From the ring-tailed lemur to the aie-aie, a nocturnal primate, more than 20 million years of unique evolutionary history could be wiped from the planet if nothing is done to prevent the extinction of Madagascar’s endangered mammals, according to a new study.
It would already take 3 million years to restore the diversity of mammal species that have been driven to extinction since humans settled on the island 2,500 years ago. But much more is at risk in the coming decades: if Madagascar’s endangered mammal species disappear, the life forms created over 23 million years of evolutionary history will be destroyed.
“Our results suggest that an extinction wave with profound evolutionary impact is imminent in Madagascar unless urgent conservation measures are taken,” the researchers wrote in a paper published in Nature Communications. Madagascar is one of the planet’s biodiversity hotspots with 90% of its species found nowhere else on the planet, but more than half of its mammal species are threatened with extinction.
So much is at stake because the island is relatively untouched and home to wildlife that has not evolved anywhere else, having split off from greater India some 88 million years ago. It is the fourth largest island in the world, about the size of Ukraine, and much of its diversity is built on species that come from Africa and then change over millions of years.
“It’s about putting things into perspective – we’re losing unique species traits that will probably never evolve again,” said lead researcher Dr Louis Valente of the Naturalis Biodiversity Center in Leiden, the Netherlands, and the University of Groningen. “Each species is valuable in its own right; it’s like destroying a piece of art, so what’s happening is very shocking.” His team collaborated with researchers from the US and the conservation organization Association Vahatra in Madagascar.
The island is particularly famous for its ring-tailed lemurs, members of a unique primate lineage found nowhere else. Other famous inhabitants include the fossa, a carnivorous cat-like animal, and the panther chameleon, as well as a wide variety of unique butterflies, orchids, baobabs and many other species.
Biologists and paleontologists created a dataset that showed all the mammal species currently present on the island, those that were alive when humans arrived, and those known only from the fossil record. Of the 249 identified species, 30 are extinct. More than 120 of the 219 species of mammals that live on the island today are threatened with extinction.
Lost species can never be brought back, so the study looked at how long it would take to regain the same levels of biodiversity through new species colonizing and evolving on the island.
Valente said: “Many of these species could become extinct in the next 10 or 20 years – they can’t wait much longer.” You can quickly reach a point where the species is no longer viable. The main message is that biodiversity will not recover quickly. Even places that we think are pristine and truly pristine can be pushed to the point of collapse pretty quickly.”
The loss of mammals would have a significant impact on other plant and insect species that depend on them. Valente said: “It’s a cascading effect – the loss of these mammals would probably cause a wider ecosystem collapse.” In total, it is likely to be more than 23 million years.
The main threats are human-induced habitat destruction, climate change and hunting. Over the past decade, the number of mammal species threatened with extinction in Madagascar has more than doubled, from 56 in 2010 to 128 in 2021. Conservation programs are needed to create livelihoods for local people, to prevent forests from turning into agricultural land and limit the exploitation of resources such as hardwood trees and animals used for bushmeat, the paper’s authors say.
Yadvinder Malhi, professor of ecosystem science at the University of Oxford, who was not involved in the research, said: “This fascinating study shows that it will take millions of years for natural processes to rebuild the levels of biodiversity that have already been lost, and tens of millions of years if currently endangered species are also lost. While this study looked at Madagascar, similar analyzes could be done for other islands and continents, and I think would tell a similar story.
He added: “The impact that humanity has already had on Earth’s biodiversity will last for millions of years, but the next few decades are critical to avoiding large-scale extinctions that could have much deeper and longer-lasting consequences.”