The rich diversity on land that we seeToday, across the globe - a phenomenon far from new: the diversity of life on land has not changed at least over the last 60 million years ago. Recall that dinosaurs became extinct about 65 million years ago. According to data from a new study conducted by scientists at the University of Birmingham, the number of species in ecological communities on land increased only sporadically during geological time. The rapid growth of diversity was followed by a plateau that lasted tens of millions of years.
How many species on earth?
Previously, many scientists argued that diversitysteadily increasing over geological time, which would mean that biodiversity today is much more than it was tens of millions of years ago. But it’s very difficult to create an accurate picture of how the diversity of life appeared on land, as the data of the fossils become more scarce the farther we go. Using modern computing technology capable of analyzing hundreds of thousands of fossils, we begin to see patterns that challenge this view.
Researchers from the School of Geography, Earth Sciences andThe University of Birmingham and other institutions in the UK, USA and Australia were able to study the fossil data collected by paleontologists over the past 200 years from 30,000 different excavations around the world. Scientists have taken as a basis data on terrestrial vertebrates, which take into account the earliest appearance of this group almost 400 million years ago.
It turned out that the average number of species inThe ecological community of terrestrial vertebrates has not increased for tens of millions of years. The results, published in Nature Ecology & Evolution, show that the interaction between species, including the competition for food and space, limits the total number of species that can coexist.
Lead researcher Dr. Roger Close says: “Scientists often believe that the diversity of species is growing uncontrollably over millions of years, and that diversity today is much greater than in the distant past. Our research shows that the number of species within terrestrial communities is limited for long periods of time, which contradicts the result of many experiments in modern ecological communities - and now we need to understand why. ”
One of the reasons why diversity inecological communities do not increase, it may be that the resources used by species, such as food and space, are limited. Competition for these resources can prevent new species from entering the ecosystem and lead to a balance between the rates of speciation and extinction. However, after the emergence of major animal groups or major environmental disturbances, such as mass extinctions, an increase in diversity can occur suddenly - by geological rather than by human standards - and long periods again without any increase follow.
"Contrary to expectations, the largest increaseDiversity in terrestrial vertebrate communities occurred after a mass extinction that destroyed dinosaurs 66 million years ago, at the end of the Cretaceous. In just a few million years, the local diversity has increased two to three times the level before extinction - mainly due to the impressive success of modern mammals. ”
Professor Richard Butler, who also enteredThe research team adds that if we understand how diversity has changed in the past, we could better understand the likely long-term consequences of the current biodiversity crisis.
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