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Consumer Control (consumer + control)

Distribution by Scientific Domains
Life Sciences80%

Selected Abstracts

Consumer Control of Salt Marshes Driven by Human Disturbance

CONSERVATION BIOLOGY, Issue 3 2008
MARK D. BERTNESS
control de consumidor; impactos humanos; conservación de pantano de sal; cascadas de trophic Abstract:,Salt marsh ecosystems are widely considered to be controlled exclusively by bottom,up forces, but there is mounting evidence that human disturbances are triggering consumer control in western Atlantic salt marshes, often with catastrophic consequences. In other marine ecosystems, human disturbances routinely dampen (e.g., coral reefs, sea grass beds) and strengthen (e.g., kelps) consumer control, but current marsh theory predicts little potential interaction between humans and marsh consumers. Thus, human modification of top,down control in salt marshes was not anticipated and was even discounted in current marsh theory, despite loud warnings about the potential for cascading human impacts from work in other marine ecosystems. In spite of recent experiments that have challenged established marsh dogma and demonstrated consumer-driven die-off of salt marsh ecosystems, government agencies and nongovernmental organizations continue to manage marsh die-offs under the old theoretical framework and only consider bottom,up forces as causal agents. This intellectual dependency of many coastal ecologists and managers on system-specific theory (i.e., marsh bottom,up theory) has the potential to have grave repercussions for coastal ecosystem management and conservation in the face of increasing human threats. We stress that marine vascular plant communities (salt marshes, sea grass beds, mangroves) are likely more vulnerable to runaway grazing and consumer-driven collapse than is currently recognized by theory, particularly in low-diversity ecosystems like Atlantic salt marshes. Resumen:,Se ha considerado extensamente que los ecosistemas de marismas son controlados exclusivamente por dinámicas abajo-arriba, pero se ha acumulado evidencia de que las perturbaciones humanas están provocando el control por consumidores en marismas del Atlántico occidental, a menudo con consecuencias catastróficas. En otros ecosistemas marinos, las perturbaciones humanas rutinariamente disminuyen (e.g., arrecifes de coral, pastos marinos) y refuerzan (e.g., varec) el control por consumidores, pero la teoría de marismas actual predice una leve interacción potencial entre humanos y consumidores en las marismas. Por lo tanto, las modificaciones humanas al control arriba-abajo en las marismas no estaba anticipada y aun era descontada en la teoría de marismas actual, a pesar de advertencias sobre el potencial de impactos humanos en cascada en trabajos en otros ecosistemas marinos. No obstante los experimentos recientes que han desafiado el dogma de marismas establecido y que han demostrado la desaparición gradual de marismas conducida por consumidores, las agencias gubernamentales y las organizaciones no gubernamentales continúan manejando la disminución de marismas en el marco de la teoría vieja y sólo consideran como agentes causales a factores abajo-arriba. Esta dependencia intelectual en la teoría sistema-específico (i.e., teoría de marismas abajo-arriba) de muchos ecólogos y manejadores costeros tiene el potencial de tener repercusiones graves para el manejo y conservación de ecosistemas costeros frente a las crecientes amenazas humanas. Enfatizamos que las comunidades plantas vasculares marinas (marismas, pastos marinos, manglares) son potencialmente más vulnerables al pastoreo descontrolado y al colapso conducido por consumidores que lo que reconoce la teoría actualmente, particularmente en ecosistemas con baja diversidad como las marismas del Atlántico. [source]

Enhanced self-determination of adults with intellectual disability as an outcome of moving to community-based work or living environments

JOURNAL OF INTELLECTUAL DISABILITY RESEARCH, Issue 5 2001
M. L. Wehmeyer
Abstract In recent years, the self-determination construct has received increased international visibility and utilization in the field of intellectual disability (ID). This has resulted in efforts to promote skills enhancing self-determination, and in efforts to change how adult services are funded to allocate resources to increase consumer control and direction. An important component to consider in both of these efforts is the role of the environment on self-determination. The present study examined the self-determination, autonomy and life choices of individuals with ID before and after they moved from a more restrictive work or living environment. The self-determination of adults with ID was measured for an average 6-months before and after a move from a more restrictive living or working environment to a community-based setting. Paired-sample t -tests indicated that there were significant changes, in each case in a more adaptive direction, in self-determination, autonomous functioning and life choices following a move to a less restrictive environment. The present findings contribute to emerging evidence that the self-determination of individuals with ID is limited by congregate living or work settings which limit opportunities for choice and decision-making. Alternatively, more normalized, community-based environments support and enhance self-determination. Because self-determination has been linked to positive adult outcomes and enhanced quality of life, it is important to consider ways to enable people with ID to live and work in their communities. [source]

Dominance by a canopy forming seaweed modifies resource and consumer control of bloom-forming macroalgae

OIKOS, Issue 7 2007
Britas Klemens Eriksson
Degradation of ecological resources by large-scale disturbances highlights the need to demonstrate biological properties that increase resistance to change and promote the resilience of ecosystem regimes. Coastal eutrophication is a global-scale disturbance that drives ecosystem change by increasing primary production and favouring ephemeral and bloom-forming life-forms. Recent synthesis indicates that consumption processes increase the resistance of coastal communities to nutrient loading by controlling the responses of ephemeral macroalgae. Here we suggest a similar ecological function for canopy cover by demonstrating that the presence of a canopy species modifies both resource and consumer control of bloom-forming algae associated with nutrient enrichment. We tested effects of canopy presence on the interaction between consumer and resource control, by field-manipulations of a dominant canopy forming seaweed (Fucus vesiculosus), grazer presence (dominated by the gastropod Littorina littorea) and nutrient enrichment (common agricultural NPK fertilizer). Canopy cover and grazers jointly controlled strong increases of ephemeral bloom-forming algae (dominated by Ulva spp) from nutrient enrichment; nutrients increased ephemeral recruitment almost 10-fold, but only in the absence of both grazers and canopy cover. Recruitment success of the canopy-forming seaweed itself decreased additively with 56.1, 71.3 and 50.5% from independent effects of canopy cover, grazers and nutrient enrichment, respectively. A meta-analysis of nine nutrient enrichment experiments including seaweed, seagrass and stream communities, showed that in the presence of canopies average nutrient effects were reduced by more than 90% compared to without canopies. This corroborates the generality of our finding that dominating canopy species are important for aquatic ecosystems by increasing community resistance to the propagation of nutrient effects. [source]