Forests contribute to livelihoods of rural people throughout the tropics. This paper adds to the emerging body of quantitative
knowledge on absolute and relative economic importance, through both cash and subsistence income, of moist forests to households.
Qualitative contextual information was collected in six villages in lowland Bolivia, followed by a structured survey of randomly
selected households (n = 118) that included four quarterly income surveys. We employed a novel data collection approach that allows detailed estimation
of total household accounts, including sources of forest income. We estimated the average forest income share of total annual
household income (forest dependency) at 20%, ranging from 18 to 24%. Adding environmental income increased the average to
26%, being fairly constant across income quartiles at 24–28%. Absolute levels of forest income increased with total household
income, while forest dependency was the highest in the best-off income quartile—the primary harvesters of forest products
are better-off households. The pattern of high forest dependency among better-off households has also been reported from other
countries, indicating that this pattern may be more common than advocated by conventional wisdom. Using ordinary least squares
(OLS) regressions, we found significant determinants of absolute forest income to be household size, sex of household head
and area of cultivated land; the significant determinants for forest dependency were level of education, whether household
head was born in village and whether household was food self-sufficient. Better-off households were able to realise cash income
from forests, while poorer households—in particular if headed by women—were more reliant on subsistence forest income. We
argue that the differential patterns of forest income across income quartiles should be considered in future development interventions
and that findings indicate a potential for forests to contribute to moving households out of poverty. 相似文献
Rural households throughout the Himalayas are regarded as dependent on non-timber forest products (NTFPs), but very few studies
have quantified this dependency. This case study, undertaken in two villages in the Central Himalayan foot hills in Nepal,
documents the absolute and relative importance of commercial NTFPs to rural household economies. Data were collected in a
one-year period and included interviews with 250 households using a semi-structured questionnaire and monthly interviews with
four sub-local NTFP traders, two local traders and two central wholesalers. The conservative estimate of NTFP-derived cash
income showed this to be a cornerstone in poorer household livelihood strategies and thus in poverty prevention. An annual
average of 578 kg of commercial NTFPs was collected in the wild per household, providing poorer households with a cash income
share of 44–78%. Better off households are not NTFP dependent but rely on income from crop production and livestock. Based
on a net marketing margin analysis, showing that harvesters capture a large share of the Indian wholesaler price, it is argued
that there is scope for pursuing NTFP-based strategies for poverty reduction through leasehold forestry and agroforestry.
Both these options are compatible with conserving forest cover and forest corridor functions and may thus present a win–win
scenario for livelihood improvement and conservation. 相似文献
The biodegradation of polycyclic aromatic hydrocarbons in microecosystems containing long-term contaminated soil was investigated. Soil was contaminated by different chemicals, including PAHs since World War II. Aging of the soil was expected to act as a principal factor limiting biodegradation. Half of the microecosystems contained ryegrass (Lolium perenne) and long-term selected natural soil microflora originally present in contaminated soil. The others contained contaminated soil with natural microflora only. Half of the microecosystems in each parallel experiment was fertilised with N-P-K fertiliser. Cultivation was carried out at 12 and 18 months in a greenhouse with a natural photoperiod and the ability to degrade 15 chosen PAH was investigated. For analysis, the soil from each pot was divided into three horizontal layers for mutual comparison among layers and each layer was further divided into four equal samples. Soil extracts were analysed using HPLC. After a one-year-cultivation period the content of the monitored PAHs declined to 50%. Mostly, there were no significant differences between the microecosystems. Best degraded were fluoranthene and pyrene, which were the major contaminants present in original soil. Also, other compounds were successfully degraded, even benzo[a]pyrene and benzo[ghi]perylene. Dibenz[a,h]anthracene and indeno[1,2,3-cd]pyrene were the only PAHs, examined that showed no significant degradation. Although some differences between the soil layers were detected, no conclusive trends could be found. However, significantly lower concentrations of PAHs were determined mostly in the bottom layer of the analysed profiles. In vegetated microecosystems the decline of PAHs concentrations was more remarkable after 18 months cultivation. 相似文献
While toxicological data are available for numerous chemicals from standard tests, little is known on effects of pollutants over several generations or regarding chronic effects of chemicals on genetic diversity. Within the experiments, effects of the model pollutant tributyltin (TBT) were investigated over eleven generations at a sublethal TBT concentration of 4.46 μg as Sn kg−1 sediment dw on life-cycle parameters and genetic variability of Chironomus riparius. Moreover, the adaptation potential towards TBT was determined. This experimental design enables the identification of TBT effects on life-cycle parameters and the determination of a potential extinction risk caused by chronic exposure. Furthermore, effects on the genetic structure can be determined, which are not predictable based solely on knowledge of the toxic mode of action of the chemical.
Genetic variety was determined via microsatellite analysis, measuring individual length differences of highly variable satellite DNA fragments. For the identification of changes in tolerances towards the stressor, acute and chronic toxicity experiments were conducted.
During the multi-generation study, significant effects on development and reproduction were determined. For some generations, the emergence was significantly (p < 0.05) delayed under TBT exposure. Reproduction seems to be a sensitive parameter as well, whereby females laid significantly larger egg masses (p < 0.05) in the latter generations. TBT did not affect the population growth rate nor the genetic variability, while clear deviations from the Hardy–Weinberg equilibrium appeared. The study also provides strong evidence for the acquirement of a higher tolerance towards the stressor in the TBT-exposed group. 相似文献
In the European 6th Framework Programme, fundamental research in the field of technology assessment regarding behavioural effects was conducted in the HASTE (Human machine interface And the Safety of Traffic in Europe) project. Methods, metrics and scenarios for the exploration of safety problems related to IVIS (in-vehicle information systems) were defined and applied to the evaluation of surrogate systems in the laboratory originally and real systems subsequently, in laboratories and field studies. The results of the laboratory and field studies led to the formulation of guidelines for a standardized test regime regarding existing and newly developed IVIS. In this way the HASTE project has succeeded in the development of a valid, reliable and efficient tool that may aid testing authorities in their safety evaluation of IVIS. 相似文献
Die geschichtliche Entwicklung der kosmologischen Modelle für den homogen–isotropen Kosmos, beginnend mit Alexander Friedmanns
epochalen Arbeiten (1922 und 1924) bis zur heutigen Diskussion aktueller Modelle wird dargestellt. Eine kardinale Rolle spielt
die offene Frage: Besteht die Materie des Kosmos zum weit überwiegenden Teil aus nicht–baryonischer (sog. exotischer) Dunkel–Materie
oder reicht die gesamte baryonische Materie aus, die aus den bekannten Atomen und Molekülen besteht, um die Entwicklung des
Kosmos zu verstehen. Auch von der normalen (baryonischen) Materie im Kosmos ist nur ein geringer Anteil (etwa 20 5 Prozent) in leuchtenden Objekten (Sterne, Gas, Staub) direkt beobachtbar. Im Abschnitt 3 wird der “Einstein–Limit” für
die kosmologische Konstante erl?utert und eine leicht einsichtige Herleitung des Zahlenwertes gegeben. 相似文献