Earthworm poop can predict past climates

Earthworm poop could provide a window into past climates, allowing scientists to piece together the prevailing weather conditions thousands of years ago, researchers say.
A laboratory study by scientists from the Universities of Reading and York has demonstrated that balls of calcium carbonate (small lumps of chalk-like material) excreted by the earthworm Lumbricus terrestris - commonly known as lobworms or nightcrawlers - maintain a memory of the temperature at which they were formed.
This means that calcite granules, commonly recorded at sites of archaeological interest, have the potential to reveal important information about past climates which could be used to enhance and benchmark climate change models, according to the study published in the journal Geochimica et Cosmochimica Acta.

"These chalk balls will allow us to reconstruct temperatures for specific time intervals in which they were formed. Reconstructions like this are interesting for archaeologists, because they give a climatic context to their finds," said lead author Dr Emma Versteegh from the Department of Geography and Environmental Science at the University of Reading.
"More importantly, climate proxies are the only means we have to study climate beyond the instrumental record, which only goes back about 150 years.
"This knowledge about past climates is of vital importance for developing and benchmarking climate models that make predictions for the future. Many different proxies already exist, but no proxy is perfect, or is available in every location, so it is good to have many different ones," Versteegh said.

The study involved keeping modern-day Lumbricus terrestris at different temperatures, then carrying out isotopic testing on the calcite granules excreted. This successfully demonstrated that the granules remembered the temperature at which they were formed.
The researchers are now gathering samples from archaeological sites dating back thousands of years in preparation for isotopic testing.
"We believe this new method of delving into past climates has distinct advantages over other biological proxies. For example, we believe it will work for the full seasonal range of temperatures, whereas methods such as tree rings, do not 'record' during winter," said Dr Stuart Black, from the University of Reading's Department of Archaeology.