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621.
This paper examines the issue of land tenure and how it influences artisanal and small-scale mining (ASM) activity in Ghana. Over the past few decades, attempts by governments in sub-Saharan Africa to regulate or formalize ASM as a result of the sector's increasing socio-economic and environmental importance have largely been unsuccessful. Even though mining laws have tended to vest all minerals in the state, increasing evidence suggests that mineral-rich lands for artisanal mining continue to be frequently traded between local landowners and miners or interested groups outside the official legal regime. This development, i.e. land trading for artisanal mining, contributes significantly towards proliferation of illegal ASM activity and hence potentially challenges attempts by governments and development partners to formalise the sector. 相似文献
622.
The Burruyacú district (Tucumán province, Northwest Argentina) has been traditionally an area with rural activities based on the exploitation of the Chaco forest for timber and livestock browsing. Since the 1960s, local institutions started promoting soybean due to favorable land conditions and good market prices. Soybean extension, as from the 1970s, has resulted in important reduction of the Chaco forest and also caused physical soil degradation, especially soil compaction and erosion. A land-use-planning exercise was carried out using the Land-Use Planning and Information System (LUPIS) as a spatial decision support system. LUPIS facilitates the generation of alternative land-use plans by adjusting the relative importance attributed by multiple stakeholders to preference and avoidance policies. The system leads to the allocation of competing land uses to land map units in accordance with their preferred resource requirements, conditional upon the resource base of the area and the stakeholders' demands. After generating a land use plan for each stakeholder category identified in the study area, including commercial farmers, conservative/conventional farmers, and conservationists, a consensus plan was established to address the land-use conflicts between mechanized agriculture, traditional agriculture and forest conservation, and to mitigate soil degradation caused by extensive dry-farming. Although the planning exercise did not directly involve the stakeholders, the results are sufficiently practical and realistic to suggest that the approach could be extended to the entire Chaco plain region. 相似文献
623.
Nsikak U. Benson Joseph P. Essien Godwin A. Ebong Akan B. Williams 《The Environmentalist》2008,28(3):275-282
The levels of total petroleum hydrocarbons in two commonly consumed benthopelagic shellfishes, Macura reptantia and Procambarus clarkii, harvested from benthic sediment of Qua Iboe Estuary were determined using a gas chromatography with flame-ionization detector.
Seventy-two (72) samples each of benthic sediment and the shellfishes were collected monthly between June 2003 and February
2004 covering the peak periods of the wet and dry seasons. Concentrations of hydrocarbons were highly variable and ranged
between 5.00 and 232.00 μg/g dry weight of benthic sediment, 3.05 and 11.30 μg/g dry weight of M. reptantia, 1.62 and 9.00 μg/g dry weight of P. clarkii. Pearson’s correlation analysis of total hydrocarbon concentrations in subtidal sediments with levels in the fauna species
yielded positive significant (P < 0.05) correlations in M. reptantia (r = 0.737) and P. clarkii (r = 0.924). This is indicative of a long term and chronic accumulation of hydrocarbons in the estuarine ecosystem, reflecting
the potential for exposure of the resident biota and the risk to human health. 相似文献
624.
A chelating resin containing a stable thiol group was synthesised, using polystyrene as the starting material. The resin is stable towards conc. HCl, 0.1M HNO(3) and 0.1M NaOH. The resin shows affinity towards Ag(+), Hg(2+), Bi(3+), Pb(2+), Cu(2+), Zn(2+) and Cd(2+). Extraction of these metal ions as a function of pH, kinetics of exchange and breakthrough capacities is evaluated. The selectivity of the resin for the metal ions is in the order Ag(+) > Hg2+ > Cu2+ > Pb2+ > Cd2+ > Zn2+. The equilibrium constants for exchange and kinetics of exchange are favourable for the recovery of mercury from lean sources. Application of the resin in the stripping of mercury from chlor-alkali plant affluent, and in the enrichment of mercury from seawater, have been investigated. Mercury sorbed resin can be regenerated using 5% thiourea in 0.1M HCl. 相似文献
625.
Jeremy P. Bird Robert Martin H. Reşit Akçakaya James Gilroy Ian J. Burfield Stephen T. Garnett Andy Symes Joseph Taylor Çağan H. Şekercioğlu Stuart H. M. Butchart 《Conservation biology》2020,34(5):1252-1261
Birds have been comprehensively assessed on the International Union for Conservation of Nature (IUCN) Red List more times than any other taxonomic group. However, to date, generation lengths have not been systematically estimated to scale population trends when undertaking assessments, as required by the criteria of the IUCN Red List. We compiled information from major databases of published life-history and trait data for all birds and imputed missing life-history data as a function of species traits with generalized linear mixed models. Generation lengths were derived for all species, based on our modeled values of age at first breeding, maximum longevity, and annual adult survival. The resulting generation lengths varied from 1.42 to 27.87 years (median 2.99). Most species (61%) had generation lengths <3.33 years, meaning that the period of 3 generations—over which population declines are assessed under criterion A—was <10 years, which is the value used for IUCN Red List assessments of species with short generation times. For these species, our trait-informed estimates of generation length suggested that 10 years is a robust precautionary value for threat assessment. In other cases, however, for whole families, genera, or individual species, generation length had a substantial impact on their estimated extinction risk, resulting in higher extinction risk in long-lived species than in short-lived species. Although our approach effectively addressed data gaps, generation lengths for some species may have been underestimated due to a paucity of life-history data. Overall, our results will strengthen future extinction-risk assessments and augment key databases of avian life-history and trait data. 相似文献
626.
Major shifts in Amazon wildlife populations from recent intensification of floods and drought
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Richard Bodmer Pedro Mayor Miguel Antunez Kimberlyn Chota Tula Fang Pablo Puertas Marlini Pittet Maire Kirkland Mike Walkey Claudia Rios Pedro Perez‐Peña Peter Henderson William Bodmer Andy Bicerra Joseph Zegarra Emma Docherty 《Conservation biology》2018,32(2):333-344
In the western Amazon Basin, recent intensification of river‐level cycles has increased flooding during the wet seasons and decreased precipitation during the dry season. Greater than normal floods occurred in 2009 and in all years from 2011 to 2015 during high‐water seasons, and a drought occurred during the 2010 low‐water season. During these years, we surveyed populations of terrestrial, arboreal, and aquatic wildlife in a seasonally flooded Amazonian forest in the Loreto region of Peru (99,780 km2) to study the effects of intensification of natural climatic fluctuations on wildlife populations and in turn effects on resource use by local people. Shifts in fish and terrestrial mammal populations occurred during consecutive years of high floods and the drought of 2010. As floods intensified, terrestrial mammal populations decreased by 95%. Fish, waterfowl, and otter (Pteronura brasiliensis) abundances increased during years of intensive floods, whereas river dolphin and caiman populations had stable abundances. Arboreal species, including, macaws, game birds, primates, felids, and other arboreal mammals had stable populations and were not affected directly by high floods. The drought of 2010 had the opposite effect: fish, waterfowl, and dolphin populations decreased, and populations of terrestrial and arboreal species remained stable. Ungulates and large rodents are important sources of food and income for local people, and large declines in these animals has shifted resource use of people living in the flooded forests away from hunting to a greater reliance on fish. 相似文献
627.
628.
Bunnell JE Tatu CA Bushon RN Stoeckel DM Brady AM Beck M Lerch HE McGee B Hanson BC Shi R Orem WH 《Environmental geochemistry and health》2006,28(6):577-587
In May and September, 2002, 14 private residential drinking water wells, one dewatering well at a lignite mine, eight surface
water sites, and lignite from an active coal mine were sampled in five Parishes of northwestern Louisiana, USA. Using a geographic
information system (GIS), wells were selected that were likely to draw water that had been in contact with lignite; control
wells were located in areas devoid of lignite deposits. Well water samples were analyzed for pH, conductivity, organic compounds,
and nutrient and anion concentrations. All samples were further tested for presence of fungi (cultures maintained for up to
28 days and colonies counted and identified microscopically) and for metal and trace element concentration by inductively-coupled
plasma mass spectrometry and atomic emission spectrometry. Surface water samples were tested for dissolved oxygen and presence
of pathogenic leptospiral bacteria. The Spearman correlation method was used to assess the association between the endpoints
for these field/laboratory analyses and incidence of cancer of the renal pelvis (RPC) based on data obtained from the Louisiana
Tumor Registry for the five Parishes included in the study. Significant associations were revealed between the cancer rate
and the presence in drinking water of organic compounds, the fungi Zygomycetes, the nutrients PO4 and NH3, and 13 chemical elements. Presence of human pathogenic leptospires was detected in four out of eight (50%) of the surface
water sites sampled. The present study of a stable rural population examined possible linkages between aquifers containing
chemically reactive lignite deposits, hydrologic conditions favorable to the␣leaching and transport of toxic organic compounds
from the lignite into the groundwater, possible microbial contamination, and RPC risk. 相似文献
629.
Breast milk is the natural and optimal food for the infants. In addition to meeting the nutritional needs, breast milk provides numerous immunological, developmental, psychological, ecological and practical advantages. The levels of the DDT and HCH residues in human milk collected from remote rural part of Agra were analysed. Beta and gamma isomers of HCH accounts for the major residue of total HCH excreted in breast milk. Delta-HCH was not detected in the samples. 95% of the samples were found to be contaminated with DDT and its metabolites. DDD was found in 88% of the samples analyzed. The total concentration of DDT and HCH were found lower than the previous studies carried out in India. The study shows the decreasing levels of these organochlorine pesticides from the environment. Total concentration of total DDT is higher than total HCH. 相似文献
630.
Variation in melanin patterns among individuals, populations, and species is common in fishes of the genus Xiphophorus. In the variable platyfish, Xiphophorus variatus, variation in metabolic rate is associated with melanin coloration and the color morphs appear to be physiological specialists adapted to particular environmental conditions. This study investigates whether a melanin polymorphism in the green swordtail, Xiphophorus helleri, is likewise associated with variation in metabolic rate. We measured metabolic rate as oxygen consumption rate of both adult male and juvenile X. helleri in static respirometers. The oxygen consumption rate does not differ significantly between the spotted and nonspotted morphs in either group, suggesting that-unlike in X. variatus-selection on metabolic rate is not involved in maintaining the polymorphism in X. helleri. We suggest that explanations need to be sought for the evolution of melanophore diversity in Xiphophorus that are pertinent to each melanin pattern polymorphism or groups of similar polymorphisms. 相似文献