Leaves may hold key to better data, study says

A new research study, coauthored by Dr. Daniel Peppe, assistant professor of geology, has found a correlation between the leave fossil record and models that determine ancient climate data.
Courtesy Photo

By Jade Mardirosian
Staff Writer

A recent study done by geologists around the world and researchers at Baylor and Wesleyan University has found a new, more accurate way to estimate climates from ancient environments: leaves.

Dr. Daniel Peppe, assistant professor of geology, has worked on this research since 2009 while employed at Wesleyan University. He continued the study at Baylor and has conducted field research in various locations, including New Zealand.

“We looked at a bunch of species of modern leaves from around the world and looked at their size and shape, then the relationship between that and temperature and precipitation,” Peppe said. “We used those relationships in order to develop a model to estimate temperature and precipitation.”

Data was collected from nine fossil plant sites from North and South America and 92 modern sites on every continent except for Africa and Antarctica.

“I went to New Zealand to collect some of the modern data, and a lot of the other modern sites were collected from other co-authors,” Peppe said. “They took photos of leaves they collected and sent them to us. Undergraduates at Wesleyan and Baylor helped us process the leaves with a computer processing protocol, and a lot of the work was done that [way], with both the modern and fossil leaves.”

Peppe said the researchers used models from fossil plant sites from about 50 million to 66 million years ago.

“What we found was the estimates the models used were better than some traditional models and were in better agreement with what we would expect from the estimates,” he said. “Temperatures in particular were in better agreement with independent temperature estimates from those periods of time than the more traditional fossil leaf methods.”

According to Peppe’s website, the “models offer improvements in both the accuracy and precision of the climate estimates relative to traditional paleobotanical techniques. Critically, the estimates made using our new models are typically warmer and wetter, and are much closer to independent climate estimates than other leaf-climate approaches offering the potential for better understanding the terrestrial world during ancient greenhouse climates.”

During the research, Peppe and the other researchers noted several factors that impact the physiognomy-climate relationships, including leaf habit, local water availability, phylogenetic history and geographic location.

Peppe said the impact of this research is on understanding ancient climate and its relation to today’s climate change.

“One of the cool things about this is I think we are beginning to better understand how leaves are functionally related to climate so that we can make better models for reconstructing temperature and precipitation in the past,” Peppe said.

“By doing that we can better understand how climate has changed through time. That really gives us a lot of potential for better understanding ancient environments and can hopefully better understand what is happening today in terms of how the climate is changing as the planet continues to get warmer.”

The study is in the May issue of New Phytologist Journal and was co-authored by 28 researchers.