Martedì 17 Gennaio 2023
Madagascar, 23 million years of evolution endangered
Madagascar launches an SOS: from the famous lemurs to the fossa, a predator similar to a small puma, and the strange bats with suction feet, there are 120 species of mammals at risk of extinction, more than 50% of the 219 present on this island symbol of biodiversity. They took 23 million years of evolution to flourish and would take as long to re-evolve a similar level of biodiversity if they were to disappear: a much longer period of time than previously thought. It is the estimate of a study published in the journal Nature Communications and led by the Naturalis Biodiversity Center of Leiden, in the Netherlands, which raises the alarm: according to the authors of the research, there are only 5 years left to save Madagascar from the point of no return.
“It's abundantly clear that there are whole lineages of unique mammals that only occur on Madagascar that have either gone extinct or are on the verge of extinction," says Steve Goodman of the Field Museum of Natural History in Chicago, co-author of the study led by Nathan Michielsen: “if
immediate action isn';t taken, Madagascar is going to lose 23 million years of evolutionary history of mammals, which means whole lineages unique to the face of the Earth will never exist again”.
Madagascar is the fifth largest island in the world, but in terms of richness of ecosystems and biodiversity present it is more like a mini-continent: its isolation has in fact allowed plants and animals to evolve in unique ways, as shown by the fact that 90% of its species are found nowhere else. A
biodiversity constantly threatened since humans settled permanently on the island, about 2,500 years ago: since then, many extinctions have already occurred, including those of giant lemurs, elephant-birds and dwarf hippos.
To quantify the risk on the island’s wildlife the researchers collected an unprecedented amount of data, describing the evolutionary relationships between all the mammal species that were present in Madagascar at the time of colonization, 249 in all. Using computer simulations, the authors of the study were able to calculate the time it would take for this biodiversity to evolve and the time that evolution would take to 'replace' all mammals in the event of extinction.
The results show that 120 species of mammals out of the 219 still present on the island are close to vanish. To reconstruct the diversity of animals already extinct will take 3 million years, but many more, 23 million years, will be needed if all the current ones will become extinct too. A period of time that surprised the researchers: "“It is much longer than what previous studies have found on other islands - comments Luis Valente, one of the authors of the study - such as New Zealand or the Caribbean islands”.
This is not to say that, if lemurs disappeared, they could return to populate the Earth in 23 million years: what the study highlights is the period necessary for evolution to reach a similar level of complexity again, even if the species would be completely new.
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