Science and Tech

The cause of the explosion of marine biodiversity that led to the current fauna

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It is known from the fossil record that life on our planet has been hit by at least five major mass extinctions over the last 500 million years. The mass extinction that occurred at the end of the Permian period, the greatest of all time, wiped out more than 90% of marine species and left ecosystems on the verge of collapse. Today, 250 million years later, life in the sea is more diverse than ever before. What happened so that biodiversity is greater today than at any previous time?

In order to answer this question, scientists have reconstructed the history of the diversity of marine animals from about 540 million years ago to today.

This international team, led by scientists from the Institute of Marine Sciences (ICM) in Barcelona, ​​attached to the Higher Council for Scientific Research (CSIC) in Spain, has developed a diversification model that allows reconstructing the history of the diversity of marine animals from the Cambrian explosion of life, about 540 million years ago, to the present.

The problem that those who have tried in the past to find out why biodiversity is greater today than it has been at any previous known time has been suffering from the fact that the fossil record is incomplete. Cermeño’s team was clear that it was convenient to develop a new computational approach that would allow reconstructing the history of life. The model is capable of recreating the geographic distribution of diversity in the current oceans, especially hot spots or hotspots, and reveals the mechanisms that have created them.

Thanks to the model, Cermeño and his colleagues have verified that the time elapsed between one mass extinction event and the next was decisive in allowing the development of biodiversity hotspots. “It was exciting to see that the pattern of global diversity resulting from our model of regional diversification was similar to that observed from the fossil record. This makes it relevant to use the model to reconstruct spatial distributions of diversity in the past, allowing us to resolve when and how marine biodiversity hotspots originated”, celebrates ICM researcher Carmen García-Comas, coordinator of the study.

The most obvious conclusion is that the Earth’s environmental stability, only disturbed by mass extinctions and lesser-impact disturbances, facilitated the explosion of biodiversity in the oceans. In other words, current biodiversity is the result of long periods of environmental stability on Earth that allowed the development of biodiversity hotspots, regions with a high number of species.

Coral regions are examples of ‘hotspots’ of marine biodiversity, regions with a high number of species. (Photo: Dwayne Meadows/NOAA/NMFS/OPR)

The new model also provides new and revealing data on one of the most controversial questions in evolutionary ecology: whether or not there is a limit to the global diversity that Earth can support. Ecological theory states that as diversity increases and biological interactions, such as competition, intensify, the diversification process slows to a stop. At this point, the appearance and establishment of a new species will inevitably cause the extinction of an old species.

However, some scientists have argued that Earth’s ecosystems are so heterogeneous that there will always be room for more species. “Our results reconcile both points of view. While most of the oceans have levels of diversity well below their maximum, the regions that are home to biodiversity hotspots could be close to their limit”, highlights Cermeño.

To prepare the work, the scientific team has used a paleogeographic model that traces the movements of the continents and the seabed over millions of years, as well as a model of the Earth system that reconstructs the environmental conditions of the seas in the past. Each tracked region accumulates diversity over time at a rate controlled by temperature and the amount of food available in each region at any given time.

“This modeling tool is very powerful, as it allows us to explore many things, including what would have happened if some of the great mass extinctions that devastated life in the past had not happened or if they had happened at another time in history. of the Earth”, emphasizes the leader of the project.

Human interference in the natural functioning of the planet’s ecosystems has caused what is considered the sixth great mass extinction. According to the United Nations, in the last century as many species have disappeared as would have become extinct in 10,000 years if a normal scenario is assumed. In addition, 25% of the species evaluated by the International Union for Conservation of Nature are in danger of extinction.

“This study highlights that, if current trends continue, the predicted loss of biodiversity by the end of this century could take millions of years to recover, possibly beyond our very existence as a species,” concludes Michael Benton, professor of science grimly. the University of Bristol in the UK and co-author of the paper.

The study is titled “Post-extinction recovery of the Phanerozoic oceans and biodiversity hotspots.” And it has been published in the academic journal Nature. (Source: ICM / CSIC)

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