“Dung beetles (Scarabaeidae: Scarabaeinae, Aphodiinae, Geotrupidae) are some of the most important invertebrate contributors to dung decomposition in both temperate and tropical agricultural grasslands. As such, they may help mitigate GHG [Greenhouse Gas] emissions and aid carbon sequestration through removing dung deposited on the pastures, increasing grass growth and fertilization” [Slade 2015: 1]. This Finland study analyzed the percent of GHGs removed by dung beetles at three levels: dung pat, pasture, and dairy/beef production life-cycle, finding reduced GHG emissions of 7%, 12%, and 0.05 to 0.13%, respectively. Dung beetles reduce methane emissions by aerating the dung pats, thereby preventing methane-producing anaerobic decomposition of the dung.
The reason dung beetles have a minimal effect in the full life-cycle analysis for Finland cattle is that the animals spend only a short portion of the year grazing in pasture, and thus emissions from dung on pasture is “dwarfed in comparison to other emissions of milk and meat production, such as methane emissions from enteric fermentation, nitrous oxide emissions from soils, and carbon dioxide emissions from energy use” [Slade 2015: 5]. However, “in regions where outdoor livestock grazing is more commonly used, the emissions from manure left on pasture will have a larger contribution to total agricultural emissions, with estimated fractions ranging from 11% in Asia up to 35% in Africa. Such patterns are combined with likely differences in dung beetle efficiency: In tropical regions, dung beetles can remove the majority of a fresh dung pat within the first few days after deposition – whereas in temperate conditions, a substantial fraction will remain throughout the grazing season” [Slade 2015: 5].
The authors recommend further research in tropical regions, predicting: “that effects at all levels from dung pats through pastures to the whole lifecycle of milk or beef production may be strongly accentuated at low latitudes” [Slade 2015: 5].
Slade, Eleanor, M., et al, 2015, The role of dung beetles in reducing greenhouse gas emissions from cattle farming, Scientific Reports 6:1814, https://www.nature.com/articles/srep18140.