The Unlikeliest Heroes in the Battle Against Climate Change? Dung Beetles

The cow poop-crunching insects play a small but vibrant role in reducing greenhouse gases, scientists report.

Image
Ben Haeringer / Flickr

In this edition of Toilet Tuesday, take a journey out into nature's vast bathroom:

The world's climatologists should put down their thermometers and take a minute to thank Atte Penttilä for absorbing the bullet on this one: After spending extensive time in the pastures of northern Europe, Penttilä and his associates can now report greenhouse-gas emissions are affected by, of all things, beetles rummaging around in cow dung.

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In a finding that's sure to confuse climate-change skeptics – it's easy to mock this research, but doing so actually hurts their case – Penttilä says that the way the beetles are tunneling through cow patties is reducing amounts of methane going into the atmosphere, according to a recent study in PLoS ONE. With cattle farming responsible for an estimated 18 percent of anthropogenic emissions worldwide – 35 to 50 percent of extremely potent methane in particular – this breakthrough is not to be brushed off. Indeed, as the study's authors write, the research provides a "seminal suggestion that dung beetles may exert a wider impact on [greenhouse-gas] fluxes from agriculture."

Scientists from the Universities of Helsinki and Oxford joined forces on the experiment. First, they wandered over a Finnish cattle field to collect the insects from their reeking brown homes. This is one of their samples (warning: poo ahead):

(Eleanor Slade)

They then set about stocking up on cow manure in a process that's best quoted verbatim:

The dung was collected from a herd of some twenty heads of Ayrshire cattle, all adult dairy cows. At the time of dung collection, the cattle had been grazing daily for approximately a month on improved pastures sown with a mix of timothy (Phleum pratense) and meadow fescue (Festuca pratensis) with a smaller component of red clover (Trifolium pratense). Outdoor grazing time ranged from 4 to 5 hours per day between 8 AM and 2 PM, with the dung collected as the cattle entered the barn for within-stall milking. When indoors, the cattle was fed additional silage ad lib, a standard concentrate (Maituri 20 and Amino-maituri 30, Raisio Oyj, Raisio, Finland) and magnesium-selenium-minerals (Pihatto-Melli; Raisio Oyj, Raisio, Finland). No animal in the herd had been given antibiotics or antiparasitic treatments. All dung was manually homogenized before partitioning into experimental pats.

Dung in one hand, several species of beetle in the other, the researchers laid out a little field of containers to measure the vapors that poured off various cow patties. It looked like this:

After weeks of field work and analysis, the team was ready with results: The manure without beetles in it produced higher amounts of methane – on one special day, as much as five times what wafted off the insect-loaded dung.

Why was that? They surmised that in making little holes and passageways in the dung, the beetles were disrupting the formation of methane, which needs a low-oxygen environment to naturally accumulate. The impact the insects are having on methane production on a day-to-day basis is "major," they report. "If the beetles can keep those methane emissions down," said the head of the team, "well then we should obviously thank them – and make sure to include them in our calculations of overall climatic effects of dairy and beef farming."

As is frequently the case with contemporary climate news, there is a dark side to this story. Here's one of the team members explaining it:

"Overall, the effects that we found are intriguing, but the implications also quite worrying", says Eleanor Slade, a researcher commuting between teams working on dung beetles in both Helsinki and Oxford. "When you combine the current increase in meat consumption around the world with the steep declines in many dung beetle species, overall emissions from cattle farming can only increase."

Top image: Ben Haeringer / Flickr

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