Birgitte Hansen

Approaches to assess the environmental impact of organic farming with particular regard to Denmark

Abstract Ever increasing attention is being paid to the environmental impact of intensive agricultural practices, and in this context organic farming is gaining recognition as a relatively friendly production system. In general, the risk of harmful environmental effects is lower with organic than with conventional farming methods, though not necessarily so. This review examines organic farming in the light of European conditions with special regard to recent research findings from Denmark. It specifies the environmental problems caused by modern farming practices and discusses appropriate indicators for assessing their impact. A driving force-state-response (DSR) framework is employed to organise and understand the processes and mechanisms that lie behind the impact of agriculture on nature and the environment. Important groups of environmental indicators are selected that characterise (a) the aquatic environment (nitrate and phosphorus leaching), (b) the soil (organic matter, biology and structure), (c) the ecosystem (arable land, semi-cultivated areas, small biotopes and landscape), and (d) resource usage and balances (nitrogen, phosphorus, potassium and energy use). The paper also reviews several empirical studies. With regard to soil biology, organic farming is usually associated with a significantly higher level of biological activity (bacteria (Monera), fungi (Mycota), springtails (Collembola), mites (Arachnida), earthworms (Lumbricus terrestris)), due to its versatile crop rotations, reduced applications of nutrients, and the ban on pesticides. In most cases there is also a lower surplus of nutrients and less leaching with organic than with conventional farming. However, poor management (e.g., the ploughing of grass and legumes (Fabates) at the wrong time of year with no subsequent crops to capture the mineralised nitrogen), low self-sufficiency in feed, and problems with certain production systems (such as those involved in organic pig farming, i.e., grazing sows, low crop yields), can lead to a high level of leaching in some organic systems. Organic farming is faced with a need to expand and develop in line with increasing demands for organic food and growing environmental concerns. This requires closer attention to the goals, values and principles on which organic practices are based, and more research into the influence of organic farming on different aspects of the environment.

Nitrogen leaching from conventional versus organic farming systems — a systems modelling approach

Abstract The level of nitrogen leaching from organic compared to conventional farming was evaluated by using a systems modelling approach. Two different methods were used for estimating and evaluating nitrate leaching. A simple function was used in which nitrate leaching is dependent on percolation, soil clay content, average nitrogen input and crop sequence. A nitrogen balance model was used to estimate the long-term potential for nitrate leaching. These methods were applied to models of both current conventional farming systems in Denmark in 1996 and of well-managed organic farming systems. On average, the total estimated nitrogen input to the organic systems was lower (104–216 kg N ha −1 year −1 ) than to the conventional farming systems (146–311 kg N ha −1 year −1 ). The N-balances in the organic fields showed a surplus of nitrogen (net input of nitrogen) in to the root zone of 60–143 kg N ha −1 year −1 . In the conventional systems the surplus varied from 25 to 155 kg N ha −1 year −1 . The modelled nitrogen leaching from the organic systems varied from 19 to 30 kg N ha −1 year −1 on loamy soils to 36–65 kg N ha −1 year −1 on sandy soils. The modelled nitrogen leaching from the organic systems was always lower than from the comparable conventional agricultural systems due to: (I) the lower total input of nitrogen to the organic systems; and (II) the composition of the organic crop rotations including extensive use of catch crops. However, the modelling of nitrogen leaching has many uncertainties, principally due to difficulties in predicting the nitrogen leaching from different types of grass fields. Comparison of the results from two methods: (i) modelling of nitrogen leaching; and (ii) N-balances for the root zones, showed that organic arable crop production and dairy/beef farming on sandy soils are farming systems with a clear potential for lower nitrogen leaching than from the selected conventional systems. It is still uncertain whether the nitrogen leaching is lower or higher from organic arable crop production systems on loamy soil and organic pig production on loamy and sandy soil than from the same conventional systems in Denmark. The results point to the need for future research in the following areas: (i) the ability to build up soil organic nitrogen in organic farming systems and the consequences for both the level of crop production and nitrogen leaching in the long term; (ii) the effects of catch crops in organic crop rotations; and (iii) a better operational understanding of nitrogen leaching from different types of organically managed grass and grass-clover fields.

Policies for agricultural nitrogen management—trends, challenges and prospects for improved efficiency in Denmark

With more than 60% of the land farmed, with vulnerable freshwater and marine environments, and with one of the most intensive, export-oriented livestock sectors in the world, the nitrogen (N) pollution pressure from Danish agriculture is severe. Consequently, a series of policy action plans have been implemented since the mid 1980s with significant effects on the surplus, efficiency and environmental loadings of N. This paper reviews the policies and actions taken and their ability to mitigate effects of reactive N (Nr) while maintaining agricultural production. In summary, the average N-surplus has been reduced from approximately 170 kg N ha?1 yr?1 to below 100 kg N ha?1 yr?1 during the past 30 yrs, while the overall N-efficiency for the agricultural sector (crop?+?livestock farming) has increased from around 20?30% to 40?45%, the N-leaching from the field root zone has been halved, and N losses to the aquatic and atmospheric environment have been significantly reduced. This has been achieved through a combination of approaches and measures (ranging from command and control legislation, over market-based regulation and governmental expenditure to information and voluntary action), with specific measures addressing the whole N cascade, in order to improve the quality of ground- and surface waters, and to reduce the deposition to terrestrial natural ecosystems. However, there is still a major challenge in complying with the EU Water Framework and Habitats Directives, calling for new approaches, measures and technologies to mitigate agricultural N losses and control N flows.

Trend reversal of nitrate in Danish groundwater--a reflection of agricultural practices and nitrogen surpluses since 1950.

This paper assesses the long-term development in the oxic groundwater nitrate concentration and nitrogen (N) loss due to intensive farming in Denmark. First, up to 20-year time-series from the national groundwater monitoring network enable a statistically systematic analysis of distribution, trends, and trend reversals in the groundwater nitrate concentration. Second, knowledge about the N surplus in Danish agriculture since 1950 is used as an indicator of the potential loss of N. Third, groundwater recharge CFC (chlorofluorocarbon) age determination allows linking of the first two data sets. The development in the nitrate concentration of oxic groundwater clearly mirrors the development in the national agricultural N surplus, and a corresponding trend reversal is found in groundwater. Regulation and technical improvements in the intensive farming in Denmark have succeeded in decreasing the N surplus by 40% since the mid 1980s, while at the same time maintaining crop yields and increasing the animal production of especially pigs. Trend analyses prove that the youngest (0-15 years old) oxic groundwater shows more pronounced significant downward nitrate trends (44%) than the oldest (25-50 years old) oxic groundwater (9%). This amounts to clear evidence of the effect of reduced nitrate leaching on groundwater nitrate concentrations in Denmark.

Association of Lithium in Drinking Water With the Incidence of Dementia

Importance Results from animal and human studies suggest that lithium in therapeutic doses may improve learning and memory and modify the risk of developing dementia. Additional preliminary studies suggest that subtherapeutic levels, including microlevels of lithium, may influence human cognition. Objective To investigate whether the incidence of dementia in the general population covaries with long-term exposure to microlevels of lithium in drinking water. Design, Setting, and Participants This Danish nationwide, population-based, nested case-control study examined longitudinal, individual geographic data on municipality of residence and data from drinking water measurements combined with time-specific data from all patients aged 50 to 90 years with a hospital contact with a diagnosis of dementia from January 1, 1970, through December 31, 2013, and 10 age- and sex-matched control individuals from the Danish population. The mean lithium exposure in drinking water since 1986 was estimated for all study individuals. Data analysis was performed from January 1, 1995, through December 31, 2013. Main Outcomes and Measures A diagnosis of dementia in a hospital inpatient or outpatient contact. Diagnoses of Alzheimer disease and vascular dementia were secondary outcome measures. In primary analyses, distribution of lithium exposure was compared between patients with dementia and controls. Results A total of 73 731 patients with dementia and 733 653 controls (median age, 80.3 years; interquartile range, 74.9-84.6 years; 44 760 female [60.7%] and 28 971 male [39.3%]) were included in the study. Lithium exposure was statistically significantly different between patients with a diagnosis of dementia (median, 11.5 µg/L; interquartile range, 6.5-14.9 µg/L) and controls (median, 12.2 µg/L; interquartile range, 7.3-16.0 µg/L; P < .001). A nonlinear association was observed. Compared with individuals exposed to 2.0 to 5.0 µg/L, the incidence rate ratio (IRR) of dementia was decreased in those exposed to more than 15.0 µg/L (IRR, 0.83; 95% CI, 0.81-0.85; P < .001) and 10.1 to 15.0 µg/L (IRR, 0.98; 95% CI, 0.96-1.01; P = .17) and increased with 5.1 to 10.0 µg/L (IRR, 1.22; 95% CI, 1.19-1.25; P < .001). Similar patterns were found with Alzheimer disease and vascular dementia as outcomes. Conclusions and Relevance Long-term increased lithium exposure in drinking water may be associated with a lower incidence of dementia in a nonlinear way; however, confounding from other factors associated with municipality of residence cannot be excluded.

Effects of N-deposition on ion trapping by B-horizons of Danish heathlands.

Coastal and inland heaths constitute a dominating fraction of the relatively few semi-natural ecosystems in Denmark. At the inland heath, the soil forming factors have been active with the same vegetation type during the last 2000 years, whereas at the coastal heath, these soil forming factors have only been active over a couple of hundred years, due to the activity of windblown sand. Effects on ion-balance and soil processes of nitrogen deposition on a young dune heath and an old inland heath have been investigated. Different levels of NH4NO3have been applied to the two heathlands, and rain, throughfall water and soil water chemistry below the experimental plots have been analysed. Results show that the ability to retain added, as well as deposited, nitrogen requires the presence and the integrity of a humifyed H-subhorizon. When the mor-layer for some reason breaks down, the nutrients will be retained by the B-horizons as a kind of back-up, and most probably be reused by the new vegetation. One year after destructive heather beetles attack on the inland heath, the mor-layer started to decompose. A large translocation of organic compounds, complexed associated cations and nitrogen-species, started from the mor-layer to the top of the B-horizon where they precipitate. The podzolic B-horizons can be seen as nutrient trap to the mor-layer.

Low-level arsenic in drinking water and risk of incident myocardial infarction: A cohort study

Background: Epidemiological studies have shown that intake of drinking water with high levels of arsenic (>100 &mgr;g/L) is associated with risk for cardiovascular diseases, but studies on lower levels of arsenic show inconsistent results. Objective: The aim of this study was to investigate the relationship between exposure to low level arsenic in drinking water and risk of myocardial infarction in Denmark. Methods: From the Danish Diet, Cancer and Health cohort of 57,053 people aged 50–64 years at enrolment in 1993–1997, we identified 2707 cases of incident myocardial infarction from enrolment to end of follow‐up in February 2012. Cohort participants were enrolled in the Copenhagen and Aarhus areas. We geocoded residential addresses of the cohort members and used a geographic information system to link addresses with water supply areas. Arsenic in tap water at each cohort members address from 1973 to 2012 was estimated for all cohort members. Poisson regression was used to estimate incidence rate ratios (IRRs) for myocardial infarction after adjustment for lifestyle factors and educational level. Results: Arsenic levels in drinking water at baseline addresses ranged from 0.03 to 25.34 &mgr;g/L, with the highest concentrations in the Aarhus area. We found no overall association between 20‐years average concentration of arsenic and risk of myocardial infarction. However, in the Aarhus area, fourth arsenic quartile (2.21–25.34 &mgr;g/L) was associated with an IRR of 1.48 (95% confidence interval (CI): 1.19–1.83) when compared with first quartile (0.05–1.83 &mgr;g/L). An IRR of 1.26 (95% CI: 0.89–1.79) was found for ever (versus never) having lived at an address with 10 &mgr;g/L or more arsenic in the drinking water. Conclusions: This study provides some support for an association between low levels of arsenic in drinking water and the risk of myocardial infarction. HighlightsHigh arsenic concentration is associated with higher risk of cardiovascular disease.Few studies have investigated association between arsenic and myocardial infarction.Low levels of arsenic may increase the risk of myocardial infarction.Research on the possible association at low arsenic levels requires further attention.

Atmospheric ammonia exchange on a heathland in Denmark

Abstract Passive flux samplers were used to determine the ammonia exchange on an inland heath in Denmark over the last 2 years. The samplers measured the horizontal ammonia flux directly. Data were sampled continuously for periods of 1–4 weeks. The micro-meteorological gradient method was used with passive flux samplers and cup anemometers at different heights above the vegetation in order to calculate the vertical fluxes of ammonia. First a fixed sampler system was used with tubes mounted in four orthogonal horizontal directions. This system has been successfully applied to measure the emission from fertilized crops. Adapting this type of sampler to measure the deposition to heathlands did not prove to be straightforward. The precision of the calculated ammonia concentrations was too poor to give an acceptable accuracy for the concentration gradient. The problems were (a) driving rain which entered the tubes, (b) too few measuring points in each concentration profile, and (c) too long sampling periods to allow for the low-concentration levels above the heath area and the detection limits. Therefore, a passive flux sampler mounted on a wind vane and fitted with a rain shelter was developed. Results from the first 5 weekly periods are very promising, yielding accurate concentration gradients. The advantages of the passive flux samplers on the wind vane are (a) the minimum measuring period can be approximately halved compared to the fixed samplers, (b) some of the directional correction terms used with the fixed passive flux samplers are dispensed with, and (c) the field and laboratory work is minimized.

Assessment of spatial variation in drinking water iodine and its implications for dietary intake: a new conceptual model for Denmark.

Iodine is essential for human health. Many countries have therefore introduced universal salt iodising (USI) programmes to ensure adequate intake for the populations. However, little attention has been paid to subnational differences in iodine intake from drinking water caused by naturally occurring spatial variations. To address this issue, we here present the results of a Danish nationwide study of spatial trends of iodine in drinking water and the relevance of these trends for human dietary iodine intake. The data consist of treated drinking water samples from 144 waterworks, representing approx. 45% of the groundwater abstraction for drinking water supply in Denmark. The samples were analysed for iodide, iodate, total iodine (TI) and other major and trace elements. The spatial patterns were investigated with Local Morans I. TI ranges from <0.2 to 126 μg L(-1) (mean 14.4 μg L(-1), median 11.9 μg L(-1)). Six speciation combinations were found. Half of the samples (n = 71) contain organic iodine; all species were detected in approx. 27% of all samples. The complex spatial variation is attributed both to the geology and the groundwater treatment. TI >40 μg L(-1) originates from postglacial marine and glacial meltwater sand and from Campanian-Maastrichtian chalk aquifers. The estimated drinking water contribution to human intake varies from 0% to >100% of the WHO recommended daily iodine intake for adults and from 0% to approx. 50% for adolescents. The paper presents a new conceptual model based on the observed clustering of high or low drinking-water iodine concentrations, delimiting zones with potentially deficient, excessive or optimal iodine status. Our findings suggest that the present coarse-scale nationwide programme for monitoring the populations iodine status may not offer a sufficiently accurate picture. Local variations in drinking-water iodine should be mapped and incorporated into future adjustment of the monitoring and/or the USI programmes.

Nitrate exposure from drinking water in Denmark over the last 35 years

In Denmark, drinking water quality data covering the entire country for over 35 years are registered in a publicly-accessible database. These data were analysed to determine the fraction of population exposed to elevated nitrate concentrations. Data from 2,852 water supply areas from the 98 Danish municipalities were collected in one dataset. Public water supplies are extensively registered; private wells supplying only few households are neither monitored nor registered sufficiently. The study showed that 5.1% of the Danish population was exposed to nitrate concentrations 25 mg L−1 in 2012. Private well users were far more prone to exposure to elevated nitrate concentrations than consumers connected to public supplies. While the fraction exposed to elevated nitrate concentrations amongst public supply users has been decreasing since the 1970s, it has been increasing amongst private well users, leading to the hypothesis that the decrease in nitrate concentrations in drinking water is mainly due to structural changes and not improvement of the groundwater quality. A combination of this new drinking water quality map with extensive Danish health registers would permit an epidemiological study on health effects of nitrate, as long as the lack of data on private well users is addressed.