Constant biodiversity levels in oceansDate: 25 April 2020 Tags: Biodiversity
A new way of looking at marine evolution over the past 540 million years has shown that levels of biodiversity in our oceans have remained fairly constant, rather than increasing continuously over the last 200 million years.
The researchers have used a big data approach to study this question, which has been disputed by palaeobiologists in recent years.
Using fossil data collected over the past two centuries, and compiled by hundreds of researchers in the Paleobiology database over the last 20 years, the team was able to show regional-scale patterns of diversity across geological time from the so-called Cambrian Explosion - the point at which most major groups of animals started to appear in the fossil record - to the present day.
The problem is that the fossil record is not really global, because both the amount and the parts of the world that are actually preserved in the fossil record changes so much through geological time. This means that so-called "global" diversity curves are misleading.
Researchers studied diversity at regional spatial scales. This meant that we could focus on places and times that are well-known in the fossil record. By comparing geographic regions that were similar in size, they could show how marine animal diversity varied across both time and space.
Using these estimates for specific geographic regions, the team was also able to estimate the influence of other environmental factors, such as coral reef systems. At this more localised level, it's possible to see significant variations in diversity across the globe within time intervals.
These studies concluded that marine animal biodiversity had increased steadily over the last 200 million years, culminating in modern levels that were greater than any point in Earth's history.
The researchers did observe one point in the fossil record where there was a step change in diversity. The team found this evidence at the end of the Cretaceous period, when the dinosaurs became extinct.
This probably had something to do with ecological reorganisation after many species were wiped out. This suggests that such a widespread species loss cleared space for other groups to explode.