Impacts of Urban Sprawl on Monarch Butterfly Populations Along the California Coast

Daniel Fernandez


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The California coast was once a breeding ground for hundreds of thousands of monarch butterflies on their migratory journey, but over the past few decades there has been a dramatic decline in overwintering populations in California. As California’s population has continued to increase to nearly 40 million, urban sprawl has affected many ecosystems and natural habitats of species in the state. This study aims to determine how monarch butterflies have been impacted by urbanization throughout different cities along the coast of California. Specifically, it investigates if the human population, number of parks, and tree cover are any indicators of the reduction in population in ten cities including Santa Cruz, Pacific Grove, Goleta, Santa Barbara, Pismo, Malibu, Huntington Beach, Dana Point, Carlsbad, and San Diego. From the data collected and analyzed, the results have shown that there is a correlation between a higher human population and a lower monarch butterfly population, however, there is not a defining relationship between number of parks, and tree cover and an increase in monarch population. These results suggest that further research must be done to look at other factors such as native nectar plants, microclimates, and whether cities have butterfly sanctuaries or pledges to help protect the species. This study addresses the many ways different cities, and the general public can get involved in the conservation of monarch butterflies, along with basic understanding of including native plants to enhance monarch well-being in your area.

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