Philip Riordan

Does organic farming reduce environmental impacts? – A meta-analysis of European research

Organic farming practices have been promoted as, inter alia, reducing the environmental impacts of agriculture. This meta-analysis systematically analyses published studies that compare environmental impacts of organic and conventional farming in Europe. The results show that organic farming practices generally have positive impacts on the environment per unit of area, but not necessarily per product unit. Organic farms tend to have higher soil organic matter content and lower nutrient losses (nitrogen leaching, nitrous oxide emissions and ammonia emissions) per unit of field area. However, ammonia emissions, nitrogen leaching and nitrous oxide emissions per product unit were higher from organic systems. Organic systems had lower energy requirements, but higher land use, eutrophication potential and acidification potential per product unit. The variation within the results across different studies was wide due to differences in the systems compared and research methods used. The only impacts that were found to differ significantly between the systems were soil organic matter content, nitrogen leaching, nitrous oxide emissions per unit of field area, energy use and land use. Most of the studies that compared biodiversity in organic and conventional farming demonstrated lower environmental impacts from organic farming. The key challenges in conventional farming are to improve soil quality (by versatile crop rotations and additions of organic material), recycle nutrients and enhance and protect biodiversity. In organic farming, the main challenges are to improve the nutrient management and increase yields. In order to reduce the environmental impacts of farming in Europe, research efforts and policies should be targeted to developing farming systems that produce high yields with low negative environmental impacts drawing on techniques from both organic and conventional systems.

Culling-induced social perturbation in Eurasian badgers Meles meles and the management of TB in cattle: an analysis of a critical problem in applied ecology.

The Eurasian badger (Meles meles) is implicated in the transmission of bovine tuberculosis (TB) to cattle in the UK and Republic of Ireland. Badger culling has been employed for the control of TB in cattle in both countries, with varying results. Social perturbation of badger populations following culling has been proposed as an explanation for the failure of culling to consistently demonstrate significant reductions in cattle TB. Field studies indicate that culling badgers may result in increased immigration into culled areas, disruption of territoriality, increased ranging and mixing between social groups. Our analysis shows that some measures of sociality may remain significantly disrupted for up to 8 years after culling. This may have epidemiological consequences because previous research has shown that even in a relatively undisturbed badger population, movements between groups are associated with increases in the incidence of Mycobacterium bovis infection. This is consistent with the results from a large-scale field trial, which demonstrated decreased benefits of culling at the edges of culled areas, and an increase in herd breakdown rates in neighbouring cattle.

The dragonfly delusion: why it is essential to sample exuviae to avoid biased surveys

Odonate populations and species numbers are declining globally. Successful conservation requires sound assessments of both odonate distributions and habitat requirements. Odonates have aquatic (larval) and terrestrial (adult) stages, but most surveys that are used to inform conservation managers are undertaken of the adult stage. This study investigates whether this bias towards adult records in odonate recording is misinterpreting the environmental quality of sites. The habitat focus is farmland ponds, a key feature of agricultural landscapes. We tested whether or not, adult, larval and exuvial surveys lead to similar conclusions on species richness and hence on pond quality. Results showed that pond surveys based upon larvae and exuviae are equally suitable for the reliable assessment of presence/absence of odonates, but that adult surveys are not interchangeable with surveys of larvae/exuviae. Larvae were also found at ponds with no emerging individuals due to changes in habitat quality, therefore presence of exuviae remains the only proof of life-cycle completion at a site. Ovipositing females were recorded at all ponds where exuviae were totally absent hence adult surveys over-estimate pond quality and low-quality ponds are functioning as ecological traps. Highly mobile and generalist species were recorded at more locations than other species. Adult surveys also bias recording towards genera, species and populations with non-territorial mate-location strategies. Odonate biodiversity monitoring would benefit from applying the best survey method (exuviae) to avoid wasting valuable financial resources while providing unbiased data, necessary to achieve conservation objectives.

Demographic correlates of bite wounding in Eurasian badgers, Meles meles L., in stable and perturbed populations

In the U.K., Eurasian badgers often live in social groups and defend a collective territory. Aggressive encounters between badgers may lead to bite wounds, which can be severe and may be a potential route of disease transmission. Using data obtained over a 5-year period, we compared patterns of bite wounding in three badger populations of differing population density and culling history in southwest and southern England. Data from 4312 live-trapping events were analysed. Bite wounds were more likely in adult badgers than in cubs, and in males than in females. Males were also more likely to have multiple bites. Bite wounding varied seasonally, peaking during December to February. Most bite wounds in adult males were on the rump, whereas females and cubs were more likely to have been bitten on the head. Bite wounds were more likely in badgers in poor body condition. The incidence of bite wounds was not related to study site or population density, but varied significantly between years. Complex interactive effects suggested that patterns of bite wounding may vary over time and at a local scale. Although culling-induced social perturbation was not associated with higher levels of bite wounding, there was evidence that female badgers endured higher rates of biting during recolonization.

Identifying high-quality pond habitats for Odonata in lowland England: implications for agri-environment schemes

Abstract.  1. Agricultural intensification has contributed to severe declines in odonate (dragonfly and damselfly) populations. The objective of our study is to benefit current measures for the conservation of odonates by establishing the conditions favourable to Odonata and focusing on ponds within agricultural land.

Culling-Induced Changes in Badger (Meles meles) Behaviour, Social Organisation and the Epidemiology of Bovine Tuberculosis

In the UK, attempts since the 1970s to control the incidence of bovine tuberculosis (bTB) in cattle by culling a wildlife host, the European badger (Meles meles), have produced equivocal results. Culling-induced social perturbation of badger populations may lead to unexpected outcomes. We test predictions from the ‘perturbation hypothesis’, determining the impact of culling operations on badger populations, movement of surviving individuals and the influence on the epidemiology of bTB in badgers using data dervied from two study areas within the UK Governments Randomised Badger Culling Trial (RBCT). Culling operations did not remove all individuals from setts, with between 34–43% of badgers removed from targeted social groups. After culling, bTB prevalence increased in badger social groups neighbouring removals, particularly amongst cubs. Seventy individual adult badgers were fitted with radio-collars, yielding 8,311 locational fixes from both sites between November 2001 and December 2003. Home range areas of animals surviving within removed groups increased by 43.5% in response to culling. Overlap between summer ranges of individuals from Neighbouring social groups in the treatment population increased by 73.3% in response to culling. The movement rate of individuals between social groups was low, but increased after culling, in Removed and Neighbouring social groups. Increased bTB prevalence in Neighbouring groups was associated with badger movements both into and out of these groups, although none of the moving individuals themselves tested positive for bTB. Significant increases in both the frequency of individual badger movements between groups and the emergence of bTB were observed in response to culling. However, no direct evidence was found to link the two phenomena. We hypothesise that the social disruption caused by culling may not only increase direct contact and thus disease transmission between surviving badgers, but may also increase social stress within the surviving population, causing immunosuppression and enhancing the expression of disease.

WHAT GROUNDS SOME BIRDS FOR LIFE? MOVEMENT AND DIVING IN THE SEXUALLY DIMORPHIC GALÁPAGOS CORMORANT

Flightlessness in previously volant birds is taxonomically widespread and thought to occur when the costs of having a functional flight apparatus outweigh the benefits. Loss of the ability to fly relaxes body mass constraints which can be particularly advantageous in divers, because underwater performance correlates with mass. The Galapagos Cormorant Phalacrocorax harrisi is flightless and the largest of its 27-member genus. Here, the loss of flight, and consequent reduced foraging range, could be compensated by enhanced dive performance. Over three years, 46 Galapagos Cormorants were successfully equipped with time-depth-temperature recorders, and 30 birds with GPS recorders during the breeding season. Birds foraged at a mean of 690 m from the nest and just 230 m from the nearest coast, confirming an extremely limited foraging range during the breeding season and corresponding increased potential for intraspecific competition. Although the maximum recorded dive depth of 73 m tallied with the species body mass, .90% of dives were conducted in water ,15 m deep. The heavier males foraged in different areas and dived longer and deeper than females, which exposed males to colder water. Consideration of how plumage insulation decreases with depth indicates that diving males should lose 30% more heat than females, although this may be partially compensated by their lower surface area : volume ratio. A simple model highlights how energy expenditure from swimming underwater due to buoyancy and energy lost as heat have opposing trends with increasing depth, leading to the prediction of an optimum foraging depth defined by the volume of plumage air and water temperature. This has ramifications for all diving seabirds. It is proposed that the reduction in wing size, together with energy- expensive flight musculature, allows the Galapagos Cormorant to be more efficient at shallow depths than other seabirds, but only in warm equatorial waters. The high prey density and predictability of benthic prey in defined areas of the Galapagos can be particularly well exploited by this flightless species, with its limited foraging range, but the Galapagos Cormorant is unlikely to be able to accommodate much change in environmental conditions.

Habitat preference and mobility of Polia bombycina: are non-tailored agri-environment schemes any good for a rare and localised species?

General agri-environment schemes (AES) have been shown to benefit widespread species, but there is little information on the extent to which rare, more localised, species may also benefit. We tested whether AES options aimed at increasing general biodiversity also benefit a highly endangered moth, Poliabombycina, without species-specific tailoring. We assessed effects on its abundance of two AES options, wide field margins and hedgerow trees, using light traps at the landscape-scale and for mark-release-recapture at the farm-scale. We hypothesized that abundance would be highest at wide field margins and at hedgerow trees, and that if hedgerow trees conferred a positive effect, individuals would be more likely to follow hedgerows than crossing exposed fields while on the move. The results showed that significantly more individuals were captured at sites with a hedgerow tree. Numbers were also higher at wide margins, but this was not statistically significant, and no individuals were caught at field centres. Our study suggests that general options within appropriately designed and implemented AES aimed at increasing overall biodiversity in intensive agricultural landscapes have the potential to not only benefit common, widespread habitat generalists, but some rare and more endangered species as well. P. bombycina serves as an example of how general AES options, existing and novel ones alike, might cater for the needs of rare and localised species. As the precise ecological requirements of most invertebrate species remain unknown, we urge scientists and governments to address the challenge to research and design truly general AES, which options should be able to deliver not only for widespread species but also for the less-widespread counterpart of farmland biodiversity.

Face Value: Towards Robust Estimates of Snow Leopard Densities

When densities of large carnivores fall below certain thresholds, dramatic ecological effects can follow, leading to oversimplified ecosystems. Understanding the population status of such species remains a major challenge as they occur in low densities and their ranges are wide. This paper describes the use of non-invasive data collection techniques combined with recent spatial capture-recapture methods to estimate the density of snow leopards Panthera uncia. It also investigates the influence of environmental and human activity indicators on their spatial distribution. A total of 60 camera traps were systematically set up during a three-month period over a 480 km2 study area in Qilianshan National Nature Reserve, Gansu Province, China. We recorded 76 separate snow leopard captures over 2,906 trap-days, representing an average capture success of 2.62 captures/100 trap-days. We identified a total number of 20 unique individuals from photographs and estimated snow leopard density at 3.31 (SE = 1.01) individuals per 100 km2. Results of our simulation exercise indicate that our estimates from the Spatial Capture Recapture models were not optimal to respect to bias and precision (RMSEs for density parameters less or equal to 0.87). Our results underline the critical challenge in achieving sufficient sample sizes of snow leopard captures and recaptures. Possible performance improvements are discussed, principally by optimising effective camera capture and photographic data quality.

Antibodies to Toxoplasma gondii in Eurasian Badgers

Antibodies to Toxoplasma gondii were detected in samples collected from 90 live-trapped adult Eurasian badgers (Meles meles) sampled at three sites (two agricultural and one woodland) in southern England. Serum was tested using a qualitative latex agglutination test procedure and 63 of 90 (70%) badgers tested positive for T. gondii antibodies. Antibody prevalence varied between the sites; 67% and 77% of badgers from agricultural sites and 39% from a nonagricul-tural site tested positive.