Sarah A. Beynon

The application of an ecosystem services framework to estimate the economic value of dung beetles to the U.K. cattle industry

1. The DEFRA ecosystem services framework was implemented in an entomological context to provide preliminary estimates of the economic value of four key ecosystem service benefits delivered by dung beetles (Coleoptera: Scarabaeidae, Geotrupidae) to the U.K. cattle industry and individual cattle farmers. These benefits included (i) reduced pest flies; (ii) reduced gastrointestinal parasites; (iii) reduced pasture fouling and (iv) increased soil nutrients.

Potential environmental consequences of administration of anthelmintics to sheep

Anthelmintics, veterinary medicines for the control of endoparasites, enter into the environment largely through faeces of the treated animals. Sheep dung is a patchily distributed, ephemeral resource, with a functionally important decomposer community. The nature of this community and the pharmacokinetics of anthelmintics in sheep mean that the ecotoxic impacts of these drugs in sheep dung may differ markedly from those in cattle dung, where most research has been focussed. The period of maximum residue excretion is generally more transient in sheep than cattle dung, but low-level excretion may continue for longer, giving the potential for extended sub-lethal effects. Here, the environmental impacts of sheep anthelmintics, as well as alternative endoparasite control methods are reviewed. Impacts are discussed in terms of the potential for residues to enter into the environment, the toxicity and the impact on ecosystem functioning at an appropriate scale. Future research priorities are also discussed; these include the need for studies of the functional contributions of dung-colonising species, as well as the development of higher-tier ecotoxicological methods bridging the gap between laboratory and field experiments. Large-scale and long-term studies, including the development of appropriate models, are necessary to allow the consequences of anthelmintic administration to be assessed, particularly within the remit of sustainable animal production.

Area‐wide impact of macrocyclic lactone parasiticides in cattle dung

Following the treatment of cattle with veterinary parasiticides and insecticides, residues are excreted into the dung in concentrations that may be toxic to functionally important dung‐colonizing insects. In the dung, these residues cause a range of well‐studied lethal and sub‐lethal effects, the magnitudes of which vary with the compound used, mode of administration and concentration, and the insect species in question. Particular concern has been associated with the use of macrocyclic lactones in this context. Loss of insect colonizers may delay pat decomposition, but field studies report contrasting results that reflect confounding factors such as weather conditions, pat moisture content, pat location, time of year and dung insect species phenologies. The question of fundamental concern is whether the impacts seen in experimental or laboratory studies are likely to have a functional impact on insect populations, community interactions and the economically important process of dung decomposition. Recent studies which have attempted to address these wider, landscape‐level impacts in temperate ecosystems are reviewed here. These show that the extent to which chemical residues may have any sustained ecological impact will depend on both a range of farm management factors, such as the temporal and spatial patterns of chemical use, the number of animals treated and the choice of active ingredient, and a range of insect‐related factors, such as abundance, population dynamics and dispersal rates. However, they also demonstrate that considerable uncertainty remains about the likely extent of such effects and that current data are insufficient to support firm conclusions regarding sustained pasture‐level effects. More large‐scale, longterm field experiments are required, particularly in relation to insect dispersal and functional interactions within the dung insect community.

Quantifying immediate and delayed effects of anthelmintic exposure on ecosystem functioning supported by a common dung beetle species

Dung beetles (Coleoptera: Scarabaeoidea) support numerous ecosystem functions in livestock-grazed pastures. Exposure to veterinary anthelmintic residues in livestock dung can have lethal and sublethal effects on dung beetles, and can reduce rates of dung removal, but the immediate and longer-term consequences for other dung beetle mediated functions have rarely been studied. We investigated the consequences of anthelmintic exposure on survival of the dung beetle Aphodius fossor and its delivery of four ecosystems functions that underpin pasture production: dung removal, soil fauna feeding activity, primary productivity, and reduction of soil compaction. We tested whether anthelmintic exposure had immediate or delayed effects on these functions individually and simultaneously (i.e., ecosystem multifunctionality). We found no evidence that ivermectin residues had a lethal effect on adult beetles. For dung removal, we found a significant interaction between the timing of exposure and functioning: while dung removal was impaired by concurrent exposure to high levels of ivermectin, functioning was unaffected when beetles that had been exposed previously to the same concentration of anthelmintic later interacted with untreated dung. Other ecosystem functions were not affected significantly by anthelmintic exposure, and there was no evidence to suggest any persistent impact of anthelmintic exposure on ecosystem multifunctionality. While anthelmintic residues remain a significant threat to dung beetle populations, for adult beetles, we found no evidence that residues have detrimental consequences for ecosystem functioning beyond the immediate point of exposure.

Effect of dung beetle species richness and chemical perturbation on multiple ecosystem functions

1. The relationship between biodiversity and ecosystem functioning is typically positive but saturating, suggesting widespread functional redundancy within ecological communities. However, theory predicts that apparent redundancy can be reduced or removed when systems are perturbed, or when multifunctionality (the simultaneous delivery of multiple functions) is considered.

Effects of the veterinary anthelmintic moxidectin on dung beetle survival and dung removal

Macrocyclic lactones (MLs) are chemical compounds administered to livestock for parasite control. These compounds are poorly metabolized and pass relatively unchanged into the dung of treated animals. When coprophagous insects such as dung beetles (Coleoptera: Scarabaeoidea) are exposed to ML residues while feeding on dung, lethal and sublethal effects are often observed. This can lead to ML residues impairing ecosystem functions that underpin agricultural production. A strategy to reduce these negative effects involves the use of compounds that offer lower risk to non‐target invertebrates, such as the ML moxidectin. Considering two dung beetle species with differing sensitivities to agricultural intensification, we asked whether exposure to moxidectin residues influenced survival, reproductive output, and functioning (short‐ and long‐term estimates of dung removal). When exposed to moxidectin, adults of the sensitive species – Geotrupes spiniger Marsham (Scarabaeidae) – experienced a 43% reduction in survival. In contrast, survival of the non‐sensitive species – Aphodius rufipes L. (Scarabaeidae) – was unaffected. We were unable to determine whether exposure affected reproductive output of either species. We found little evidence to suggest moxidectin impaired dung removal. However, high densities of a species with relatively low individual functional importance (A. rufipes) can compensate for the loss of a functionally dominant species (G. spiniger). Over a longer time frame, earthworms decomposed dung fully, irrespective of moxidectin residues. This functional redundancy reinforces that wider justification for the conservation of biodiversity should remain integrated into agricultural policy and practice.

Effects of the veterinary anthelmintic moxidectin on dung beetle survival and ecosystem functioning

Macrocyclic lactones (MLs) are a class of chemical compounds administered to livestock for parasite control. These compounds are poorly metabolized and are predominately excreted in dung. When coprophagous insects such as dung beetles (Coleoptera: Scarabaeoidea) are exposed to ML residues, lethal and sublethal effects are often observed. Indirectly this can lead to ML residues impairing ecosystem functions that underpin production. A strategy to reduce these negative effects involves selecting compounds that offer lower risk to non-target invertebrates such as the ML moxidectin. Considering two dung beetle species with differing sensitivities to agricultural intensification, we asked whether exposure to moxidectin residues influenced survival, reproductive output, and functioning (short- and long-term estimates of dung removal). When exposed to moxidectin, adults of the sensitive species (Geotrupes spiniger Marsham) experienced a 43% reduction in survival. In contrast, survival of the non-sensitive species (Aphodius rufipes L.) was unaffected. We were unable to determine whether exposure affected reproductive output of either species. We found little evidence to suggest moxidectin impaired dung removal. We found however, that high densities of a species with relatively low functional importance (A. rufipes) can compensate for the loss of a functionally dominant species (G. spiniger). Over a longer timeframe, earthworms fully decomposed dung irrespective of moxidectin residues.