Browsing by Author "Schlesinger, William"

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    Expanding the Life Cycle Analysis Boundaries for Corn-based Ethanol to Include Land-Use Change: Implications for Greenhouse Gas Emissions
    (2007-08-27T13:59:13Z) Bolcar, Kathleen
    Current life cycle analyses of corn-based ethanol assume that CO2 fluxes from soils are negligible. This paper asks if it is necessary to include this flux for corn grown on lands previously enrolled in the Conservation Reserve Program. The analysis shows that CO2 fluxes from soils is indeed an important variable to consider when determining the overall impact of corn-based ethanol on greenhouse gas emissions.
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    Modeling N2O Emissions from Agricultural Soils Using a Multi-level Linear Regression
    (2007-08-29T23:43:14Z) Carey, Kyle
    Nitrous oxide (N2O) is a potent greenhouse gas emitted from soils through the microbial processes of denitrification/nitrification. In agricultural soils these natural processes and thus N2O emission are significantly enhanced by the use of nitrogen fertilizers. Use of fertilizer has grown rapidly since the 2nd half of the 20th century and will likely continue to grow as more countries develop advanced agricultural management strategies and demand for food increases. Though fertilizer enhanced N2O emissions from agriculture contribute only a small amount to the current anthropogenic global climate warming, it is expected that these emissions will play a larger role in the future. This study consists of a statistical meta-analysis of an agricultural N2O emission database made up of data taken from peer-reviewed literature. A multi-level linear regression is used to investigate the relationship between N fertilizer input and N2O emissions; (1) independent of variation between each study, (2) as a categorical function of crop type and (3) as a categorical function of fertilizer type. An understanding of these relationships could help to establish management strategies to more efficiently use N fertilizers, reducing N2O emissions and lowering expenses for agricultural producers. The results of the multi-level linear analysis of the dataset indicate that the relationship between N input and N2O emissions is not independent of the conditional variation between studies. The categorical analysis of differences in crop type also did not have a significant influence on N2O emissions. The categorical analysis of N fertilizer forms did show a significant influence on emissions. Differences in the slopes of the fertilizer type models provide relative comparability of expected N2O emissions of different chemical forms of N fertilizer for a given N input. The analysis performed in this study yielded important insight into the factors influencing N2O emissions from agricultural soils. These findings can be used to guide both management strategies and further research dealing with an increasingly important topic.
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    REDUCING SEA TURTLE DAMAGE TO CRAB POTS USING A LOW-PROFILE POT DESIGN IN CORE SOUND, NORTH CAROLINA
    (2002) Marsh, Jesse C.
    The blue crab (Callinectes sapidus) supports North Carolina's most valuable commercial fishery; the value of hard blue crabs landed in 2000 was over $30 million dollars. This lucrative fishery may be adversely affected by loggerhead sea turtles (Caretta caretta), which are listed as threatened under the Endangered Species Act of 1973. Crabbers in Core Sound, North Carolina, report that sea turtle damage to crab pots has become an increasingly serious issue. Turtles damage crab pots by overturning them while trying to get the bait, tearing up the bottoms and sides of the pots; this damage results in higher gear replacement costs and losses in crab catch. Experimental fishing was conducted to test for differences in crab catch and pot damage using three types of crab pots: low-profile, square mesh, and hexagonal mesh. The hexagonal mesh pot is the most common pot type used by crabbers in Core Sound, and the low-profile pot was designed to reduce the sea turtles' ability to overturn the pots. The number and size of all crabs caught in the experimental pots were recorded. An analysis of variance (ANDVA) was used to analyze the relationship between number of crabs caught per pot and the effect of pot type, location, date, the interaction of date and location, and the interaction of pot type and location. Tukey-Kramer multiple comparison tests were used to determine significant differences among treatments. There was no significant difference in crab catch between the low-profile and the square mesh pots at any of the three experimental fishing locations. There was a significant difference in catch between the low-profile and hexagonal mesh pots at one location. The lowprofile pots sustained considerably less damage than both the square mesh and hexagonal mesh pot types. In interviews with 19 Core and Pamlico Sound crabbers, crabbers estimated that 62% of all crab pot damage, and 37% of lost crab catch, is due to sea turtle damage. The low-profile crab pot has the potential to improve this situation by allowing crabbers to maintain crab catch with a reduction in gear replacement costs.
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    The environmental justice dimensions of climate change
    (Environmental Justice, 2011-03-01) Miranda, ML; Hastings, Douglas; Aldy, Joseph; Schlesinger, William
    Nations around the world are considering strategies to mitigate the severe impacts of climate change predicted to occur in the twenty-first century. Many countries, however, lack the wealth, technology, and government institutions to effectively cope with climate change. This study investigates the varying degrees to which developing and developed nations will be exposed to changes in three key variables: temperature, precipitation, and runoff. We use Geographic Information Systems (GIS) analysis to compare current and future climate model predictions on a country level. We then compare our calculations of climate change exposure for each nation to several metrics of political and economic well-being. Our results indicate that the impacts of changes in precipitation and runoff are distributed relatively equally between developed and developing nations. In contrast, we confirm research suggesting that developing nations will be affected far more severely by changes in temperature than developed nations. Our results also suggest that this unequal impact will persist throughout the twenty-first century. Our analysis further indicates that the most significant temperature changes will occur in politically unstable countries, creating an additional motivation for developed countries to actively engage with developing nations on climate mitigation strategies. © 2011, Mary Ann Liebert, Inc.