New estimates of the impacts of germplasm improvement in the major staple crops between 1965 and 2004 on global land-cover change are presented, based on simulations carried out using a global economic model (Global Trade Analysis Project Agro-Ecological Zone), a multicommodity, multiregional computable general equilibrium model linked to a global spatially explicit database on land use. We estimate the impact of removing the gains in cereal productivity attributed to the widespread adoption of improved varieties in developing countries. Here, several different effects—higher yields, lower prices, higher land rents, and trade effects—have been incorporated in a single model of the impact of Green Revolution research (and subsequent advances in yields from crop germplasm improvement) on land-cover change. Our results generally support the Borlaug hypothesis that increases in cereal yields as a result of widespread adoption of improved crop germplasm have saved natural ecosystems from being converted to agriculture. However, this relationship is complex, and the net effect is of a much smaller magnitude than Borlaug proposed. We estimate that the total crop area in 2004 would have been between 17.9 and 26.7 million hectares larger in a world that had not benefited from crop germplasm improvement since 1965. Of these hectares, 12.0–17.7 million would have been in developing countries, displacing pastures and resulting in an estimated 2 million hectares of additional deforestation. However, the negative impacts of higher food prices on poverty and hunger under this scenario would likely have dwarfed the welfare effects of agricultural expansion.
Silicosis may be defined as the disease resulting from chronic occupational exposure to silica dust. Silica is primarily composed of quartz dust and has been classified since 2000 as a known human carcinogen by the U.S. government. Silicosis may lead to impairment of lung function resulting from fibrosis of the lungs. This may in turn lead to an increased susceptibility to the development of tuberculosis. Respirable particles are in the size range of less than one micrometer to as large as 30 micrometers. Silicosis is an untreatable, but preventable disease. This review explores the history of silicosis in the U.S. mining industry, including case studies of occupational silicosis.
The role of straw yield and quality in farmers' decisions about the adoption of pearl millet cultivars in western Rajasthan was examined using farm household surveys. Information on the relative importance of grain versus straw yield, the perceived risks associated with the use of new cultivars under variable climatic conditions and perceptions of straw quality indicated that improved cultivars of pearl millet were not adopted primarily because of poor grain yield in years with low rainfall, though poor straw yield in such years was also important. These results are particularly pertinent in the light of farmers' perceptions of the likelihood of experiencing drought or low rainfall. If new cultivars of pearl millet are to replace the traditional ones, they must perform better under conditions of limited rainfall.
Use of antibiotics in subtherapeutic doses as growth-promoting feed additives for animal production is widespread in the U.S. and throughout the world. Previous studies by our research group concluded that size fractionation of poultry (broiler) litter followed by storage facilitated reutilization of litter as a soil amendment or bedding supplement. However, litter microbial contamination, including antibiotic-resistant populations, and accumulation of metals and other elements may limit litter reutilization. Litter from four broiler houses was separated into a fine fraction for use as a soil amendment, and a coarse fraction for reutilization as a bedding supplement in growing subsequent flocks of broilers. Fractions and whole litter were stored in indoor piles simulating farm storage conditions for 4 mo with periodic analysis for metals, other elements, and culturable bacteria (including total and fecal coliform, Aeromonas hydrophila, Pseudomonas aeruginosa, Yersinia enterocolitica, and Campylobacter jejuni). Representative bacterial isolates were tested for their sensitivity to 12 common antibiotics (ampicillin, bacitracin, cephalothin, erythromycin, gentamicin, kanamycin, nalidixic acid, neomycin, penicillin, streptomycin, sulfisoxazole, and tetracycline) using the Kirby-Bauer technique. Pathogens and indicator bacteria tested were found to be resistant to multiple antibiotics. Data suggest that microbial contamination of litter should be reduced or eliminated prior to reutilization to minimize environmental health risks related to transfer of antibiotic-resistant bacteria to humans or other animals.
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