Evaluating long‐term ivermectin use and the role of dung beetles in reducing short‐term CH₄ and CO₂ emissions from livestock faeces: a mesocosm design under Mediterranean conditions

Abstract

1. Greenhouse gas (GHG) emissions from livestock contribute significantly to global warming, and a reduction of this source of emissions is crucial in achieving the goal of mitigating global warming.2. CO2 and CH4 emissions from dung pats were analysed by means of a mesocosm experiment in a Mediterranean ecosystem. The experiment consisted of a total of 30 mesocosms distributed across three treatments: a well‐preserved, undisturbed dung beetle assemblage associated with organic livestock; a dung beetle assemblage that was impoverished as a result of the long‐term use of veterinary medical products; and a control treatment without dung beetles.3. Corrections related to insect respiration allow researchers to provide more precise measurements of CO2 emissions from dung, especially in the initial and final phases of dung exposure, when the percentage of CO2 emitted by dung beetles can become greater than the emissions from the dung pats themselves.4. The effects of dung beetles on CO2 and CH4 emissions are much more accentuated in warm‐temperate conditions than in northern temperate areas previously studied. Mediterranean assemblages remove and spread dung faster and more effectively than do northern dung beetle assemblages characterised by a lower functional richness and beetle abundance and biomass.5. From a livestock management viewpoint, mesocosms representing areas with impoverished dung beetle assemblages, due to the long‐term use of veterinary medical products, such as ivermectin, emitted 1.6‐ and 2.8‐fold higher total CO2 and CH4, respectively, than mesocosms mimicking sites with untreated livestock.

The conservation status and distribution of Mediterranean dung beetles

“…It has been estimated that dung beetles provide benefits worth US$ 350 million yr-1 to the US livestock sector (Losey & Vaughan, 2006) and an amount within the same order of magnitude (€412 million yr-1) to the UK cattle industry (Beynon et al, 2015). Dung beetles are involved in numerous ecological functions, such as nutrient recycling (Yokoyama et al, 1991), soil improvement (Mittal, 1993), seed dispersal (Andresen, 1999), pest control (Miller et al, 1961) and reduction of methane emissons (Penttilä et al, 2013;Verdú et al, 2020) (see Box 2).…”

“…These harmful effects have deleterious impacts on dung beetle communities, which in turn have serious consequences for the basic ecosystem functions that dung beetles provide in terms of dung burial and soil nitrification (Verdú et al, 2018;Tonelli et al, 2020), and also the reduction of greenhouse gas emissions from livestock faeces (Verdú et al, 2020). All these studies demonstrate that the role played by large-bodied roller dung beetles is especially important in Mediterranean ecosystems: these species are often those that contribute most to dung removal, but they are also the ones most affected by these chemical products due to their quick arrival at dung pats and their lower population growth rates.…”

“…• Greenhouse gas emissions: dung beetle activity significantly reduces total CO 2 and CH 4 emissions from dung pats in Mediterranean ecosystems (Verdú et al, 2020). A pivotal requirement for sustainable management in the livestock sector is maintaining the diversity of dung decomposer insects, since a decrease in their ecological activity is responsible for an increase in greenhouse gas emissions (Penttilä et al, 2013;Verdú et al, 2020).…”

Dung beetle trophic ecology: are we misunderstanding resources attraction?

“…This is a consequence of the ecological functions performed by this group of organisms, which are essential to ecosystem functioning both within natural and anthropic land‐uses (Hanski & Cambefort, 1991; Andresen & Feer, 2005; Nichols et al ., 2008; Verdú et al ., 2018). These functions are directly linked to their trophic ecology: dung beetles use mainly vertebrates dung and carrion for feeding and nesting and, during these processes, they usually bury large amounts of organic matter, which leads to improving soil quality, reducing parasite incidence, facilitating seed germination through secondary seed dispersal, and reduce greenhouse gas emissions (Gittings et al ., 1994; Davis, 1996; Andresen, 2003; Gardner et al ., 2008; Penttilä et al ., 2013; Slade et al ., 2016; Verdú et al ., 2020); with some exceptions (Fowler et al ., 2020).…”

Spatiotemporal patterns of taxonomic and functional β‐diversity of dung beetles in native and introduced pastures in the Brazilian Pantanal

“…They also can improve herbaceous plant growth (Badenhorst et al 2018), reduce livestock gastrointestinal parasite (Sands & Wall 2017) and dung-fly availability (Braga et al 2012), and greenhouse gas emissions from dung pats (Slade et al 2016;Piccini et al 2017). On the other hand, the long-term use of veterinary medical products in cattle, such as ivermectin, can negatively affect the dung beetle performance of ecological functions and services (Verd u et al 2018;Verd u et al 2020). These beetles have been widely used as both ecological and biodiversity indicators because they are sensitive to natural and anthropogenic changes (Halffter & Favila 1993;Nichols et al 2007;da Silva et al 2019) and are easily sampled with standardised protocols (Gardner et al 2008;da Silva & Hern andez 2015;Correa et al 2018).…”