Mass species loss stunts evolution for millions of years
By Brandon Keim
26 October 2011 When searching for causes of Earth’s mass extinctions, scientists instinctively turn to geophysical calamities: erupting volcanoes, methane bursts, asteroid strikes, and other obvious dooms. But in the most massive extinction of all, when most of everything that lived died out some 250 million years ago, a more subtle form of destruction has been suggested. Following an initial volcanic upset, the loss of life itself may have fueled further extinctions, then slowed life’s recovery. That possibility, suggested by massive analyses of fossils and chemical signals left during the Permian-Triassic extinction event, represents more than an interesting wrinkle to a notable period in history. By this reading of the fossil record, biological diversity — something that’s now imperiled by human appetites — may be a sustaining, stabilizing force on planetary scales, and its disruption self-perpetuating. “Earlier interpretations have looked at the Permian-Triassic extinction as purely the result of external physical processes,” said paleobiologist Jessica Whiteside of Brown University. “But low diversity itself can be a feedback.” Whiteside’s specialty is mass extinctions and their geophysical consequences, cycles of energy and nutrients that play out over millions of years. Her latest study, co-authored with University of Utah paleobiologist Randall Irmis and published Oct. 26 in Proceedings of the Royal Society B, follows on earlier findings that the taxonomic richness of ammonoids, a once-dominant class of marine invertebrates, rose and fell in tandem with fluctuations in Earth’s carbon cycle for 10 million years after the Permian-Triassic extinction. During that time, the carbon cycle — the flow of life’s essential element through all Earth’s systems — oscillated wildly, a period known as a “chaotic carbon interval.” And rather than rebounding and steadily filling suddenly open niches, as might be expected, life appears to have entered a boom-and-bust cycle. Species flourished and collapsed, over and over, a planet-level version of the jellyfish bloom-and-bust cycles now seen in overfished oceans. One seemingly plausible explanation is ongoing Permian-Triassic volcanic activity, which could have decimated new species as they arose. However, carbon chaos continued for millions of years after volcanoes cooled. A newer explanation, favored by Whiteside, draws from the work of ecological theorists who say that, at planetary scales as well as local, complexity generates resilience. Applied to mass extinctions, this idea is somewhat radical — but in a coral reef or rainforest, or even a computer network, it’s an accepted notion. Just as distributed systems are more secure than a handful of mainframes, ecosystems composed of many interlocking and sometimes redundant species are especially sturdy. Because they’re stable, they in turn nourish life’s diversification over evolutionary time. It’s a biological catch-22: A richness of life requires stability to develop, but stability requires a richness of life. […] Scientists say that Earth may now be entering another period of mass extinction, with species dying at a pace seen only five times in life’s history, including the Permian-Triassic. Exactly how current extinction rates compare to those episodes is an open question, all the more pressing if modern extinctions represent not just the loss of a lineage but a constraint on evolution for the foreseeable future, if not millions of years to come. […]
DNA is nature's repository for high quality information, developed, expanded, diversified, and stored over millions of years. The internet has become man's repository for high quality information developed, expanded, diversified and stored over the past 200 years.
Most of both information systems are going to go up in a flash in the next decade or two, as we pump, drill, and burn everything that's left in order to try to maintain the complexity and size of a system in overshoot that only runs on fossil fuels? Great post, thanks.