1,721,149 research outputs found
How much does agriculture depend on pollinators? Lessons from long-term trends in crop production
Get PDFFil: Aizen, Marcelo A. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio Ecotono; Argentina.Fil: Garibaldi, Lucas Alejandro. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio Ecotono; Argentina.Fil: Cunningham, Saul A. CSIRO Entomology; Australia.Fil: Klein, Alexandra M. University of California; USA.Fil: Aizen, Marcelo A. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Argentina.Fil: Aizen, Marcelo A. Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA); Argentina.Fil: Garibaldi, Lucas Alejandro. Universidad de Buenos Aires (UBA). Facultad de Agronomía; Argentina.Fil: Klein, Alexandra M. University of Goettingen; Alemania.Abstract
Background and Aims
Productivity of many crops benefits from the presence of pollinating insects, so a decline in pollinator abundance should compromise global agricultural production. Motivated by the lack of accurate estimates of the size of this threat, we quantified the effect of total loss of pollinators on global agricultural production and crop production diversity. The change in pollinator dependency over 46 years was also evaluated, considering the developed and developing world separately.
Methods
Using the extensive FAO dataset, yearly data were compiled for 1961–2006 on production and cultivated area of 87 important crops, which we classified into five categories of pollinator dependency. Based on measures of the aggregate effect of differential pollinator dependence, the consequences of a complete loss of pollinators in terms of reductions in total agricultural production and diversity were calculated. An estimate was also made of the increase in total cultivated area that would be required to compensate for the decrease in production of every single crop in the absence of pollinators.
Key Results
The expected direct reduction in total agricultural production in the absence of animal pollination ranged from 3 to 8 %, with smaller impacts on agricultural production diversity. The percentage increase in cultivated area needed to compensate for these deficits was several times higher, particularly in the developing world, which comprises two-thirds of the land devoted to crop cultivation globally. Crops with lower yield growth tended to have undergone greater expansion in cultivated area. Agriculture has become more pollinator-dependent over time, and this trend is more pronounced in the developing than developed world.
Conclusions
We propose that pollination shortage will intensify demand for agricultural land, a trend that will be more pronounced in the developing world. This increasing pressure on supply of agricultural land could significantly contribute to global environmental change
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Insectos en bosques de lenga
No full textFil: Garibaldi, Lucas A. Universidad Nacional de Río Negro. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural. Río Negro, Argentina.Fil: Garibaldi, Lucas A. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural. Río Negro, Argentina.Fil: Mazía, Noemi. Universidad de Buenos Aires. Buenos Aires, Argentina.
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Pollinator shortage and global crop yield
Get PDFFil: Garibaldi, Lucas Alejandro. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio Ecotono; Argentina.Fil: Aizen, Marcelo A. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio Ecotono; Argentina.Fil: Cunningham, Saul A. CSIRO Entomology; Australia.Fil: Klein, Alexandra M. University of California; USA.Fil: Klein, Alexandra M. University of Goettingen; Alemania.Fil: Aizen, Marcelo A. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Argentina.Fil: Aizen, Marcelo A. Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA); Argentina.Fil: Garibaldi, Lucas Alejandro. Universidad de Buenos Aires (UBA). Facultad de Agronomía; Argentina.A pollinator decline caused by environmental degradation might be compromising the production of pollinator-dependent crops. In a recent article, we compared 45 year series (1961–2006) in yield, production, and cultivated area of pollinator-dependent and nondependent crop around the world. If pollinator shortage is occurring globally, we expected a lower annual growth rate in yield for pollinator-dependent than nondependent crops, but a higher growth in cultivated area to compensate the lower yield. We have found little evidence for the first “yield” prediction but strong evidence for the second “area” prediction. Here, we present an additional analysis to show that the first and second predictions are both supported for crops that vary in dependency levels from nondependent to moderate dependence (i.e. up to 65% average yield reduction without pollinators). However, those crops for which animal pollination is essential (i.e. 95% average yield reduction without pollinators) showed higher growth in yield and lower expansion in area than expected in a pollination shortage scenario. We propose that pollination management for highly pollinator-dependent crops, such us renting hives or hand pollination, might have compensated for pollinator limitation of yield
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Intercropping functionally similar species reduces yield losses due to herbivory. A meta-analytical approach
Get PDFAgroecosystem diversification is often implemented to diminish herbivory and reduce yield losses. However, increasing plant richness does not always reduce herbivory levels, so there is a need for better understanding which polyculture characteristics are effective in deterring herbivores. Here, we evaluated the hypothesis that functional and phylogenetic distances between intercropped species reduce herbivory pressure and enhance natural enemy response. Diminishing herbivory would be brought about by the complementarity and synergy of traits that deter herbivores and benefit herbivore natural enemies, and as a result of a decrease in the availability of host plants for specialized herbivores. Using a meta-analytical approach, we observed lower herbivore
abundance and herbivory damage in focal plants when they grew in polycultures. In addition, polycultures showed increased levels of herbivore parasitism and greater abundance of predators and parasitoids, although the effect of the latter two was negligible. Interestingly, the functional distance between crops affected herbivore abundance and herbivory damage in opposite ways, but had no effect on herbivore natural enemy response.
Contrary to our expectations, neither herbivory pressure nor natural enemy response appeared to be influenced
by phylogenetic distance between intercropped species. Overall, our study provides valuable insights for agro-ecosystem design aimed at reducing yield loss by strategically intercropping functionally similar species.Fil: Fernandez, Anahí R. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural; Argentina.Fil: Fernandez, Anahí R. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Gleiser, Gabriela. Universidad Nacional de Río Negro. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural; Argentina.Fil: Gleiser, Gabriela. Universidad Nacional del Comahue. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina.Fil: Aizen, Marcelo A. Universidad Nacional del Comahue. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina.Fil: Aizen, Marcelo A. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Garibaldi, Lucas A. Universidad Nacional de Río Negro. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural; Argentina.Fil: Garibaldi, Lucas A. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Incremental contribution of pollination and other ecosystem services to agricultural productivity: effects of service quantity and quality
No full textFil: Garibaldi, Lucas A. Universidad Nacional de Río Negro. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural. Río Negro, Argentina.Fil: Garibaldi, Lucas A. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural. Río Negro, Argentina.Fil: Aizen, Marcelo A. Universidad Nacional del Comahue. Instituto de Investigaciones en Biodiversidad y Medioambiente. Río Negro, Argentina.Fil: Cunningham, Saul A. Australian National University. Australia.Fil: Harder, Lawrence. University of Calgary. Canada.Fil: Klein, Alexandra M. University of Freiburg. Alemania.
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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