Greenhouse gas emissions from dung pats vary with dung beetle species and with assemblage composition

Abstract

Cattle farming is a major source of greenhouse gases (GHGs). Recent research suggests that GHG fluxes from dung pats could be affected by biotic interactions involving dung beetles. Whether and how these effects vary among beetle species and with assemblage composition is yet to be established. To examine the link between GHGs and different dung beetle species assemblages, we used a closed chamber system to measure fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from cattle dung pats. Targeting a total of four dung beetle species (a pat-dwelling species, a roller of dung balls, a large and a small tunnelling species), we ran six experimental treatments (four monospecific and two mixed) and two controls (one with dung but without beetles, and one with neither dung nor beetles). In this setting, the overall presence of beetles significantly affected the gas fluxes, but different species contributed unequally to GHG emissions. When compared to the control with dung, we detected an overall reduction in the total cumulative CO2 flux from all treatments with beetles and a reduction in N2O flux from the treatments with the three most abundant dung beetle species. These reductions can be seen as beneficial ecosystem services. Nonetheless, we also observed a disservice provided by the large tunneler, Copris lunaris, which significantly increased the CH4 flux–an effect potentially traceable to the species’ nesting strategy involving the construction of large brood balls. When fluxes were summed into CO2-equivalents across individual GHG compounds, dung with beetles proved to emit less GHGs than did beetle-free dung, with the mix of the three most abundant species providing the highest reduction (-32%). As the mix of multiple species proved the most effective in reducing CO2-equivalents, the conservation of diverse assemblages of dung beetles emerges as a priority in agro-pastoral ecosystems.

Stronger dung removal in forests compared with grassland is driven by trait composition and biomass of dung beetles

“…Dung beetles (Coleoptera: Geotrupidae, Scarabaeidae, Aphodiidae) are model organisms that are frequently used to test relations between biodiversity and ecosystem functioning. Both mesocosm and field experiments showed that different species contribute highly unevenly to ecosystem functioning and that trait-based trade-offs in space and time regarding ecosystem functions are likely (Larsen et al, 2005;Slade et al, 2007;Rosenlew & Roslin, 2008;Slade et al, 2011;Manning et al, 2016;Piccini et al, 2017). One of the basic functions provided by dung beetles is dung removal, to which the other functions are highly connected (Holter, 1979;Slade et al, 2007;Nichols et al, 2008;Nervo et al, 2014).…”

Ecosystem functioning in relation to species identity, density, and biomass in two tunneller dung beetles

“…Even though the total biomasses in the treatments between the two species were comparable, the results in terms of ecosystem functioning are very different: higher efficiency of C. lunaris species in comparison with O. illyricus . This is in agreement with previous studies that have shown that, even at the same total biomass, larger beetles are more effective than smaller ones (Kaartinen et al ., ; Nervo et al ., ; Piccini et al ., ). Moreover, based on the results from previous work on dung removal by monospecific (Tixier et al ., ) and mixed (Yamada et al ., ) assemblages of dung beetle species at high densities (Giller & Doube, ), we hypothesised that beetle abundance, biomass, and species identity would have a positive effect on dung removal across treatments.…”

Newly released non‐native dung beetle species provide enhanced ecosystem services in New Zealand pastures

“…Although limited in factors such as scale/replication, time frame, geographic range and dung beetle species, our results add to the literature showing that there are important ecosystem service benefits from dung beetles (e.g. Slade et al ., ; Beynon et al ., ; Manning et al ., ; Manning et al ., ; Piccini et al ., ). These findings are relevant both to agricultural systems where native dung beetle faunas are at risk from intensification of agriculture (Hutton & Giller, ) or systems where there are naturally impoverished dung beetle faunas, with active release programmes aiming to increase species richness (Edwards, ; Forgie et al ., ).…”

“…If an entire country has a naturally impoverished pastoral dung beetle fauna, then many species of dung beetle may require to be introduced to achieve improvements in ecosystem services over seasons and in pastures that will vary in factors such as farming types, soils, or climates (Tyndale-Biscoe, 1994;Edwards, 2009). Furthermore, evidence suggests that more diverse dung beetle communities can provide better benefits to ecosystem services than comparatively species-poor communities, but that species composition effects can be complex and warrant further study (Slade et al, 2007;Beynon et al, 2015;Manning et al, 2016;Manning et al, 2017;Piccini et al, 2017;Slade et al, 2017).…”