Date of Graduation

Fall 12-18-2015

Document Type

Project

Degree Name

Master of Science in Environmental Management (MSEM)

College/School

College of Arts and Sciences

Department/Program

Environmental Management

First Advisor

Allison Luengen

Abstract

San Francisco Peninsula grasslands have seen an influx of non-native invasive species starting in the 1500’s, threatening ecological stability by reducing biological diversity. To combat these invasive species, multiple public agencies have begun to adopt an integrated pest management (IPM) approach. This ecologically-based approach to pest management utilizes three controversial techniques, which are presently used or are under consideration for use on the San Francisco Peninsula: herbicide application, conservation grazing, and prescribed fire. In this paper, I will evaluate the use of the taxa Lepidoptera as a bioindicator of biodiversity to assess the environmental impacts of these techniques. The application of herbicide is the most commonly used vegetation management technique evaluated. Spot spraying minimizes the direct effects to Lepidoptera, which can include reduction in number of pupae, size of adult butterflies, and wing size reduction. Unintended movement of herbicide off target is of concern. During conservation grazing with cattle, the environment must be highly managed and monitored to ensure varied sward height and heterogeneity of plant communities. Heavy grazing intensity (6.9 AMU ha-1)has large negative impacts to the environment. After a prescribed fire, plant biodiversity spikes and then declines with time while the biodiversity of Lepidoptera is inversely correlated, with recovery taking 70 months or more. As impacts to Lepidoptera from herbicide application do not disproportionately affect them, their use as a bioindicator is substantiated. This paper has found that Lepidoptera is an effective bioindicator of biodiversity for conservation grazing. Due to the disproportionate impacts to Lepidoptera during and after a fire, their ability to act as a bioindicator is not substantiated. Lepidoptera recovery time after a prescribe fire might be best utilized as a bioindicator to fire frequency. The difference in the reviewed results may be the result of the difference in disturbance characteristics that these techniques display.

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