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Dung Beetles: Unlikely Heroes in the Battle Against Global Warming

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Agriculture is known to be one of the largest contributors to greenhouse gas emissions, with large ruminants such as cows, buffalo, sheep, and goats emitting more gases than the transportation industry. These animals are responsible for about a third of the global methane emissions, a gas that makes up half of farming's contribution and is even more potent than CO2. But the dung beetle, with its peculiar habit of laying eggs in and eating cow dung, might be a weapon in the fight against global warming.

The Role of Dung Beetles in Reducing Methane Emissions

In a recent study published in the journal PLOS ONE, Atte Penttilä and colleagues from the University of Helsinki investigated the impact of dung beetles on methane emissions from cow dung. The study found that cow dung with beetles, specifically Aphodius species, released nearly 40% less methane over a summer period than beetle-free cow dung.

How Do Beetles Help Reduce Methane Emissions?

The beetles' good work happens mainly as they dig around in the dung. Methane is produced under anaerobic, or oxygen-free, conditions. As the insects tunnel through the dung, they aerate it, changing the conditions so that less methane is produced within the dung. This translates to less methane gas released into the atmosphere.

The Presence of Beetles and Nitrous Oxide

The study also showed that the presence of the beetles in aging cow dung increased the release of another greenhouse gas, nitrous oxide. Further studies are needed to determine whether this cancels out their methane-related efforts.

Decline of Dung Beetles

Sadly, dung beetles are in decline, with over half of dung beetle species threatened or near endangered in Finland. This is due to the lack of diversity in both dung and pasture, as well as the reduced quality of the dung, which now contains more chemicals such as anti-parasite drugs given to farm animals.

Wrapping Up

Beetles alone cannot contain greenhouse gases, but it is important to understand and account for the effects of live agents in changing gas fluxes from dung. The best way to help beetles thrive and reduce methane emissions is to let cattle graze on variable types of outdoor pasture. By blocking the very cycles that might make a silent but significant contribution to one of the world's hottest problems, we may miss the mark in our efforts to fight global warming.

William H. McDaniel, MD

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School.

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