Madagascar would take 23 million years to replace its mammals

10 Jan. () –

A study has calculated the time for a similar set of new mammalian species to be replaced by evolution at 23 million years. those living in Madagascar if they became extinct.

This is far more than scientists have found for any other island, the authors report in the journal ‘Nature Communications’.

Simply put, it’s very bad news, scientists warn. In many ways, Madagascar is a biologist’s dream, a real experiment in how isolation on an island can trigger evolution. About 90% of the plants and animals of Madagascar are found nowhere else on Earth. But these plants and animals are in grave danger from habitat loss, overhunting, and climate change. Of the 219 known mammal species on the island, including 109 lemur species, more than 120 are threatened with extinction.

“It is very clear that there are entire lineages of mammals unique to Madagascar that are extinct or are on the verge of extinction, and if immediate action is not taken, Madagascar is going to lose 23 million years of mammalian evolutionary history. , which means that entire single lineages on the face of the Earth will not exist again“, warns Steve Goodman, a MacArthur field biologist at the Field Museum in Chicago (United States) and scientific director of the Vahatra Association of Antananarivo (Madagascar), and one of the authors of the article.

Madagascar is the fifth largest island in the world, about the size of France, but “in terms of all the different ecosystems present in Madagascar, it is less like an island and more like a mini-continent,” Goodman explains.

In the 150 million years since Madagascar broke away from the African continent and the 80 million years since it broke away from India, plants and animals have followed their own evolutionary path, isolated from the rest of the world. This smaller gene pool, coupled with Madagascar’s wide variety of habitats, from montaneous rainforests to lowland deserts, it has allowed mammals to divide into different species much more quickly than their continental relatives.

But this incredible biodiversity comes at a cost: evolution is faster on islands, but so is extinction. Smaller populations, especially adapted to smaller and more unique habitats, are more vulnerable to extinction, and once they’re gone, they’re gone.

More than half of Madagascar’s mammals are listed on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. These animals are in danger above all due to the action of man in the last two hundred years, especially due to the destruction of their habitat and excessive hunting.

An international team of Malagasy, European and American scientists, including Goodman, collaborated to study the impending extinction of Madagascar’s threatened mammals. They created a data set of all known mammal species to have coexisted with humans in Madagascar for the past 2,500 years. Humans have lived on the island, perhaps intermittently, for the past 10,000 years, but they have remained there steadily for the last 2,500.

The scientists arrived at the 219 known mammal species living today, plus another 30 that have gone extinct in the last two millennia, including a gorilla-sized lemur that went extinct between 500 and 2,000 years ago.

Using this data set of all known Malagasy mammals that have interacted with humans, the researchers built genetic family trees to establish the relationship between all these species. and how long it took them to evolve from their various common ancestors.

They were then able to extrapolate how long it took for this amount of biodiversity to evolve, and thus estimate how long it would take for evolution to “replace” all endangered mammals if they went extinct.

To reconstruct the diversity of terrestrial mammals that have already gone extinct in the last 2,500 years, it would take about 3 million years. But most alarmingly, models suggest that if all currently endangered mammals went extinct, it would take 23 million years to rebuild that level of diversity.

That doesn’t mean that if we let all lemurs and tenrecs and fossa and other unique Malagasy mammals go extinct, evolution will recreate them if we wait another 23 million years. “It would simply be impossible to get them back.“, says Goodman. Instead, the model means that it would take 23 million years to reach a similar level of evolutionary complexity, whatever those new species might look like.

Luis Valente, corresponding author of the study, acknowledges that he was surprised by this finding. “It is much longer than what previous studies have found on other islands, such as New Zealand or the Caribbean,” says Valente, a biologist at the Naturalis Center for Biodiversity and the University of Groningen in the Netherlands.

“Madagascar was already known to be a biodiversity hotspot, but this new research puts into context how valuable this diversity is,” he adds. “These findings underscore the potential benefits of nature conservation in Madagascar from a novel evolutionary perspective“.

According to Goodman, Madagascar is at a tipping point in protecting its biodiversity. “There are still possibilities to fix things, but basically, we have about five years to make real progress in conserving Madagascar’s forests and the organisms that those forests harbor“, it states.

This urgent conservation effort is hampered by inequality and political corruption that keep land use decisions out of the reach of most Malagasy people, Goodman says. “Madagascar’s biological crisis has nothing to do with biology. It has to do with socioeconomics,” she warns, but as dire as the situation is, she says, “we cannot throw in the towel. We are obligated to advance this cause as far as we can and try to make the world understand that it is now or never.”