Papers by John Vandermeer
In a classic study, Huffaker demonstrated that abiotic forms of spatial heterogeneity could induc... more In a classic study, Huffaker demonstrated that abiotic forms of spatial heterogeneity could induce stability in predator–prey interactions. Recent theories suggest that space can also act to destabilize predator–prey systems and that stability can arise from coupling of unstable units. Here, using Huffaker's classic experimental design refitted with modern empirical and statistical techniques, we reassess the effect of space on predator–prey interactions when the prey are pests of agriculture and when predators must compete with pathogens for shared prey resources. Using an empirical system including aphids, ladybird beetles, and entomopathogenic fungi, we show that while two different control agents were ineffective at controlling pests in insolation, coupling them together not only improved control of the pest but also reduced the occurrence of large, spatially clustered pest outbreaks. Our results suggest that as agriculture becomes increasingly isolated and consolidated across landscapes, endogenous forms of spatial hetero-geneity, which arise from interactions between diverse assemblages of control agents, may break down. We suggest that improving connectivity across landscapes is important for maintaining effective biological control in agroecosystems.
ABSTRACT Background/Question/Methods According to the Intergovernmental Panel of Climate Change a... more ABSTRACT Background/Question/Methods According to the Intergovernmental Panel of Climate Change agriculture is responsible for a significant portion of the increase of greenhouse gases. But not all agriculture has the same impact on global warming. We conducted an extensive review of the literature on the contributions of agriculture to climate change, organized into four major areas: a) transportation of agricultural inputs, outputs, and products; b) general effects of agriculture on greenhouse gas (GHG) emissions, carbon and nitrogen cycles; c) effects on biodiversity and land use change, and d) comparative energy efficiencies. Results/Conclusions We arrived at a conservative estimate of industrial, large-scale agriculture contributing 22% of total anthropogenic GHG emissions. Agriculture-related transportation was roughly estimated to be almost one-fifth of this amount. Food sovereignty and reinvigoration of local food systems have the potential to decrease the contribution of transportation, especially where small-scale, local practices are more efficient than practices in exporting countries. In terms of general effects of agriculture on emissions, small-scale agriculture using biodiverse, integrated systems has the potential to decrease emissions and increase carbon sequestration. We found that small-scale agriculture is also better suited to supporting mitigating effects on the nitrogen and carbon cycles, in part by maintaining biodiversity-related ecosystem services. The literature also shows that small-scale farmers in many areas are directly responsible for the minority of deforestation; where they are the dominant land-clearers, this tends to still be tied to pressure from industrial and government structures pushing them onto marginal lands. Lastly, we found that small-scale agriculture was more energy efficient, on average maintaining a higher ratio of energy output to energy input. This higher energy efficiency can thus also contribute to lower related emissions of GHGs.
F1000 Research
No Comments Yet 2 1 REVIEW Food sovereignty: an alternative paradigm for poverty reduction and bi... more No Comments Yet 2 1 REVIEW Food sovereignty: an alternative paradigm for poverty reduction and biodiversity conservation in Latin America [v1; ref status: indexed,
Frontiers in Ecology and the Environment, 2009
We compared post-agricultural succession across the range of farming activities practiced in Gua-... more We compared post-agricultural succession across the range of farming activities practiced in Gua-temala's northern lowlands: agroforestry, swidden, ranching, and input-intensive monocultures. At 10 sites over 13 to 40 months we assessed the following characteristics of trees and shrubs that were 1 cm diameter at breast height: height, basal-area accumulation, recruitment of all individuals and fleshy-fruited individuals , and accumulation of all species and fleshy-fruited species. Succession, as measured by all these response variables except height, was dramatically faster on agroforestry and swidden sites than on pastures or input-intensive monocultures. Overall recruitment was faster for swiddens than for agroforests, but other response variables did not differ significantly between the two treatments. Regression results suggest that initial ground cover by herbs inhibited recruitment of woody colonists. The significant positive coefficient for initial basal area and the significant negative coefficient for distance from forest for accumulation of both fleshy-fruited individuals and species are probably explained by the behavioral responses of seed-dispersing animals. Our results suggest that the conservation strategy of discouraging swidden agriculture in favor of sedentary , input-intensive agriculture to relieve pressure on old-growth forest may be counterproductive over the long term. Resumen: Comparamos la sucesión post-agrícola a lo largo de una serie de actividades de producción prac-ticadas en las tierras bajas del Norte de Guatemala: agroforestería, agricultura migratoria, ganadería, y monocultivos de alto insumo. Durante 13 a 40 meses, en 10 sitios, evaluamos las siguientes características de árboles y arbustos de 1 cm de diámetro a la altura del pecho: altura, acumulación de área basal, re-clutamiento de todos los individuos e individuos con frutas carnosas, acumulación de todas las especies y to-das las especies con frutas carnosas. La sucesión, medida por todas estas variables de respuesta con excepción de la altura, fue dramáticamente más rápida en agroforestería y en los sitios con agricultura migratoria que en las pasturas o monocultivos con intensos insumos. El reclutamiento fue más rápido en los sitios con agri-cultura migratoria que en aquéllos con agroforestería, pero otras variables de respuestas no difirieron signif-icativamente entre los dos tratamientos. Los resultados de regresiones sugieren que la cobertura inicial del suelo por hierbas inhibió el reclutamiento de colonizadores leñosos. Los coeficientes positivos significativos para el área basal inicial y los coeficientes negativos significativos para la distancia del bosque para la acumulación de ambos individuos y especies con frutos leñosos se explican posiblemente por las respuestas conductuales de animales dispersores de semillas. Nuestros resultados sugieren que las estrategias de conser-vación para desalentar la agricultura migratoria a favor de la agricultura sedentaria con insumos intensi-vos para liberar la presión sobre de bosques maduros puede ser contraproducente a largo plazo. ‡ email [email protected]
Journal of theoretical biology, Jan 21, 2010
Numerous situations exist in which a consumer uses two different kinds of resources, one fixed, t... more Numerous situations exist in which a consumer uses two different kinds of resources, one fixed, the other renewable, e.g., nesting resources and food resources. With an elementary modification of the basic Lotka-Volterra consumer resource equations, we investigate the population dynamics of a consumer dependent on two resources, one fixed, the other renewable. Emerging from this structure is a situation of alternative attractors that remain qualitatively robust over a significant range of parameter values. However, a dramatic change in basins of attraction is induced by very small changes in parameters due to a global bifurcation. Noteworthy is the fact that the qualitative nature of the alternative equilibria remains constant but the dramatic change in the basins does not arise from subtle differences in initial conditions. Rather, there is a major restructuring of the vector field such that a permanent change involving large sets of initial conditions results from very small changes in parameters.
F1000Research, 2013
No Comments Yet 2 1 REVIEW Food sovereignty: an alternative paradigm for poverty reduction and bi... more No Comments Yet 2 1 REVIEW Food sovereignty: an alternative paradigm for poverty reduction and biodiversity conservation in Latin America [v1; ref status: indexed,
Agriculture and Human Values, 1993
Having lost 73% of its purchasing power and 42% of it gross national product since the fall of th... more Having lost 73% of its purchasing power and 42% of it gross national product since the fall of the Soviet Union, Cuba faces a crisis with the modern agricultural system it had developed over the past 30 years. The response has been to put an alternative model into practice. The successes and problems associated with this model are discussed.
Ecology, 2004
It is commonly thought that diverse agroecosystems are less prone to pest outbreaks because they ... more It is commonly thought that diverse agroecosystems are less prone to pest outbreaks because they support a high diversity of natural enemies. The idea that diversity stabilizes functional properties of communities to environmental perturbation is formalized in the ecological literature as the ''insurance hypothesis.'' Recently this hypothesis has been examined theoretically and in microcosm experiments. However it has not been tested empirically in an agroecosystem. Here we provide a test of the insurance hypothesis by examining insect predation by birds in coffee farms with different levels of plant diversity. Lepidopteran larvae were placed in coffee plants, and larval disappearance rates were measured within and outside bird exclosures in two farms with distinct levels of shade. Significant differences were found associated with the exclosure treatment, indicating that birds can potentially prevent pest outbreaks. Furthermore, the effect was significant only for the farm with a high floristic diversity, providing partial evidence in support of the insurance hypothesis.
Journal of Theoretical Biology, 1991
The concepts of dynamic boundedness and indirect interactions are used to analyze the global prop... more The concepts of dynamic boundedness and indirect interactions are used to analyze the global properties of the two prey, one predator classical Lotka-Volterra (LV) system. Based on a classification of limit points in the various two-and onedimensional subspaces, 12 qualitatively distinct cases are generated. Of the 12 topologically possible cases, four are unfeasible under the assumptions of the classic LV equations, and only one of the 12 represents the situation of complete dynamic boundedness. Some biological interpretations of the various cases are provided, especially with regard to the role of indirect interactions in determining various cases. 545
Science, 2000
The debate over the maintenance of high diversity of tree species in tropical forests centers on ... more The debate over the maintenance of high diversity of tree species in tropical forests centers on the role of tree-fall gaps as a primary source of disturbance. Using a 10-year data series accumulated since Hurricane Joan struck the Caribbean coast of Nicaragua in 1988, we examined the pattern of species accumulation over time and with increased sampling of individuals. Our analysis shows that the pattern after a hurricane differs from the pattern after a simple tree-fall disturbance, and we conclude that pioneers are limited in large disturbances and thus do not suppress other species the way they do in smaller disturbances.
Frontiers in Ecology and the Environment, 2009
Forest Ecology and Management, 2004
Understanding the maintenance of the large diversity of tree species in a tropical rain forest ha... more Understanding the maintenance of the large diversity of tree species in a tropical rain forest has become something of a holy grail. Among the many factors thought to be involved is disturbance. One hypothesis is that repeated disturbance sets the process of competition anew, thus that competitive exclusion never occurs. In the context of a forest massive damage from storms is potentially the source of the damage that could preserve species diversity. After damage from a storm the canopy of the forest begins with a rapid growth, known as the building phase. Soon a very dense canopy is formed, called the ''thinning canopy'' which dictates the subsequent dynamic process of competition, where those individuals located near the top of the canopy will have a competitive advantage over those in the subcanopy. We here report on the first 14 years of the development and dynamics of the thinning canopy after the catastrophic hurricane damage occasioned by the landfall of Hurricane Joan in October 1988 in the general area of Bluefields, Nicaragua. The overall pattern of growth is clear, where larger trees have been growing and smaller ones more-or-less stagnant, for the past 8 years. The upper canopy was somewhere on the order of 11-18 m in 1996 and is somewhere between about 15 and 22 m in 2003. The dynamic pattern reflects the basic story of growth into the thinning canopy followed by intense competition where some individuals overtop others, thus creating a platykurtic distribution with a skewed bias towards smaller individuals, because of the few individuals overtopping the others. Mortality rates were between 7 and 33 stems per thousand per year, and were concentrated in individuals located beneath the canopy. #
Ecological Modelling, 1997
... Certain common features may thus be expected from all of these situations. References Andow, ... more ... Certain common features may thus be expected from all of these situations. References Andow, DA and Hidaka, K., 1989. ... In: JA Logan and FP Hain (Editors) Chaos and Insect Ecology. Virginia Exp. Star. Info. Series, 91(3): 3961. Vandermeer, JH, 1990. ...
Ecological Modelling, 1996
... Identifying codes for transects explained in Vandermeer et al. (1990a) Transect % pioneers Ra... more ... Identifying codes for transects explained in Vandermeer et al. (1990a) Transect % pioneers Rate Ojos 53.88 - 0.096 Judy 42.48 0.029 Molly 17.33 0.053 Colibri 14.83 0.034 Ernesto 6.05 0.052 Luvy 4.62 0.433 Katarina 3.31 0.055 eral pattern is qualitatively as expected from the ...
Agriculture and Human Values, 1993
The Cuban government has undertaken the task of transforming insect pest and weed management from... more The Cuban government has undertaken the task of transforming insect pest and weed management from conventional to organic and more sustainable approaches on a nationwide basis. This paper addresses past programs and current major areas of research and implementation as well as provides examples of programs in insect and weed management. Topics covered include the newly constructed network of Centers for the Reproduction of Entomophages and Entomopathogens (CREEs), which provide the ...
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Papers by John Vandermeer