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Changes in the arrangement of Earth’s crustal plates impact the variety of life on the planet.

A reef teems with life in shallow water.

Over the course of 250 million years, various species have evolved and become extinct as the Earth’s tectonic plates have shifted and sea levels have fluctuated in the background.

New research has discovered a connection between the lithosphere and ocean levels, which impacts the accessibility of shallow marine habitats that support thriving life forms.

One of the main inquiries for paleobiologists is the reason for cycles in diversity and biodiversity.

Slah Boulila, a geologist at Sorbonne University and the lead researcher of the study, stated that the main inquiry for paleobiologists is the reason behind the existence of cycles in diversity and biodiversity.

Tectonic plates are large pieces of the Earth’s upper mantle and crust that are broken into fragments and cover the entire planet. These plates rest on a layer of partially molten rock and are constantly moving due to processes that occur beneath the surface. This movement, known as plate tectonics, is responsible for many geological features such as volcanoes, mountains, and ocean trenches. These processes occur over time and can change in intensity.

Researchers have observed a cyclical pattern in the diversity of marine species over time.

Seafloor Seesaw

Boulila and his team utilized various data sets on geology, marine life, and marine biodiversity to determine if these cycles were in sync. They examined over 18,000 samples of marine rocks and almost 32,000 genera, primarily from the Paleobiology Database, which is a publicly accessible database of paleontological information. Additionally, they incorporated the latest tectonic data by utilizing the GPlates software from the University of Sydney.

A colorful relief map of Earth

The formation and erosion of the ocean bottom impact the height of the sea. Source: NOAA, Public Domain.

The scientists compared the sets of data and discovered a pattern of 36 million-year cycles in marine biodiversity that aligned with fluctuations in seafloor production and subduction rates. Subduction is the process in which one tectonic plate is pushed beneath another, leading to the formation of thin oceanic crust where plates separate. Water present within the cracks of the subducting plate is drawn into the mantle and eventually released back into the ocean at a mid-ocean ridge, although this process is delayed. When these processes occur at a rapid pace, a larger amount of water is removed, resulting in lower sea levels.

Changes in sea levels, caused by the movement of continents and ocean basins, alter the habitat options for marine creatures. Higher sea levels submerge previously exposed land masses and deepen shallow ocean areas, leading to an increase in marine life. In contrast, lower sea levels create less space for marine organisms, according to Boulila.

“This highlights the crucial link between environmental changes and the processes of evolution and extinction.”

According to Bruce Lieberman, a researcher at the University of Kansas who studies prehistoric life and the development of species, previous studies have also demonstrated this pattern and proposed a shared explanation. However, Lieberman believes that this new study adds to the increasing amount of evidence found in fossil records. He emphasizes the significance of this evidence, as it highlights the crucial link between environmental changes and the process of evolution and extinction. Additionally, he suggests that there may be recurring environmental influences that contribute to the complexity of this phenomenon.

According to Boulila, while the concept of a link between tectonic plate movements and biodiversity has been around for some time, this study provides evidence to support it. This is due to the fact that there is now more data accessible compared to 30 years ago when the idea was first suggested. Boulila noted, “It’s fascinating that our data supports and verifies a significant hypothesis.”

Some scientists do not believe that plate tectonics follow a cyclical pattern, according to Boulila. They argue that it is instead random. However, this study demonstrates that there is indeed a cyclical nature, and the question remains as to why.

Boulila stated that the most intriguing aspect is identifying patterns in tectonic movements.

Lieberman expressed uncertainty regarding whether this study conclusively clarifies if increases in biodiversity are inherent to the planet or are influenced by external factors such as solar system events. He believes that the study is unlikely to definitively resolve the ongoing discussion on the validity of these biodiversity cycles.

—Danielle Beurteaux, Science Writer

Reference: Beurteaux, D. (2023). Changes in tectonic plates affect biodiversity. Eos, 104. Retrieved from Published on September 19, 2023.

Text © 2023. The authors. CC BY-NC-ND 3.0

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