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Rafflesia in the rainforest of Sumatra

Photo: Chris Thorogood / dpa

The pleasant scent of flowers is used to advertise bath additives and perfumes - but some plants fall out of this range. Rafflesias, for example, which are considered the largest and most foul-smelling flowers in the world. A study now shows that the iconic plants, which only occur in the jungles of Southeast Asia and are still a mystery to experts today, are in great danger. "All 42 known species are now severely threatened," says an international study led by the University of Oxford, which was published last week in the journal "Plants People Planet". Nevertheless, only one species is listed on the Red List of Endangered Species of the International Union for Conservation of Nature (IUCN).

The authors, on the other hand, now classify 25 Rafflesia species as "critically endangered", 15 as "critically endangered" and two as "endangered". The main cause is the loss of their natural habitat. According to the study, many of the remaining populations are limited to a few individuals that are in unprotected areas. At the same time, attempts to breed rafflesia in botanical gardens have so far shown little success.

Rafflesias are parasites. With their stench of rotting meat, they attract flies for pollination – a clever way to ensure survival. At the same time, the plant lacks almost all the characteristics of a "normal" flower: it has no leaves, no stem and no root, but anchors itself as a parasite on its host plant. Most of these are liana or vine plants. Only the flowers are well developed and huge: some are one meter in diameter. But the colossal splendor is short-lived. After only three to seven days, the thick, leathery flowers wither. The distribution area of the flower ranges from Thailand to the Philippines to Malaysia and Indonesia. Researchers refer to them as miracles of evolution – while they continue to try to unravel their secrets.

Botanists still regularly describe new Rafflesia species. "But we assume that at least 67 percent of known habitats are outside protected areas, which increases their vulnerability," the study says. Previously unknown species are probably already extinct before they are even discovered.

The authors propose an urgent action plan and coordinated action by governments, researchers and conservation organisations. The focus must be on protecting the habitats of the most threatened populations. Nowhere did the rainforests disappear faster than in Southeast Asia – and many Rafflesia lived dangerously close to growing human settlements.

But it is also important to better study the entire group of plants and to develop new methods to propagate them outside their natural habitat. In addition, ecotourism initiatives could help, the botanists are convinced. Financial support and training for the local population is an effective means of raising awareness of rafflesia and their protection.