Eocene fossils provide a glimpse of the future

Stories from the collections I (page 1 of 2)

The impact of global warming is understandably a topic of concern. Researchers in numerous disciplines are using models to predict changes in sea level, ocean currents, and climate and the effect that long-term warming will have on Earth’s flora and fauna. It is difficult to determine the accuracy of these models unless we wait hundreds or thousands of years to see if their predictions prove correct. We can, however, learn from the past. By identifying a period in the past during which there was a significant warming trend over a long period of time, we can examine the fossil record prior to, during, and following that time interval, and we can see the effects on biodiversity. Such a study of floral and faunal change can serve as an independent test of hypotheses about the effects of warming today.
The Eocene offers just such a model as it is a time during which the Earth was much warmer than today. From the early to middle Eocene (55–45 million years ago), the Earth experienced a huge warming spike. Oxygen isotope data from Wyoming shows a temperature increase of 10°C in only one million years. The UCMP houses extensive collections from these past warm periods, and the analysis of these collections using a variety of approaches is a fertile avenue of ongoing research into how the North American flora and fauna responded to global climate change.

The plants tell the climate story
Fossil plants have provided us with powerful evidence of paleoclimate and have helped document periods of

global warming and cooling throughout the Cenozoic. Today we expect to see small, waxy leaves on plants growing in arid conditions and broad leaves on plants in areas of high rainfall and warm temperature. Thus, leaf morphology (shape, size, and thickness) provides information about temperature, precipitation, and other environmental conditions. We can apply the same kind of general analysis to past floras since we can infer that fossil plants lived under similar climatic conditions as their living counterparts. Using this approach, early studies of Eocene floras revealed that tropical to subtropical forests covered most of the continental United States, while at higher latitudes, temperate conifer-hardwood forests were dominant and reached well up into the Arctic Circle.

Large palmate leaf of Macginitiea, an extinct sycamore from the Chalk Bluffs flora and a common element in many North American Eocene floras. (photo by Diane Erwin)