Madagascar extinctions could take up to 23 million years to recover

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Known for its distinctive diversity, with animals such as lemurs and the smallest chameleon in the world, the fauna of Madagascar, an island on the African continent some 470 kilometers from the eastern coast, is threatened with extinction —and it is not now.

In the last 2,500 years, since the arrival of man on the island, at least 30 species of mammals have disappeared and around 130 are threatened with extinction.

This is because the impacts of human activity in recent decades have accelerated the so-called rate of extinction of living beings and have direct consequences on the balance of species of Malagasy fauna.

If no preservation action is taken, the natural course of species evolution would take up to 23 million years to recover this diversity, considering the island’s non-flying mammals (primates, rodents, sea urchins and others), and about 3 million additional years for bats.

These are the main findings of a study published this Tuesday (10) in the scientific journal Nature Communications.

Led by the Portuguese Luis Valente, a researcher at the Naturalis Center for Biodiversity and the University of Groningen, both in the Netherlands, the research sought to understand the already verified effect of human action and the possible future consequences due to environmental degradation and hunting on the island’s biodiversity .

To arrive at these numbers, the study calculated the so-called evolutionary return time (ERT, for its acronym in English) necessary to recover the species that have become extinct in the last two millennia —two bats and 28 non-flying mammals— and those threatened with extinction according to the IUCN (International Union for Conservation of Nature) Red List if nothing is done now to stop its disappearance.

The island currently has 249 species of mammals, 43 of which are bats, the majority endemic but with some colonizing species, and 206 divided into the other families of the group.

The evolutionary turnaround time grows as more species are added to the endangered list —the number jumped from 110 in 2015 to 128 in 2021, the latest edition of the assessment. In 2010, there were only 56 species considered critically endangered.

In the case of bats, recovery to pre-human occupation levels would take 1.6 million years (confidence interval, or CI, 1.2–2.2). As for endangered species, according to an assessment by the international body, recovery could take from 1.9 to 2.9 million years (CI 1.5–3.6).

On the other hand, non-flying mammals, many of which have a slower rate of evolution —and which cannot easily move from the island to the mainland by flying—, the estimated return time is greater, with 2.9 million years (CI 2.3–3.6) for the prehuman condition and 7.1 to 23.3 million years (CI 5.6–28.3).

According to Luis Valente, although the recovery in that time does not lead to the return of species that have already become extinct, the study is unique because it brings a message of action. “The main message we would like to leave is that it is still in our hands to ‘save’ about 20 million years of evolution, that it really is worth protecting nature”, he said, in an interview with Sheet.

“Any loss of species has an impact in terms of time that is difficult even for a human being to imagine. We are destroying a unique evolutionary history, which took millions of years to evolve, in the space of just a few decades,” he said.

The researcher recalls that the rates of natural extinction (generally very slow) and those caused by man are different. While bats have virtually wiped out the Caribbean islands and around half of all New Zealand bird species have disappeared over the past 700 years, Madagascar has maintained a very low extinction rate. “However, in recent decades, the opposite is true: threats have escalated much faster in Madagascar than in most other island systems,” he explains.

As in other island systems, Madagascar is considered a biodiversity hotspot, that is, the diversity of plant and animal species found there does not exist anywhere else in the world. Almost all mammalian species that inhabit the island are unique to the island. “But even in the case of bats, their natural extinction rate is high, and recovering a single endemic species could take even longer than recovering the biodiversity of mammals on other islands”, he says.

For this reason, the author reinforces that it is essential to act now to guarantee the preservation of species that are already threatened and eventually those that can still be discovered by science.

“The extinction of mammals will follow with the extinction of plant and animal species that depend on them, and as a consequence the loss of one of the most important remaining tropical forests, with enormous implications for the CO2 balance. It is a potential source of unique biodiversity”, stated.

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