The history of “deep time” is written into the Earth’s rocks. There’s a lot to learn, but perhaps our most relevant topics for right now are the records of life and of climate. A new book entitled Planet Earth – In Deep Time is the result of a five-year UNESCO-funded project (more about UNESCO) looking at the interaction between climate change and the earth’s biodiversity in deep time. It features the work of some 114 scientists from more than 30 countries and carries a mission to improve scientific collaboration in the third world. I spoke with the book’s co-editor, Dr. Johnny Waters, professor of Invertebrate Paleontology at Appalachian State University, about the project and how deep-time events relate to our place in history.
The goal was to study paleoenvironment and ecological response to environmental changes, specifically in two intervals of time; the Devonian and the Carboniferous, about 350 million years ago to about 250 million years ago. The oldest forests and the oldest true soils are developed here, and, in particular, it’s the first time when large amounts of carbon dioxide get fixed in plants and get buried. The oldest coal deposits and significant petroleum and shale gas come from this interval. If you take all the carbon dioxide out of the air by burying it, it changes the climate very dramatically. We have a major transition from a greenhouse earth condition to one of the longest ice-house earth conditions in the last 500 million years.
Greenhouse earth conditions mean the planet is very hot and has no continental glaciers. Oppositely, icehouse earth conditions are characterized by glaciers advancing and retreating over the continents. We are currently in an icehouse situation, in a period between “ice age” glaciations. These two opposite periods last for millions of years.
Four of the eleven largest ecological perturbations in the last 500 million years happened during the Devonian. It was a prolonged interval of ecological crisis, sort of a rolling extinction, taking out different groups of plants at different times. One of these events took out the coral reef ecosystems. Another one took out the plankton, and another one took out the fledgling terrestrial ecosystems going on at the time.
Deep time refers to millions and billions of years of earth’s geologic history; time spans that are difficult to relate to or comprehend. So, why are the events of earth’s deep time relevant to us today?
What studying these intervals of environmental perturbation in the geologic past do, is they show us what happened the last time. In the modern world, we have great concern about the impact of rapid environmental change on ecosystems, and today what we’re seeing is the rapid increase in carbon dioxide, and we’re seeing ecological responses to that. Tropical taxa are spreading more and more into mid-latitudes, It’s not just things like snakes coming out of the tropics that we now find in the Everglades; it’s tropical diseases that are now being found at latitudes where we didn’t find them before. What the geologic record does is, it gives us the track record of what happened in the past, when we see situations that parallel what we see today. In the Devonian, we’re looking at a rapid decrease in carbon dioxide, the world is getting colder; today we’re looking at a rapid increase of carbon dioxide, the world is getting warmer. But the thing that’s significant to ecosystems is the rate of change. When you have rapid rates of environmental change, the ecosystems simply cannot adapt to those, and there are major extinctions.