This slide is based on data reported about five years ago in the journal Nature [R. A. Rohde and R. A. Muller. “Cycles in fossil diversity.” Nature 434 (2005): 209–210]. It tracks marine organisms over the past half billion years—the period for which good fossils exist. Each data point covers just under 2 million years. The top chart indicates the total number of genera (the taxonomic category above species). The space between the green and gray curves reflects uncertainty in the data. The bottom chart indicates, for each time period, the percentage of genera that are missing in the next time period.
Five times in the last 500 million years, there have been catastrophic mass extinctions. Most people know about the one 65 million years ago that wiped out the dinosaurs, but there were four of them before that. Each time the earth has recovered, after a period of several million years, but with a completely altered biosphere.
But now look at what’s happening today. Biologists estimate that we are losing something like 30,000 species per year. At that rate, we will lose somewhere between 1/3 and 2/3 of all the species on the planet within the next 100 years. If we managed to stop at that point, and wiped out nothing else for the next 2 million years, we’d still have engineered a die-off somewhere in the circles I’ve drawn in red on the charts. We are the sixth great catastrophe to strike the planet Earth. At historical rates of speciation, it will take 5 to 10 million years—25–50 times the history of the human race, or nearly 1000 times the history of civilization—to recover the diversity of species that we are wiping out in couple hundred years.