Dissertations, Theses, and Capstone Projects

Date of Degree

2-2024

Document Type

Dissertation

Degree Name

Ph.D.

Program

Earth & Environmental Sciences

Advisor

Peter M. Groffman

Committee Members

Andrew Reinmann

Cindi Katz

Tara Trammell

Subject Categories

African American Studies | Biodiversity | Biogeochemistry | Ecology and Evolutionary Biology | Environmental Health and Protection | Human Geography | Indigenous Studies | Other Environmental Sciences | Political History | Social Justice | Soil Science | United States History | Urban, Community and Regional Planning | Urban Studies and Planning

Keywords

biogeochemistry, nitrogen, urban studies, soil science, water quality, yards

Abstract

The ecological impacts of changes to land use are relevant to concerns about climate change, eutrophication of waterbodies, and reductions in biodiversity. As a foundational component of ecosystem functioning, changes to soil biogeochemistry have significant effects on overall ecosystem health. With cities continuing to grow and develop in extent, the impacts of urbanization and suburbanization on soils are of particular concern. Despite a wide range of natural climatic and geologic conditions, several factors have driven similar patterns of land transformation and management across the United States. In particular, federal initiatives including the Home Owners Loan Corporation, the Federal Housing Administration, the Servicemen’s Readjustment Act (known as the GI Bill), the Housing Act of 1954, and the Federal-Aid Highway Act of 1956 all helped to shape cities across the country, particularly in suburban areas, creating a vast area of structurally homogeneous land use characterized by houses with yards dominated by turfgrass lawns and racial disparity driven by racist policies promoting white homeownership. In this dissertation, analyses of soils sampled from residential areas (urban, suburban, and exurban) and native ecosystem soils in six U.S. cities (Baltimore, Maryland; Boston, Massachusetts; Los Angeles, California; Miami, Florida; Minneapolis-St. Paul, Minnesota; and Phoenix, Arizona) found that this homogenization extends to soil biogeochemistry, with important implications for water and air quality. Further research was conducted in these six cities to evaluate the impact of conversion away from turfgrass lawns to alternative yard types, such as wildlife certified yards or hydrologic focused yards (rain gardens in wet cities and xeriscaping in dry cities). This research found that regardless of yard type, all residential soils had elevated soil nitrate levels (an important water quality concern), and do not become more similar to native soils. While transforming yards away from turfgrass lawns towards alternative yard types may have a range of ecological benefits, impacts to soil chemistry are not immediately apparent. A final component of this dissertation focused on residential land use in the Long Island Sound (LIS), a waterbody significantly impacted by eutrophication due to excess nutrient input. Land use in this watershed is dominated by single family homes and lawns, creating concern about nutrient pollution to the LIS from these landscapes. These highly individualized and parceled patches of private property are the long-term outcome of Indigenous land dispossession within the region. Surveys of homeowners in conjunction with ecological research conducted in yards within the watershed found that a lawn quality rating scale adapted from as an assessment tool developed for turfgrass breeders is effective for assessing a range of ecological conditions in these yards. Higher quality lawns were fertilized more frequently than medium and low quality lawns, and soil nitrate levels increased with lawn quality. Lawn quality evaluations may be amenable to free, rapid, and non-extractive approaches to evaluating pollution problems associated with lawn management. These approaches may be important and useful as homeowners and decision-makers attempt to balance desires for lawn quality and environmental concerns. More broadly, a deeper historical perspective in analyses of land, land use, and environmental transformation may help to achieve this balance. Understanding, past and current dynamics regarding recognition and sovereignty of the Algonquian people within the LIS watershed and across the U.S. may help land managers grapple with the values and perceptions that underlie the decisions that they make that affect environmental quality and social disparity.

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