The impact of cattle drinking points on aquatic macroinvertebrates in streams in south-east Ireland

peer-reviewedTeagasc PublicationMeasures that prevent cattle access to watercourses are commonly implemented through agri-environment schemes, in an effort to address the objectives of the Water Framework Directive. Despite the widespread implementation, few studies have assessed the impact of cattle access to streams on aquatic macroinvertebrates. This study assessed the local-scale impact of cattle drinking points on water quality parameters (i.e. macroinvertebrate and water chemistry metrics) on 39 intensively-managed grassland farms in the south-east of Ireland. The results indicate that sites that were more than or equal to good quality upstream of cattle drinking points, were more susceptible to cattle access impacts than sites where upstream water quality was less than good. The European Court of Auditors (2011) recommended that there should be a higher rate of EU contribution for measures with higher environmental potential, in this instance, for cattle exclusion measures targeted to sites where background quality is more than or equal to good. Appropriate efforts should thus be made to incentivise farmers in good to high status sites to adopt cattle exclusion measures

Biological control of pestiferous slugs using Tetanocera elata (Fabricius) (Diptera: Sciomyzidae): Larval behavior and feeding on slugs exposed to Phasmarhabditis hermaphrodita (Schneider, 1859)

While the larval stage of Tetanocera elata (Diptera: Sciomyzidae) is a known parasitoid and predator of pestiferous slugs, its biology and predatory behavior as well as its interaction with slug parasitic nematodes requires further investigation. In this study, survival of larvae fed from the neonate stage on Deroceras reticulatum Müller (a previously known prey species) was significantly greater (P = 0.023) than for larvae fed on Deroceras invadens Reise with 100% and 40% survival respectively. However, when fed solely on D. reticulatum which were previously exposed to P. hermaphrodita, only 20% of neonate larvae pupariated successfully. Ninety percent of neonate larvae maintained without food for the first four days and subsequently fed on D. reticulatum pupariated successfully although this decreased to below 50% for ≥6 days without food. Predatory third instar T. elata larvae appeared to select nematode-exposed D. reticulatum over non-exposed slugs with the continued feeding on nematode-exposed slugs also reducing the chances of successful pupariation by 25%. Records of maximum egg-laying by laboratory-reared female adults were greater (487 eggs) than previously recorded for field-caught adults (3 7 3). The implications of these results for the potential use of T. elata as a biological control agent of pestiferous slugs are discussed. © 2019 Elsevier Inc

Influence of a cattle access point on temporal changes in stream turbidity

Unrestricted cattle access can have negative impacts on aquatic systems, including increases in stream water turbidity and suspended sediment levels. Many agri-environmental policies require the exclusion of livestock from waterbodies; however, data that quantify these impacts are scarce. This study used sensors measuring turbidity, a proxy for suspended sediment, together with motion-detecting cameras, to examine the influence of cattle in-stream activity on water quality in north-east Ireland. Two nephelometers, which automatically measured and logged turbidity, were placed upstream and downstream of a cattle access point in July 2017, while cameras were used to record cattle behaviour. A second deployment was made during February 2018 when cattle were absent. During low flows, frequent short-lived increases in turbidity were recorded at the downstream nephelometer only. These coincided with cattle accessing the water. There was a significant positive relationship between the longitudinal differences (downstream − upstream) in turbidity and the total number of cattle accessing the stream. There was no relationship between turbidity and stream discharge in July (when cattle were present), although that period was dominated by lower flow levels, with only 2 days in which discharge increased above baseflow. In contrast, there were no similar short-lived increases in turbidity in February 2018 when cattle were absent from the field, but there was a strong significant positive relationship between stream discharge and turbidity. These results highlight the consequences of cattle access for water column turbidity levels, particularly during periods of low streamflow, and therefore inform future agri-environmental policy in Ireland

Selecting appropriate plant indicator species for Result-Based Agri-Environment Payments schemes

peer-reviewedAgri-Environment Schemes (AES) have long been implemented across Europe to incentivise farmers to alter their management practices to improve biodiversity and water, air and soil quality. However, the cost-effectiveness of traditional action-based schemes has been questioned, and Result-Based Payment (RBP) schemes have been recommended as an alternative. To evaluate the effectiveness of management actions, RBP approaches often rely on indicator species to monitor changes in environmental conditions. The selection of appropriate indicator species for RBP follows several steps and criteria. One of the mentioned criteria is that the species should react to the farmer’s management choices. Thus, the main objective of this study is to understand how existing lists of indicator plant species (aimed at assessing ecological integrity of grasslands and hedgerows in Ireland) are suitable for RBP schemes, by assessing how different environmental and management variables are related to the presence of the plant species selected. Extensive field surveys were conducted to assess the presence and cover of indicator species in grasslands and hedgerows in two study regions in Ireland. The indicator plant species occurrence and diversity (species richness and Simpson’s Diversity Index) were correlated with variables within farmers’ control and variables outside farmers’ control. Results showed that grassland indicator species occurrence and diversity was mainly related to grassland semi-naturalness and to the diversity of habitats existing on the farm – both variables within farmers’ control – and thus were appropriate indicators for assessing the effectiveness of management and suitable for use in RBP schemes. Conversely, the occurrence and diversity of hedgerow indicator species was not strongly related to any of the explanatory variables, making them unsuitable for use in a RBP scheme. For a RBP scheme targeted at hedgerows, clear objectives will need to be established and the farmers’ management choices need to be better linked to the selected indicator species. The selection of indicator species needs to undergo scientific scrutiny to develop fair results assessments as shown by the results of this study. The analyses conducted highlight the importance of testing if the species react to the farmers’ management choices and should be a key methodological step before final indicator species lists are implemented in RBP schemes. Recommendations for results assessments in RBP approaches are discussed based on the results of this study

The interactions of site-specific factors on riparian buffer effectiveness across multiple pollutants:A review

Following decades of riparian buffer zone (RBZ) studies there remains a need to look across individual site data for collective evidence on the site-specific pollution mitigation and river water quality. We explored primary study evidence on runoff, sediment, P, N, coliforms and pesticides using complimentary styles of metadata interpretation. A quantitative assessment of pollution retention (75 studies, 474 data rows) derived relationships for retention versus width, including significant covariates of clay particle size and buffer slope for sediment, total and dissolved P. Total N and coliforms related to texture and slope but were independent of width. Other factors across pollutants were inconsistently reported. With limitations on quantitative studies a second approach examined factor significance (formal testing versus inferred; 93 studies) across source pressure, transport/physical, vegetation and soil biogeochemical factors on pollution effectiveness. The RBZ evidence showed considerable disagreement and bias in shorter term study implications on longer-term processes. Screening for stronger evidence by study number and agreement left fifteen factors informing on at least one pollutant, whereas only rainfall intensity, preferential deposition, tree planting, soil infiltration remained addressing three or more pollutants. Key messages were that: data complexities, from short-term trapping in upper buffer edges and so-called ‘negative effectiveness’ associated with internal recycling and/or errors in constraining mass inputs for dissolved pollutant and subsurface transport require careful interpretation; RBZ intervention and study durations were limited compared to effect times (particularly vegetation management and changing soil conditions); factors affect pollutants with particulate and dissolved phases differently and must be understood to limit RBZ pollution swapping. Buffer functioning is highly site-specific. To understand this better attention should be given to revisiting studies of vegetation management to extend timeframes, wider study of belowground (soil biogeochemical and transport) processes and studies should document site contexts across source pressures, riparian hydrological, soil and vegetation factors

The utility of spatial data to delineate river riparian functions and management zones:A review

Riparian zones of rivers are transitional environments between land and water ecosystems with distinct hydrological gradients, soils and habitats strongly related to their functioning. When these functions are intact, they integrate multi-directional processes across the land-river channel (e.g. canopy shade effects on the stream, flood inundation effects on the land) with mutual beneficial effects. In many managed landscapes these functions have been degraded. To restore them, considerable efforts have been directed over the last 20 years to understand and place effective riparian ‘buffer’ zones, particularly to enhance water quality and biodiversity. Since water quality targets are not easily met by current practices in many managed landscapes (as additive pressures increase), catchment managers will have to increasingly restore riparian functions to enhance aquatic ecosystem resilience to land and climate change. Targeting effective restoration within site-specific contexts requires availability of spatial data, in combinations that inform on individual and multiple functions. There are accelerating developments with spatial data, arising from increased spatial resolution of key underlying datasets, availability of soil and landcover data and increasing secondary derived attributes. Hence, a review is timely into the best practices in the use of these data for delineating riparian functions and management zones for rivers. Our review evaluates the application of spatial data and is structured around three conceptual methods of riparian delineation; fixed width, variable width by river corridor features and variable width by context of local pressures or required outcomes. We explore process representation and incorporation into management across main riparian functions (hydrological connectivity, water quality, shading, resource transfers and habitat provision). Translating spatial data into functions informs the ability to go beyond contemporary, generally fixed width approaches using basic structural components towards planning to better target functional attributes to optimise ecosystem protection. © 2020 Elsevier B.V

Livestock exclusion from watercourses:Policy effectiveness and implications

The deterioration of water quality in Ireland over the past thirty years and the nutrient losses from agriculture are of particular concern to policy makers. Agri-environmental schemes (AES) are designed to improve the environment and water quality. One of the more common AES measures is the exclusion of cattle from watercourses. Cattle exclusion provides a number of benefits such as reduction in nitrogen, phosphorus and sediment run-off, riverbank stability and improved vegetation cover and biodiversity. Using GIS methods a new national farm boundary spatial database SLIDE (Spatial Land Identification Database for Eire) is created utilising national administrative data and a spatial data storage model. This is the first examination of cattle exclusion and its cost effectiveness at the individual farm level across a national population of farms. Benefits are measured in the form of reduced in-stream faecal deposits. The spatial distribution of cost-effectiveness at the sub-catchment level highlights the differences between areas in terms of costs, benefits and extent. A cluster analysis is used to aggregate results. This information is utilised to undertake an ex-ante examination of the implications of a national policy to restrict cattle access to waterbodies for specific categories of farmers, under the EU Nitrates Directive. The analysis of the clusters show that due to the reduction of faecal deposition in watercourses, fencing on medium and high intensity farms is similar to 20 % more cost effective relative to farms with lower livestock densities. This study makes an important contribution to the literature in broadening our understanding of the impacts of policy decision making at the individual farm level and also the costs and scale of AES measures at a national level