Migration Within the Frontier: The Second Generation Colonization in the Ecuadorian Amazon

Since the 1970s, migration to the Amazon has led to a growing human presence and resulting dramatic changes in the physical landscape of the Northern Ecuadorian Amazon frontier, including considerable deforestation. Over time, a second demographic phenomenon has emerged with the children of the original migrants leaving settler farms to set out on their own. The vast majority have remained in the Amazon region, some contributing to further changes in land use via rural-rural migration to establish new farms and others to incipient urbanization. This paper uses longitudinal, multi-scale data on settler colonists between 1990 and 1999 to analyze rural-rural and rural-urban migration among second-generation colonists within the region. Following a description of migrants and settlers in terms of their individual, household and community characteristics, a multinomial discrete-time hazard model is used to estimate the determinants of out-migration of the second generation settlers to both urban and rural areas. We find significant differences in the determinants of migration to the two types of destinations in personal characteristics, human capital endowments, stage of farm and household lifecycles, migration networks, and access to community resources and infrastructure. The paper concludes with a discussion of policy implications of migrants' choice of rural versus urban destinations.

Migration to the Maya Biosphere Reserve, Guatemala: Why place matters

Virtually all migration research examines international migration or urbanization. Yet understudied rural migrants are of critical concern for environmental conservation and rural sustainable development. Despite the fact that a relatively small number of all migrants settle remote rural frontiers, these are the agents responsible for perhaps most of the tropical deforestation on the planet. Further, rural migrants are among the most destitute people worldwide in terms of economic and human development. While a host of research has investigated deforestation resulting from frontier migration, and a modest literature has emerged on frontier development, this article explores the necessary antecedent to tropical deforestation and poverty along agricultural frontiers: out-migration from origin areas. The data come from a 2000 survey with community leaders and key informants in 16 municipios of migrant origin to the Maya Biosphere Reserve (MBR), Petén, Guatemala. A common denominator among communities of migration origin to the Petén frontier was unequal resource access, usually land. Nevertheless, the factors driving resource scarcity were widely variable. Land degradation, land consolidation, and population growth prevailed in some communities but not in others. Despite similar exposure to community and regional level push factors, most people in the sampled communities did not out-migrate, suggesting that any one or combination of factors is not necessarily sufficient for out-migration.

[A multilevel analysis of population and deforestation in the Sierra de Lacandon National Park, Peten, Guatemala]

The paper examines depopulation factors associated with deforestation in the Natural park of the Sierra de Lacandón (PNSL), using multilevel regresión analysis.More than 10 percent of the park area has been deforested since the mid 1980s because of rural population growth and agricultural practices. By means of a two-level regression analysis the study use dem ographic and other household data to explain variations in deforested land in 241 agricultural estates in 8 communities of the PNSL. The methodology, not applied before in the tropics, takes into account spatial variations between communities and households. Multilvel regression allows for better results on the impacts of socioeconomic factors on deforestation, both at the community and at the household levels with important implications for development policies.

Resource management and fertility in Mexico's Sian Ka'an Biosphere Reserve: Campos, cash, and contraception in the lobster-fishing village of Punta Allen

This case study examines the link between marine resource management, and the universal contraceptive use among married couples in the lobster- fishing village of Punta Allen, located in the Sian Ka'an Biosphere Reserve, Quintana Roo, Mexico. Several reasons appear to contribute to small desired and actual family sizes. Some of these include a medical clinic staff effective in promoting family planning, cooperative and private resource ownership, changing cultural attitudes, geographical limitations to population and economic growth, and a desire to conserve the environment for aesthetic and economic motives. Lastly, families desired to preserve a sustained balance between benefiting from lobster harvests today and safeguarding this marine resource for their children in the future.

Declining fertility on the frontier: the Ecuadorian Amazon

This paper examines farm and household characteristics associated with a rapid fertility decline in a forest frontier of the Ecuadorian Amazon. The Amazon basin and other rainforests in the tropics are among the last frontiers in the ongoing global fertility transition. The pace of this transition along agricultural frontiers will likely have major implications for future forest transitions, rural development, and ultimately urbanization in frontier areas. The study here is based upon data from a probability sample of 172 women who lived on the same farm in 1990 and 1999. These data are from perhaps the first region-wide longitudinal survey of fertility in an agricultural frontier. Descriptive analyses indicate that fertility has plummeted in the region, which is surprising since it had remained high and unchanging among migrant colonists up to 1990. Thus only half of the women in our sample reported having a birth during the 1990-1999 time period, and most women report in 1999 that they do not want to have any more children. Analyses, controlling for women's age, corroborate hypotheses about land-fertility relations. For example, women from households with a legal land title had fewer than half as many children as those from households without a title. Large cattle (pasture) holdings and hiring laborers to work on the farm (which may replace household labor) are both related to socio-economic status that is traditionally associated with lower fertility. Similarly, distance to the nearest community center is positively related to fertility. Factors negatively related to fertility include increasing temporary out-migration of adult men or women from the household, asset accumulation, and access to electricity.

Gender-specific out-migration, deforestation and urbanization in the Ecuadorian Amazon

The Ecuadorian Amazon, one of the richest reserves of biodiversity in the world, has faced one of the highest rates of deforestation of any Amazonian nation. Most of this forest elimination has been caused by agricultural colonization that followed the discovery of oil fields in 1967. Since the 1990s, an increasing process of urbanization has also engendered new patterns of population mobility within the Amazon, along with traditional ways by which rural settlers make their living. However, while very significant in its effects on deforestation, urbanization and regional development, population mobility within the Amazon has hardly been studied at all, as well as the distinct migration patterns between men and women. This paper uses a longitudinal dataset of 250 farm households in the Northern Ecuadorian Amazon to understand differentials between men and women migrants to urban and rural destinations and between men and women non-migrants. First, we use hazard analysis based on the Kaplan-Meier (KM) estimator to obtain the cumulative probability that an individual living in the study area in 1990 or at time t, will out-migrated at some time, t+n, before 1999. Results indicate that out-migration to other rural areas in the Amazon, especially pristine areas is considerably greater than out-migration to the growing, but still incipient, Amazonian urban areas. Furthermore, men are more likely to out-migrate to rural areas than women, while the reverse occurs for urban areas. Difference-of-means tests were employed to examine potential factors accounting for differentials between male and female out-migration to urban and rural areas. Among the key results, relative to men younger women are more likely to out-migrate to urban areas; more difficult access from farms to towns and roads constrains women's migration; and access to new lands in the Amazon-an important cause of further deforestation-is more associated with male out-migration. Economic factors such as engagement in on-farm work, increasing resource scarcity-measured by higher population density at the farm and reduction in farm land on forest and crops-and increase in pasture land are more associated with male out-migration to rural areas. On the other hand, increasing resource scarcity, higher population density and weaker migration networks are more associated with female out-migration to urban areas. Thus, a "vicious cycle" is created: Pressure over land leads to deforestation in most or all farm forest areas and reduces the possibilities for further agricultural extensification (deforestation); out-migration, especially male out-migration, occurs to other rural or forest areas in the Amazon (with women being more likely to choose urban destinations); and, giving continuing population growth and pressures in the new settled areas, new pressures promote further out-migration to rural destinations and unabated deforestation.

Population Dynamics and Tropical Deforestation: State of the Debate and Conceptual Challenges

What is the role of population in driving deforestation? This question was put forth as a discussion topic in the cyberseminar hosted by Population Environment Research Network (PERN) in Spring, 2003. Contributors from diverse backgrounds weighed in on the discussion, citing key factors in the population-deforestation nexus and suggesting further courses of action and research. Participants explored themes of their own choosing, with many coming to the forefront. Scale, time, and place-based effects were cited as areas in need of particular attention. Consumption patterns as the mechanism for spurring deforestation were discussed, drawing attention to the differential patterns associated with urban vs. rural demands on forest resources and land. The applicability of the IPAT formula and the influence of its component parts, affluence and technology, when operating in tandem with population, was debated. The relation of demographic factors to these pathways was critically examined. Institutional and governmental influence, such as infrastructure and policies affecting access and incentives, the valuation of resources, and institutional failures such as mismanagement and corruption emerged as a crucial set of factors. This article synthesizes the critical debates in the population-deforestation literature, makes suggestions for future paths of research, and discussed possible policy and direct action initiatives.

Proximate Population Factors and Deforestation in Tropical Agricultural Frontiers

Forest conversion for agriculture expansion is the most salient signature of human occupation of the earth's land surface. Although population growth and deforestation are significantly associated at the global and regional scales, evidence for population links to deforestation at micro-scales-where people are actually clearing0020forests-is scant. Much of the planet's forest elimination is proceeding along tropical agricultural frontiers. This article examines the evolution of thought on population-environment theories relevant to deforestation in tropical agricultural frontiers. Four primary ways by which population dynamics interact with frontier forest conversion are examined: population density, fertility, and household demographic composition, and in-migration.

Mutagenesis disrupts posttranslational processing of the Na,K-ATPase catalytic subunit

The first 5 amino acids of the catalytic alpha 1 isoform from Na,K-ATPase are cleaved enzymatically during or after translation. To evaluate the structural requirements for that cleavage, we constructed amino-terminal mutants of alpha 1 in which an epitope tag from the c-myc oncogene product was added. Immunoblots of isolated membranes from transfected monkey kidney cells revealed binding of an antibody specific for the first 9 residues of the alpha 1 nascent protein. Because this antibody does not recognize the shorter sequence corresponding to the processed polypeptide, these results indicate that the epitope tag prevented normal processing, a conclusion confirmed by the observed binding of an anti-myc antibody. In contrast, membranes from cells expressing deletion mutants that lack residues 10-24 and 10-31 of the nascent chain failed to bind the amino-terminal-directed antibody, suggesting that the mutants were cleaved normally and that amino acids downstream of the first 9 are not required for proteolysis. Amino-terminal mutants produced in other laboratories have shown an anomalous stimulation of ATPase activity by K+ when measured in low ATP concentrations. The myc-tagged and downstream deletion mutants were sensitive to K+ in the range from 0.05 to 5 mM, similar to wild-type enzyme, despite the differences in posttranslational processing. A mutant missing the first 40 residues of the nascent chain, however, displayed an activation by K+. These results suggest that amino-terminal processing of the alpha 1 isoform was prevented by mutation, yet that processing had little influence on the kinetic parameter most likely to be influenced by such changes.

Mechanisms underlying very-low-frequency RR-interval oscillations in humans

BACKGROUND

Survival of post-myocardial infarction patients is related inversely to their levels of very-low-frequency (0.003 to 0.03 Hz) RR-interval variability. The physiological basis for such oscillations is unclear. In our study, we used blocking drugs to evaluate potential contributions of sympathetic and vagal mechanisms and the renin-angiotensin-aldosterone system to very-low-frequency RR-interval variability in 10 young healthy subjects.

METHODS AND RESULTS

We recorded RR intervals and arterial pressures during three separate sessions, with the patient in supine and 40 degree upright tilt positions, during 20-minute frequency (0.25 Hz) and tidal volume-controlled breathing after intravenous injections: saline (control), atenolol (0.2 mg/kg, beta-adrenergic blockade), atropine sulfate (0.04 mg/kg, parasympathetic blockade), atenolol and atropine (complete autonomic blockade), and enalaprilat (0.02 mg/kg, ACE blockade). We integrated fast Fourier transform RR-interval spectral power at very low (0.003 to 0.03 Hz), low (0.05 to 0. 15 Hz), and respiratory (0.2 to 0.3 Hz) frequencies. Beta-adrenergic blockade had no significant effect on very-low- or low-frequency RR-interval power but increased respiratory frequency power 2-fold. ACE blockade had no significant effect on low or respiratory frequency RR-interval power but modestly (approximately 21%) increased very-low-frequency power in the supine (but not upright tilt) position (P<0.05). The most profound effects were exerted by parasympathetic blockade: Atropine, given alone or with atenolol, abolished nearly all RR-interval variability and decreased very-low-frequency variability by 92%.

CONCLUSIONS

Although very-low-frequency heart period rhythms are influenced by the renin-angiotensin-aldosterone system, as low and respiratory frequency RR-interval rhythms, they depend primarily on the presence of parasympathetic outflow. Therefore the prognostic value of very-low-frequency heart period oscillations may derive from the fundamental importance of parasympathetic mechanisms in cardiovascular health.

Effect of dietary lipid supplementation on progesterone concentration and reproductive performance in suckled beef cows

Using whole cottonseed as a lipid source, silage-based diets that were isocaloric and isonitrogenous yet varied in lipid level were fed to multiparous cows. In Experiment 1, 48 cows (n = 12 per treatment) were allotted to 1 of 4 treatments where diets were formulated to supply 3.9, 4.3, 5.3 and 6.3% of total lipid. In Experiment 2, 66 cows (n = 22 per treatment) were allotted to 1 of 3 treatments where diets were formulated to supply 3.1, 5.5 and 8.3% of total lipid. Length of the first ovarian cycle, length of the first normal estrous cycle, postpartum intervals to onset of ovarian luteal activity and to first estrus were not affected by diet (P>0.10) in either experiment. Mean progesterone (P(4)) concentrations for first normal estrous cycles were not different (P>0.10) in either experiment. Anestrous periods were divided into 3 phases for analyses: Phase I) parturition to onset of ovarian luteal activity, Phase II) first ovarian luteal activity and Phase III) first normal estrous cycle. No differences were observed in P(4) concentrations during any phase of the postpartum period. In conclusion, isocaloric and isonitrogenous diets with increasing levels of lipid had no effect on reproductive performance in suckled beef in these experiments.

Rapid, colorimetric identification of Candida albicans

A total of 706 yeast isolates were evaluated in parallel by the Candida albicans Screen (CAS; Carr-Scarborough Microbiologicals, Inc., Stone Mountain, Ga.) test and the germ tube (GT) test in comparison with the API 20C Yeast Identification System. The CAS and GT tests correctly identified 419 of the 422 isolates of C. albicans (99.3%). Two of the false-negative reactions occurring with the CAS were with GT-negative strains of C. albicans. There were two false-positive CAS reactions involving a single strain each of C. parapsilosis and C. tropicalis. Sensitivity and specificity for both tests exceeded 99%, with positive and negative predictive values of 99 and 98%, respectively.

Accuracy of a rapid carbohydrate oxidation microtube method for identification of nonfermentative gram-negative bacilli

A rapid carbohydrate oxidation microtube system (Carr Microbiologicals, Wichita, Kans.), designed for detecting the saccharolytic activity of gram-negative, nonfermenting bacilli, was evaluated and compared with the conventional oxidation-fermentation method. The oxidation of glucose, maltose, lactose, and xylose was tested with 430 strains of Pseudomonas, Acinetobacter, Achromobacter, Alcaligenes, Moraxella, Flavobacterium, and Bordetella species. More than 95% of the isolates tested gave correct oxidation reactions within 4 h in the rapid carbohydrate oxidation microtubes, whereas oxidation-fermentation media required 24 h to achieve the same sensitivity. The microtube system was found to be simple, accurate, rapid, and economical.

Temporal study of the staphylococci and micrococci of normal infant skin

Staphylococcus and Micrococcus populations were collected from the healthy skin of 10 infant subjects. Infants were sampled from 1 day to 32 weeks of age. Species were characterized by approximately 30 different morphological, physiological, and biochemical characters. Staphylococci were the predominant inhabitants of normal skin, whereas micrococci were found only occasionally in this environment. Staphylococcus epidermidid, S. haemolyticus, and S. hominis were the predominant and persistent staphylococci. These species constituted a high percentage of the total aerobic bacterial flora of infant skin. Micrococcus luteus and M. kristinae were the prevalent micrococci found on infant skin. Only limited correlation between Staphyloccus and Micrococcus populations and infant age or body area sampled was indicated by this study.

Effects of systematic sensory-motor training on sensory-motor, visual perception and concept-formation performance of mentally retarded children

This study investigated the effects of an extended, systematic training program of sensory-motor activities on sensory-motor, visual perception and concept-formation tasks. 10 identical criterion measures were utilized as pretests and posttests in conjunction with a 2-mo. training program. Both the experimental and control groups' mean scores on all criterion measures reflected improvement from pretest to posttest administrations. However, when the analysis of covariance was applied, no significant differences were evident between the adjusted posttest mean scores of the two groups.