Summary1. Many studies document high levels of functional redundancy in ecosystems, suggesting that species extinctions will not be detrimental to ecosystem functions and services. However, apparently redundant taxa may prove critical for sustaining ecosystem functions and services in the context of environmental perturbations. 2. Dung beetles (Coleoptera:Scarabaeidae) provide a valuable ecosystem service in temperate agro-ecosystems by increasing rates of dung decomposition and nutrient cycling. However, there is concern that these services may be negatively affected by changes in species richness and composition due to changes in pasture management and negative effects of anthelmintics used to control livestock parasites. 3. We used a mesocosm experiment to investigate the functional importance of dung beetle species richness in a system perturbed by the anthelmintic, ivermectin. We varied dung beetle species richness within three functional groups in factorial combination with ivermectin treatment. 4. In the short term (1-4 weeks), multi-species dung beetle assemblages achieved higher decomposition rates than monocultures, but only in ivermectin-treated dung. Varying speciesspecific sensitivities to ivermectin meant that species-rich assemblages sustained ecosystem functioning in the context of this anthropogenic perturbation. 5. Over the longer term (36 weeks), there was a significant, positive effect of species richness on dung decomposition in both ivermectin-treated and untreated dung, underlining the functional importance of maintaining a species-rich dung processing community even in the absence of perturbations to the system. 6. Synthesis and applications. The interacting effects of dung beetle species richness and ivermectin highlight the importance of maintaining diverse assemblages in the face of anthropogenic perturbations and suggest that apparent functional redundancy of species in agroecosystems should be interpreted cautiously. Furthermore, different farm management practices (e.g. pesticide use and fragmentation of habitats) may have consequences for ecosystem functions and services that exceed the effects of each when considered in isolation.

Abstract. 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.2. A mesocosm experiment was carried out to quantify the impacts of anthelmintic treatment on dung removal by dung beetles when (i) cattle were excreting anthelmintics (which affect dung beetles) in a sufficient concentration to impact dung beetles and (ii) when cattle were not excreting dung containing anthelmintics (which affect dung beetles) in a sufficient concentration to impact dung beetles.3. Inferring from our mesocosm experiment and existing data, the value of the benefits of dung beetles under current farming practices (and current anthelmintic usage) was estimated. We estimated the potential economic benefits if dung beetles were protected (i) under all entry-level agri-environment schemes; (ii) under organic schemes; or (iii) if farmers stopped treating adult cattle with anthelmintics during the grazing season.4. While these estimates are preliminary, and should not be treated as definitive values, we suggest that dung beetles may be currently saving the U.K. cattle industry c. £367 million each year: c. £354 million in conventional systems and c. £13 million in organic systems. Annual benefits per cow are greater in organic systems (£43.47) compared with conventional systems (£37.42).5. Protecting dung beetles under agri-environment schemes could save the U.K. cattle industry an additional £40.2 million year −1 (£4.36 per cow), while protecting dung beetles under organic schemes could save £378 k year −1 (£1.26 per cow). The cessation of, largely unnecessary, treatment of adult cattle with anthelmintics could save the U.K. cattle industry an additional £6.2 million year −1 (£1.40 per cow) in addition to savings on the anthelmintics themselves.6. These estimates are based on a large number of underlying assumptions and, thus, may be overestimating or underestimating the economic value of ecosystem services delivered by dung beetles.7. The potential for using the DEFRA ecosystem services framework in an entomological context is highlighted. These estimates emphasise the contribution of dung beetles as key Ecosystem Service Providers (ESP's) within the U.K. cattle sector and, by extension, emphasise the importance of valuing supporting ecosystem services derived from invertebrates.

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