Natuuraanleg op landbouwgrond: belangstelling gemeten

Sinds een aantal jaren neemt particuliere natuuraanleg deels de plaats in van grondaankopen door de overheid. De deelname van particulieren aan natuuraanleg blijft echter achter bij de verwachtingen. Ook blijkt de belangstelling bij particuliere grondeigenaren onvoldoende om het beleidsdoel van 42.770 ha in 2018 te realiseren

Natuurbeheer nog zwakke inkomenspeiler

In Natuurbalans 2002 is het effect van agrarisch natuurbeheer op de vitaliteit van de landbouw geanalyseerd. De gedachte hierbij is dat een vitaal platteland gebaat is bij een rendabele landbouw

Traditional African vegetables: Directory of research and development specialists

The main function of this directory lies in the usefulness of the information it conveys. It has a record of contact information drawn from an IPGRI database of traditional vegetable workers, institutions and networks in sub-Saharan Africa. An international community of experts and workers in the area of ”Traditional African Vegetables” already exists and is engaged in productive research and dialogue. With the presentation of this first edition of the directory of ”Traditional African Vegetable Workers” we look forward to enabling direct contacts between these researchers and workers on all aspects of traditional African vegetables. The scope of the directory is to give information on who works on African vegetables in the region and to provide a vehicle for fostering links between the workers. We would like to create an environment where information is exchanged easily between researchers and workers. The challenge is that the role and the potential of information and information exchange, and the sharing of experiences is becoming much more important in the face of growing threat of genetic erosion to our traditional African vegetable resources. The workers listed in this directory have responded to the challenge by ensuring conservation and continued use of the genetic resources of traditional African vegetables through their research, and we laud their efforts

Landbouwpraktijk en waterkwaliteit op landbouwbedrijven aangemeld voor derogatie in 2015

Dutch manure policy tries to limit the harmful environmental impact of agriculture. This is in line with international agreements on fertilizer use. The European Nitrates Directive prescribes Member States to limit the use of animal manure to 170 kg nitrogen per hectare. Farms with at least 80 percent of grassland may, under certain conditions, use more manure from grazing animals such as cows and sheep (derogation). Over the last 10 years, nitrate leaching from the manure to the upper groundwater has decreased or remained the same for these farms. By 2015, on average, the concentration is in all regions below the EU standard of 50 milligrams of nitrate per liter. This is according to the annual report by RIVM and Wageningen Economic Research. They follow agricultural practices and the effects on water quality at 300 derogation farms and report their results to the EU annually. This report describes the situation in 2015 and the development between 2006 and 2016 (trend). Management. The permissible amount of nitrogen from grazing manure is, depending on the soil and region, 250 kilograms per hectare (in the Clay region. Peat region and northern part of the Sand region) or 230 kg/ha (in the Loess region and the rest of the Sand region). On average, derogation companies have used 238 kilograms of nitrogen from animal manure per hectare in 2015. The amount of nitrogen that can leached as nitrate to groundwater is determined, among others, by the so-called nitrogen soil surplus. This is the difference between the input of nitrogen (such as fertilizers) and their output (including through grass and maize). The average nitrogen surplus over the regions has decreased over the period considered. Groundwater quality. By 2015, the average nitrate concentration in the groundwater in Sand 250 was 26 milligrams per liter (mg/l). The highest concentration is measured in the Loess region (42 mg/l) and in Sand 230 (45 mg/l). On the average, farms in the Clay region and the Peat region had lower nitrate concentrations in leaching water (22 and 13 mg/l respectively). The difference between the regions can be explained by the proportion of soils prone to nitrate leaching. Especially in Sand 230 and in the Loess region there are grounds for which nitrate is reduced in a lesser extent, and therefore can leach more to groundwater.Het Nederlandse mestbeleid probeert de schadelijke milieueffecten van de landbouw te beperken. Dit sluit aan bij internationale afspraken over het mestgebruik, die onder meer zijn vastgelegd in de Europese Nitraatrichtlijn. Die schrijft lidstaten voor om het gebruik van dierlijke mest te beperken tot 170 kg stikstof per hectare. Bedrijven met ten minste 80 procent grasland mogen onder bepaalde voorwaarden meer mest gebruiken, afkomstig van graasdieren zoals koeien en schapen (derogatie). Op deze bedrijven is in de periode 2006 tot en met 2016 de uitspoeling van nitraat uit de mest naar het grondwater gedaald of gelijk gebleven. In 2015 ligt op derogatiebedrijven de concentratie gemiddeld in alle regio's onder de EU-norm van 50 milligram nitraat per liter. Dit blijkt uit de jaarlijkse rapportage van het RIVM en Wageningen Economic Research. Zij volgen op 300 derogatiebedrijven de bedrijfsvoering en de effecten op de waterkwaliteit en zij rapporteren de resultaten hiervan jaarlijks aan de EU. In deze rapportage is de situatie in 2015 beschreven en de ontwikkeling tussen 2006 en 2016 (trend). Bedrijfsvoering. De toegestane hoeveelheid stikstof uit graasdiermest is, afhankelijk van de bodemsoort en regio, 250 kilogram per hectare (in de Kleiregio, Veenregio en het noordelijke deel van de Zandregio) of 230 kg/ha (in de Lössregio en het overige deel van de Zandregio). Gemiddeld hebben derogatiebedrijven in 2015 238 kilogram stikstof uit dierlijke mest per hectare gebruikt. De hoeveelheid stikstof die als nitraat kan uitspoelen naar het grondwater wordt onder andere bepaald door het zogenoemde stikstofbodemoverschot. Dit is het verschil tussen de aanvoer van stikstof (zoals meststoffen) en de afvoer ervan (waaronder via gras en maïs). Het stikstofbodemoverschot is gemiddeld over de regio's tijdens de onderzochte periode gedaald met 16%. Grondwaterkwaliteit. In 2015 was de gemiddelde nitraatconcentratie in het grondwater 26 milligram per liter (mg/l) in Zand 250. De hoogste concentratie wordt gemeten in de Lössregio (42 mg/l) en in Zand 230 (45 mg/l). Bedrijven in de Kleiregio en de Veenregio hadden gemiddeld een lagere nitraatconcentratie (respectievelijk 22 en 13 mg/l). Het verschil tussen de regio's kan verklaard worden door het aandeel uitspoelingsgevoelige gronden. Vooral in Zand 230 en in de Lössregio komen gronden voor waar nitraat in mindere mate in de bodem wordt afgebroken en daardoor meer kan uitspoelen naar het grondwater.Ministerie van Economische Zake

Financial Evaluation of Different Vaccination Strategies for Controlling the Bluetongue Virus Serotype 8 Epidemic in the Netherlands in 2008

Background: Bluetongue (BT) is a vector-borne disease of ruminants caused by bluetongue virus that is transmitted by biting midges (Culicoides spp.). In 2006, the introduction of BTV serotype 8 (BTV-8) caused a severe epidemic in Western and Central Europe. The principal effective veterinary measure in response to BT was believed to be vaccination accompanied by other measures such as movement restrictions and surveillance. As the number of vaccine doses available at the start of the vaccination campaign was rather uncertain, the Dutch Ministry of Agriculture, Nature and Food Quality and the Dutch agricultural industry wanted to evaluate several different vaccination strategies. This study aimed to rank eight vaccination strategies based on their efficiency (i.e. net costs in relation to prevented losses or benefits) for controlling the bluetongue virus serotype 8 epidemic in 2008 Methodology/Principal Findings: An economic model was developed that included the Dutch professional cattle, sheep and goat sectors together with the hobby farms. Strategies were evaluated based on the least cost - highest benefit frontier, the benefit-cost ratio and the total net returns. Strategy F, where all adult sheep at professional farms in the Netherlands would be vaccinated was very efficient at lowest costs, whereas strategy D, where additional to all adult sheep at professional farms also all adult cattle in the four Northern provinces would be vaccinated, was also very efficient but at a little higher costs. Strategy C, where all adult sheep and cattle at professional farms in the whole of the Netherlands would be vaccinated was also efficient but again at higher costs. Conclusions/Significance: This study demonstrates that a financial analysis differentiates between vaccination strategies and indicates important decision rules based on efficienc

There Is No Safe Dose of Prions

Understanding the circumstances under which exposure to transmissible spongiform encephalopathies (TSEs) leads to infection is important for managing risks to public health. Based upon ideas in toxicology and radiology, it is plausible that exposure to harmful agents, including TSEs, is completely safe if the dose is low enough. However, the existence of a threshold, below which infection probability is zero has never been demonstrated experimentally. Here we explore this question by combining data and mathematical models that describe scrapie infections in mice following experimental challenge over a broad range of doses. We analyse data from 4338 mice inoculated at doses ranging over ten orders of magnitude. These data are compared to results from a within-host model in which prions accumulate according to a stochastic birth-death process. Crucially, this model assumes no threshold on the dose required for infection. Our data reveal that infection is possible at the very low dose of a 1000 fold dilution of the dose that infects half the challenged animals (ID50). Furthermore, the dose response curve closely matches that predicted by the model. These findings imply that there is no safe dose of prions and that assessments of the risk from low dose exposure are right to assume a linear relationship between dose and probability of infection. We also refine two common perceptions about TSE incubation periods: that their mean values decrease linearly with logarithmic decreases in dose and that they are highly reproducible between hosts. The model and data both show that the linear decrease in incubation period holds only for doses above the ID50. Furthermore, variability in incubation periods is greater than predicted by the model, not smaller. This result poses new questions about the sources of variability in prion incubation periods. It also provides insight into the limitations of the incubation period assay

Evaluating the Influence of Epidemiological Parameters and Host Ecology on the Spread of Phocine Distemper Virus through Populations of Harbour Seals

Catriona Harris was supported by a grant from the UK Natural Environment Research Council. The funders had no role in study design, data collections and analysis, decision to publish, or preparation of the manuscript.Background: Outbreaks of phocine distemper virus (PDV) in Europe during 1988 and 2002 were responsible for the death of around 23,000 and 30,000 harbour seals, respectively. These epidemics, particularly the one in 2002, provided an unusual opportunity to estimate epidemic parameters for a wildlife disease. There were marked regional differences in the values of some parameters both within and between epidemics. Methodology and Principal Findings: We used an individual-based model of seal movement that allowed us to incorporate realistic representations of space, time and animal behaviour into a traditional epidemiological modelling framework. We explored the potential influence of a range of ecological (foraging trip duration, time of epidemic onset, population size) and epidemiological (length of infectious period, contact rate between infectious and susceptible individuals, case mortality) parameters on four readily-measurable epidemic characteristics (number of dead individuals, duration of epidemic, peak mortality date and prevalence) and on the probability that an epidemic would occur in a particular region. We analysed the outputs as if they were the results of a series of virtual experiments, using Generalised Linear Modelling. All six variables had a significant effect on the probability that an epidemic would be recognised as an unusual mortality event by human observers. Conclusions: Regional and temporal variation in contact rate was the most likely cause of the observed differences between the two epidemics. This variation could be a consequence of differences in the way individuals divide their time between land and sea at different times of the year.Publisher PDFPeer reviewe