Calcium Carbonate From Earthworm Poop Provides A Good Measurement Of Past Climate

Susan Bowen for – Your Universe Online

A recent discovery about earthworm excrement could help scientists improve our models of future climate change. Most earthworms excrete balls of calcium carbonate crystals, a chalk-like material. What makes these crystals interesting is that they retain a memory of the temperature at which they were created.

Scientists at the Universities of Reading and York conducted an experiment in which earthworms were kept at differing temperatures and their excretions measured using isotopic testing. These modern earthworms produced chalk balls that maintained a record of the temperature at which they were created.

Principal Investigator, Professor Mark Hodson, stated, “There are many conflicting theories about why earthworms produce calcite granules, but until now, the small lumps of chalk-like material found in earthworm poo have been seen as little more than a biological curiosity. However, our research shows they may well have an important role to play, offering a window into past climates.”

These chalky crystals are commonly found at archeological sites, and will help archaeologists in determining the climatic context of their finds. They will also provide an additional way of determining what the climate was like in ages past. Scientists are now gathering samples from archaeological sites that are thousands of years old for sampling.

Climate data using instruments only goes back about 150 years. Prior to that period other methods have to be used. In addition to human records, scientists use such techniques as measuring tree rings and ice cores and analyzing pollen distribution.

Adding earthworm poop to the arsenal has several advantages. Tree ring thickness, for example, can be influenced by other things besides climate, including the clearing of surrounding trees. In addition, many of the other methods may use samples that are thousands of miles from the archaeological site. These chalk deposits are right there in the exact same context as the surrounding dig site. This proximity will provide data on more localized environments and increase the accuracy of the climate data at any given place.

The part of the value of this localized data will be in improving current climate models. In an article in the journal Geochimica et Cosmochimica Acta, lead author Dr Emma Versteegh explains, “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.”

The more accurately we are able to measure climate fluctuations in the past and their consequences, the better we will be able to predict what might befall our planet in the future.