Today’s Factismal: There have been ten mass extinctions in Earth’s history.
One of the more interesting predictions of the Theory of Evolution is that there should be a long-term trend toward more different types of life. And, by and large, that is true. Today, there exists more species of life than at any time in the history of the world.
And yet, there have been times when the overall number of species went down. The best known of these is the Cretaceous-Permian boundary, better known as “the death of the dinosaurs” some 65 million years ago, which killed about 75% of all species. Events like this are known as mass extinction events or, more poetically, as “great dyings”. They range in severity from the End-Edicarian event 542 million years ago in which some 20% of species went extinct to the Permian-Triassic event 252.8 million years ago that killed off some 96% of all life on Earth.
These events hold a fascination for both the scientist and the layman. Part of that is the sheer scale of the disaster; outside of a few B-movies, nothing imagined by Hollywood is half so dramatic nor as disastrous as a mass extinction. And part of that is trying to understand why these events happen. Is it asteroid impacts? Climate changes? Disease? Volcanic eruptions? Or could it be some combination of all of these? (Full disclosure: I am in the “all of the above” camp.) But the largest part of the fascination comes from the frisson of fear these events generate: could it happen again?
Today, there are many biologists who believe that we are at the start of another mass extinction event. They note the increased number of endangered species and recent extinctions dating from the Pleistocene. These scientists would like your help in measuring Earth’s current biodiversity. To help them, all you have ot do is join Project NOAH (Networked Organisms And Habitats). On their website, you’ll find missions that seek to detail the level of biodiversity at every level and one every continent.. So why not give them a try? If nothing else, they have lots of pretty pictures to look at!