New research has found that prehistoric coral reefs dating back as far as 250 million years are much further from Earth’s equator than they are today.
The new study, published in Nature Communications, shows how changes in temperature and plate tectonics, where the positions of Earth’s continents were in very different positions than now, have shaped the distribution of corals over the centuries.
Although climate has often been considered the main driver of the location of coral reefs, this has yet to be proven due to limited fossils. Now, for the first time, a team of international scientists has used habitat modeling and reconstructions of past climates to predict the distribution of suitable environments for coral reefs over the past 250 million years.
The researchers, from the University of Vigo, in Spain, the University of Bristol and University College London in the UK, then checked their predictions using fossil evidence from warm water coral reefs. They showed that in the past, from 250 to about 35 million years ago, corals existed much further from the equator than they do today, due to warmer climatic conditions and a more even distribution of the shallow ocean floor.
“Our work shows that warm water coral reefs track tropical to subtropical climatic conditions over geologic time scales. In warmer intervals, coral reefs expanded polarward. However, at colder intervals they were confined to tropical and subtropical latitudes,” said first author Dr. Lewis Jones, a computational scientist. paleobiologist researcher at the University of Vigo.
Suitable coral habitats were restricted to the tropical regions from about 35 million years ago, driven by global cooling and increase in shallow oceans due to tectonic changes of the Indo-Australian archipelago, which is recognized as a hotspot for marine biodiversity.
While this suggests that warm temperatures in the past allowed long-term poleward expansions of corals, the researchers say coral reef ecosystems are unlikely to match the rapid rate of human-induced climate change.
“Current anthropogenic climate change will result in the poleward expansion of suitable habitat for coral reefs. In fact, we are already witnessing the expansion of some tropical reef corals. Whether coral reef ecosystems — and all the biodiversity they support — can keep up with the current rapid rate of anthropogenic climate change is another question,” Jones said.
“Limiting global warming is fundamental to saving coral reefs, as well as the biodiversity they host. But perhaps even more important is curbing global warming.”
Warm water coral reefs, also known as ‘rainforests of the sea’, support the greatest biodiversity of marine organisms on Earth. In today’s oceans, these biologically rich ecosystems, including reef fish, are limited to the tropics and subtropics, where ocean surface temperatures typically do not fall below 18ºC. A significant portion of this modern biodiversity is found in the Indo-Australian archipelago. In the geological past, however, coral reef ecosystems also existed outside the tropics and subtropics, with their fossil remains much further from the equator.
Co-author Dr. Alex Farnsworth, Senior Research Associate in Meteorology and Climate Modeling at the University of Bristol Cabot Institute for the Environment, said: “The climate has changed significantly over geological time, but it has been difficult to understand how coral reef ecosystems are affected. has led to a lack of quantifiable data showing significant gaps.
“Using this new combined data modeling approach, we can better understand the evolution and behavior of reef ecosystems.”
Previous work has not found a strong relationship between temperature and coral reef distribution because the fossil record is incomplete and biased. For example, not all remnants of organisms or ecosystems that existed in the past are recorded in the fossil record, and the main factor explaining the sampled distribution of ancient reefs has been shown to be gross domestic product, with most known fossil reef data coming from rich countries purely because these are the regions where we searched the hardest.
Co-author Dan Lunt, professor of climate science at the University of Bristol Cabot Institute for the Environment, added: “This work highlights that climate and ecosystems are closely intertwined in Earth’s history. This has crucial implications for ecosystems today. given the current global warming.”
‘Climatic and tectonic drivers have shaped the tropical distribution of coral reefs’ by Lewis Jones et al in Nature Communications
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