1,721,189 research outputs found
Genetically modified (GM) corn in the Philippines : Ecological impacts on agroecosystems, effects on the economic status and farmers’ experiences
Full text linkTo seek answers to the issues on GM corn adoption in the Philippines, the thesis focused to find answers on the general question: How can genetically modified (GM) corn and its attributed changes in agricultural practices affect the agro-ecosystem's biodiversity and the economic status and social life of the farmers? Survey of Asian corn borer (ACB) in Chapter2 showed that Bt corn efficiently reduce borer pest problem and damage to plants by 44%. No secondary pest outbreak was found in Bt cornfields yet, occurrence of ACB though at an insignificant level, could imply potential development of Bt toxin resistance. On biodiversity (Chapters3 and 4), the total invertebrate abundance, surface dwellers and soil dwellers were significantly higher in non-GM cornfields than in Bt and BtHT cornfields. Insecticide-sprayed non-GM cornfields harbored more invertebrates than unsprayed Bt or BtHT cornfield. Surveyed cornfields with a minimum of two years cultivation of GM corn manifested that non-Bt cornfields had significantly higher abundance and species richness of non-target invertebrates than the Bt and BtHT fields. On economic aspect (Chapter5), the non-GM corn was not statistically different from Bt, BtHT and HT corn in terms of production output(PO), net income(NI), production-cost ratio(M) and return on investments(ROI). Results of econometric and Blinder-Oaxaca analyses demonstrate that at present GM corn hybrids do not explicitly manifest economic advantage compared to non-GM corn. On social aspect (Chapter6), GM corn adoption proved to be influenced by the perceived economic advantage, extent of knowledge, level of satisfaction and extent of first-hand experience. The foremost reason for not adopting GM corn was the cost of seed. Herbicide-tolerant (HT) corn, Bacillus thuringiensis (Bt) corn, BtHT corn, abundance, species richness, Asian corn borer, secondary pest, genetically modified (GM) corn, non-GM corn, farm economics, decomposition analysisConservation Biolog
Environmental footprints: assessing anthropogenic effects on the planet's environment
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The aims of this thesis are to conduct a comprehensive investigation into the theoretical and methodological aspects of environmental footprints and into the disciplinary relationship with the latest science in defining planetary boundaries for human activities. Main conclusions are as follows: (1) environmental footprints are measures of anthropogenic pressure or impact on the planet's environment irrespective of their precise units and dimensions; (2) environmental footprints are classified into the inventory-oriented footprints and impact-oriented footprints, which offer two competing paradigms for footprint indicators; (3) integrating the impact-oriented footprints provides policy makers with a unified approach to assessing overall environmental impacts and has a broader scope of applicability than life cycle assessment; (4) life cycle assessment cannot be interpreted as a versatile tool for accounting for all possible environmental footprints, although the footprint community has indeed learned and borrowed much from it; (5) latest science in planetary boundaries is found to complement environmental footprints in assessing environmental sustainability that is a critical prerequisite for the economic and social pillars of sustainable development; and (6) the sustainability gap between the converted footprint and boundary metrics plays a central role in understanding the national performance on individual and collective environmental issues.Industrial Ecolog
Development of life cycle assessment for residue-based bioenergy
Full text linkThe overall framework of the thesis is to develop an approach to compare the impacts between leaving biomass residues in fields and utilizing them for bioenergy. In this regard, residue-based bioenergy should be managed differently from product-based bioenergy. The objectives of this thesis are to identify the key issues when conducting a life cycle assessment (LCA) of residue-based bioenergy and to propose improvement in LCA procedures, specifically in the areas of life cycle inventory (LCI), life cycle impact assessment (LCIA), and methodological choices in the comparative LCA. It was discovered that the key issues associated with residue-based bioenergy relate to four primary characteristics with respect to its raw materials (biomass residues), i.e., excessive removal from plantation fields which can affect soil fertility; valuation (relative to biomass products); competing uses (bioenergy, feed, fiber, fertilizers); and treatment of biogenic carbon (assumptions of carbon neutrality vs. complete inventory). These unique features require specific LCA approaches which vary from those of conventional product-based bioenergy. These approaches include: [1] solutions to the existing dissimilar practices in the LCI of biogenic carbon; [2] an LCIA method of removing biomass residues from soil on biomass productivity; and [3] methodological choices in comparative LCA of biomass residues utilization.Dutch Ministry of Foreign Affairs through the Netherlands Fellowship Programme (grant number CF7412/2011)Industrial Ecolog
Unsprayed field margins: implications for environment, biodiversity and agricultural practice. The Dutch Field Margin Project in the Haarlemmermeerpolder.
Full text linkLEI Universiteit LeidenEnvironmental Biology - ol
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Succesvol natuur beschermen
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Diesoratie uitgesproken door prof.dr. Geert R. de Snoo hoogleraar Conservation Biology
tijdens de 441ste dies natalis op maandag 8 februari 2016 in de PieterskerkConservation Biolog
Ecology and conservation of spotted hyena (Crocuta crocuta Erxleben 1777)in human dominated landscapes in Northern Ethiopia
Full text linkMost scientific literature on hyena-human interrelationships in Africa sug-gests conflict situations, often resulting in the killing of hyenas. Hyenas survive with difficulty in human-altered habitats and coexistence between hyenas and local communities is problematic. This is because hyenas need extensive areas, usually with few people and sufficient prey. In contrast to this, the present dissertation presents an exceptional case of peaceful co-existence between hyenas and humans. Based on regular observations of hyenas and anecdotal reports, I hypothesized that hyenas in the Tigray re-gion, northern Ethiopia, survive in human-dominated landscapes because of a unique combination of adaptation to anthropogenic food and cultural tolerance towards hyenas. My research aimed to investigate hyena ecology and behavior in human-dominated and prey-depleted landscapes in Tigray. Hyenas are common in many parts of Ethiopia, and in most of those areas, prey populations have been depleted. In northern Ethiopia, the natural prey base is depleted due to agricultural expansion, deforestation, human settle-ment, and habitat fragmentation and degradationMU_UMB and VLIR_UOSConservation Biolog
The interactions of human mobility and farming systems and impacts on biodiversity and soil quality in the Western Highlands of Cameroon
Full text linkPopulation growth and the drop in the returns from the major cash crop (coffee) for small farmers are the main drivers that have influenced the farming systems and mobility of farmers in the Western Highlands of Cameroon (WHC). The main objective of this research activity was to determine the interactions between farming systems and human mobility in the WHC. A comparative study was conducted through household and field surveys in three villages and conceptualized based on the systems approach. The different types of mobility were influenced by household social factors, the quest for ‘high valued' farm plots and hired labour. Urban-rural migration contributed to occupation diversification and social mobility. The sustainability factor was a function of land use intensity, intensity of off-farm inputs, the household adjustment factor and mobility of the household. The sacred groves were rich in plant diversity of varied ecological and economic importance. Nitrogen mining was common at all levels of the farming system. These determinants and types of mobility claims are pertinent to the research area; the sustainability results of the farming systems reflect the reality on the ground; the nutrient flux evaluated at the crop and farm levels constitute a valuable database for future research.Volkswagen FoundationConservation Biolog
Using commitment to improve environmental quality
Full text linkThe making of commitments is often used as an intervention aimed at increasing pro-environmental behavior. Research shows that when people commit to changing their environmental behaviors, they tend to adhere to their commitments. In this dissertation it is investigated whether commitment making is effective in improving agricultural nature conservation and with that, environmental quality of farm lands. Furthermore, a conceptual review is offered, as well as an experimental investigation of the conditions under which people are willing to make such commitments. Results show that commitment making combined with tailored information is indeed effective in improving farmers’ nature conservation. Several explanations of the effect of commitment making on behavior are offered. Also, it is shown that that the willingness to invest in commitment making is contingent on the interplay of dispositional trust
and situational expectations. Taken together, this dissertation aims to provide the reader with a perspective on the entire process of commitment making: under which conditions people engage in it, if it is successful in altering behavior, and how it is successful.LEI Universiteit LeidenSocial decision makin
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