris Thorogood.