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Beyond Population and Environment: Household Demographic Life Cycles and Land Use Allocation Among Small Farms in the Amazon 总被引:1,自引:0,他引:1
Stephen G. Perz Robert T. Walker Marcellus M. Caldas 《Human ecology: an interdisciplinary journal》2006,34(6):829-849
Most research featuring demographic factors in environmental change has focused on processes operating at the level of national or global populations. This paper focuses on household-level demographic life cycles among colonists in the Amazon, and evaluates the impacts on land use allocation. The analysis goes beyond prior research by including a broader suite of demographic variables, and by simultaneously assessing their impacts on multiple land uses with different economic and ecological implications. We estimate a system of structural equations that accounts for endogeneity among land uses, and the findings indicate stronger demographic effects than previous work. These findings bear implications for modeling land use, and the place of demography in environmental research.
相似文献
Marcellus M. CaldasPhone: +1-517-4327058Fax: +1-517-4321671 |
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Robin E. Snyder 《Theoretical Ecology》2008,1(3):129-139
The ability of environmental variation to affect species coexistence is much studied, yet environmental variation is not always
important. I present an approximate calculation for the long-run growth rate of a species in the presence of spatially and
temporally correlated environmental variation. I then perform a factorial numerical experiment, varying the mean seed dispersal
distances, competition radii, and overwinter seed survival probabilities for two competing species for an array of variational
regimes, noting the effects on their long-run growth rates. I find, first, that purely spatial variation has a greater capacity
for influence than variation with a temporal component. Second, spatiotemporal variation can promote coexistence as strongly
as purely temporal variation or more so, given the right species traits. Third, if the environmental variation has a spatial
component, traits which enable species to become spatially segregated promote coexistence most strongly. That is, it is the
possibility of spatial segregation which gives spatial variation its large potential to promote coexistence.
相似文献
Robin E. SnyderEmail: |
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Studies on the effects of a variety of exogenous and anthropogenic environmental factors, including endocrine disruptors,
heavy metals, UV light, high temperature, and others, on marine organisms have been presented at the 2nd Bilateral Seminar
Italy–Japan held in November 2006. Reports were discussed in order to reveal the current situation of marine ecosystems, aiming
at evaluation and prediction of environmental risks.
相似文献
V. MatrangaEmail: |
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Millions of coral reef fishes are collected each year for sale on the international aquarium market. Several marine ornamental species, including the Banggai cardinalfish, are biologically unsuitable for large-scale exploitation, yet their trade continues largely unmonitored. With little known about the Banggai cardinalfish or its trade, we interviewed trade participants from north and central Sulawesi, Indonesia, to document the organization, scale, and price structure of the species local collection and sale. Interviews revealed a large and growing commerce in Banggai cardinalfish, with at least 118,000 fish per month being sold in the Banggai region during the study period. Given the scale of the trade, the species restricted geographic range, and its natural susceptibility to exploitation, we propose that long-term monitoring is needed to safeguard Banggai cardinalfish populations and to serve as a much-needed example for monitoring and managing other marine ornamental fishes at risk of over-exploitation.
相似文献
M.-A. MoreauEmail: Phone: +1-514-3984111Fax: +1-514-3987437 |
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Sub-Antarctic Marion Island has had a permanent research station for 50 years and the islands Wandering Albatrosses have been intensively studied for 20 years. The reactions of breeding birds to approaches by a human on foot were recorded. Three response variables were calculated: intensity of vocal reaction (IVR), intensity of non-vocal reaction (INR) and overall response index (ORI). At 5 m from the nest, twice as many birds stood and/or vocalised as at 15 m. Nearest neighbour distance, age and gender did not explain individual variability of responses. Study colony birds had higher IVR scores than non-study colony birds; birds at colonies closest to the station had the highest ORI scores. A better breeding record was associated with lower IVR and ORI scores, but a causative relationship remains to be demonstrated. A minimum viewing distance of 25 m is recommended for breeding Wandering Albatrosses.
相似文献
Marienne S. de VilliersEmail: Fax: +27-21-6503434 |
John CooperEmail: |
Peter G. RyanEmail: |
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Robin E. Snyder 《Theoretical Ecology》2009,2(2):79-87
When a pattern of spatial or temporal environmental variation changes, it takes time for populations to reach their new stationary
distributions, and during this time, the competitive landscape is also in flux. As a first step toward understanding community
responses to altered variational regimes, I investigate the convergence of an annual–perennial plant system to its stationary
spatiotemporal distribution following a change in environmental variation. I find that, to good approximation, convergence
is the sum of two separate processes: global convergence, which governs changes in the total population, and local convergence,
which governs population redistribution. While the slower process (global or local) eventually governs convergence, the faster
process may initially dominate if it starts further from its stationary distribution, so that the populations converge quickly
at first, then slow down. That is, when disturbances are spatially heterogeneous, a system may be initially more resilient
under some initial conditions than others.
相似文献
Robin E. SnyderEmail: |
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Threatened species and the spatial concentration of humans 总被引:1,自引:1,他引:0
Public policies that encourage high-density human living arrangements have been predicated explicitly on the assumption that
certain spatial distributions of a fixed-size human population are less environmentally damaging than others. We examine the
empirical validity of this assumption across 127 countries by analyzing whether the concentration of human presence in each
country is related statistically to the percentage of species that were on the IUCN Red List in 2004. Our findings indicate
that concentration of the human population is associated with reduced imperilment among amphibians but increased imperilment
among reptiles, and birds.
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Ram PanditEmail: |
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Norman Morrison Dan Bearden Jacob G. Bundy Tim Collette Felicity Currie Matthew P. Davey Nathan S. Haigh David Hancock Oliver A. H. Jones Simone Rochfort Susanna-Assunta Sansone Dalibor Štys Quincy Teng Dawn Field Mark R. Viant 《Metabolomics : Official journal of the Metabolomic Society》2007,3(3):203-210
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Roger Sansom 《Biology & philosophy》2009,24(4):441-459
One current version of the internalism/externalism debate in evolutionary theory focuses on the relative importance of developmental
constraints in evolutionary explanation. The received view of developmental constraints sees them as an internalist concept
that tend to be shared across related species as opposed to selective pressures that are not. Thus, to the extent that constraints
can explain anything, they can better explain similarity across species, while natural selection is better able to explain
their differences. I challenge both of these aspects of the received view and propose a hierarchical view of constraints.
相似文献
Roger SansomEmail: |
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Michael H. Kido 《Environmental Biology of Fishes》2008,82(3):223-235
In Limahuli Stream on the Hawaiian island of Kauai, species assemblage structure was monitored from catchment-to-sea over
a 6-year period to determine how individual species utilized the stream continuum spatiotemporally. A persistent pattern was
identified in which ten fish and macroinvertebrate species (nine native and one alien) were distributed into distinct zones
of highest abundances with overlapping species ranges. Species diversity, as quantified by a dominance measure (Berger–Parker
Index), was highest and least variable at the midpoint of the continuum where upstream–downstream species’ ranges converged.
Reciprocal fluctuations in the population abundances of dominant species limited overall variation in species diversity to
a 22% range which was interpreted as evidence of spatiotemporal persistence of the species assemblage structure. The pattern
was captured in a testable, conceptual model which partitions an idealized Hawaiian stream from catchment-to-sea into five
functional zones (Estuarine, Lower–Middle–Upper Reach, and Headwaters) positioned as percentages of continuum length. This
model may be overlaid upon other Hawaiian streams for testing its applicability as well as to ask a variety of ecological
questions about the manner in which species partition habitat spatiotemporally along biophysical gradients.
相似文献
Michael H. KidoEmail: |
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A key point in the analysis of dynamical models of biological systems is to handle systems of relatively high dimensions.
In the present paper we propose a method to hierarchically organize a certain type of piecewise affine (PWA) differential
systems. This specific class of systems has been extensively studied for the past few years, as it provides a good framework
to model gene regulatory networks. The method, shown on several examples, allows a qualitative analysis of the asymptotic
behavior of a PWA system, decomposing it into several smaller subsystems. This technique, based on the well-known strongly
connected components decomposition, is not new. However, its adaptation to the non-smooth PWA differential equations turns
out to be quite relevant because of the strong discrete structure underlying these equations. Its biological relevance is
shown on a 7-dimensional PWA system modeling the gene network responsible for the carbon starvation response in Escherichia coli.
相似文献
Laurent Tournier (Corresponding author)Email: |
Jean-Luc GouzéEmail: |
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The recent contribution by Jarmila Kukalová-Peck on Hennigian phylogenetics and hexapod limb evolution is critically evaluated.
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Michael S. Engel (Corresponding author)Email: |
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Terry Harmer 《Cluster computing》2007,10(3):277-285
Gridcast is an R&D project investigating grid ideas and technologies in the broadcasting technical infrastructure. In this
paper I discuss the business and technical issues in building infrastructures to support broadcasters and outline the structure
of the Gridcast grid-based service oriented architecture for broadcasting playout support.
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Terry HarmerEmail: |
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Peter Godfrey-Smith 《Biology & philosophy》2007,22(3):429-437
Jablonka and Lamb's claim that evolutionary biology is undergoing a ‘revolution’ is queried. But the very concept of revolutionary
change has uncertain application to a field organized in the manner of contemporary biology. The explanatory primacy of sequence
properties is also discussed.
相似文献
Peter Godfrey-SmithEmail: |
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With the increased complexity of platforms, the growing demand of applications and data centers’ servers sprawl, power consumption
is reaching unsustainable limits. The need to improved power management is becoming essential for many reasons including reduced
power consumption & cooling, improved density, reliability & compliance with environmental standards. This paper presents
a theoretical framework and methodology for autonomic power and performance management in e-business data centers. We optimize
for power and performance (performance-per-watt) at each level of the hierarchy while maintaining scalability. We adopt mathematically-rigorous
optimization approach to minimize power while meeting performance constraints. Our experimental results show around 72% savings
in power while maintaining performance as compared to static power management techniques and 69.8% additional savings with
both global and local optimizations.
相似文献
Mazin S. YousifEmail: |
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Event-related brain potentials (ERP) are important neural correlates of cognitive processes. In the domain of language processing,
the N400 and P600 reflect lexical-semantic integration and syntactic processing problems, respectively. We suggest an interpretation
of these markers in terms of dynamical system theory and present two nonlinear dynamical models for syntactic computations
where different processing strategies correspond to functionally different regions in the system’s phase space.
相似文献
Peter beim GrabenEmail: |