Ecosystems take two million years to recover after mass extinctions

It takes ecosystems two million years to recover after a mass extinction and for them to become functional and resilient again, according to new UCL co-led research. The study Hojung Kim and Dr Sarah Alvarez) and academics from Southampton, Frankfurt and California. The team looked at 13 million years' worth of fossil plankton records in the aftermath of near annihilation of ocean plankton, during the Cretaceous/Paleogene mass extinction, providing a remarkable glimpse into how the marine ecosystem 'reboots'. Lead author, Dr Alvarez (UCL Earth Sciences, University of Gibraltar, University of Bristol) said: "We wanted to find out how long the ocean ecosystems took to recover and how this happened so we looked at the best fossil record of ocean plankton we could find - calcareous nannofossils (they are still around today) - and collected 13 million years of information from a sample every 13,000 years. "We measured abundance, diversity and cell size from over 700,000 fossils, probably the largest fossil dataset ever produced from one site." The researchers were investigating the aftermath of a mass extinction event 66 million years ago that wiped out three-quarters of the planet's plant and animal species, including all non-avian dinosaurs, that was caused by an asteroid striking the Earth. Dr Alvarez and co-authors found that plant-like (photosynthetic) plankton bounced back almost immediately after the mass extinction but that the early communities were highly unstable and cell sizes were unusually small.