A new study tracks the distribution of corals through the ages, showing how their position on the planet was influenced by plate tectonics and changes in temperature. Due to a limited fossil record, it has been difficult to demonstrate the relationship between coral reefs and climate change. Researchers have now used a combination of habitat modelling and reconstruction of palaeoclimate to predict the distribution of coral reefs over the last 250 million years. The predictions were then checked using fossil evidence of warm water coral reefs. The researchers were able to demonstrate that coral reefs existed at greater distances to the equator than today till about 35 million years ago, because of warmer climatic conditions and a more even distribution of shallow ocean floor.
First author of the paper, computational palaeobiologist Lewis Jones says “Our work demonstrates that warm-water coral reefs track tropical-to-subtropical climatic conditions over geological timescales. In warmer intervals, coral reefs expanded poleward. However, in colder intervals, they became constrained to tropical and subtropical latitudes.” Tectonic activity and global cooling restricted suitable coral habitats to tropical regions around 35 million years ago. According to the researchers, coral reef ecosystems are unlikely to be able to match the rapid rate of human-induced climate change.
Jones says, “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. However, whether coral reef ecosystems – and all the biodiversity they support – can keep pace with the current rapid rate of anthropogenic climate change is another question. Limiting global warming is fundamental to saving coral reefs, as well as the biodiversity they house. Yet, perhaps even more important is reducing the rate of global warming.”
Warm water coral reefs support the greatest biodiversity of marine organisms, and are known as rainforests of the sea. These ecosystems that include reef fishes are restricted to tropical and subtropical regions, where ocean temperatures do not fall below 18ºC. Co-author of the paper, meteorologist Alexander Farnsworth says, “Climate has changed significantly throughout geological time, however understanding how it has impacted coral reef ecosystems has been difficult due to a lack of quantifiable data which has significant gaps. Using this new combined data-model approach we can start to better understand reef ecosystems evolution and behaviour.”
Sampling bias in the fossil record has stymied previous investigations along similar lines. Sampling distribution is linked to GDP, with the wealthier nations more likely to have found ancient coral fossils, as they have looked the hardest. Co-author of the paper, Dan Lunt says, “This work highlights that climate and ecosystems have been intimately entwined together in Earth’s past history. This has crucial implications for ecosystems today, given current global warming.”
A paper describing the findings has been published in Nature Communications.