1,721,172 research outputs found
Global food security, biodiversity conservation and the future of agricultural intensification
No full textUnder the current scenario of rapid human population increase, achieving efficient and productive agricultural land use while conserving biodiversity is a global challenge. There is an ongoing debate whether land for nature and for production should be segregated (land sparing) or integrated on the same land (land sharing, wildlife-friendly farming). While recent studies argue for agricultural intensification in a land sparing approach, we suggest here that it fails to account for real-world complexity. We argue that agriculture practiced under smallholder farmer-dominated landscapes and not large-scale farming, is currently the backbone of global food security in the developing world. Furthermore, contemporary food usage is inefficient with one third wasted and a further third used inefficiently to feed livestock and that conventional intensification causes often overlooked environmental costs. A major argument for wildlife friendly farming and agroecological intensification is that crucial ecosystem services are provided by “planned” and “associated” biodiversity, whereas the land sparing concept implies that biodiversity in agroecosystems is functionally negligible. However, loss of biological control can result in dramatic increases of pest densities, pollinator services affect a third of global human food supply, and inappropriate agricultural management can lead to environmental degradation. Hence, the true value of functional biodiversity on the farm is often inadequately acknowledged or understood, while conventional intensification tends to disrupt beneficial functions of biodiversity. In conclusion, linking agricultural intensification with biodiversity conservation and hunger reduction requires well-informed regional and targeted solutions, something which the land sparing vs sharing debate has failed to achieve so far
Investigating Opportunities to Strengthen the Local Food System in South Eastern Michigan
Full text linkIn 2004, a local food system report, entitled Toward a Sustainable Food System: Assessment and Action Plan for
Localization in Washtenaw County, Michigan, was released at the conclusion of a master’s project conducted
by a team of students at the University of Michigan’s School of Natural Resources and Environment.
This research and report made a compelling argument for the viability of a local food system in
Washtenaw County, Michigan, and was the first of its kind to assess the intricacies of the existing local
food system within a single county of southeastern Michigan (Davis et al. 2004).
Building upon this previous research, in early 2006 a second research team comprised of master’s
students from the University of Michigan’s School of Natural Resources and Environment joined with
members of the Food System Economic Partnership (FSEP) to develop resources and tools to identify
unmet local consumer demands and opportunities for agricultural economic development in a fivecounty
area of southeastern Michigan (i.e., Jackson, Lenawee, Monroe, Washtenaw and Wayne counties).
FSEP, an urban-rural collaboration working to enable strong farms, healthy cities, community wealth,
and job creation in southeastern Michigan, was officially launched in the beginning of 2005 to identify
economic opportunities and implement creative solutions to chronic issues relevant to the food system
in the region. As a new organization, FSEP required additional knowledge and data about the local food
system, particularly from system participants, to develop the resources and tools needed to carry out
their mission to catalyze change in the food system of southeastern Michigan through research,
education and outreach.Master of Science (MS)School of Natural Resources and EnvironmentUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/50468/3/Southeastern Michigan Community Food Profile.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/50468/2/Local Food Systems Final Report.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/50468/1/Local Food Systems Executive Summary.pd
Effects of management intensification on coccids and parasitic hymenopterans in coffee agroecosystems in Mexico.
No full textBiodiversity maintained in agroecosystems contribute both to conservation and economic goals via various ecosystem services. However, management intensification can negatively affect biodiversity in agroecosystems. Effects of management intensification on biodiversity and its function in agroecosystems need to be explored to develop agricultural practices where conservation and economic goals are successfully integrated. I conducted studies in 4 coffee agroecosystems under low to high management intensities in Chiapas, Mexico to investigate (1) the diversity and abundance of hymenopteran parasitoids, and (2) the function of a natural enemy complex in controlling a potential pest species, the coffee green scale, Coccus viridis. Parasitoid collections produced a total of 17,366 individuals and 308 morphospecies representing 29 families. Total estimated species richness exceeded 200 in all sites, however, negative effects of management intensification was indicated by >10% reduction in species richness. The abundance of parasitoids also declined along the intensification gradient. Similarities in species compositions were affected more by the proximity of sites than similarities in management intensity. In addition, the shade layer had greater species richness regardless of management intensity and species compositions of the canopy and coffee layers showed >50% overlap. Surveys showed low abundance of C. viridis regardless of management intensity; however, C. viridis infestation caused 40% reduction in coffee fruits weight. Experiments showed that 90% of C. viridis mortality was caused by the coccinelid beetle, Azya orbigera; however, in a more intensively managed site where insect natural enemies were less abundant, 61% of C. viridis mortality was caused by the entomophagous fungus, Verticillium lecanii , and 39% by predation. Surveys showed that parasitism of C. viridis could be >10%; however, experimental results indicated that the presence of coccinelids reduces it to C. viridis appeared to change under different conditions. Thus maintaining a diverse set of natural enemies can be important in achieving an effective pest control in coffee agroecosystems.PhDBiological SciencesEcologyParasitologyPlant sciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/126581/2/3253423.pd
In a country without forest, no life is good: Participatory action research in the neoliberal context of Nicaragua.
No full textThis study begins by providing a synopsis of the trends in tropical coastal management, and the history and natural history of Pearl Lagoon which is located on the Caribbean Coast of Nicaragua. In response to local residents' concerns about a deteriorating environment, the Coastal Area Monitoring Project (CAMP) was initiated in Pearl Lagoon beginning in 1993. CAMP relies on participatory action research (PAR) as its principal research methodology. The CAMP PAR process involves local residents, resource managers, and scientists in an iterative process of problem identification, information collection, analysis, and evaluation. With data collected by local people, Pearl Lagoon's pine forest, water, and artisanal fishery resources are assessed. Pinus caribaea-dominated savannas are heavily exploited for lumber except where protected and reforested by local people involved in CAMP. Fresh water resources are deteriorating as water sources are contaminated and the agriculture frontier expands. There are indications from interviews and catch monitoring that increased commercialization of fishery products and the introduction of new gear types may be resulting in declining catch-per-unit-effort, although further monitoring is necessary. Using data from participant observation, interviews, and document analysis, the factors are identified which influence CAMP PAR process viability---defined as efficacy and sustainability---over six years. The observed pattern of program activity and quiescence is correlated with access to resources (e.g. funds, expertise, opportunity), enabling horizontal institutional structures, and process resonance with local residents' aspirations and social norms. Most importantly, the CAMP PAR process resonates with local residents' aspirations to sustainably manage their coastal resources for local benefit. These aspirations contradict the current Nicaraguan neo-liberal political economy favoring unsustainable exploitation of natural resources for export. A detailed analysis of the contentious interactions between CAMP and a government-led fisheries development project highlights the consequences of neo-liberal policies for coastal communities, PAR, and resource co-management. The leaders of this fisheries development project attempted to marginalize CAMP, mainly because Pearl Lagoon residents resisted their neo-liberal prescriptions through the PAR process. This finding suggests that community empowerment---prior to the articulation of resource users with governments---is a prerequisite to ensure power-sharing, the basis for meaningful co-management.PhDAquatic sciencesBiological SciencesEnvironmental scienceForestryHealth and Environmental SciencesSocial SciencesSocial researchUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/131620/2/9929800.pd
Diversity and function of leaf litter ants in Colombian coffee agroecosystems.
No full textThe loss of biodiversity and associated functions in managed ecosystems is one of the most critical issues for conservation because it affects the long-term sustainability of the planet. This dissertation investigates causes and effects of agricultural intensification on the structure and function of ant assemblages in coffee plantations and forest patches of Andean Colombia. Coffee intensification significantly reduced vegetation complexity and increased management index values, as measured from 14 habitat variables. Using a leaf-litter sampling protocol I found that less intensified coffee farms harboured significantly higher ant species richness. Ant communities in polygeneric shaded coffee were significantly more similar to forest patches than any other management type. Additionally, significant positive associations among ant communities and the number of species involved in ant mosaics dropped sharply with intensification. I carried out nesting resource augmentation experiments to examine how the quantity and quality of nesting resources affect ant biodiversity. Ants responded quickly to the addition of nesting resources across the intensification gradient. In the quality resources experiment, the diversity of ants nesting in multi-species groups of twigs was significantly higher than in monoespecific groups across all scales. These results suggest that bottom-up mechanisms are important for ant species loss throughout the technification process although other biotic and abiotic factors such as microhabitat and competition might also play a role. Finally, ant predation in shaded vs. unshaded coffee plantations was studied in the field and laboratory. Exclosure experiments demonstrated that ant communities prey on the coffee berry borer (Hypothenemus hampei) in both shaded and unshaded coffee plantations, but this function increased with shade in the wet season, when most infestation takes place. Ants were more effective predators in laboratory conditions than in the field. Predation in the field fluctuated between 2%--27% of borer adults. My studies strongly support the conclusion that the structure and function of ant biodiversity are negatively affected by intensification of coffee agriculture. I recommend that immediate action be taken to stop the destruction of traditional coffee practices and prevent further biodiversity loss in hotspots of tropical biodiversity.PhDAgronomyBiological SciencesEcologyEnvironmental scienceHealth and Environmental SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/123782/2/3106009.pd
Mitigation of microclimate variation through agroforestry: Protecting coffee agriculture from the impacts of climate change.
No full textBecause crops have narrow climate thresholds for developmental success, an increasing occurrence of extreme climate events will affect farmers who depend on rainfed agriculture. Increasing patterns of agricultural intensification may lead to still greater vulnerability for farmers because more intensively managed systems may be less resilient to the impacts of climate extremes. Because of farmer vulnerability, the different responses of management intensities to climate extremes should be explored so that sustainable management strategies can be developed to protect farmers from increased climate variability. This thesis explores the potential of agroforestry systems to protect coffee agriculture from climate variability in Chiapas, Mexico. A set of experiments were conducted from July 2004 to November 2005 in the Soconusco region of Chiapas in a high (60-80%), medium (30-65%), and low (10-30%) shade coffee system, where shade is an indicator of management intensity. These sites were chosen to explore the qualitative differences among management systems as they relate to climate. Microclimate variables and soil moisture were measured in these systems to examine the effect of shade cover on microhabitat modification. Evapotranspiration rates were measured to examine water loss as a function of shade cover. Additionally, flower and fruit development were assessed to examine the effects of microclimate and soil moisture on coffee production. Microclimate measurements showed that fluctuations in ambient microclimate decreased significantly as shade cover increased, with similar patterns in soil moisture measurements. Coffee plant evapotranspiration rates were reduced at shade levels ≥30%, with significant effects of light and vapor pressure deficit. Shade cover also affected flowering and fruit set. Flower development was significantly enhanced in sites with ≥30% shade cover, where greater soil moisture measurements were found. Fruit development was also greatly controlled by microclimate because of soil moisture and wind measurements associated with greater shade cover. These results show that shade tree use in agroforestry systems can mitigate microclimate and soil moisture fluctuations in agricultural sites and in turn, affect flowering, fruit development, and ultimately, coffee yield. Thus, the implementation of agroforestry management systems can enhance coffee production and should be considered an adaptive farming strategy in areas with increasing climate variability.PhDBiological SciencesEcologyEnvironmental scienceHealth and Environmental SciencesPlant sciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/125810/2/3224678.pd
Pest control and soil management in the Guatemalan highlands: Understanding traditional agricultural practices.
No full textExtension of integrated pest management (IPM) technology in recently introduced vegetable export crops in the Guatemalan highlands has been largely unsuccessful. Efforts to overcome the failure of the IPM diffusion-adoption process have been ineffective, in part because farmers are not generally taken into account in the research process. Understanding farmers' agricultural knowledge must be an early step in research. I conducted a semi-structured survey of 75 Cakchiquel Maya farmers in Patzun, Guatemala, to begin documenting their pest control practices. Their knowledge of biological and curative pest control is limited. Nevertheless, their broad knowledge of preventive agronomic pest control practices explains why they had few pest problems in their milpas (traditional intercrops of corn, beans, and other edible plants). According to agroecological theory, the majority of these preventive practices are efficient and environmentally innocuous. However, scientists know little about the pest control practice that farmers mentioned most: application of organic fertilizers. I conducted a series of experiments to test the impact of fertilizers on corn pests. Field trials compared effects of organic and synthetic fertilizers on herbivorous insects and their natural enemies. Corn plants treated with traditional organic fertilizer applied for at least two years hosted fewer aphids (9.14 aphids/plant), than those treated with synthetic fertilizer (19.18 aphids/plant). Complimentary bioassays in an olfactometer and with corn growing in screened boxes, revealed that aphids are attracted to plants treated with synthetic fertilizers 3.42 times as frequently as to those grown with manure. Aphid reproductive rates on the synthetically fertilized corn were 1.07 times those on the organically treated plants. Foliar nitrogen concentration was higher in synthetically fertilized plots (2.97%) than in the organic fertilized (2.67%), explaining in part the aphids' response. Natural enemies appear to play a role as well, as Coccinellidae populations were 3.6 times higher in organically fertilized plots. The effect of synthetic fertilizers on aphids persists for at least one year after their application. Fertilizer treatments had no effect on yields, suggesting that traditional fertilization practices in Patzun are ecologically and economically appropriate.PhDAgricultureAgronomyBiological SciencesEcologyEnvironmental scienceHealth and Environmental SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/131281/2/9840606.pd
Soil nutrient heterogeneity and root foraging in a Nicaraguan rainforest: Patterns, processes and potential implications for competitive dynamics.
No full textSoil nutrient heterogeneity at spatial scales that allow individual plants to experience multiple belowground environments is potentially an important influence on the competitive dynamics of plant communities. I investigated three topics related to soil heterogeneity in a Nicaraguan rainforest: spatial and temporal soil heterogeneity, morphological root foraging by plants, and the interaction between nutrient heterogeneity and root foraging on belowground competition. In the field, I examined soil properties to quantify their heterogeneity, and to determine the influence of aboveground plant inputs and natural wildfires on soil nutrients. Both univariate and geostatistical methods were used to quantify the forests heterogeneity. Variability as measured by the coefficient of variation ranged between 12% and 92%. While N and K variability tended to be low, leaf litter and P tended to be on the high end of this range. The range over which soil components were autocorrelated (patch size) for the majority of soil properties in the forest was ≤20 meters. Burning altered the spatial variability by decreasing average patch size (12m vs. 7m). However, it had a variable effect on soil nutrient availability. Burning increased P, left K unchanged, and increased N at one site but decreased it in a second. It appears that site differences in N values were due to variable fire temperatures at the two locations. Overall, plants in this forest forage morphologically for nutrients by growing roots prolifically into nutrient-rich substrates though a greenhouse study showed this to be a species-specific response. In addition, evidence was found that roots of some species are finer when growing into nutrient-rich substrates and that growing in a heterogeneous soil environment may be advantageous to some species. In greenhouse experiments, I examined how soil heterogeneity and root foraging may interact to influence competition within plant populations through an effect on the size-symmetry of belowground competition. This work found that when combined with morphological root foraging, soil heterogeneity increases the symmetry of competition. This result goes in a direction contrary to traditional theory and suggests the nature of belowground competition is more complicated than previously thought.PhDBiological SciencesEcologySoil sciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/123132/2/3068829.pd
The effect of exotic tree plantations on the biodiversity of leaflitter arthropods in tropical islands.
No full textReplacing native forests by plantations of exotic tree species causes a reduction in the local biodiversity because plantations are commonly simplified systems. This practice would have greater impacts on islands, where the biota is especially vulnerable to environmental changes. I studied leaflitter arthropod diversity associated with native forests and abandoned (45 years) exotic wood plantations of mahogany, Casuarina and Caribbean pine in tropical islands. My general hypotheses were: (1) native forests harbor higher species richness than abandoned exotic wood plantations; (2) leaflitter structural complexity influences positively the arthropod species richness, and (3) endemic and native arthropods will be more diverse in native forests than in the plantations. I found a general tendency of higher species richness in the native forests than in the plantations. Nevertheless, the arthropod species richness was higher in one of the mahogany plantation study sites. Consequently, I seek to identify a mechanism behind these patterns. Since the complexity of the leaflitter habitat is related to the diversity of the surrounding forest, one would expect that a natural, diverse forest would exhibit more complexity in the leaflitter habitat than a timber plantation. I tested this hypothesis using leaflitter interstitial space as a surrogate for leaflitter complexity. Although the native forest exhibited higher leaflitter habitat complexity, it was not correlated with higher arthropod species richness. Then, I conducted a translocation experiment using native forest, mahogany and Casuarina leaflitter, and found that the arthropod species composition was influenced by the leaflitter type more than by the surrounding forest. For my third hypothesis, I used leaflitter ants as the target group. I found that endemic, native and exotic ants were diverse in native forest and exotic plantations, and concluded that this change did not have a differential impact on endemic, native, or exotic ant species. In general, this study found native forests had higher species richness of leaflitter arthropods than Casuarina and pine plantations, even after the plantations were abandon for 45 years. It also indicates that for wood plantations, certain tree species harbor higher biological diversity than others. Hence, forest management decisions need to incorporate ecological knowledge of the systems to conserve their biodiversity.PhDBiological SciencesEcologyEntomologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/124672/2/3150201.pd
Predators of aphids in cacao plantations in Brazil: Effectiveness in biological control and mechanisms of coexistence.
No full textThe need to stop biodiversity loss and to develop sustainable farming systems makes cacao agroforestry a balanced way to sustain biological diversity while providing ecological services to agroforestry systems. One of the ecological services provided by biodiversity in cacao plantations is insect pest control. This dissertation investigates whether different levels of shade tree diversity in cacao plantations increase the abundance and effectiveness of predators of the aphid Toxoptera aurantii (Boy.) (Hemiptera: Aphididae). Furthermore, it addresses processes in assemblages of natural enemies that determine the strengthening or disruption of top-down herbivore regulation, focusing on mechanisms of coexistence amongst predator species. Exclusion experiments showed that the predators of T. aurantii, mainly Syrphidae (Diptera), Coccinellidae (Coleoptera), Chrysopidae and Hemerobiidae (Neuroptera), are effective in reducing aphid populations in cacao farms. However, no difference was detected in predator effectiveness between different levels of shade tree diversity. A laboratory experiment found a Type II functional response of larvae of Ocyptamus antiphates (Walker) (Syrphidae: Diptera) in relation to the density of T. aurantii. The larva of O. antiphates consumed an average of 301.1 aphids, the same average maximum density of aphids occurring under field conditions when predators are absent. This explains the effectiveness of aphid control by this species. However, the presence of five additional predators in this tri-trophic system required understanding how all the species can coexist while competing for a scarce resource. Therefore, I conducted field studies to assess the spatial association of predators of T. aurantii and found that spatially independent distribution is one of the mechanisms of coexistence among the aphid predators. The role of anti-predator behavior of aphid-attending ants on the spatial distribution and coexistence of predators was also studied. Ants attacked the syrphid O. antiphates but never attacked a species of Coccinellidae. This ant behavior could be a parallel, spatially structured, mechanism of coexistence among predators, for it can benefit the non-attacked species by increasing the number of prey patches free of competitors or intraguild predators.PhDAgronomyBiological SciencesEcologyEntomologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/126558/2/3253402.pd
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