Decisions that reduce insect diversity and decrease the network strength in insect communities result in higher pest abundance.

We propose a fear index for corn using the variance swap rate synthesized from out-of-the-money call and put options as a measure of implied variance. We find negative and time-varying variance risk premiums (realized variance minus implied variance) in the corn market from 1987 to 2009. Our results contrast with Egelkraut, Garcia, and Sherrick (2007), but are in line with the findings of Simon (2002). We conclude that our synthesized model-free implied variance

Increases in agricultural conversion are leading to declines in native grasslands and natural resources critical for beneficial insects. However, little is known regarding how these changes affect pollinator diversity. Land use types were categorized within 300 m and 3 km radii of pollinator sampling locations in Brookings County, SD. Pollinator abundance and species richness were regressed on the proportion of the landscape dedicated to row crops, grass and pasture, forage crops, small grains, and aquatic habitats using variance components modeling. Row crops had a negative effect on bee abundance at 300 m, after fixed effects modeling accounted for outliers skewing this relationship. At 3 km, corn positively affected bee abundance and richness, while soybean acreage decreased species richness. The landscape matrix of outlying sites consisted of large monocultured areas with few alternative habitat types available, leading to inflated populations of Melissodes and Halictidae. Syrphids had a positive parabolic relationship between diversity and row crops, indicating potential for competitive exclusion from intermediate landscapes. Unlike other studies, landscape diversity within 300 m was not found to significantly benefit pollinator diversity. Within especially agriculturally developed areas of the region, high abundances of pollinators suggest selection for a few dominant species. There was no effect of forage crops or aquatic habitats on pollinator diversity, indicating that less highly managed areas still represent degraded habitat within the landscape. Incorporating pollinator-friendly crops at the farm level throughout the region is likely to enhance pollinator diversity by lessening the negative effects of large monocultures.

No abstract

This paper focuses on NAFTA's impact on intra-industry and inter-industry trade in agricultural food products. Bilateral trade among the United States, Canada, and Mexico and their trade with the rest of the world during 1990 and 1995 are investigated. The study shows that U.S. trade patterns for agricultural food products are slowly changing. The proportion of the intra-industry trade was higher for food products involving a greater degree of processing, whereas trade in bulk commodities with little or no processing was predominantly inter-industry. U.S.-Canada bilateral trade has been increasingly more dominated by intra-industry trade. On the other hand, Mexican bilateral trade with both the United States and Canada has been predominantly inter-industry in nature. The study also indicated a decline in the proportion of intra-industry trade in U.S. trade with the rest of the world during this period. [EconLit citations: F120, F190]. © 2001 John Wiley & Sons, Inc.