Leaf wax offers insight into Earth's climate history

Without a time machine, scientists can’t possibly know what Earth’s ancient climates looked like, right? Not exactly. Researchers have an array of tools they can use to peek at the ancient environment, and they’ve just added a new one to the kit: leaf wax.

Plants produce a protective, waxy substance in the cuticle of their leaves that changes depending on the environmental circumstances when the leaf budded and grew. The waxy substance helps to minimize water loss and protect leaves from UV radiation.

The makeup of this leaf wax changes depending on the conditions the plant is growing in. In dry conditions, for example, plants use different organic compounds and distribute them differently to hold onto more water and increase odds of survival.

The team of scientists, led by Dr. Yvette Eley of the University of Birmingham, theorized that if they collected leaf wax lipids from organic soil and analyzed them, they could determine the growing conditions their parent plants grew in.

“Looking at soil today, you’re observing the integrated history of all the plant matter that went into forming that soil over the course of hundreds to thousands of years,” Dr. Michael Hren of the University of Connecticut said in a press release.

Eley and Hren examined leaf wax compounds in topsoil in North and South America, comparing their findings with modern climate records. They found a clear correlation with climate changes and distribution of leaf wax lipid compounds.

Paleoclimate scientists can get an idea of Earth’s past environment by analyzing stable isotopes in mammal bones and teeth, or ice core chemistry. But the new method fills an important gap, the researchers said.

“One of the huge gaps in the past is we didn’t have great quantitative records of moisture,” Hren said. “We’re now managing to get a really nice glimpse of the whole ecosystem and how it’s responding.”

The study has been published in the journal Scientific Reports. Funding was provided by the National Science Foundation.

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By Kyla Cathey, Earth.com staff writer